lightning: v8.2 lightning failed to import data to v8.1 version tidb cluster

[AkiraXie]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. setup v8.1 tidb cluster
2. use v8.2 lightning import data and use check-requirement = true

2. What did you expect to see? (Required)

success

3. What did you see instead (Required)

failed

4. What is your TiDB version? (Required)

v8.2

[AkiraXie]

/severity major

[D3Hunter]

the cause is PD and pd-client 8.2 introduced a new API which doesn't exists in 8.1, and lightning reports unknown method BatchScanRegions for service pdpb.PD during split-scatter, see https://github.com/pingcap/tidb/pull/54153

lightning doesn't support import into clusters of lower version officially, but it DOES can do it in theory before 8.2

[AkiraXie]

after #54365 merged, the issue cannot reproduce