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etcd_dlock.go
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/
etcd_dlock.go
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package dlock
// References:
// https://etcd.io/docs/v3.5/dev-guide/api_reference_v3/
// https://github.com/etcd-io/etcd
import (
"context"
"sync/atomic"
"time"
clientv3 "go.etcd.io/etcd/client/v3"
concv3 "go.etcd.io/etcd/client/v3/concurrency"
"go.uber.org/multierr"
"github.com/benz9527/xboot/lib/infra"
)
var _ DLocker = (*etcdDLock)(nil)
type etcdDLock struct {
*etcdDLockOptions
session *concv3.Session
mutexes []*concv3.Mutex
startTime time.Time
}
func (dl *etcdDLock) Lock() error {
if len(dl.mutexes) < 1 {
return infra.NewErrorStack("etcd dlock is not initialized")
}
var (
merr error
fallbackUnlockIndex int
retry = dl.strategy
ticker *time.Ticker
)
// TODO pay attention to the context has been cancelled.
for {
for i, mu := range dl.mutexes {
if err := /* reentrant */ mu.TryLock(*dl.ctx.Load()); err != nil {
merr = multierr.Append(merr, err)
fallbackUnlockIndex = i
break
}
}
if merr == nil {
return noErr
} else {
for i := fallbackUnlockIndex - 1; i >= 0; i-- {
if err := dl.mutexes[i].Unlock(*dl.ctx.Load()); err != nil {
return err
}
}
}
// Retry.
backoff := retry.Next()
if backoff.Milliseconds() < 1 {
if ticker != nil {
return infra.WrapErrorStackWithMessage(multierr.Combine(merr, ErrDLockAcquireFailed), "etcd dlock lock retry reach to max")
}
// No retry strategy.
return noErr
}
if ticker == nil {
ticker = time.NewTicker(backoff)
defer ticker.Stop() // Avoid ticker leak.
} else {
ticker.Reset(backoff)
}
select {
case <-(*dl.ctx.Load()).Done():
return infra.WrapErrorStack((*dl.ctx.Load()).Err())
case <-ticker.C:
// continue
}
}
}
func (dl *etcdDLock) Renewal(newTTL time.Duration) error {
return infra.NewErrorStack("etcd dlock not support to refresh ttl")
}
func (dl *etcdDLock) TTL() (time.Duration, error) {
if dl.startTime.IsZero() {
return 0, infra.NewErrorStack("etcd dlock is not initialized or has been closed")
}
diff := time.Now().Sub(dl.startTime)
return dl.ttl - diff, nil
}
func (dl *etcdDLock) Unlock() error {
if len(dl.mutexes) < 1 {
return infra.NewErrorStack("etcd dlock is not initialized")
}
var merr error
// TODO pay attention to the context has been cancelled.
for _, mu := range dl.mutexes {
if err := mu.Unlock(*dl.ctx.Load()); err != nil {
merr = multierr.Append(merr, err)
}
}
if merr == nil && dl.session != nil {
merr = multierr.Append(merr, dl.session.Close())
if cancelPtr := dl.ctxCancel.Load(); cancelPtr != nil {
(*cancelPtr)()
}
dl.startTime = time.Time{} // Zero time
}
return merr
}
type etcdDLockOptions struct {
client *clientv3.Client
ctx atomic.Pointer[context.Context]
ctxCancel atomic.Pointer[context.CancelFunc]
strategy RetryStrategy
keys []string
ttl time.Duration
}
func EtcdDLockBuilder(ctx context.Context, client *clientv3.Client) *etcdDLockOptions {
if ctx == nil {
ctx = context.Background()
}
opts := &etcdDLockOptions{client: client}
opts.ctx.Store(&ctx)
return opts
}
func (opt *etcdDLockOptions) TTL(ttl time.Duration) *etcdDLockOptions {
opt.ttl = ttl
return opt
}
func (opt *etcdDLockOptions) Keys(keys ...string) *etcdDLockOptions {
opt.keys = make([]string, len(keys))
for i, key := range keys {
opt.keys[i] = key
}
return opt
}
func (opt *etcdDLockOptions) Retry(strategy RetryStrategy) *etcdDLockOptions {
opt.strategy = strategy
return opt
}
func (opt *etcdDLockOptions) Build() (DLocker, error) {
if opt.client == nil {
return nil, infra.NewErrorStack("etcd dlock client is nil")
}
if opt.ttl.Seconds() < 1 {
return nil, infra.NewErrorStack("etcd dlock with zero second TTL")
}
if len(opt.keys) <= 0 {
return nil, infra.NewErrorStack("etcd dlock with zero keys")
}
if opt.strategy == nil {
opt.strategy = NoRetry()
}
var (
ctx context.Context
cancel context.CancelFunc
)
ctx, cancel = context.WithTimeout(*opt.ctx.Load(), opt.ttl)
if ctx == nil || cancel == nil {
return nil, infra.NewErrorStack("etcd dlock build with nil context or nil context cancel function")
}
startTime := time.Now()
opt.ctx.Store(&ctx)
opt.ctxCancel.Store(&cancel)
session, err := concv3.NewSession(opt.client,
concv3.WithTTL(int(opt.ttl.Seconds())),
concv3.WithLease(clientv3.NoLease), // Grant new lease ID by new session.
)
if err != nil {
return nil, infra.WrapErrorStack(err)
}
var mutexes = make([]*concv3.Mutex, 0, len(opt.keys))
for _, prefix := range opt.keys {
mutexes = append(mutexes, concv3.NewMutex(session, prefix))
}
return &etcdDLock{
etcdDLockOptions: opt,
session: session,
startTime: startTime,
mutexes: mutexes,
}, nil
}
type EtcdDLockOption func(opt *etcdDLockOptions)
func WithEtcdDLockTTL(ttl time.Duration) EtcdDLockOption {
return func(opt *etcdDLockOptions) {
opt.TTL(ttl)
}
}
func WithEtcdDLockKeys(keys ...string) EtcdDLockOption {
return func(opt *etcdDLockOptions) {
opt.Keys(keys...)
}
}
func WithEtcdDLockRetry(strategy RetryStrategy) EtcdDLockOption {
return func(opt *etcdDLockOptions) {
opt.Retry(strategy)
}
}
func EtcdDLock(ctx context.Context, client *clientv3.Client, opts ...EtcdDLockOption) (DLocker, error) {
builderOpts := EtcdDLockBuilder(ctx, client)
for _, o := range opts {
o(builderOpts)
}
return builderOpts.Build()
}