Nop ALTER SEQUENCE crashed Binlog Drainer due to SchemaVersion=0

[kennytm]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. Setup a TiDB → Binlog → (Anything) cluster

2. On TiDB, execute the following SQL:

   CREATE SEQUENCE test.seq START WITH 200001;
   ALTER SEQUENCE test.seq START WITH 200001;

2. What did you expect to see? (Required)

The DDLs being successfully synchronized to drainer.

3. What did you see instead (Required)

Drainer crashed and cannot be restarted

[2022/07/18 12:36:45.700 +08:00] [ERROR] [main.go:69] ["start drainer server failed"] [error="version: 0 not found"] [errorVerbose="version: 0 not found\ngithub.com/pingcap/errors.NotFoundf\n\t/go/pkg/mod/github.com/pingcap/errors@v0.11.5-0.20211224045212-9687c2b0f87c/juju_adaptor.go:117\ngithub.com/pingcap/tidb-binlog/drainer.(*Schema).getSchemaTableAndDelete\n\t/home/jenkins/agent/workspace/build-common/go/src/github.com/pingcap/tidb-binlog/drainer/schema.go:566\ngithub.com/pingcap/tidb-binlog/drainer.(*Syncer).run\n\t/home/jenkins/agent/workspace/build-common/go/src/github.com/pingcap/tidb-binlog/drainer/syncer.go:468\ngithub.com/pingcap/tidb-binlog/drainer.(*Syncer).Start\n\t/home/jenkins/agent/workspace/build-common/go/src/github.com/pingcap/tidb-binlog/drainer/syncer.go:151\ngithub.com/pingcap/tidb-binlog/drainer.(*Server).Start.func4\n\t/home/jenkins/agent/workspace/build-common/go/src/github.com/pingcap/tidb-binlog/drainer/server.go:291\ngithub.com/pingcap/tidb-binlog/drainer.(*taskGroup).start.func1\n\t/home/jenkins/agent/workspace/build-common/go/src/github.com/pingcap/tidb-binlog/drainer/util.go:79\nruntime.goexit\n\t/usr/local/go/src/runtime/asm_amd64.s:1571"] 

4. What is your TiDB version? (Required)

v5.4.0

[kennytm]

The root cause is this,

1. When ALTER SEQUENCE is no-op, the shouldUpdateVer variable in onAlterSequence() is set to false:

   tidb/ddl/sequence.go

   Line 262 in 4cade24

   shouldUpdateVer := !reflect.DeepEqual(*tblInfo.Sequence, copySequenceInfo) || restart

2. This leads to updateVersionAndTableInfo simply return ver=0

   tidb/ddl/table.go

   Lines 1337 to 1347 in 4cade24

   	if shouldUpdateVer {
   	ver, err = updateSchemaVersion(d, t, job)
   	if err != nil {
   	return 0, errors.Trace(err)
   	}
   	}
   	if tblInfo.State == model.StatePublic {
   	tblInfo.UpdateTS = t.StartTS
   	}
   	return ver, t.UpdateTable(job.SchemaID, tblInfo)

   
   

   tidb/ddl/sequence.go

   Lines 278 to 284 in 4cade24

   	// Store the sequence info into kv.
   	ver, err = updateVersionAndTableInfo(d, t, job, tblInfo, shouldUpdateVer)
   	if err != nil {
   	return ver, errors.Trace(err)
   	}
   	// Finish this job.
   	job.FinishTableJob(model.JobStateDone, model.StatePublic, ver, tblInfo)

3. Such ver=0 is used in (*Job).FinishTableJob() and eventually used to set its BinlogInfo.SchemaVersion

   tidb/parser/model/ddl.go

   Lines 410 to 414 in 4cade24

   	func (job *Job) FinishTableJob(jobState JobState, schemaState SchemaState, ver int64, tblInfo *TableInfo) {
   	job.State = jobState
   	job.SchemaState = schemaState
   	job.BinlogInfo.AddTableInfo(ver, tblInfo)
   	}

   
   

   tidb/parser/model/ddl.go

   Lines 195 to 198 in 4cade24

   	func (h *HistoryInfo) AddTableInfo(schemaVer int64, tblInfo *TableInfo) {
   	h.SchemaVersion = schemaVer
   	h.TableInfo = tblInfo
   	}

4. This value is propagated undisturbed to drainer (https://github.com/pingcap/tidb-binlog/blob/fa2543d767a29c98ad8f088e8878b294dab49a6a/drainer/syncer.go#L468), which caused the above NotFound error (https://github.com/pingcap/tidb-binlog/blob/fa2543d767a29c98ad8f088e8878b294dab49a6a/drainer/schema.go#L563-L566).

The DP devs felt that such SchemaVersion=0 binlogs breaks the monotonicity of the field, and thus the issue is filed here.

cc @lichunzhu @arenatlx

(internal reference: TICKET-353)

[niubell]

/remove-label affects-6.2