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* server: use leader lease to determine tso service validity#1676 Signed-off-by: nolouch <nolouch@gmail.com>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,140 @@ | ||
| // Copyright 2019 PingCAP, Inc. | ||
| // | ||
| // 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, | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
|
|
||
| package server | ||
|
|
||
| import ( | ||
| "context" | ||
| "sync/atomic" | ||
| "time" | ||
|
|
||
| "github.com/pingcap/log" | ||
| "github.com/pkg/errors" | ||
| "go.etcd.io/etcd/clientv3" | ||
| "go.uber.org/zap" | ||
| ) | ||
|
|
||
| // LeaderLease is used for renewing leadership of PD server. | ||
| type LeaderLease struct { | ||
| client *clientv3.Client | ||
| lease clientv3.Lease | ||
| ID clientv3.LeaseID | ||
| leaseTimeout time.Duration | ||
|
|
||
| expireTime atomic.Value | ||
| } | ||
|
|
||
| // NewLeaderLease creates a lease. | ||
| func NewLeaderLease(client *clientv3.Client) *LeaderLease { | ||
| return &LeaderLease{ | ||
| client: client, | ||
| lease: clientv3.NewLease(client), | ||
| } | ||
| } | ||
|
|
||
| // Grant uses `lease.Grant` to initialize the lease and expireTime. | ||
| func (l *LeaderLease) Grant(leaseTimeout int64) error { | ||
| start := time.Now() | ||
| ctx, cancel := context.WithTimeout(l.client.Ctx(), requestTimeout) | ||
| leaseResp, err := l.lease.Grant(ctx, leaseTimeout) | ||
| cancel() | ||
| if err != nil { | ||
| return errors.WithStack(err) | ||
| } | ||
| if cost := time.Since(start); cost > slowRequestTime { | ||
| log.Warn("lease grants too slow", zap.Duration("cost", cost)) | ||
| } | ||
| l.ID = leaseResp.ID | ||
| l.leaseTimeout = time.Duration(leaseTimeout) * time.Second | ||
| l.expireTime.Store(start.Add(time.Duration(leaseResp.TTL) * time.Second)) | ||
| return nil | ||
| } | ||
|
|
||
| const revokeLeaseTimeout = time.Second | ||
|
|
||
| // Close releases the lease. | ||
| func (l *LeaderLease) Close() error { | ||
| // Reset expire time. | ||
| l.expireTime.Store(time.Time{}) | ||
| // Try to revoke lease to make subsequent elections faster. | ||
| ctx, cancel := context.WithTimeout(l.client.Ctx(), revokeLeaseTimeout) | ||
| defer cancel() | ||
| l.lease.Revoke(ctx, l.ID) | ||
| return l.lease.Close() | ||
| } | ||
|
|
||
| // IsExpired checks if the lease is expired. If it returns true, current PD | ||
| // server should step down and try to re-elect again. | ||
| func (l *LeaderLease) IsExpired() bool { | ||
| return time.Now().After(l.expireTime.Load().(time.Time)) | ||
| } | ||
|
|
||
| // KeepAlive auto renews the lease and update expireTime. | ||
| func (l *LeaderLease) KeepAlive(ctx context.Context) { | ||
| ctx, cancel := context.WithCancel(ctx) | ||
| defer cancel() | ||
| timeCh := l.keepAliveWorker(ctx, l.leaseTimeout/3) | ||
|
|
||
| var maxExpire time.Time | ||
| for { | ||
| select { | ||
| case t := <-timeCh: | ||
| if t.After(maxExpire) { | ||
| maxExpire = t | ||
| l.expireTime.Store(t) | ||
| } | ||
| case <-time.After(l.leaseTimeout): | ||
| return | ||
| case <-ctx.Done(): | ||
| return | ||
| } | ||
| } | ||
| } | ||
|
|
||
| // Periodically call `lease.KeepAliveOnce` and post back latest received expire time into the channel. | ||
| func (l *LeaderLease) keepAliveWorker(ctx context.Context, interval time.Duration) <-chan time.Time { | ||
| ch := make(chan time.Time) | ||
|
|
||
| go func() { | ||
| ticker := time.NewTicker(interval) | ||
| defer ticker.Stop() | ||
|
|
||
| for { | ||
| go func() { | ||
| start := time.Now() | ||
| ctx1, cancel := context.WithTimeout(ctx, time.Duration(l.leaseTimeout)) | ||
| defer cancel() | ||
| res, err := l.lease.KeepAliveOnce(ctx1, l.ID) | ||
| if err != nil { | ||
| log.Warn("leader lease keep alive failed", zap.Error(err)) | ||
| return | ||
| } | ||
| if res.TTL > 0 { | ||
| expire := start.Add(time.Duration(res.TTL) * time.Second) | ||
| select { | ||
| case ch <- expire: | ||
| case <-ctx1.Done(): | ||
| } | ||
| } | ||
| }() | ||
|
|
||
| select { | ||
| case <-ctx.Done(): | ||
| return | ||
| case <-ticker.C: | ||
| } | ||
| } | ||
| }() | ||
|
|
||
| return ch | ||
| } |
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