// Copyright 2016 The etcd Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package embed

import (
	"crypto/tls"
	"errors"
	"flag"
	"fmt"
	"math"
	"net"
	"net/http"
	"net/netip"
	"net/url"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"go.uber.org/zap"
	"golang.org/x/crypto/bcrypt"
	"google.golang.org/grpc"
	"sigs.k8s.io/yaml"

	bolt "go.etcd.io/bbolt"
	"go.etcd.io/etcd/client/pkg/v3/logutil"
	"go.etcd.io/etcd/client/pkg/v3/srv"
	"go.etcd.io/etcd/client/pkg/v3/tlsutil"
	"go.etcd.io/etcd/client/pkg/v3/transport"
	"go.etcd.io/etcd/client/pkg/v3/types"
	clientv3 "go.etcd.io/etcd/client/v3"
	"go.etcd.io/etcd/pkg/v3/featuregate"
	"go.etcd.io/etcd/pkg/v3/flags"
	"go.etcd.io/etcd/pkg/v3/netutil"
	"go.etcd.io/etcd/server/v3/config"
	"go.etcd.io/etcd/server/v3/etcdserver"
	"go.etcd.io/etcd/server/v3/etcdserver/api/membership"
	"go.etcd.io/etcd/server/v3/etcdserver/api/rafthttp"
	"go.etcd.io/etcd/server/v3/etcdserver/api/v3compactor"
	"go.etcd.io/etcd/server/v3/etcdserver/api/v3discovery"
	"go.etcd.io/etcd/server/v3/features"
)

const (
	ClusterStateFlagNew      = "new"
	ClusterStateFlagExisting = "existing"

	DefaultName                        = "default"
	DefaultMaxSnapshots                = 5
	DefaultMaxWALs                     = 5
	DefaultMaxTxnOps                   = uint(128)
	DefaultWarningApplyDuration        = 100 * time.Millisecond
	DefaultWarningUnaryRequestDuration = 300 * time.Millisecond
	DefaultMaxRequestBytes             = 1.5 * 1024 * 1024
	DefaultMaxConcurrentStreams        = math.MaxUint32
	DefaultGRPCKeepAliveMinTime        = 5 * time.Second
	DefaultGRPCKeepAliveInterval       = 2 * time.Hour
	DefaultGRPCKeepAliveTimeout        = 20 * time.Second
	DefaultDowngradeCheckTime          = 5 * time.Second
	DefaultAutoCompactionMode          = "periodic"
	DefaultAutoCompactionRetention     = "0"
	DefaultAuthToken                   = "simple"
	DefaultCompactHashCheckTime        = time.Minute
	DefaultLoggingFormat               = "json"

	DefaultDiscoveryDialTimeout       = 2 * time.Second
	DefaultDiscoveryRequestTimeOut    = 5 * time.Second
	DefaultDiscoveryKeepAliveTime     = 2 * time.Second
	DefaultDiscoveryKeepAliveTimeOut  = 6 * time.Second
	DefaultDiscoveryInsecureTransport = true
	DefaultSelfSignedCertValidity     = 1
	DefaultTLSMinVersion              = string(tlsutil.TLSVersion12)

	DefaultListenPeerURLs   = "http://localhost:2380"
	DefaultListenClientURLs = "http://localhost:2379"

	DefaultLogOutput = "default"
	JournalLogOutput = "systemd/journal"
	StdErrLogOutput  = "stderr"
	StdOutLogOutput  = "stdout"

	// DefaultLogRotationConfig is the default configuration used for log rotation.
	// Log rotation is disabled by default.
	// MaxSize    = 100 // MB
	// MaxAge     = 0 // days (no limit)
	// MaxBackups = 0 // no limit
	// LocalTime  = false // use computers local time, UTC by default
	// Compress   = false // compress the rotated log in gzip format
	DefaultLogRotationConfig = `{"maxsize": 100, "maxage": 0, "maxbackups": 0, "localtime": false, "compress": false}`

	// ExperimentalDistributedTracingAddress is the default collector address.
	// TODO: delete in v3.7
	// Deprecated: Use DefaultDistributedTracingAddress instead. Will be decommissioned in v3.7.
	ExperimentalDistributedTracingAddress = "localhost:4317"
	// DefaultDistributedTracingAddress is the default collector address.
	DefaultDistributedTracingAddress = "localhost:4317"
	// ExperimentalDistributedTracingServiceName is the default etcd service name.
	// TODO: delete in v3.7
	// Deprecated: Use DefaultDistributedTracingServiceName instead. Will be decommissioned in v3.7.
	ExperimentalDistributedTracingServiceName = "etcd"
	// DefaultDistributedTracingServiceName is the default etcd service name.
	DefaultDistributedTracingServiceName = "etcd"

	DefaultExperimentalTxnModeWriteWithSharedBuffer = true

	// DefaultStrictReconfigCheck is the default value for "--strict-reconfig-check" flag.
	// It's enabled by default.
	DefaultStrictReconfigCheck = true

	// maxElectionMs specifies the maximum value of election timeout.
	// More details are listed on etcd.io/docs > version > tuning/#time-parameters
	maxElectionMs = 50000
	// backend freelist map type
	freelistArrayType = "array"

	ServerFeatureGateFlagName = "feature-gates"
)

var (
	ErrConflictBootstrapFlags = fmt.Errorf("multiple discovery or bootstrap flags are set. " +
		"Choose one of \"initial-cluster\", \"discovery\", \"discovery-endpoints\" or \"discovery-srv\"")
	ErrUnsetAdvertiseClientURLsFlag = fmt.Errorf("--advertise-client-urls is required when --listen-client-urls is set explicitly")
	ErrLogRotationInvalidLogOutput  = fmt.Errorf("--log-outputs requires a single file path when --log-rotate-config-json is defined")

	DefaultInitialAdvertisePeerURLs = "http://localhost:2380"
	DefaultAdvertiseClientURLs      = "http://localhost:2379"

	defaultHostname   string
	defaultHostStatus error

	// indirection for testing
	getCluster = srv.GetCluster

	// in 3.6, we are migration all the --experimental flags to feature gate and flags without the prefix.
	// This is the mapping from the non boolean `experimental-` to the new flags.
	// TODO: delete in v3.7
	experimentalFlagMigrationMap = map[string]string{
		"experimental-compact-hash-check-time":              "compact-hash-check-time",
		"experimental-corrupt-check-time":                   "corrupt-check-time",
		"experimental-compaction-batch-limit":               "compaction-batch-limit",
		"experimental-watch-progress-notify-interval":       "watch-progress-notify-interval",
		"experimental-warning-apply-duration":               "warning-apply-duration",
		"experimental-bootstrap-defrag-threshold-megabytes": "bootstrap-defrag-threshold-megabytes",
		"experimental-max-learners":                         "max-learners",
		"experimental-memory-mlock":                         "memory-mlock",
		"experimental-snapshot-catchup-entries":             "snapshot-catchup-entries",
		"experimental-compaction-sleep-interval":            "compaction-sleep-interval",
		"experimental-downgrade-check-time":                 "downgrade-check-time",
		"experimental-peer-skip-client-san-verification":    "peer-skip-client-san-verification",
		"experimental-enable-distributed-tracing":           "enable-distributed-tracing",
		"experimental-distributed-tracing-address":          "distributed-tracing-address",
		"experimental-distributed-tracing-service-name":     "distributed-tracing-service-name",
		"experimental-distributed-tracing-instance-id":      "distributed-tracing-instance-id",
		"experimental-distributed-tracing-sampling-rate":    "distributed-tracing-sampling-rate",
	}
)

var (
	// CompactorModePeriodic is periodic compaction mode
	// for "Config.AutoCompactionMode" field.
	// If "AutoCompactionMode" is CompactorModePeriodic and
	// "AutoCompactionRetention" is "1h", it automatically compacts
	// compacts storage every hour.
	CompactorModePeriodic = v3compactor.ModePeriodic

	// CompactorModeRevision is revision-based compaction mode
	// for "Config.AutoCompactionMode" field.
	// If "AutoCompactionMode" is CompactorModeRevision and
	// "AutoCompactionRetention" is "1000", it compacts log on
	// revision 5000 when the current revision is 6000.
	// This runs every 5-minute if enough of logs have proceeded.
	CompactorModeRevision = v3compactor.ModeRevision
)

func init() {
	defaultHostname, defaultHostStatus = netutil.GetDefaultHost()
}

// Config holds the arguments for configuring an etcd server.
type Config struct {
	Name string `json:"name"`
	Dir  string `json:"data-dir"`
	//revive:disable-next-line:var-naming
	WalDir string `json:"wal-dir"`

	// SnapshotCount is the number of committed transactions that trigger a snapshot to disk.
	// TODO: remove it in 3.7.
	// Deprecated: Will be decommissioned in v3.7.
	SnapshotCount uint64 `json:"snapshot-count"`

	// ExperimentalSnapshotCatchUpEntries is the number of entries for a slow follower
	// to catch-up after compacting the raft storage entries.
	// We expect the follower has a millisecond level latency with the leader.
	// The max throughput is around 10K. Keep a 5K entries is enough for helping
	// follower to catch up.
	// TODO: remove in v3.7.
	// Note we made a mistake in https://github.com/etcd-io/etcd/pull/15033. The json tag
	// `*-catch-up-*` isn't consistent with the command line flag `*-catchup-*`.
	// Deprecated: Use SnapshotCatchUpEntries instead. Will be removed in v3.7.
	ExperimentalSnapshotCatchUpEntries uint64 `json:"experimental-snapshot-catch-up-entries"`

	// SnapshotCatchUpEntries is the number of entires for a slow follower
	// to catch-up after compacting the raft storage entries.
	// We expect the follower has a millisecond level latency with the leader.
	// The max throughput is around 10K. Keep a 5K entries is enough for helping
	// follower to catch up.
	SnapshotCatchUpEntries uint64 `json:"snapshot-catchup-entries"`

	// MaxSnapFiles is the maximum number of snapshot files.
	// TODO: remove it in 3.7.
	// Deprecated: Will be removed in v3.7.
	MaxSnapFiles uint `json:"max-snapshots"`
	//revive:disable-next-line:var-naming
	MaxWalFiles uint `json:"max-wals"`

	// TickMs is the number of milliseconds between heartbeat ticks.
	// TODO: decouple tickMs and heartbeat tick (current heartbeat tick = 1).
	// make ticks a cluster wide configuration.
	TickMs     uint `json:"heartbeat-interval"`
	ElectionMs uint `json:"election-timeout"`

	// InitialElectionTickAdvance is true, then local member fast-forwards
	// election ticks to speed up "initial" leader election trigger. This
	// benefits the case of larger election ticks. For instance, cross
	// datacenter deployment may require longer election timeout of 10-second.
	// If true, local node does not need wait up to 10-second. Instead,
	// forwards its election ticks to 8-second, and have only 2-second left
	// before leader election.
	//
	// Major assumptions are that:
	//  - cluster has no active leader thus advancing ticks enables faster
	//    leader election, or
	//  - cluster already has an established leader, and rejoining follower
	//    is likely to receive heartbeats from the leader after tick advance
	//    and before election timeout.
	//
	// However, when network from leader to rejoining follower is congested,
	// and the follower does not receive leader heartbeat within left election
	// ticks, disruptive election has to happen thus affecting cluster
	// availabilities.
	//
	// Disabling this would slow down initial bootstrap process for cross
	// datacenter deployments. Make your own tradeoffs by configuring
	// --initial-election-tick-advance at the cost of slow initial bootstrap.
	//
	// If single-node, it advances ticks regardless.
	//
	// See https://github.com/etcd-io/etcd/issues/9333 for more detail.
	InitialElectionTickAdvance bool `json:"initial-election-tick-advance"`

	// BackendBatchInterval is the maximum time before commit the backend transaction.
	BackendBatchInterval time.Duration `json:"backend-batch-interval"`
	// BackendBatchLimit is the maximum operations before commit the backend transaction.
	BackendBatchLimit int `json:"backend-batch-limit"`
	// BackendFreelistType specifies the type of freelist that boltdb backend uses (array and map are supported types).
	BackendFreelistType string `json:"backend-bbolt-freelist-type"`
	QuotaBackendBytes   int64  `json:"quota-backend-bytes"`
	MaxTxnOps           uint   `json:"max-txn-ops"`
	MaxRequestBytes     uint   `json:"max-request-bytes"`

	// MaxConcurrentStreams specifies the maximum number of concurrent
	// streams that each client can open at a time.
	MaxConcurrentStreams uint32 `json:"max-concurrent-streams"`

	//revive:disable:var-naming
	ListenPeerUrls, ListenClientUrls, ListenClientHttpUrls []url.URL
	AdvertisePeerUrls, AdvertiseClientUrls                 []url.URL
	//revive:enable:var-naming

	ClientTLSInfo transport.TLSInfo
	ClientAutoTLS bool
	PeerTLSInfo   transport.TLSInfo
	PeerAutoTLS   bool

	// SelfSignedCertValidity specifies the validity period of the client and peer certificates
	// that are automatically generated by etcd when you specify ClientAutoTLS and PeerAutoTLS,
	// the unit is year, and the default is 1
	SelfSignedCertValidity uint `json:"self-signed-cert-validity"`

	// CipherSuites is a list of supported TLS cipher suites between
	// client/server and peers. If empty, Go auto-populates the list.
	// Note that cipher suites are prioritized in the given order.
	CipherSuites []string `json:"cipher-suites"`

	// TlsMinVersion is the minimum accepted TLS version between client/server and peers.
	//revive:disable-next-line:var-naming
	TlsMinVersion string `json:"tls-min-version"`

	// TlsMaxVersion is the maximum accepted TLS version between client/server and peers.
	//revive:disable-next-line:var-naming
	TlsMaxVersion string `json:"tls-max-version"`

	ClusterState          string `json:"initial-cluster-state"`
	DNSCluster            string `json:"discovery-srv"`
	DNSClusterServiceName string `json:"discovery-srv-name"`
	Dproxy                string `json:"discovery-proxy"`

	Durl         string                      `json:"discovery"`
	DiscoveryCfg v3discovery.DiscoveryConfig `json:"discovery-config"`

	InitialCluster      string `json:"initial-cluster"`
	InitialClusterToken string `json:"initial-cluster-token"`
	StrictReconfigCheck bool   `json:"strict-reconfig-check"`

	// AutoCompactionMode is either 'periodic' or 'revision'.
	AutoCompactionMode string `json:"auto-compaction-mode"`
	// AutoCompactionRetention is either duration string with time unit
	// (e.g. '5m' for 5-minute), or revision unit (e.g. '5000').
	// If no time unit is provided and compaction mode is 'periodic',
	// the unit defaults to hour. For example, '5' translates into 5-hour.
	AutoCompactionRetention string `json:"auto-compaction-retention"`

	// GRPCKeepAliveMinTime is the minimum interval that a client should
	// wait before pinging server. When client pings "too fast", server
	// sends goaway and closes the connection (errors: too_many_pings,
	// http2.ErrCodeEnhanceYourCalm). When too slow, nothing happens.
	// Server expects client pings only when there is any active streams
	// (PermitWithoutStream is set false).
	GRPCKeepAliveMinTime time.Duration `json:"grpc-keepalive-min-time"`
	// GRPCKeepAliveInterval is the frequency of server-to-client ping
	// to check if a connection is alive. Close a non-responsive connection
	// after an additional duration of Timeout. 0 to disable.
	GRPCKeepAliveInterval time.Duration `json:"grpc-keepalive-interval"`
	// GRPCKeepAliveTimeout is the additional duration of wait
	// before closing a non-responsive connection. 0 to disable.
	GRPCKeepAliveTimeout time.Duration `json:"grpc-keepalive-timeout"`

	// GRPCAdditionalServerOptions is the additional server option hook
	// for changing the default internal gRPC configuration. Note these
	// additional configurations take precedence over the existing individual
	// configurations if present. Please refer to
	// https://github.com/etcd-io/etcd/pull/14066#issuecomment-1248682996
	GRPCAdditionalServerOptions []grpc.ServerOption `json:"grpc-additional-server-options"`

	// SocketOpts are socket options passed to listener config.
	SocketOpts transport.SocketOpts `json:"socket-options"`

	// PreVote is true to enable Raft Pre-Vote.
	// If enabled, Raft runs an additional election phase
	// to check whether it would get enough votes to win
	// an election, thus minimizing disruptions.
	PreVote bool `json:"pre-vote"`

	CORS map[string]struct{}

	// HostWhitelist lists acceptable hostnames from HTTP client requests.
	// Client origin policy protects against "DNS Rebinding" attacks
	// to insecure etcd servers. That is, any website can simply create
	// an authorized DNS name, and direct DNS to "localhost" (or any
	// other address). Then, all HTTP endpoints of etcd server listening
	// on "localhost" becomes accessible, thus vulnerable to DNS rebinding
	// attacks. See "CVE-2018-5702" for more detail.
	//
	// 1. If client connection is secure via HTTPS, allow any hostnames.
	// 2. If client connection is not secure and "HostWhitelist" is not empty,
	//    only allow HTTP requests whose Host field is listed in whitelist.
	//
	// Note that the client origin policy is enforced whether authentication
	// is enabled or not, for tighter controls.
	//
	// By default, "HostWhitelist" is "*", which allows any hostnames.
	// Note that when specifying hostnames, loopback addresses are not added
	// automatically. To allow loopback interfaces, leave it empty or set it "*",
	// or add them to whitelist manually (e.g. "localhost", "127.0.0.1", etc.).
	//
	// CVE-2018-5702 reference:
	// - https://bugs.chromium.org/p/project-zero/issues/detail?id=1447#c2
	// - https://github.com/transmission/transmission/pull/468
	// - https://github.com/etcd-io/etcd/issues/9353
	HostWhitelist map[string]struct{}

	// UserHandlers is for registering users handlers and only used for
	// embedding etcd into other applications.
	// The map key is the route path for the handler, and
	// you must ensure it can't be conflicted with etcd's.
	UserHandlers map[string]http.Handler `json:"-"`
	// ServiceRegister is for registering users' gRPC services. A simple usage example:
	//	cfg := embed.NewConfig()
	//	cfg.ServiceRegister = func(s *grpc.Server) {
	//		pb.RegisterFooServer(s, &fooServer{})
	//		pb.RegisterBarServer(s, &barServer{})
	//	}
	//	embed.StartEtcd(cfg)
	ServiceRegister func(*grpc.Server) `json:"-"`

	AuthToken  string `json:"auth-token"`
	BcryptCost uint   `json:"bcrypt-cost"`

	// AuthTokenTTL in seconds of the simple token
	AuthTokenTTL uint `json:"auth-token-ttl"`

	// ExperimentalInitialCorruptCheck defines to check data corrution on boot.
	// TODO: delete in v3.7
	// Deprecated: Use InitialCorruptCheck Feature Gate instead. Will be decommissioned in v3.7.
	ExperimentalInitialCorruptCheck bool `json:"experimental-initial-corrupt-check"`
	// ExperimentalCorruptCheckTime is the duration of time between cluster corruption check passes.
	// TODO: delete in v3.7
	// Deprecated: Use CorruptCheckTime instead. Will be decommissioned in v3.7.
	ExperimentalCorruptCheckTime time.Duration `json:"experimental-corrupt-check-time"`
	// CorruptCheckTime is the duration of time between cluster corruption check passes.
	CorruptCheckTime time.Duration `json:"corrupt-check-time"`
	// ExperimentalCompactHashCheckEnabled enables leader to periodically check followers compaction hashes.
	// TODO: delete in v3.7
	// Deprecated: Use CompactHashCheck Feature Gate. Will be decommissioned in v3.7.
	ExperimentalCompactHashCheckEnabled bool `json:"experimental-compact-hash-check-enabled"`
	// ExperimentalCompactHashCheckTime is the duration of time between leader checks followers compaction hashes.
	// TODO: delete in v3.7
	// Deprecated: Use CompactHashCheckTime instead. Will be decommissioned in v3.7.
	ExperimentalCompactHashCheckTime time.Duration `json:"experimental-compact-hash-check-time"`
	// CompactHashCheckTime is the duration of time between leader checks followers compaction hashes.
	CompactHashCheckTime time.Duration `json:"compact-hash-check-time"`

	// ExperimentalEnableLeaseCheckpoint enables leader to send regular checkpoints to other members to prevent reset of remaining TTL on leader change.
	ExperimentalEnableLeaseCheckpoint bool `json:"experimental-enable-lease-checkpoint"`
	// ExperimentalEnableLeaseCheckpointPersist enables persisting remainingTTL to prevent indefinite auto-renewal of long lived leases. Always enabled in v3.6. Should be used to ensure smooth upgrade from v3.5 clusters with this feature enabled.
	// Requires experimental-enable-lease-checkpoint to be enabled.
	// TODO: Delete in v3.7
	// Deprecated: To be decommissioned in v3.7.
	ExperimentalEnableLeaseCheckpointPersist bool `json:"experimental-enable-lease-checkpoint-persist"`
	// ExperimentalCompactionBatchLimit Sets the maximum revisions deleted in each compaction batch.
	// TODO: Delete in v3.7
	// Deprecated: Use CompactionBatchLimit instead. Will be decommissioned in v3.7.
	ExperimentalCompactionBatchLimit int `json:"experimental-compaction-batch-limit"`
	// CompactionBatchLimit Sets the maximum revisions deleted in each compaction batch.
	CompactionBatchLimit int `json:"compaction-batch-limit"`
	// ExperimentalCompactionSleepInterval is the sleep interval between every etcd compaction loop.
	// TODO: Delete in v3.7
	// Deprecated: Use CompactionSleepInterval instead. Will be decommissioned in v3.7.
	ExperimentalCompactionSleepInterval time.Duration `json:"experimental-compaction-sleep-interval"`
	// CompactionSleepInterval is the sleep interval between every etcd compaction loop.
	CompactionSleepInterval time.Duration `json:"compaction-sleep-interval"`
	// ExperimentalWatchProgressNotifyInterval is the time duration of periodic watch progress notifications.
	// TODO: Delete in v3.7
	// Deprecated: Use WatchProgressNotifyInterval instead. Will be decommissioned in v3.7.
	ExperimentalWatchProgressNotifyInterval time.Duration `json:"experimental-watch-progress-notify-interval"`
	// WatchProgressNotifyInterval is the time duration of periodic watch progress notifications.
	WatchProgressNotifyInterval time.Duration `json:"watch-progress-notify-interval"`
	// ExperimentalWarningApplyDuration is the time duration after which a warning is generated if applying request
	// takes more time than this value.
	// TODO: Delete in v3.7
	// Deprecated: Use WarningApplyDuration instead. Will be decommissioned in v3.7.
	ExperimentalWarningApplyDuration time.Duration `json:"experimental-warning-apply-duration"`
	// WarningApplyDuration is the time duration after which a warning is generated if applying request
	WarningApplyDuration time.Duration `json:"warning-apply-duration"`
	// ExperimentalBootstrapDefragThresholdMegabytes is the minimum number of megabytes needed to be freed for etcd server to
	// consider running defrag during bootstrap. Needs to be set to non-zero value to take effect.
	// TODO: Delete in v3.7
	// Deprecated: Use BootstrapDefragThresholdMegabytes instead. Will be decommissioned in v3.7.
	ExperimentalBootstrapDefragThresholdMegabytes uint `json:"experimental-bootstrap-defrag-threshold-megabytes"`
	// BootstrapDefragThresholdMegabytes is the minimum number of megabytes needed to be freed for etcd server to
	BootstrapDefragThresholdMegabytes uint `json:"bootstrap-defrag-threshold-megabytes"`
	// WarningUnaryRequestDuration is the time duration after which a warning is generated if applying
	// unary request takes more time than this value.
	WarningUnaryRequestDuration time.Duration `json:"warning-unary-request-duration"`
	// ExperimentalWarningUnaryRequestDuration is the time duration after which a warning is generated if applying
	// TODO: Delete in v3.7
	// Deprecated: Use WarningUnaryRequestDuration. Will be decommissioned in v3.7.
	ExperimentalWarningUnaryRequestDuration time.Duration `json:"experimental-warning-unary-request-duration"`
	// ExperimentalMaxLearners sets a limit to the number of learner members that can exist in the cluster membership.
	// TODO: Delete in v3.7
	// Deprecated: Use MaxLearners instead. Will be decommissioned in v3.7.
	ExperimentalMaxLearners int `json:"experimental-max-learners"`
	// MaxLearners sets a limit to the number of learner members that can exist in the cluster membership.
	MaxLearners int `json:"max-learners"`

	// ForceNewCluster starts a new cluster even if previously started; unsafe.
	ForceNewCluster bool `json:"force-new-cluster"`

	EnablePprof           bool   `json:"enable-pprof"`
	Metrics               string `json:"metrics"`
	ListenMetricsUrls     []url.URL
	ListenMetricsUrlsJSON string `json:"listen-metrics-urls"`

	// ExperimentalEnableDistributedTracing indicates if experimental tracing using OpenTelemetry is enabled.
	// TODO: delete in v3.7
	// Deprecated: Use EnableDistributedTracing instead. Will be decommissioned in v3.7.
	ExperimentalEnableDistributedTracing bool `json:"experimental-enable-distributed-tracing"`
	// EnableDistributedTracing indicates if tracing using OpenTelemetry is enabled.
	EnableDistributedTracing bool `json:"enable-distributed-tracing"`
	// ExperimentalDistributedTracingAddress is the address of the OpenTelemetry Collector.
	// Can only be set if ExperimentalEnableDistributedTracing is true.
	// TODO: delete in v3.7
	// Deprecated: Use DistributedTracingAddress instead. Will be decommissioned in v3.7.
	ExperimentalDistributedTracingAddress string `json:"experimental-distributed-tracing-address"`
	// DistributedTracingAddress is the address of the OpenTelemetry Collector.
	// Can only be set if EnableDistributedTracing is true.
	DistributedTracingAddress string `json:"distributed-tracing-address"`
	// ExperimentalDistributedTracingServiceName is the name of the service.
	// Can only be used if ExperimentalEnableDistributedTracing is true.
	// TODO: delete in v3.7
	// Deprecated: Use DistributedTracingServiceName instead. Will be decommissioned in v3.7.
	ExperimentalDistributedTracingServiceName string `json:"experimental-distributed-tracing-service-name"`
	// DistributedTracingServiceName is the name of the service.
	// Can only be used if EnableDistributedTracing is true.
	DistributedTracingServiceName string `json:"distributed-tracing-service-name"`
	// ExperimentalDistributedTracingServiceInstanceID is the ID key of the service.
	// This ID must be unique, as helps to distinguish instances of the same service
	// that exist at the same time.
	// Can only be used if ExperimentalEnableDistributedTracing is true.
	// TODO: delete in v3.7
	// Deprecated: Use DistributedTracingServiceInstanceID instead. Will be decommissioned in v3.7.
	ExperimentalDistributedTracingServiceInstanceID string `json:"experimental-distributed-tracing-instance-id"`
	// DistributedTracingServiceInstanceID is the ID key of the service.
	// This ID must be unique, as helps to distinguish instances of the same service
	// that exist at the same time.
	// Can only be used if EnableDistributedTracing is true.
	DistributedTracingServiceInstanceID string `json:"distributed-tracing-instance-id"`
	// ExperimentalDistributedTracingSamplingRatePerMillion is the number of samples to collect per million spans.
	// Defaults to 0.
	// TODO: delete in v3.7
	// Deprecated: Use DistributedTracingSamplingRatePerMillion instead. Will be decommissioned in v3.7.
	ExperimentalDistributedTracingSamplingRatePerMillion int `json:"experimental-distributed-tracing-sampling-rate"`
	// DistributedTracingSamplingRatePerMillion is the number of samples to collect per million spans.
	// Defaults to 0.
	DistributedTracingSamplingRatePerMillion int `json:"distributed-tracing-sampling-rate"`

	// ExperimentalPeerSkipClientSanVerification determines whether to skip verification of SAN field
	// in client certificate for peer connections.
	// TODO: Delete in v3.7
	// Deprecated: Use `peer-skip-client-san-verification` instead. Will be decommissioned in v3.7.
	ExperimentalPeerSkipClientSanVerification bool `json:"experimental-peer-skip-client-san-verification"`

	// Logger is logger options: currently only supports "zap".
	// "capnslog" is removed in v3.5.
	Logger string `json:"logger"`
	// LogLevel configures log level. Only supports debug, info, warn, error, panic, or fatal. Default 'info'.
	LogLevel string `json:"log-level"`
	// LogFormat set log encoding. Only supports json, console. Default is 'json'.
	LogFormat string `json:"log-format"`
	// LogOutputs is either:
	//  - "default" as os.Stderr,
	//  - "stderr" as os.Stderr,
	//  - "stdout" as os.Stdout,
	//  - file path to append server logs to.
	// It can be multiple when "Logger" is zap.
	LogOutputs []string `json:"log-outputs"`
	// EnableLogRotation enables log rotation of a single LogOutputs file target.
	EnableLogRotation bool `json:"enable-log-rotation"`
	// LogRotationConfigJSON is a passthrough allowing a log rotation JSON config to be passed directly.
	LogRotationConfigJSON string `json:"log-rotation-config-json"`
	// ZapLoggerBuilder is used to build the zap logger.
	ZapLoggerBuilder func(*Config) error

	// logger logs server-side operations. The default is nil,
	// and "setupLogging" must be called before starting server.
	// Do not set logger directly.
	loggerMu *sync.RWMutex
	logger   *zap.Logger
	// EnableGRPCGateway enables grpc gateway.
	// The gateway translates a RESTful HTTP API into gRPC.
	EnableGRPCGateway bool `json:"enable-grpc-gateway"`

	// UnsafeNoFsync disables all uses of fsync.
	// Setting this is unsafe and will cause data loss.
	UnsafeNoFsync bool `json:"unsafe-no-fsync"`

	// ExperimentalDowngradeCheckTime is the duration between two downgrade status checks (in seconds).
	// TODO: Delete `ExperimentalDowngradeCheckTime` in v3.7.
	// Deprecated: Use DowngradeCheckTime instead. Will be decommissioned in v3.7.
	ExperimentalDowngradeCheckTime time.Duration `json:"experimental-downgrade-check-time"`
	// DowngradeCheckTime is the duration between two downgrade status checks (in seconds).
	DowngradeCheckTime time.Duration `json:"downgrade-check-time"`

	// MemoryMlock enables mlocking of etcd owned memory pages.
	// The setting improves etcd tail latency in environments were:
	//   - memory pressure might lead to swapping pages to disk
	//   - disk latency might be unstable
	// Currently all etcd memory gets mlocked, but in future the flag can
	// be refined to mlock in-use area of bbolt only.
	MemoryMlock bool `json:"memory-mlock"`

	// ExperimentalMemoryMlock enables mlocking of etcd owned memory pages.
	// TODO: Delete in v3.7
	// Deprecated: Use MemoryMlock instad. To be decommissioned in v3.7.
	ExperimentalMemoryMlock bool `json:"experimental-memory-mlock"`

	// ExperimentalTxnModeWriteWithSharedBuffer enables write transaction to use a shared buffer in its readonly check operations.
	// TODO: Delete in v3.7
	// Deprecated: Use TxnModeWriteWithSharedBuffer Feature Flag. Will be decommissioned in v3.7.
	ExperimentalTxnModeWriteWithSharedBuffer bool `json:"experimental-txn-mode-write-with-shared-buffer"`

	// ExperimentalStopGRPCServiceOnDefrag enables etcd gRPC service to stop serving client requests on defragmentation.
	// TODO: Delete in v3.7
	// Deprecated: Use StopGRPCServiceOnDefrag Feature Flag. Will be decommissioned in v3.7.
	ExperimentalStopGRPCServiceOnDefrag bool `json:"experimental-stop-grpc-service-on-defrag"`

	// V2Deprecation describes phase of API & Storage V2 support.
	// Do not set this field for embedded use cases, as it has no effect. However, setting it will not cause any harm.
	// TODO: Delete in v3.8
	// Deprecated: The default value is enforced, to be removed in v3.8.
	V2Deprecation config.V2DeprecationEnum `json:"v2-deprecation"`

	// ServerFeatureGate is a server level feature gate
	ServerFeatureGate featuregate.FeatureGate
	// FlagsExplicitlySet stores if a flag is explicitly set from the cmd line or config file.
	FlagsExplicitlySet map[string]bool
}

// configYAML holds the config suitable for yaml parsing
type configYAML struct {
	Config
	configJSON
}

// configJSON has file options that are translated into Config options
type configJSON struct {
	ListenPeerURLs       string `json:"listen-peer-urls"`
	ListenClientURLs     string `json:"listen-client-urls"`
	ListenClientHTTPURLs string `json:"listen-client-http-urls"`
	AdvertisePeerURLs    string `json:"initial-advertise-peer-urls"`
	AdvertiseClientURLs  string `json:"advertise-client-urls"`

	CORSJSON          string `json:"cors"`
	HostWhitelistJSON string `json:"host-whitelist"`

	ClientSecurityJSON securityConfig `json:"client-transport-security"`
	PeerSecurityJSON   securityConfig `json:"peer-transport-security"`

	ServerFeatureGatesJSON string `json:"feature-gates"`
}

type securityConfig struct {
	CertFile            string   `json:"cert-file"`
	KeyFile             string   `json:"key-file"`
	ClientCertFile      string   `json:"client-cert-file"`
	ClientKeyFile       string   `json:"client-key-file"`
	CertAuth            bool     `json:"client-cert-auth"`
	TrustedCAFile       string   `json:"trusted-ca-file"`
	AutoTLS             bool     `json:"auto-tls"`
	AllowedCNs          []string `json:"allowed-cn"`
	AllowedHostnames    []string `json:"allowed-hostname"`
	SkipClientSANVerify bool     `json:"skip-client-san-verification,omitempty"`
}

// NewConfig creates a new Config populated with default values.
func NewConfig() *Config {
	lpurl, _ := url.Parse(DefaultListenPeerURLs)
	apurl, _ := url.Parse(DefaultInitialAdvertisePeerURLs)
	lcurl, _ := url.Parse(DefaultListenClientURLs)
	acurl, _ := url.Parse(DefaultAdvertiseClientURLs)
	cfg := &Config{
		MaxSnapFiles: DefaultMaxSnapshots,
		MaxWalFiles:  DefaultMaxWALs,

		Name: DefaultName,

		SnapshotCount:                      etcdserver.DefaultSnapshotCount,
		ExperimentalSnapshotCatchUpEntries: etcdserver.DefaultSnapshotCatchUpEntries,
		SnapshotCatchUpEntries:             etcdserver.DefaultSnapshotCatchUpEntries,

		MaxTxnOps:            DefaultMaxTxnOps,
		MaxRequestBytes:      DefaultMaxRequestBytes,
		MaxConcurrentStreams: DefaultMaxConcurrentStreams,
		WarningApplyDuration: DefaultWarningApplyDuration,

		GRPCKeepAliveMinTime:  DefaultGRPCKeepAliveMinTime,
		GRPCKeepAliveInterval: DefaultGRPCKeepAliveInterval,
		GRPCKeepAliveTimeout:  DefaultGRPCKeepAliveTimeout,

		SocketOpts: transport.SocketOpts{
			ReusePort:    false,
			ReuseAddress: false,
		},

		TickMs:                     100,
		ElectionMs:                 1000,
		InitialElectionTickAdvance: true,

		ListenPeerUrls:      []url.URL{*lpurl},
		ListenClientUrls:    []url.URL{*lcurl},
		AdvertisePeerUrls:   []url.URL{*apurl},
		AdvertiseClientUrls: []url.URL{*acurl},

		ClusterState:        ClusterStateFlagNew,
		InitialClusterToken: "etcd-cluster",

		StrictReconfigCheck: DefaultStrictReconfigCheck,
		Metrics:             "basic",

		CORS:          map[string]struct{}{"*": {}},
		HostWhitelist: map[string]struct{}{"*": {}},

		AuthToken:              DefaultAuthToken,
		BcryptCost:             uint(bcrypt.DefaultCost),
		AuthTokenTTL:           300,
		SelfSignedCertValidity: DefaultSelfSignedCertValidity,
		TlsMinVersion:          DefaultTLSMinVersion,

		PreVote: true,

		loggerMu:              new(sync.RWMutex),
		logger:                nil,
		Logger:                "zap",
		LogFormat:             DefaultLoggingFormat,
		LogOutputs:            []string{DefaultLogOutput},
		LogLevel:              logutil.DefaultLogLevel,
		EnableLogRotation:     false,
		LogRotationConfigJSON: DefaultLogRotationConfig,
		EnableGRPCGateway:     true,

		ExperimentalDowngradeCheckTime: DefaultDowngradeCheckTime,
		DowngradeCheckTime:             DefaultDowngradeCheckTime,
		MemoryMlock:                    false,
		// TODO: delete in v3.7
		ExperimentalMemoryMlock:             false,
		ExperimentalStopGRPCServiceOnDefrag: false,
		MaxLearners:                         membership.DefaultMaxLearners,
		// TODO: delete in v3.7
		ExperimentalMaxLearners: membership.DefaultMaxLearners,

		ExperimentalTxnModeWriteWithSharedBuffer:  DefaultExperimentalTxnModeWriteWithSharedBuffer,
		ExperimentalDistributedTracingAddress:     DefaultDistributedTracingAddress,
		DistributedTracingAddress:                 DefaultDistributedTracingAddress,
		ExperimentalDistributedTracingServiceName: DefaultDistributedTracingServiceName,
		DistributedTracingServiceName:             DefaultDistributedTracingServiceName,

		CompactHashCheckTime: DefaultCompactHashCheckTime,
		// TODO: delete in v3.7
		ExperimentalCompactHashCheckTime: DefaultCompactHashCheckTime,

		V2Deprecation: config.V2DeprDefault,

		DiscoveryCfg: v3discovery.DiscoveryConfig{
			ConfigSpec: clientv3.ConfigSpec{
				DialTimeout:      DefaultDiscoveryDialTimeout,
				RequestTimeout:   DefaultDiscoveryRequestTimeOut,
				KeepAliveTime:    DefaultDiscoveryKeepAliveTime,
				KeepAliveTimeout: DefaultDiscoveryKeepAliveTimeOut,

				Secure: &clientv3.SecureConfig{
					InsecureTransport: true,
				},
				Auth: &clientv3.AuthConfig{},
			},
		},

		AutoCompactionMode:      DefaultAutoCompactionMode,
		AutoCompactionRetention: DefaultAutoCompactionRetention,
		ServerFeatureGate:       features.NewDefaultServerFeatureGate(DefaultName, nil),
		FlagsExplicitlySet:      map[string]bool{},
	}
	cfg.InitialCluster = cfg.InitialClusterFromName(cfg.Name)
	return cfg
}

func (cfg *Config) AddFlags(fs *flag.FlagSet) {
	// member
	fs.StringVar(&cfg.Dir, "data-dir", cfg.Dir, "Path to the data directory.")
	fs.StringVar(&cfg.WalDir, "wal-dir", cfg.WalDir, "Path to the dedicated wal directory.")
	fs.Var(
		flags.NewUniqueURLsWithExceptions(DefaultListenPeerURLs, ""),
		"listen-peer-urls",
		"List of URLs to listen on for peer traffic.",
	)
	fs.Var(
		flags.NewUniqueURLsWithExceptions(DefaultListenClientURLs, ""), "listen-client-urls",
		"List of URLs to listen on for client grpc traffic and http as long as --listen-client-http-urls is not specified.",
	)
	fs.Var(
		flags.NewUniqueURLsWithExceptions("", ""), "listen-client-http-urls",
		"List of URLs to listen on for http only client traffic. Enabling this flag removes http services from --listen-client-urls.",
	)
	fs.Var(
		flags.NewUniqueURLsWithExceptions("", ""),
		"listen-metrics-urls",
		"List of URLs to listen on for the metrics and health endpoints.",
	)
	fs.UintVar(&cfg.MaxSnapFiles, "max-snapshots", cfg.MaxSnapFiles, "Maximum number of snapshot files to retain (0 is unlimited). Deprecated in v3.6 and will be decommissioned in v3.7.")
	fs.UintVar(&cfg.MaxWalFiles, "max-wals", cfg.MaxWalFiles, "Maximum number of wal files to retain (0 is unlimited).")
	fs.StringVar(&cfg.Name, "name", cfg.Name, "Human-readable name for this member.")
	fs.Uint64Var(&cfg.SnapshotCount, "snapshot-count", cfg.SnapshotCount, "Number of committed transactions to trigger a snapshot to disk. Deprecated in v3.6 and will be decommissioned in v3.7.")
	fs.UintVar(&cfg.TickMs, "heartbeat-interval", cfg.TickMs, "Time (in milliseconds) of a heartbeat interval.")
	fs.UintVar(&cfg.ElectionMs, "election-timeout", cfg.ElectionMs, "Time (in milliseconds) for an election to timeout.")
	fs.BoolVar(&cfg.InitialElectionTickAdvance, "initial-election-tick-advance", cfg.InitialElectionTickAdvance, "Whether to fast-forward initial election ticks on boot for faster election.")
	fs.Int64Var(&cfg.QuotaBackendBytes, "quota-backend-bytes", cfg.QuotaBackendBytes, "Raise alarms when backend size exceeds the given quota. 0 means use the default quota.")
	fs.StringVar(&cfg.BackendFreelistType, "backend-bbolt-freelist-type", cfg.BackendFreelistType, "BackendFreelistType specifies the type of freelist that boltdb backend uses(array and map are supported types)")
	fs.DurationVar(&cfg.BackendBatchInterval, "backend-batch-interval", cfg.BackendBatchInterval, "BackendBatchInterval is the maximum time before commit the backend transaction.")
	fs.IntVar(&cfg.BackendBatchLimit, "backend-batch-limit", cfg.BackendBatchLimit, "BackendBatchLimit is the maximum operations before commit the backend transaction.")
	fs.UintVar(&cfg.MaxTxnOps, "max-txn-ops", cfg.MaxTxnOps, "Maximum number of operations permitted in a transaction.")
	fs.UintVar(&cfg.MaxRequestBytes, "max-request-bytes", cfg.MaxRequestBytes, "Maximum client request size in bytes the server will accept.")
	fs.DurationVar(&cfg.GRPCKeepAliveMinTime, "grpc-keepalive-min-time", cfg.GRPCKeepAliveMinTime, "Minimum interval duration that a client should wait before pinging server.")
	fs.DurationVar(&cfg.GRPCKeepAliveInterval, "grpc-keepalive-interval", cfg.GRPCKeepAliveInterval, "Frequency duration of server-to-client ping to check if a connection is alive (0 to disable).")
	fs.DurationVar(&cfg.GRPCKeepAliveTimeout, "grpc-keepalive-timeout", cfg.GRPCKeepAliveTimeout, "Additional duration of wait before closing a non-responsive connection (0 to disable).")
	fs.BoolVar(&cfg.SocketOpts.ReusePort, "socket-reuse-port", cfg.SocketOpts.ReusePort, "Enable to set socket option SO_REUSEPORT on listeners allowing rebinding of a port already in use.")
	fs.BoolVar(&cfg.SocketOpts.ReuseAddress, "socket-reuse-address", cfg.SocketOpts.ReuseAddress, "Enable to set socket option SO_REUSEADDR on listeners allowing binding to an address in `TIME_WAIT` state.")

	fs.Var(flags.NewUint32Value(cfg.MaxConcurrentStreams), "max-concurrent-streams", "Maximum concurrent streams that each client can open at a time.")

	// raft connection timeouts
	fs.DurationVar(&rafthttp.ConnReadTimeout, "raft-read-timeout", rafthttp.DefaultConnReadTimeout, "Read timeout set on each rafthttp connection")
	fs.DurationVar(&rafthttp.ConnWriteTimeout, "raft-write-timeout", rafthttp.DefaultConnWriteTimeout, "Write timeout set on each rafthttp connection")

	// clustering
	fs.Var(
		flags.NewUniqueURLsWithExceptions(DefaultInitialAdvertisePeerURLs, ""),
		"initial-advertise-peer-urls",
		"List of this member's peer URLs to advertise to the rest of the cluster.",
	)

	fs.Var(
		flags.NewUniqueURLsWithExceptions(DefaultAdvertiseClientURLs, ""),
		"advertise-client-urls",
		"List of this member's client URLs to advertise to the public.",
	)

	fs.StringVar(&cfg.Durl, "discovery", cfg.Durl, "Discovery URL used to bootstrap the cluster for v2 discovery. Will be deprecated in v3.7, and be decommissioned in v3.8.")

	fs.Var(
		flags.NewUniqueStringsValue(""),
		"discovery-endpoints",
		"V3 discovery: List of gRPC endpoints of the discovery service.",
	)
	fs.StringVar(&cfg.DiscoveryCfg.Token, "discovery-token", "", "V3 discovery: discovery token for the etcd cluster to be bootstrapped.")
	fs.DurationVar(&cfg.DiscoveryCfg.DialTimeout, "discovery-dial-timeout", cfg.DiscoveryCfg.DialTimeout, "V3 discovery: dial timeout for client connections.")
	fs.DurationVar(&cfg.DiscoveryCfg.RequestTimeout, "discovery-request-timeout", cfg.DiscoveryCfg.RequestTimeout, "V3 discovery: timeout for discovery requests (excluding dial timeout).")
	fs.DurationVar(&cfg.DiscoveryCfg.KeepAliveTime, "discovery-keepalive-time", cfg.DiscoveryCfg.KeepAliveTime, "V3 discovery: keepalive time for client connections.")
	fs.DurationVar(&cfg.DiscoveryCfg.KeepAliveTimeout, "discovery-keepalive-timeout", cfg.DiscoveryCfg.KeepAliveTimeout, "V3 discovery: keepalive timeout for client connections.")
	fs.BoolVar(&cfg.DiscoveryCfg.Secure.InsecureTransport, "discovery-insecure-transport", true, "V3 discovery: disable transport security for client connections.")
	fs.BoolVar(&cfg.DiscoveryCfg.Secure.InsecureSkipVerify, "discovery-insecure-skip-tls-verify", false, "V3 discovery: skip server certificate verification (CAUTION: this option should be enabled only for testing purposes).")
	fs.StringVar(&cfg.DiscoveryCfg.Secure.Cert, "discovery-cert", "", "V3 discovery: identify secure client using this TLS certificate file.")
	fs.StringVar(&cfg.DiscoveryCfg.Secure.Key, "discovery-key", "", "V3 discovery: identify secure client using this TLS key file.")
	fs.StringVar(&cfg.DiscoveryCfg.Secure.Cacert, "discovery-cacert", "", "V3 discovery: verify certificates of TLS-enabled secure servers using this CA bundle.")
	fs.StringVar(&cfg.DiscoveryCfg.Auth.Username, "discovery-user", "", "V3 discovery: username[:password] for authentication (prompt if password is not supplied).")
	fs.StringVar(&cfg.DiscoveryCfg.Auth.Password, "discovery-password", "", "V3 discovery: password for authentication (if this option is used, --user option shouldn't include password).")

	fs.StringVar(&cfg.Dproxy, "discovery-proxy", cfg.Dproxy, "HTTP proxy to use for traffic to discovery service. Will be deprecated in v3.7, and be decommissioned in v3.8.")
	fs.StringVar(&cfg.DNSCluster, "discovery-srv", cfg.DNSCluster, "DNS domain used to bootstrap initial cluster.")
	fs.StringVar(&cfg.DNSClusterServiceName, "discovery-srv-name", cfg.DNSClusterServiceName, "Service name to query when using DNS discovery.")
	fs.StringVar(&cfg.InitialCluster, "initial-cluster", cfg.InitialCluster, "Initial cluster configuration for bootstrapping.")
	fs.StringVar(&cfg.InitialClusterToken, "initial-cluster-token", cfg.InitialClusterToken, "Initial cluster token for the etcd cluster during bootstrap.")
	fs.BoolVar(&cfg.StrictReconfigCheck, "strict-reconfig-check", cfg.StrictReconfigCheck, "Reject reconfiguration requests that would cause quorum loss.")

	fs.BoolVar(&cfg.PreVote, "pre-vote", cfg.PreVote, "Enable the raft Pre-Vote algorithm to prevent disruption when a node that has been partitioned away rejoins the cluster.")

	// security
	fs.StringVar(&cfg.ClientTLSInfo.CertFile, "cert-file", "", "Path to the client server TLS cert file.")
	fs.StringVar(&cfg.ClientTLSInfo.KeyFile, "key-file", "", "Path to the client server TLS key file.")
	fs.StringVar(&cfg.ClientTLSInfo.ClientCertFile, "client-cert-file", "", "Path to an explicit peer client TLS cert file otherwise cert file will be used when client auth is required.")
	fs.StringVar(&cfg.ClientTLSInfo.ClientKeyFile, "client-key-file", "", "Path to an explicit peer client TLS key file otherwise key file will be used when client auth is required.")
	fs.BoolVar(&cfg.ClientTLSInfo.ClientCertAuth, "client-cert-auth", false, "Enable client cert authentication.")
	fs.StringVar(&cfg.ClientTLSInfo.CRLFile, "client-crl-file", "", "Path to the client certificate revocation list file.")
	fs.Var(flags.NewStringsValue(""), "client-cert-allowed-hostname", "Comma-separated list of allowed SAN hostnames for client cert authentication.")
	fs.StringVar(&cfg.ClientTLSInfo.TrustedCAFile, "trusted-ca-file", "", "Path to the client server TLS trusted CA cert file.")
	fs.BoolVar(&cfg.ClientAutoTLS, "auto-tls", false, "Client TLS using generated certificates")
	fs.StringVar(&cfg.PeerTLSInfo.CertFile, "peer-cert-file", "", "Path to the peer server TLS cert file.")
	fs.StringVar(&cfg.PeerTLSInfo.KeyFile, "peer-key-file", "", "Path to the peer server TLS key file.")
	fs.StringVar(&cfg.PeerTLSInfo.ClientCertFile, "peer-client-cert-file", "", "Path to an explicit peer client TLS cert file otherwise peer cert file will be used when client auth is required.")
	fs.StringVar(&cfg.PeerTLSInfo.ClientKeyFile, "peer-client-key-file", "", "Path to an explicit peer client TLS key file otherwise peer key file will be used when client auth is required.")
	fs.BoolVar(&cfg.PeerTLSInfo.ClientCertAuth, "peer-client-cert-auth", false, "Enable peer client cert authentication.")
	fs.StringVar(&cfg.PeerTLSInfo.TrustedCAFile, "peer-trusted-ca-file", "", "Path to the peer server TLS trusted CA file.")
	fs.BoolVar(&cfg.PeerAutoTLS, "peer-auto-tls", false, "Peer TLS using generated certificates")
	fs.UintVar(&cfg.SelfSignedCertValidity, "self-signed-cert-validity", 1, "The validity period of the client and peer certificates, unit is year")
	fs.StringVar(&cfg.PeerTLSInfo.CRLFile, "peer-crl-file", "", "Path to the peer certificate revocation list file.")
	fs.Var(flags.NewStringsValue(""), "peer-cert-allowed-cn", "Comma-separated list of allowed CNs for inter-peer TLS authentication.")
	fs.Var(flags.NewStringsValue(""), "peer-cert-allowed-hostname", "Comma-separated list of allowed SAN hostnames for inter-peer TLS authentication.")
	fs.Var(flags.NewStringsValue(""), "cipher-suites", "Comma-separated list of supported TLS cipher suites between client/server and peers (empty will be auto-populated by Go).")
	fs.BoolVar(&cfg.ExperimentalPeerSkipClientSanVerification, "experimental-peer-skip-client-san-verification", false, "Skip verification of SAN field in client certificate for peer connections.Deprecated in v3.6 and will be decommissioned in v3.7. Use peer-skip-client-san-verification instead")
	fs.BoolVar(&cfg.PeerTLSInfo.SkipClientSANVerify, "peer-skip-client-san-verification", false, "Skip verification of SAN field in client certificate for peer connections.")
	fs.StringVar(&cfg.TlsMinVersion, "tls-min-version", string(tlsutil.TLSVersion12), "Minimum TLS version supported by etcd. Possible values: TLS1.2, TLS1.3.")
	fs.StringVar(&cfg.TlsMaxVersion, "tls-max-version", string(tlsutil.TLSVersionDefault), "Maximum TLS version supported by etcd. Possible values: TLS1.2, TLS1.3 (empty defers to Go).")

	fs.Var(
		flags.NewUniqueURLsWithExceptions("*", "*"),
		"cors",
		"Comma-separated white list of origins for CORS, or cross-origin resource sharing, (empty or * means allow all)",
	)
	fs.Var(flags.NewUniqueStringsValue("*"), "host-whitelist", "Comma-separated acceptable hostnames from HTTP client requests, if server is not secure (empty means allow all).")

	// logging
	fs.StringVar(&cfg.Logger, "logger", "zap", "Currently only supports 'zap' for structured logging.")
	fs.Var(flags.NewUniqueStringsValue(DefaultLogOutput), "log-outputs", "Specify 'stdout' or 'stderr' to skip journald logging even when running under systemd, or list of comma separated output targets.")
	fs.StringVar(&cfg.LogLevel, "log-level", logutil.DefaultLogLevel, "Configures log level. Only supports debug, info, warn, error, panic, or fatal. Default 'info'.")
	fs.StringVar(&cfg.LogFormat, "log-format", logutil.DefaultLogFormat, "Configures log format. Only supports json, console. Default is 'json'.")
	fs.BoolVar(&cfg.EnableLogRotation, "enable-log-rotation", false, "Enable log rotation of a single log-outputs file target.")
	fs.StringVar(&cfg.LogRotationConfigJSON, "log-rotation-config-json", DefaultLogRotationConfig, "Configures log rotation if enabled with a JSON logger config. Default: MaxSize=100(MB), MaxAge=0(days,no limit), MaxBackups=0(no limit), LocalTime=false(UTC), Compress=false(gzip)")

	fs.StringVar(&cfg.AutoCompactionRetention, "auto-compaction-retention", "0", "Auto compaction retention for mvcc key value store. 0 means disable auto compaction.")
	fs.StringVar(&cfg.AutoCompactionMode, "auto-compaction-mode", "periodic", "interpret 'auto-compaction-retention' one of: periodic|revision. 'periodic' for duration based retention, defaulting to hours if no time unit is provided (e.g. '5m'). 'revision' for revision number based retention.")

	// pprof profiler via HTTP
	fs.BoolVar(&cfg.EnablePprof, "enable-pprof", false, "Enable runtime profiling data via HTTP server. Address is at client URL + \"/debug/pprof/\"")

	// additional metrics
	fs.StringVar(&cfg.Metrics, "metrics", cfg.Metrics, "Set level of detail for exported metrics, specify 'extensive' to include server side grpc histogram metrics")

	// experimental distributed tracing
	fs.BoolVar(&cfg.ExperimentalEnableDistributedTracing, "experimental-enable-distributed-tracing", false, "Enable experimental distributed tracing using OpenTelemetry Tracing. Deprecated in v3.6 and will be decommissioned in v3.7. Use --enable-distributed-tracing instead.")
	fs.BoolVar(&cfg.EnableDistributedTracing, "enable-distributed-tracing", false, "Enable distributed tracing using OpenTelemetry Tracing.")

	fs.StringVar(&cfg.ExperimentalDistributedTracingAddress, "experimental-distributed-tracing-address", cfg.ExperimentalDistributedTracingAddress, "Address for distributed tracing used for OpenTelemetry Tracing (if enabled with experimental-enable-distributed-tracing flag). Deprecated in v3.6 and will be decommissioned in v3.7. Use --distributed-tracing-address instead.")
	fs.StringVar(&cfg.DistributedTracingAddress, "distributed-tracing-address", cfg.DistributedTracingAddress, "Address for distributed tracing used for OpenTelemetry Tracing (if enabled with enable-distributed-tracing flag).")

	fs.StringVar(&cfg.ExperimentalDistributedTracingServiceName, "experimental-distributed-tracing-service-name", cfg.ExperimentalDistributedTracingServiceName, "Configures service name for distributed tracing to be used to define service name for OpenTelemetry Tracing (if enabled with experimental-enable-distributed-tracing flag). 'etcd' is the default service name. Use the same service name for all instances of etcd. Deprecated in v3.6 and will be decommissioned in v3.7. Use --distributed-tracing-service-name instead.")
	fs.StringVar(&cfg.DistributedTracingServiceName, "distributed-tracing-service-name", cfg.DistributedTracingServiceName, "Configures service name for distributed tracing to be used to define service name for OpenTelemetry Tracing (if enabled with enable-distributed-tracing flag). 'etcd' is the default service name. Use the same service name for all instances of etcd.")

	fs.StringVar(&cfg.ExperimentalDistributedTracingServiceInstanceID, "experimental-distributed-tracing-instance-id", "", "Configures service instance ID for distributed tracing to be used to define service instance ID key for OpenTelemetry Tracing (if enabled with experimental-enable-distributed-tracing flag). There is no default value set. This ID must be unique per etcd instance. Deprecated in v3.6 and will be decommissioned in v3.7. Use --distributed-tracing-instance-id instead.")
	fs.StringVar(&cfg.DistributedTracingServiceInstanceID, "distributed-tracing-instance-id", "", "Configures service instance ID for distributed tracing to be used to define service instance ID key for OpenTelemetry Tracing (if enabled with enable-distributed-tracing flag). There is no default value set. This ID must be unique per etcd instance.")

	fs.IntVar(&cfg.ExperimentalDistributedTracingSamplingRatePerMillion, "experimental-distributed-tracing-sampling-rate", 0, "Number of samples to collect per million spans for OpenTelemetry Tracing (if enabled with experimental-enable-distributed-tracing flag). Deprecated in v3.6 and will be decommissioned in v3.7. Use --distributed-tracing-sampling-rate instead.")
	fs.IntVar(&cfg.DistributedTracingSamplingRatePerMillion, "distributed-tracing-sampling-rate", 0, "Number of samples to collect per million spans for OpenTelemetry Tracing (if enabled with enable-distributed-tracing flag).")

	// auth
	fs.StringVar(&cfg.AuthToken, "auth-token", cfg.AuthToken, "Specify auth token specific options.")
	fs.UintVar(&cfg.BcryptCost, "bcrypt-cost", cfg.BcryptCost, "Specify bcrypt algorithm cost factor for auth password hashing.")
	fs.UintVar(&cfg.AuthTokenTTL, "auth-token-ttl", cfg.AuthTokenTTL, "The lifetime in seconds of the auth token.")

	// gateway
	fs.BoolVar(&cfg.EnableGRPCGateway, "enable-grpc-gateway", cfg.EnableGRPCGateway, "Enable GRPC gateway.")

	// experimental
	fs.BoolVar(&cfg.ExperimentalInitialCorruptCheck, "experimental-initial-corrupt-check", cfg.ExperimentalInitialCorruptCheck, "Enable to check data corruption before serving any client/peer traffic.")
	// TODO: delete in v3.7
	fs.DurationVar(&cfg.ExperimentalCorruptCheckTime, "experimental-corrupt-check-time", cfg.ExperimentalCorruptCheckTime, "Duration of time between cluster corruption check passes. Deprecated in v3.6 and will be decommissioned in v3.7. Use --corrupt-check-time instead")
	fs.DurationVar(&cfg.CorruptCheckTime, "corrupt-check-time", cfg.CorruptCheckTime, "Duration of time between cluster corruption check passes.")
	// TODO: delete in v3.7
	fs.BoolVar(&cfg.ExperimentalCompactHashCheckEnabled, "experimental-compact-hash-check-enabled", cfg.ExperimentalCompactHashCheckEnabled, "Enable leader to periodically check followers compaction hashes. Deprecated in v3.6 and will be decommissioned in v3.7. Use '--feature-gates=CompactHashCheck=true' instead")
	fs.DurationVar(&cfg.ExperimentalCompactHashCheckTime, "experimental-compact-hash-check-time", cfg.ExperimentalCompactHashCheckTime, "Duration of time between leader checks followers compaction hashes. Deprecated in v3.6 and will be decommissioned in v3.7. Use --compact-hash-check-time instead.")

	fs.DurationVar(&cfg.CompactHashCheckTime, "compact-hash-check-time", cfg.CompactHashCheckTime, "Duration of time between leader checks followers compaction hashes.")

	fs.BoolVar(&cfg.ExperimentalEnableLeaseCheckpoint, "experimental-enable-lease-checkpoint", false, "Enable leader to send regular checkpoints to other members to prevent reset of remaining TTL on leader change.")
	// TODO: delete in v3.7
	fs.BoolVar(&cfg.ExperimentalEnableLeaseCheckpointPersist, "experimental-enable-lease-checkpoint-persist", false, "Enable persisting remainingTTL to prevent indefinite auto-renewal of long lived leases. Always enabled in v3.6. Should be used to ensure smooth upgrade from v3.5 clusters with this feature enabled. Requires experimental-enable-lease-checkpoint to be enabled.")
	// TODO: delete in v3.7
	fs.IntVar(&cfg.ExperimentalCompactionBatchLimit, "experimental-compaction-batch-limit", cfg.ExperimentalCompactionBatchLimit, "Sets the maximum revisions deleted in each compaction batch. Deprecated in v3.6 and will be decommissioned in v3.7. Use --compaction-batch-limit instead.")
	fs.IntVar(&cfg.CompactionBatchLimit, "compaction-batch-limit", cfg.CompactionBatchLimit, "Sets the maximum revisions deleted in each compaction batch.")
	fs.DurationVar(&cfg.ExperimentalCompactionSleepInterval, "experimental-compaction-sleep-interval", cfg.ExperimentalCompactionSleepInterval, "Sets the sleep interval between each compaction batch. Deprecated in v3.6 and will be decommissioned in v3.7. Use --compaction-sleep-interval instead.")
	fs.DurationVar(&cfg.CompactionSleepInterval, "compaction-sleep-interval", cfg.CompactionSleepInterval, "Sets the sleep interval between each compaction batch.")
	// TODO: delete in v3.7
	fs.DurationVar(&cfg.ExperimentalWatchProgressNotifyInterval, "experimental-watch-progress-notify-interval", cfg.ExperimentalWatchProgressNotifyInterval, "Duration of periodic watch progress notifications. Deprecated in v3.6 and will be decommissioned in v3.7. Use --watch-progress-notify-interval instead.")
	fs.DurationVar(&cfg.WatchProgressNotifyInterval, "watch-progress-notify-interval", cfg.WatchProgressNotifyInterval, "Duration of periodic watch progress notifications.")
	fs.DurationVar(&cfg.DowngradeCheckTime, "downgrade-check-time", cfg.DowngradeCheckTime, "Duration of time between two downgrade status checks.")
	// TODO: delete in v3.7
	fs.DurationVar(&cfg.ExperimentalDowngradeCheckTime, "experimental-downgrade-check-time", cfg.ExperimentalDowngradeCheckTime, "Duration of time between two downgrade status checks. Deprecated in v3.6 and will be decommissioned in v3.7. Use --downgrade-check-time instead.")
	// TODO: delete in v3.7
	fs.DurationVar(&cfg.ExperimentalWarningApplyDuration, "experimental-warning-apply-duration", cfg.ExperimentalWarningApplyDuration, "Time duration after which a warning is generated if request takes more time. Deprecated in v3.6 and will be decommissioned in v3.7. Use --warning-watch-progress-duration instead.")
	fs.DurationVar(&cfg.WarningApplyDuration, "warning-apply-duration", cfg.WarningApplyDuration, "Time duration after which a warning is generated if watch progress takes more time.")
	fs.DurationVar(&cfg.WarningUnaryRequestDuration, "warning-unary-request-duration", cfg.WarningUnaryRequestDuration, "Time duration after which a warning is generated if a unary request takes more time.")
	fs.DurationVar(&cfg.ExperimentalWarningUnaryRequestDuration, "experimental-warning-unary-request-duration", cfg.ExperimentalWarningUnaryRequestDuration, "Time duration after which a warning is generated if a unary request takes more time. It's deprecated, and will be decommissioned in v3.7. Use --warning-unary-request-duration instead.")
	// TODO: delete in v3.7
	fs.BoolVar(&cfg.ExperimentalMemoryMlock, "experimental-memory-mlock", cfg.ExperimentalMemoryMlock, "Enable to enforce etcd pages (in particular bbolt) to stay in RAM.")
	fs.BoolVar(&cfg.MemoryMlock, "memory-mlock", cfg.MemoryMlock, "Enable to enforce etcd pages (in particular bbolt) to stay in RAM.")
	fs.BoolVar(&cfg.ExperimentalTxnModeWriteWithSharedBuffer, "experimental-txn-mode-write-with-shared-buffer", true, "Enable the write transaction to use a shared buffer in its readonly check operations.")
	fs.BoolVar(&cfg.ExperimentalStopGRPCServiceOnDefrag, "experimental-stop-grpc-service-on-defrag", cfg.ExperimentalStopGRPCServiceOnDefrag, "Enable etcd gRPC service to stop serving client requests on defragmentation.")
	// TODO: delete in v3.7
	fs.UintVar(&cfg.ExperimentalBootstrapDefragThresholdMegabytes, "experimental-bootstrap-defrag-threshold-megabytes", 0, "Enable the defrag during etcd server bootstrap on condition that it will free at least the provided threshold of disk space. Needs to be set to non-zero value to take effect. It's deprecated, and will be decommissioned in v3.7. Use --bootstrap-defrag-threshold-megabytes instead.")
	fs.UintVar(&cfg.BootstrapDefragThresholdMegabytes, "bootstrap-defrag-threshold-megabytes", 0, "Enable the defrag during etcd server bootstrap on condition that it will free at least the provided threshold of disk space. Needs to be set to non-zero value to take effect.")
	// TODO: delete in v3.7
	fs.IntVar(&cfg.ExperimentalMaxLearners, "experimental-max-learners", membership.DefaultMaxLearners, "Sets the maximum number of learners that can be available in the cluster membership. Deprecated in v3.6 and will be decommissioned in v3.7. Use --max-learners instead.")
	fs.IntVar(&cfg.MaxLearners, "max-learners", membership.DefaultMaxLearners, "Sets the maximum number of learners that can be available in the cluster membership.")
	fs.Uint64Var(&cfg.ExperimentalSnapshotCatchUpEntries, "experimental-snapshot-catchup-entries", cfg.ExperimentalSnapshotCatchUpEntries, "Number of entries for a slow follower to catch up after compacting the raft storage entries. Deprecated in v3.6 and will be decommissioned in v3.7. Use --snapshot-catchup-entries instead.")
	fs.Uint64Var(&cfg.SnapshotCatchUpEntries, "snapshot-catchup-entries", cfg.SnapshotCatchUpEntries, "Number of entries for a slow follower to catch up after compacting the raft storage entries.")

	// unsafe
	fs.BoolVar(&cfg.UnsafeNoFsync, "unsafe-no-fsync", false, "Disables fsync, unsafe, will cause data loss.")
	fs.BoolVar(&cfg.ForceNewCluster, "force-new-cluster", false, "Force to create a new one member cluster.")

	// featuregate
	cfg.ServerFeatureGate.(featuregate.MutableFeatureGate).AddFlag(fs, ServerFeatureGateFlagName)
}

func ConfigFromFile(path string) (*Config, error) {
	cfg := &configYAML{Config: *NewConfig()}
	if err := cfg.configFromFile(path); err != nil {
		return nil, err
	}
	return &cfg.Config, nil
}

func (cfg *configYAML) configFromFile(path string) error {
	b, err := os.ReadFile(path)
	if err != nil {
		return err
	}

	defaultInitialCluster := cfg.InitialCluster

	err = yaml.Unmarshal(b, cfg)
	if err != nil {
		return err
	}

	if cfg.configJSON.ServerFeatureGatesJSON != "" {
		err = cfg.Config.ServerFeatureGate.(featuregate.MutableFeatureGate).Set(cfg.configJSON.ServerFeatureGatesJSON)
		if err != nil {
			return err
		}
	}

	// parses the yaml bytes to raw map first, then getBoolFlagVal can get the top level bool flag value.
	var cfgMap map[string]any
	err = yaml.Unmarshal(b, &cfgMap)
	if err != nil {
		return err
	}

	for flg := range cfgMap {
		cfg.FlagsExplicitlySet[flg] = true
	}

	if peerTransportSecurity, ok := cfgMap["peer-transport-security"]; ok {
		peerTransportSecurityMap, isMap := peerTransportSecurity.(map[string]any)
		if !isMap {
			return fmt.Errorf("invalid peer-transport-security")
		}
		for k := range peerTransportSecurityMap {
			cfg.FlagsExplicitlySet[fmt.Sprintf("peer-%s", k)] = true
		}
	}

	// attempt to fix a bug introduced in https://github.com/etcd-io/etcd/pull/15033
	// both `experimental-snapshot-catch-up-entries` and `experimental-snapshot-catchup-entries` refer to the same field,
	// 	map the YAML field "experimental-snapshot-catch-up-entries" to the flag "experimental-snapshot-catchup-entries".
	if val, ok := cfgMap["experimental-snapshot-catch-up-entries"]; ok {
		cfgMap["experimental-snapshot-catchup-entries"] = val
		cfg.ExperimentalSnapshotCatchUpEntries = uint64(val.(float64))
		cfg.FlagsExplicitlySet["experimental-snapshot-catchup-entries"] = true
	}

	getBoolFlagVal := func(flagName string) *bool {
		flagVal, ok := cfgMap[flagName]
		if !ok {
			return nil
		}
		boolVal := flagVal.(bool)
		return &boolVal
	}
	err = SetFeatureGatesFromExperimentalFlags(cfg.ServerFeatureGate, getBoolFlagVal, cfg.configJSON.ServerFeatureGatesJSON)
	if err != nil {
		return err
	}

	if cfg.configJSON.ListenPeerURLs != "" {
		u, err := types.NewURLs(strings.Split(cfg.configJSON.ListenPeerURLs, ","))
		if err != nil {
			fmt.Fprintf(os.Stderr, "unexpected error setting up listen-peer-urls: %v\n", err)
			os.Exit(1)
		}
		cfg.Config.ListenPeerUrls = u
	}

	if cfg.configJSON.ListenClientURLs != "" {
		u, err := types.NewURLs(strings.Split(cfg.configJSON.ListenClientURLs, ","))
		if err != nil {
			fmt.Fprintf(os.Stderr, "unexpected error setting up listen-client-urls: %v\n", err)
			os.Exit(1)
		}
		cfg.Config.ListenClientUrls = u
	}

	if cfg.configJSON.ListenClientHTTPURLs != "" {
		u, err := types.NewURLs(strings.Split(cfg.configJSON.ListenClientHTTPURLs, ","))
		if err != nil {
			fmt.Fprintf(os.Stderr, "unexpected error setting up listen-client-http-urls: %v\n", err)
			os.Exit(1)
		}
		cfg.Config.ListenClientHttpUrls = u
	}

	if cfg.configJSON.AdvertisePeerURLs != "" {
		u, err := types.NewURLs(strings.Split(cfg.configJSON.AdvertisePeerURLs, ","))
		if err != nil {
			fmt.Fprintf(os.Stderr, "unexpected error setting up initial-advertise-peer-urls: %v\n", err)
			os.Exit(1)
		}
		cfg.Config.AdvertisePeerUrls = u
	}

	if cfg.configJSON.AdvertiseClientURLs != "" {
		u, err := types.NewURLs(strings.Split(cfg.configJSON.AdvertiseClientURLs, ","))
		if err != nil {
			fmt.Fprintf(os.Stderr, "unexpected error setting up advertise-peer-urls: %v\n", err)
			os.Exit(1)
		}
		cfg.Config.AdvertiseClientUrls = u
	}

	if cfg.ListenMetricsUrlsJSON != "" {
		u, err := types.NewURLs(strings.Split(cfg.ListenMetricsUrlsJSON, ","))
		if err != nil {
			fmt.Fprintf(os.Stderr, "unexpected error setting up listen-metrics-urls: %v\n", err)
			os.Exit(1)
		}
		cfg.ListenMetricsUrls = u
	}

	if cfg.CORSJSON != "" {
		uv := flags.NewUniqueURLsWithExceptions(cfg.CORSJSON, "*")
		cfg.CORS = uv.Values
	}

	if cfg.HostWhitelistJSON != "" {
		uv := flags.NewUniqueStringsValue(cfg.HostWhitelistJSON)
		cfg.HostWhitelist = uv.Values
	}

	// If a discovery or discovery-endpoints flag is set, clear default initial cluster set by InitialClusterFromName
	if (cfg.Durl != "" || cfg.DNSCluster != "" || len(cfg.DiscoveryCfg.Endpoints) > 0) && cfg.InitialCluster == defaultInitialCluster {
		cfg.InitialCluster = ""
	}
	if cfg.ClusterState == "" {
		cfg.ClusterState = ClusterStateFlagNew
	}

	copySecurityDetails := func(tls *transport.TLSInfo, ysc *securityConfig) {
		tls.CertFile = ysc.CertFile
		tls.KeyFile = ysc.KeyFile
		tls.ClientCertFile = ysc.ClientCertFile
		tls.ClientKeyFile = ysc.ClientKeyFile
		tls.ClientCertAuth = ysc.CertAuth
		tls.TrustedCAFile = ysc.TrustedCAFile
		tls.AllowedCNs = ysc.AllowedCNs
		tls.AllowedHostnames = ysc.AllowedHostnames
		tls.SkipClientSANVerify = ysc.SkipClientSANVerify
	}
	copySecurityDetails(&cfg.ClientTLSInfo, &cfg.ClientSecurityJSON)
	copySecurityDetails(&cfg.PeerTLSInfo, &cfg.PeerSecurityJSON)
	cfg.ClientAutoTLS = cfg.ClientSecurityJSON.AutoTLS
	cfg.PeerAutoTLS = cfg.PeerSecurityJSON.AutoTLS
	if cfg.SelfSignedCertValidity == 0 {
		cfg.SelfSignedCertValidity = 1
	}
	return cfg.Validate()
}

// SetFeatureGatesFromExperimentalFlags sets the feature gate values if the feature gate is not explicitly set
// while their corresponding experimental flags are explicitly set, for all the features in ExperimentalFlagToFeatureMap.
// TODO: remove after all experimental flags are deprecated.
func SetFeatureGatesFromExperimentalFlags(fg featuregate.FeatureGate, getExperimentalFlagVal func(string) *bool, featureGatesVal string) error {
	m := make(map[featuregate.Feature]bool)
	// verify that the feature gate and its experimental flag are not both set at the same time.
	for expFlagName, featureName := range features.ExperimentalFlagToFeatureMap {
		flagVal := getExperimentalFlagVal(expFlagName)
		if flagVal == nil {
			continue
		}
		if strings.Contains(featureGatesVal, string(featureName)) {
			return fmt.Errorf("cannot specify both flags: --%s=%v and --%s=%s=%v at the same time, please just use --%s=%s=%v",
				expFlagName, *flagVal, ServerFeatureGateFlagName, featureName, fg.Enabled(featureName), ServerFeatureGateFlagName, featureName, fg.Enabled(featureName))
		}
		m[featureName] = *flagVal
	}

	// filter out unknown features for fg, because we could use SetFeatureGatesFromExperimentalFlags both for
	// server and cluster level feature gates.
	allFeatures := fg.(featuregate.MutableFeatureGate).GetAll()
	mFiltered := make(map[string]bool)
	for k, v := range m {
		if _, ok := allFeatures[k]; ok {
			mFiltered[string(k)] = v
		}
	}
	return fg.(featuregate.MutableFeatureGate).SetFromMap(mFiltered)
}

func updateCipherSuites(tls *transport.TLSInfo, ss []string) error {
	if len(tls.CipherSuites) > 0 && len(ss) > 0 {
		return fmt.Errorf("TLSInfo.CipherSuites is already specified (given %v)", ss)
	}
	if len(ss) > 0 {
		cs, err := tlsutil.GetCipherSuites(ss)
		if err != nil {
			return err
		}
		tls.CipherSuites = cs
	}
	return nil
}

func updateMinMaxVersions(info *transport.TLSInfo, min, max string) {
	// Validate() has been called to check the user input, so it should never fail.
	var err error
	if info.MinVersion, err = tlsutil.GetTLSVersion(min); err != nil {
		panic(err)
	}
	if info.MaxVersion, err = tlsutil.GetTLSVersion(max); err != nil {
		panic(err)
	}
}

// Validate ensures that '*embed.Config' fields are properly configured.
func (cfg *Config) Validate() error {
	// make sure there is no conflict in the flag settings in the ExperimentalNonBoolFlagMigrationMap
	// TODO: delete in v3.7
	for oldFlag, newFlag := range experimentalFlagMigrationMap {
		if cfg.FlagsExplicitlySet[oldFlag] && cfg.FlagsExplicitlySet[newFlag] {
			return fmt.Errorf("cannot set --%s and --%s at the same time, please use --%s only", oldFlag, newFlag, newFlag)
		}
	}

	if err := cfg.setupLogging(); err != nil {
		return err
	}
	if err := checkBindURLs(cfg.ListenPeerUrls); err != nil {
		return err
	}
	if err := checkBindURLs(cfg.ListenClientUrls); err != nil {
		return err
	}
	if err := checkBindURLs(cfg.ListenClientHttpUrls); err != nil {
		return err
	}
	if len(cfg.ListenClientHttpUrls) == 0 {
		cfg.logger.Warn("Running http and grpc server on single port. This is not recommended for production.")
	}
	if err := checkBindURLs(cfg.ListenMetricsUrls); err != nil {
		return err
	}
	if err := checkHostURLs(cfg.AdvertisePeerUrls); err != nil {
		addrs := cfg.getAdvertisePeerURLs()
		return fmt.Errorf(`--initial-advertise-peer-urls %q must be "host:port" (%w)`, strings.Join(addrs, ","), err)
	}
	if err := checkHostURLs(cfg.AdvertiseClientUrls); err != nil {
		addrs := cfg.getAdvertiseClientURLs()
		return fmt.Errorf(`--advertise-client-urls %q must be "host:port" (%w)`, strings.Join(addrs, ","), err)
	}
	// Check if conflicting flags are passed.
	nSet := 0
	for _, v := range []bool{cfg.Durl != "", cfg.InitialCluster != "", cfg.DNSCluster != "", len(cfg.DiscoveryCfg.Endpoints) > 0} {
		if v {
			nSet++
		}
	}

	if cfg.ClusterState != ClusterStateFlagNew && cfg.ClusterState != ClusterStateFlagExisting {
		return fmt.Errorf("unexpected clusterState %q", cfg.ClusterState)
	}

	if nSet > 1 {
		return ErrConflictBootstrapFlags
	}

	// Check if both v2 discovery and v3 discovery flags are passed.
	v2discoveryFlagsExist := cfg.Dproxy != ""
	v3discoveryFlagsExist := len(cfg.DiscoveryCfg.Endpoints) > 0 ||
		cfg.DiscoveryCfg.Token != "" ||
		cfg.DiscoveryCfg.Secure.Cert != "" ||
		cfg.DiscoveryCfg.Secure.Key != "" ||
		cfg.DiscoveryCfg.Secure.Cacert != "" ||
		cfg.DiscoveryCfg.Auth.Username != "" ||
		cfg.DiscoveryCfg.Auth.Password != ""

	if v2discoveryFlagsExist && v3discoveryFlagsExist {
		return errors.New("both v2 discovery settings (discovery, discovery-proxy) " +
			"and v3 discovery settings (discovery-token, discovery-endpoints, discovery-cert, " +
			"discovery-key, discovery-cacert, discovery-user, discovery-password) are set")
	}

	// If one of `discovery-token` and `discovery-endpoints` is provided,
	// then the other one must be provided as well.
	if (cfg.DiscoveryCfg.Token != "") != (len(cfg.DiscoveryCfg.Endpoints) > 0) {
		return errors.New("both --discovery-token and --discovery-endpoints must be set")
	}

	if cfg.TickMs == 0 {
		return fmt.Errorf("--heartbeat-interval must be >0 (set to %dms)", cfg.TickMs)
	}
	if cfg.ElectionMs == 0 {
		return fmt.Errorf("--election-timeout must be >0 (set to %dms)", cfg.ElectionMs)
	}
	if 5*cfg.TickMs > cfg.ElectionMs {
		return fmt.Errorf("--election-timeout[%vms] should be at least as 5 times as --heartbeat-interval[%vms]", cfg.ElectionMs, cfg.TickMs)
	}
	if cfg.ElectionMs > maxElectionMs {
		return fmt.Errorf("--election-timeout[%vms] is too long, and should be set less than %vms", cfg.ElectionMs, maxElectionMs)
	}

	// check this last since proxying in etcdmain may make this OK
	if cfg.ListenClientUrls != nil && cfg.AdvertiseClientUrls == nil {
		return ErrUnsetAdvertiseClientURLsFlag
	}

	switch cfg.AutoCompactionMode {
	case CompactorModeRevision, CompactorModePeriodic:
	case "":
		return errors.New("undefined auto-compaction-mode")
	default:
		return fmt.Errorf("unknown auto-compaction-mode %q", cfg.AutoCompactionMode)
	}

	// Validate distributed tracing configuration but only if enabled.
	if cfg.EnableDistributedTracing {
		if err := validateTracingConfig(cfg.DistributedTracingSamplingRatePerMillion); err != nil {
			return fmt.Errorf("distributed tracing configurition is not valid: (%w)", err)
		}
	}

	if !cfg.ServerFeatureGate.Enabled(features.LeaseCheckpointPersist) && cfg.ServerFeatureGate.Enabled(features.LeaseCheckpoint) {
		cfg.logger.Warn("Detected that checkpointing is enabled without persistence. Consider enabling feature gate LeaseCheckpointPersist")
	}

	if cfg.ServerFeatureGate.Enabled(features.LeaseCheckpointPersist) && !cfg.ServerFeatureGate.Enabled(features.LeaseCheckpoint) {
		return fmt.Errorf("enabling feature gate LeaseCheckpointPersist requires enabling feature gate LeaseCheckpoint")
	}
	// TODO: delete in v3.7
	if cfg.ExperimentalCompactHashCheckTime <= 0 {
		return fmt.Errorf("--experimental-compact-hash-check-time must be >0 (set to %v)", cfg.ExperimentalCompactHashCheckTime)
	}
	if cfg.CompactHashCheckTime <= 0 {
		return fmt.Errorf("--compact-hash-check-time must be >0 (set to %v)", cfg.CompactHashCheckTime)
	}

	// If `--name` isn't configured, then multiple members may have the same "default" name.
	// When adding a new member with the "default" name as well, etcd may regards its peerURL
	// as one additional peerURL of the existing member which has the same "default" name,
	// because each member can have multiple client or peer URLs.
	// Please refer to https://github.com/etcd-io/etcd/issues/13757
	if cfg.Name == DefaultName {
		cfg.logger.Warn(
			"it isn't recommended to use default name, please set a value for --name. "+
				"Note that etcd might run into issue when multiple members have the same default name",
			zap.String("name", cfg.Name))
	}

	minVersion, err := tlsutil.GetTLSVersion(cfg.TlsMinVersion)
	if err != nil {
		return err
	}
	maxVersion, err := tlsutil.GetTLSVersion(cfg.TlsMaxVersion)
	if err != nil {
		return err
	}

	// maxVersion == 0 means that Go selects the highest available version.
	if maxVersion != 0 && minVersion > maxVersion {
		return fmt.Errorf("min version (%s) is greater than max version (%s)", cfg.TlsMinVersion, cfg.TlsMaxVersion)
	}

	// Check if user attempted to configure ciphers for TLS1.3 only: Go does not support that currently.
	if minVersion == tls.VersionTLS13 && len(cfg.CipherSuites) > 0 {
		return fmt.Errorf("cipher suites cannot be configured when only TLS1.3 is enabled")
	}

	return nil
}

// PeerURLsMapAndToken sets up an initial peer URLsMap and cluster token for bootstrap or discovery.
func (cfg *Config) PeerURLsMapAndToken(which string) (urlsmap types.URLsMap, token string, err error) {
	token = cfg.InitialClusterToken
	switch {
	case cfg.Durl != "":
		urlsmap = types.URLsMap{}
		// If using v2 discovery, generate a temporary cluster based on
		// self's advertised peer URLs
		urlsmap[cfg.Name] = cfg.AdvertisePeerUrls
		token = cfg.Durl

	case len(cfg.DiscoveryCfg.Endpoints) > 0:
		urlsmap = types.URLsMap{}
		// If using v3 discovery, generate a temporary cluster based on
		// self's advertised peer URLs
		urlsmap[cfg.Name] = cfg.AdvertisePeerUrls
		token = cfg.DiscoveryCfg.Token

	case cfg.DNSCluster != "":
		clusterStrs, cerr := cfg.GetDNSClusterNames()
		lg := cfg.logger
		if cerr != nil {
			lg.Warn("failed to resolve during SRV discovery", zap.Error(cerr))
		}
		if len(clusterStrs) == 0 {
			return nil, "", cerr
		}
		for _, s := range clusterStrs {
			lg.Info("got bootstrap from DNS for etcd-server", zap.String("node", s))
		}
		clusterStr := strings.Join(clusterStrs, ",")
		if strings.Contains(clusterStr, "https://") && cfg.PeerTLSInfo.TrustedCAFile == "" {
			cfg.PeerTLSInfo.ServerName = cfg.DNSCluster
		}
		urlsmap, err = types.NewURLsMap(clusterStr)
		// only etcd member must belong to the discovered cluster.
		// proxy does not need to belong to the discovered cluster.
		if which == "etcd" {
			if _, ok := urlsmap[cfg.Name]; !ok {
				return nil, "", fmt.Errorf("cannot find local etcd member %q in SRV records", cfg.Name)
			}
		}

	default:
		// We're statically configured, and cluster has appropriately been set.
		urlsmap, err = types.NewURLsMap(cfg.InitialCluster)
	}
	return urlsmap, token, err
}

// GetDNSClusterNames uses DNS SRV records to get a list of initial nodes for cluster bootstrapping.
// This function will return a list of one or more nodes, as well as any errors encountered while
// performing service discovery.
// Note: Because this checks multiple sets of SRV records, discovery should only be considered to have
// failed if the returned node list is empty.
func (cfg *Config) GetDNSClusterNames() ([]string, error) {
	var (
		clusterStrs       []string
		cerr              error
		serviceNameSuffix string
	)
	if cfg.DNSClusterServiceName != "" {
		serviceNameSuffix = "-" + cfg.DNSClusterServiceName
	}

	lg := cfg.GetLogger()

	// Use both etcd-server-ssl and etcd-server for discovery.
	// Combine the results if both are available.
	clusterStrs, cerr = getCluster("https", "etcd-server-ssl"+serviceNameSuffix, cfg.Name, cfg.DNSCluster, cfg.AdvertisePeerUrls)
	if cerr != nil {
		clusterStrs = make([]string, 0)
	}
	lg.Info(
		"get cluster for etcd-server-ssl SRV",
		zap.String("service-scheme", "https"),
		zap.String("service-name", "etcd-server-ssl"+serviceNameSuffix),
		zap.String("server-name", cfg.Name),
		zap.String("discovery-srv", cfg.DNSCluster),
		zap.Strings("advertise-peer-urls", cfg.getAdvertisePeerURLs()),
		zap.Strings("found-cluster", clusterStrs),
		zap.Error(cerr),
	)

	defaultHTTPClusterStrs, httpCerr := getCluster("http", "etcd-server"+serviceNameSuffix, cfg.Name, cfg.DNSCluster, cfg.AdvertisePeerUrls)
	if httpCerr == nil {
		clusterStrs = append(clusterStrs, defaultHTTPClusterStrs...)
	}
	lg.Info(
		"get cluster for etcd-server SRV",
		zap.String("service-scheme", "http"),
		zap.String("service-name", "etcd-server"+serviceNameSuffix),
		zap.String("server-name", cfg.Name),
		zap.String("discovery-srv", cfg.DNSCluster),
		zap.Strings("advertise-peer-urls", cfg.getAdvertisePeerURLs()),
		zap.Strings("found-cluster", clusterStrs),
		zap.Error(httpCerr),
	)

	return clusterStrs, errors.Join(cerr, httpCerr)
}

func (cfg *Config) InitialClusterFromName(name string) (ret string) {
	if len(cfg.AdvertisePeerUrls) == 0 {
		return ""
	}
	n := name
	if name == "" {
		n = DefaultName
	}
	for i := range cfg.AdvertisePeerUrls {
		ret = ret + "," + n + "=" + cfg.AdvertisePeerUrls[i].String()
	}
	return ret[1:]
}

// InferLocalAddr tries to determine the LocalAddr used when communicating with
// an etcd peer. If SetMemberLocalAddr is true, then it will try to get the host
// from AdvertisePeerUrls by searching for the first URL with a specified
// non-loopback address. Otherwise, it defaults to empty string and the
// LocalAddr used will be the default for the Golang HTTP client.
func (cfg *Config) InferLocalAddr() string {
	if !cfg.ServerFeatureGate.Enabled(features.SetMemberLocalAddr) {
		return ""
	}

	lg := cfg.GetLogger()
	lg.Info(
		"searching for a suitable member local address in AdvertisePeerURLs",
		zap.Strings("advertise-peer-urls", cfg.getAdvertisePeerURLs()),
	)
	for _, peerURL := range cfg.AdvertisePeerUrls {
		if addr, err := netip.ParseAddr(peerURL.Hostname()); err == nil {
			if addr.IsLoopback() || addr.IsUnspecified() {
				continue
			}
			lg.Info(
				"setting member local address",
				zap.String("LocalAddr", addr.String()),
			)
			return addr.String()
		}
	}
	lg.Warn(
		"unable to set a member local address due to lack of suitable local addresses",
		zap.Strings("advertise-peer-urls", cfg.getAdvertisePeerURLs()),
	)
	return ""
}

func (cfg *Config) IsNewCluster() bool { return cfg.ClusterState == ClusterStateFlagNew }
func (cfg *Config) ElectionTicks() int { return int(cfg.ElectionMs / cfg.TickMs) }

func (cfg *Config) V2DeprecationEffective() config.V2DeprecationEnum {
	if cfg.V2Deprecation == "" {
		return config.V2DeprDefault
	}
	return cfg.V2Deprecation
}

func (cfg *Config) defaultPeerHost() bool {
	return len(cfg.AdvertisePeerUrls) == 1 && cfg.AdvertisePeerUrls[0].String() == DefaultInitialAdvertisePeerURLs
}

func (cfg *Config) defaultClientHost() bool {
	return len(cfg.AdvertiseClientUrls) == 1 && cfg.AdvertiseClientUrls[0].String() == DefaultAdvertiseClientURLs
}

func (cfg *Config) ClientSelfCert() (err error) {
	if !cfg.ClientAutoTLS {
		return nil
	}
	if !cfg.ClientTLSInfo.Empty() {
		cfg.logger.Warn("ignoring client auto TLS since certs given")
		return nil
	}
	chosts := make([]string, 0, len(cfg.ListenClientUrls)+len(cfg.ListenClientHttpUrls))
	for _, u := range cfg.ListenClientUrls {
		chosts = append(chosts, u.Host)
	}
	for _, u := range cfg.ListenClientHttpUrls {
		chosts = append(chosts, u.Host)
	}
	cfg.ClientTLSInfo, err = transport.SelfCert(cfg.logger, filepath.Join(cfg.Dir, "fixtures", "client"), chosts, cfg.SelfSignedCertValidity)
	if err != nil {
		return err
	}
	return updateCipherSuites(&cfg.ClientTLSInfo, cfg.CipherSuites)
}

func (cfg *Config) PeerSelfCert() (err error) {
	if !cfg.PeerAutoTLS {
		return nil
	}
	if !cfg.PeerTLSInfo.Empty() {
		cfg.logger.Warn("ignoring peer auto TLS since certs given")
		return nil
	}
	phosts := make([]string, len(cfg.ListenPeerUrls))
	for i, u := range cfg.ListenPeerUrls {
		phosts[i] = u.Host
	}
	cfg.PeerTLSInfo, err = transport.SelfCert(cfg.logger, filepath.Join(cfg.Dir, "fixtures", "peer"), phosts, cfg.SelfSignedCertValidity)
	if err != nil {
		return err
	}
	return updateCipherSuites(&cfg.PeerTLSInfo, cfg.CipherSuites)
}

// UpdateDefaultClusterFromName updates cluster advertise URLs with, if available, default host,
// if advertise URLs are default values(localhost:2379,2380) AND if listen URL is 0.0.0.0.
// e.g. advertise peer URL localhost:2380 or listen peer URL 0.0.0.0:2380
// then the advertise peer host would be updated with machine's default host,
// while keeping the listen URL's port.
// User can work around this by explicitly setting URL with 127.0.0.1.
// It returns the default hostname, if used, and the error, if any, from getting the machine's default host.
// TODO: check whether fields are set instead of whether fields have default value
func (cfg *Config) UpdateDefaultClusterFromName(defaultInitialCluster string) (string, error) {
	if defaultHostname == "" || defaultHostStatus != nil {
		// update 'initial-cluster' when only the name is specified (e.g. 'etcd --name=abc')
		if cfg.Name != DefaultName && cfg.InitialCluster == defaultInitialCluster {
			cfg.InitialCluster = cfg.InitialClusterFromName(cfg.Name)
		}
		return "", defaultHostStatus
	}

	used := false
	pip, pport := cfg.ListenPeerUrls[0].Hostname(), cfg.ListenPeerUrls[0].Port()
	if cfg.defaultPeerHost() && pip == "0.0.0.0" {
		cfg.AdvertisePeerUrls[0] = url.URL{Scheme: cfg.AdvertisePeerUrls[0].Scheme, Host: fmt.Sprintf("%s:%s", defaultHostname, pport)}
		used = true
	}
	// update 'initial-cluster' when only the name is specified (e.g. 'etcd --name=abc')
	if cfg.Name != DefaultName && cfg.InitialCluster == defaultInitialCluster {
		cfg.InitialCluster = cfg.InitialClusterFromName(cfg.Name)
	}

	cip, cport := cfg.ListenClientUrls[0].Hostname(), cfg.ListenClientUrls[0].Port()
	if cfg.defaultClientHost() && cip == "0.0.0.0" {
		cfg.AdvertiseClientUrls[0] = url.URL{Scheme: cfg.AdvertiseClientUrls[0].Scheme, Host: fmt.Sprintf("%s:%s", defaultHostname, cport)}
		used = true
	}
	dhost := defaultHostname
	if !used {
		dhost = ""
	}
	return dhost, defaultHostStatus
}

// checkBindURLs returns an error if any URL uses a domain name.
func checkBindURLs(urls []url.URL) error {
	for _, url := range urls {
		if url.Scheme == "unix" || url.Scheme == "unixs" {
			continue
		}
		host, _, err := net.SplitHostPort(url.Host)
		if err != nil {
			return err
		}
		if host == "localhost" {
			// special case for local address
			// TODO: support /etc/hosts ?
			continue
		}
		if net.ParseIP(host) == nil {
			return fmt.Errorf("expected IP in URL for binding (%s)", url.String())
		}
	}
	return nil
}

func checkHostURLs(urls []url.URL) error {
	for _, url := range urls {
		host, _, err := net.SplitHostPort(url.Host)
		if err != nil {
			return err
		}
		if host == "" {
			return fmt.Errorf("unexpected empty host (%s)", url.String())
		}
	}
	return nil
}

func (cfg *Config) getAdvertisePeerURLs() (ss []string) {
	ss = make([]string, len(cfg.AdvertisePeerUrls))
	for i := range cfg.AdvertisePeerUrls {
		ss[i] = cfg.AdvertisePeerUrls[i].String()
	}
	return ss
}

func (cfg *Config) getListenPeerURLs() (ss []string) {
	ss = make([]string, len(cfg.ListenPeerUrls))
	for i := range cfg.ListenPeerUrls {
		ss[i] = cfg.ListenPeerUrls[i].String()
	}
	return ss
}

func (cfg *Config) getAdvertiseClientURLs() (ss []string) {
	ss = make([]string, len(cfg.AdvertiseClientUrls))
	for i := range cfg.AdvertiseClientUrls {
		ss[i] = cfg.AdvertiseClientUrls[i].String()
	}
	return ss
}

func (cfg *Config) getListenClientURLs() (ss []string) {
	ss = make([]string, len(cfg.ListenClientUrls))
	for i := range cfg.ListenClientUrls {
		ss[i] = cfg.ListenClientUrls[i].String()
	}
	return ss
}

func (cfg *Config) getMetricsURLs() (ss []string) {
	ss = make([]string, len(cfg.ListenMetricsUrls))
	for i := range cfg.ListenMetricsUrls {
		ss[i] = cfg.ListenMetricsUrls[i].String()
	}
	return ss
}

func parseBackendFreelistType(freelistType string) bolt.FreelistType {
	if freelistType == freelistArrayType {
		return bolt.FreelistArrayType
	}

	return bolt.FreelistMapType
}
