Changefeed stuck when overwriteTs resume a changefeeed with a forward checkpointTs if changefeed is enable syncpoint

[hongyunyan]

What did you do?

1. start a changefeed with syncpoint
2. pause the changefeed
3. resume the changefeed with a forward checkpointTs
4. check the changefeed's checkpointTs and resolvedTs

What did you expect to see?

the checkpointTs and resolvedTs can be forwarded normally

What did you see instead?

the changefeed is stuck

Versions of the cluster

Upstream TiDB cluster version (execute SELECT tidb_version(); in a MySQL client):

(paste TiDB cluster version here)

Upstream TiKV version (execute tikv-server --version):

(paste TiKV version here)

TiCDC version (execute cdc version):

v6.5, v7.1, v7.5

[asddongmen]

The root cause lies in the fact that the user enabled the syncpoint fuction. When resuming a changefeed, the initial syncpoint was set to the changefeed’s resolvedTs.

This could lead to issues when resuming a changefeed with a overwrite-checkpointTs larger than its old resolvedTs. (In this case, the overwrite-checkpointTs is 455573074482299058 and the old resolvedTs is 455573074482299057)

Because in the handlerBarrier() method, the globalBarrier is blocked by the syncpointTs, so the changefeed can never advances.