DM-worker can't boot up when it's assigned relay and can't connect downstream

[lance6716]

What did you do?

1. start-relay -s source1 worker1
2. start a task of source1
3. kill downstream
4. restart worker1

What did you expect to see?

worker1 is started and report friendly error

What did you see instead?

worker1 will exit after a short time

Versions of the cluster

DM version (run dmctl -V or dm-worker -V or dm-master -V):

5.3.0

Upstream MySQL/MariaDB server version:

(paste upstream MySQL/MariaDB server version here)

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

(paste TiDB cluster version here)

How did you deploy DM: tiup or manually?

(leave TiUP or manually here)

Other interesting information (system version, hardware config, etc):

>
>

current status of DM cluster (execute query-status <task-name> in dmctl)

(paste current status of DM cluster here)

[XuJianxu]

Need to Add
Versions of the cluster
DM version (run dmctl -V or dm-worker -V or dm-master -V):
5.3.0