vstreamer to throttle on source endpoint

[shlomi-noach]

Description

VReplication works by hooking to a source tablet, pulling data as a replica as well as scanning tables, then to be applied on a target tablet.

On source, VReplication (via vstreamer) can cause a high load by aggressively pulling data, such that:

• if source is a replica, it can start lagging
• if source is a primary, it becomes sluggish

With this PR, vstreamer throttles based on check-self, introduced in #7319 , which is a throttle endpoint that tests the health of a specific tablet, the source tablet in our scenario. Right now, as described in #7319, whether replica or primary, we test for replication lag, which is an actual indicator on primary, too.

Related Issue(s)

Tracking issue: #7362

This PR extends and depends on #7319

Checklist

• Should this PR be backported?
• Tests were added or are not required
• Documentation was added or is not required

Deployment Notes

Impacted Areas in Vitess

Components that this PR will affect:

• Query Serving
• VReplication
• Cluster Management
• Build
• VTAdmin

[shlomi-noach]

@rohit-nayak-ps please see my recent changes. On vstreamer.go, I only throttle on the events channel, so that I'm not blocking venets and ctx.Done() and timer.C.

Otherwise, added throttling in rowstreamer and resultstreamer.

[shlomi-noach]

Next up, I'l create an endtoend test

[shlomi-noach]

I've moved rowstreamer and resultstreamer throttling inside their main loops, where throttling is more granular. In my understanding, where we initially placed throttling (at beginning of Stream() function) was a one time check at the point of initially setting up the streaming.

[shlomi-noach]

Ready for review! Tests are now good.

Reminder that this PR extends #7319, so it's best to first merge #7319

[rohit-nayak-ps]

The new workflow yaml file for the e2e test should be created by updating the test/ci_workflow_gen.go codegen script and running it. Otherwise any updates to the cluster template file will not reflect in this yaml.

[rohit-nayak-ps]

looks great!
test script / e2e workflow yaml needs to be updated as per comment.

[shlomi-noach]

The new workflow yaml file for the e2e test should be created by updating the test/ci_workflow_gen.go codegen script

Oh, I completely missed this!

[shlomi-noach]

because this PR introduced a named endtoend shard (vreplication_basic), I took it to now normalize all shards to be strings, not numbers. So, for example, shard 22 is now shard "22".