Lightning sets empty string as service ID for UpdateServiceGCSafePoint API

[MyonKeminta]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do? If possible, provide a recipe for reproducing the error.

Submitted a PR in PD's repo which added non-empty check for service ID in UpdateServiceGCSafePoint API: tikv/pd#3146

2. What did you expect to see?

Everything works well

3. What did you see instead?

CI failed at lightning test because lightning sets empty string as the service ID when invoking UpdaetServiceGCSafePoint

[2020-11-09T07:30:13.887Z] tidb lightning encountered error:  restore table `alter_random`.`t` failed: rpc error: code = Unknown desc = service id of service safepoint cannot be empty.

And I read the code. It invokes the API here:

tidb-lightning/lightning/restore/checksum.go

Lines 386 to 387 in 25a3711

	_, err = m.pdClient.UpdateServiceGCSafePoint(ctx,
	m.serviceID, serviceSafePointTTL, ts)

and m.serviceID seems never set.

By the way, it also didn't check the return value of UpdateServiceGCSafePoint, which is useful for checking whether the actual GC safepoint has already exceeded the current set value. Please consider check it.

4. Versions of the cluster

   It occurs in CI and doesn't have detailed version info.

   • TiDB-Lightning version (run tidb-lightning -V):

     master
     

   • TiKV-Importer version (run tikv-importer -V)

     master
     

   • TiKV version (run tikv-server -V):

     master
     

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

     master
     

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

     The issue may also exist in 4.0 branch.

5. Operation logs

   • No need

6. Configuration of the cluster and the task

   • No need

7. Screenshot/exported-PDF of Grafana dashboard or metrics' graph in Prometheus for TiDB-Lightning if possible

   • No need