Examples, Flakes: Wait for Shard's VReplication Engine to Open

[mattlord]

Description

The local examples CI workflow is still flaky — failing ~ 35% of the time — and it always fails here (or in the same way in later VReplication steps):

+ for shard in "customer/0"
+ true
+ command mysql --no-defaults -h 127.0.0.1 -P 15306 customer/0 -e 'show tables'
+ break
+ ./202_move_tables.sh
E0306 18:54:21.968491   13432 main.go:96] E0306 18:54:21.967743 traffic_switcher.go:208] buildTrafficSwitcher failed: rpc error: code = Unknown desc = TabletManager.VReplicationExec on zone1-0000000200 error: vreplication engine is closed: vreplication engine is closed
E0306 18:54:21.969504   13432 main.go:105] remote error: rpc error: code = Unknown desc = TabletManager.VReplicationExec on zone1-0000000200 error: vreplication engine is closed: vreplication engine is closed
MoveTables Error: rpc error: code = Unknown desc = TabletManager.VReplicationExec on zone1-0000000200 error: vreplication engine is closed: vreplication engine is closed

You can see an example here (see any of the previous 4 failed runs): https://github.com/vitessio/vitess/actions/runs/4346133011

The CI test specifically waits for the shard to be able to successfully serve a query through the vtgate, but for some reason that doesn't always work as expected in the CI; I have not been able to repeat it locally — so perhaps a bash version difference or some other missing context variable OR perhaps the vtgate is able to serve queries but the VReplication engine takes much longer to open (GitHub runners being very slow at times is a common factor in our tests). Given that users can also run into this when running the steps as a sequence: ./101...; ./201...; ./202...; ./203... I added a VReplication engine check to the wait_for_healthy_shard library function.

With the changes in this PR, the workflow ran successfully 10 times in a row in the CI with each workflow run containing 3 subtests: 1 each for consul, etcd, and k8s topos, so the base test really passed 30 times in a row: https://github.com/vitessio/vitess/actions/runs/4347322200

Related Issue(s)

Checklist

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[frouioui]

listall here exits with 1 or another value than 0 if the list is not valid?

[mattlord]

I'm not sure what you mean by "the list is not valid", but:

$ vtctlclient Workflow -- commerce listall; echo $?
Workflow Error: rpc error: code = Unknown desc = no primary found for shard commerce/0
1

$ vtctlclient Workflow -- commerce listall; echo $?
Workflow Error: rpc error: code = Unknown desc = TabletManager.VReplicationExec on zone1-0000000100 error: vreplication engine is closed: vreplication engine is closed
1

$ vtctlclient Workflow -- foobar listall; echo $?
Workflow Error: rpc error: code = Unknown desc = node doesn't exist: /vitess/global/keyspaces/foobar/shards/
1

$ vtctlclient Workflow -- commerce listall; echo $?
No workflows found in keyspace commerce
0

[rohit-nayak-ps]

lgtm