pingcap / pingcap/ticdc

Changefeed stop replicating after TiCDC server scale in

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type/bug
Dominant language
Go
Stars
56
Forks
63
Avg merge
2d 20h
Merged PRs (30d)
34

Description

What did you do?
  1. Start up a cluster with 10+ TiCDC instances.
  2. Create changefeed, and wait for becoming normal.
  3. Scale in TiCDC to only 1 instance.
What did you expect to see?

The changefeeed is normal.

What did you see instead?

The changefeed stop replicating since about 10:52.

After scale out TiCDC back to 10+ instances at about 12:18, the changefeed become normal again.

Image Image

Metrics: link.
Logs: link

Versions of the cluster

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

v8.5.3 (CSE)

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

v26.3.11-nextgen

TiCDC version (execute cdc version):

v26.3.4-nextgen

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the issue by creating a changefeed with 10+ TiCDC instances, scaling in to one, and reviewing the linked Grafana metrics and TiCDC logs. Use the reported TiDB, TiKV, and TiCDC versions as context; done means the changefeed remains normal and continues replicating after scale-in without requiring scale-out.

Written by the indexing model from the issue text.

Assessment

Tech stack
go
Domain
distributed-systems
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Active
Clarity
Mostly clear
Newbie friendliness
48/100

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