message center may block on shutdown when downstream receive channel is full

What did you do?

In message center, the remote receive loop forwards decoded messages into the downstream receive channel. https://github.com/pingcap/ticdc/blob/8a067c41df29c525ec3dc3cadf4b38546c3190b8/pkg/messaging/remote_target.go#L658

Today this forwarding path can block indefinitely if:

• the downstream receive channel is full, and
• the stream is being closed during shutdown or reconnect

In that case, the receive goroutine may not exit promptly, which can lead to:

• stuck shutdown
• delayed reconnect cleanup
• goroutine leak risk

What did you expect to see?

No response

What did you see instead?

None

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):

(paste TiCDC version here)

Start at pkg/messaging/remote_target.go around line 658 and trace the remote receive loop's forwarding path, including the shutdown and reconnect signals. Reproduce or inspect the case where the downstream receive channel is full while the stream closes. Done means the receive goroutine exits promptly without leaving shutdown or reconnect cleanup blocked.