Increase sync watchers period to 1 second

[serathius]

Ref #16839

Picked based on

object size	streams	sync duration[s]	response throughput[MB/s]	etcd memory [GB]	50%ile latency[s]	90%ile latency[s]	99%ile latency[s]	99.9%ile latency[s]
1MB	20	0.1	1579	14.9	3.47	6.32	8.22	9.4
30KB	1000	0.1	2006	5.5	4.26	12.74	18.81	22.69
3KB	10000	0.1	2061	1.8	4.78	12.82	19.33	23.68
1MB	20	1	1634	9	3.45	5.63	7.98	9.34
30KB	1000	1	2257	1.4	4.07	11.76	17.8	21.87
3KB	10000	1	2154	1.1	4.29	11.74	18.01	22.36

[ahrtr]

Propose to add a config item, which defaults to 1s in main branch, and defaults to 100ms in the stable releases to keep the existing behaviour by default.

#16839 (comment)

[ahrtr]

Propose to add a config item

This is a simple change. If there is no any objection, we can delegate the change to other contributor to share your load.

[serathius]

Right, with K8s mitigation to stop sending watch to etcd, I don't think it's critical for now. Leaving it for someone to pick up.

[k8s-ci-robot]

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[serathius]

Updated the PR to provide context about how the variable was picked. I don't think there is a reason to expose is as configuration option, as benchmark results showed clear improvements.

ping @ahrtr for review

[k8s-ci-robot]

@serathius: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-etcd-integration-2-cpu-arm64	5f029e0	link	true	/test pull-etcd-integration-2-cpu-arm64
pull-etcd-integration-4-cpu-arm64	5f029e0	link	true	/test pull-etcd-integration-4-cpu-arm64
pull-etcd-integration-1-cpu-arm64	5f029e0	link	true	/test pull-etcd-integration-1-cpu-arm64
pull-etcd-integration-1-cpu-amd64	5f029e0	link	true	/test pull-etcd-integration-1-cpu-amd64
pull-etcd-integration-4-cpu-amd64	5f029e0	link	true	/test pull-etcd-integration-4-cpu-amd64
pull-etcd-integration-2-cpu-amd64	5f029e0	link	true	/test pull-etcd-integration-2-cpu-amd64

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[serathius]

Ok, test results showed the issue of many existing etcd client recepies depending on time to first event from watch created on concrete revision. Don't think we can move forward with this solution without separating newly created wachers from misbehaving ones.

[serathius]

At that point it would be better to do #17563

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 66.31%. Comparing base (4068189) to head (2c61a00).
Report is 10 commits behind head on main.

Additional details and impacted files

Files with missing lines	Coverage Δ
server/storage/mvcc/watchable_store.go	93.44% <100.00%> (-0.03%)	⬇️

... and 85 files with indirect coverage changes

@@            Coverage Diff             @@
##             main   #17583      +/-   ##
==========================================
- Coverage   68.67%   66.31%   -2.37%     
==========================================
  Files         420      420              
  Lines       35583    35582       -1     
==========================================
- Hits        24438    23595     -843     
- Misses       9713    10527     +814     
- Partials     1432     1460      +28     

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