dmctl 8.5.1 can not config export from 7.5.1 cluster

[bolt-leandro]

What did you do?

We upgraded tiup dmctl from v.7.5.4 to v.8.5.1.

• dmctl:v7.5.4 can config export from DM cluster running on 7.5.1 without problems
• dmctl:v8.5.1 gives an error on config export from DM cluster running on 7.5.1

shell> tiup dm display dm-cluster
Starting component dm: /root/.tiup/components/dm/v1.16.1/tiup-dm display dm-cluster
Cluster type:       dm
Cluster name:       dm-cluster
Cluster version:    v7.5.1

shell> tiup dmctl:v7.5.4 --master-addr dm-cluster-dm_master-1.domain:8261 config export
Starting component dmctl: /root/.tiup/components/dmctl/v7.5.4/dmctl/dmctl --master-addr dm-cluster-dm_master-1.domain:8261 config export
export configs to directory `configs` succeed

shell> tiup dmctl:v8.5.1 --master-addr dm-cluster-dm_master-1.domain:8261 config export
Starting component dmctl: /root/.tiup/components/dmctl/v8.5.1/dmctl/dmctl --master-addr dm-cluster-dm_master-1.domain:8261 config export
Error: rpc error: code = Unimplemented desc = unknown method ListSourceConfigs for service pb.Master

What did you expect to see?

A successful backup of configs created:
export configs to directory `configs` succeed

• dmctl 8.5.1 should be backwards compatible with previous 7.5.x major version

What did you see instead?

An error and no task and source backup files were created.
Error: rpc error: code = Unimplemented desc = unknown method ListSourceConfigs for service pb.Master

Versions of the cluster

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

Starting component dmctl: /root/.tiup/components/dmctl/v8.5.1/dmctl/dmctl -V
Release Version: v8.5.1
Git Commit Hash: 0a10d1fae9245c480e31df30f8b13ca4810c3b04
Git Branch: HEAD
UTC Build Time: 2025-01-10 06:50:25
Go Version: go1.23.4
Failpoint Build: false

How did you deploy DM: tiup or manually?

TiUP

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

(paste current status of DM cluster here)

[dveeden]

I think this should either work, or there should be a version check when connecting to DM master. And maybe a version matrix in the docs?