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ddl: Use etcd to elect the owner (pingcap#3158)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,176 @@ | ||
| // Copyright 2017 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 ddl | ||
|
|
||
| import ( | ||
| "sync/atomic" | ||
| "time" | ||
|
|
||
| "github.com/coreos/etcd/clientv3" | ||
| "github.com/coreos/etcd/clientv3/concurrency" | ||
| "github.com/coreos/etcd/mvcc/mvccpb" | ||
| "github.com/juju/errors" | ||
| "github.com/ngaut/log" | ||
| goctx "golang.org/x/net/context" | ||
| ) | ||
|
|
||
| // ChangeOwnerInNewWay is used for testing. | ||
| var ChangeOwnerInNewWay = false | ||
|
|
||
| const ( | ||
| ddlOwnerKey = "/tidb/ddl/owner" | ||
| bgOwnerKey = "/tidb/ddl/bg/owner" | ||
| newSessionDefaultRetryCnt = 3 | ||
| ) | ||
|
|
||
| // worker represents the structure which is used for electing owner. | ||
| type worker struct { | ||
| ddlOwner int32 | ||
| bgOwner int32 | ||
| ddlID string | ||
| etcdClient *clientv3.Client | ||
| etcdSession *concurrency.Session | ||
| } | ||
|
|
||
| func (w *worker) isOwner() bool { | ||
| return atomic.LoadInt32(&w.ddlOwner) == 1 | ||
| } | ||
|
|
||
| func (w *worker) setOwner(isOwner bool) { | ||
| if isOwner { | ||
| atomic.StoreInt32(&w.ddlOwner, 1) | ||
| } else { | ||
| atomic.StoreInt32(&w.ddlOwner, 0) | ||
| } | ||
| } | ||
|
|
||
| func (w *worker) isBgOwner() bool { | ||
| return atomic.LoadInt32(&w.bgOwner) == 1 | ||
| } | ||
|
|
||
| func (w *worker) setBgOwner(isOwner bool) { | ||
| if isOwner { | ||
| atomic.StoreInt32(&w.bgOwner, 1) | ||
| } else { | ||
| atomic.StoreInt32(&w.bgOwner, 0) | ||
| } | ||
| } | ||
|
|
||
| func (w *worker) newSession(ctx goctx.Context, retryCnt int) error { | ||
| var err error | ||
| for i := 0; i < retryCnt; i++ { | ||
| w.etcdSession, err = concurrency.NewSession(w.etcdClient, concurrency.WithContext(ctx)) | ||
| if err != nil { | ||
| log.Warnf("[ddl] failed to new session, err %v", err) | ||
| time.Sleep(200 * time.Millisecond) | ||
| continue | ||
| } | ||
| break | ||
| } | ||
| return errors.Trace(err) | ||
| } | ||
|
|
||
| func (d *ddl) campaignOwners(ctx goctx.Context) error { | ||
| err := d.worker.newSession(ctx, newSessionDefaultRetryCnt) | ||
| if err != nil { | ||
| return errors.Trace(err) | ||
| } | ||
|
|
||
| d.wait.Add(2) | ||
| ddlCtx, _ := goctx.WithCancel(ctx) | ||
| go d.campaignLoop(ddlCtx, ddlOwnerKey) | ||
|
|
||
| bgCtx, _ := goctx.WithCancel(ctx) | ||
| go d.campaignLoop(bgCtx, bgOwnerKey) | ||
| return nil | ||
| } | ||
|
|
||
| func (d *ddl) campaignLoop(ctx goctx.Context, key string) { | ||
| defer d.wait.Done() | ||
| worker := d.worker | ||
| for { | ||
| select { | ||
| case <-worker.etcdSession.Done(): | ||
| // TODO: Create session again? | ||
| log.Warnf("etcd session is done.") | ||
| case <-ctx.Done(): | ||
| return | ||
| default: | ||
| } | ||
|
|
||
| elec := concurrency.NewElection(worker.etcdSession, key) | ||
| err := elec.Campaign(ctx, worker.ddlID) | ||
| if err != nil { | ||
| log.Infof("[ddl] worker %s failed to campaign, err %v", worker.ddlID, err) | ||
| continue | ||
| } | ||
|
|
||
| // Get owner information. | ||
| resp, err := elec.Leader(ctx) | ||
| if err != nil { | ||
| // If no leader elected currently, it returns ErrElectionNoLeader. | ||
| log.Infof("[ddl] failed to get leader, err %v", err) | ||
| continue | ||
| } | ||
| leader := string(resp.Kvs[0].Value) | ||
| log.Info("[ddl] %s worker is %s, owner is %v", key, worker.ddlID, leader) | ||
| if leader == worker.ddlID { | ||
| worker.setOwnerVal(key, true) | ||
| } else { | ||
| log.Warnf("[ddl] worker %s isn't the owner", worker.ddlID) | ||
| continue | ||
| } | ||
|
|
||
| // TODO: Use content instead of quitCh. | ||
| worker.watchOwner(ctx, string(resp.Kvs[0].Key)) | ||
| worker.setOwnerVal(key, false) | ||
| d.hookMu.Lock() | ||
| d.hook.OnWatched(ctx) | ||
| d.hookMu.Unlock() | ||
| } | ||
| } | ||
|
|
||
| func (w *worker) setOwnerVal(key string, val bool) { | ||
| if key == ddlOwnerKey { | ||
| w.setOwner(val) | ||
| } else { | ||
| w.setBgOwner(val) | ||
| } | ||
| } | ||
|
|
||
| func (w *worker) watchOwner(ctx goctx.Context, key string) { | ||
| log.Debugf("[ddl] worker %s watch owner key %v", w.ddlID, key) | ||
| watchCh := w.etcdClient.Watch(ctx, key) | ||
| for { | ||
| select { | ||
| case resp := <-watchCh: | ||
| if resp.Canceled { | ||
| log.Infof("[ddl] worker %s watch owner key %v failed, no owner", | ||
| w.ddlID, key) | ||
| return | ||
| } | ||
|
|
||
| for _, ev := range resp.Events { | ||
| if ev.Type == mvccpb.DELETE { | ||
| log.Infof("[ddl] worker %s watch owner key %v failed, owner is deleted", w.ddlID, key) | ||
| return | ||
| } | ||
| } | ||
| case <-w.etcdSession.Done(): | ||
| return | ||
| case <-ctx.Done(): | ||
| return | ||
| } | ||
| } | ||
| } |
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