*: add experimental flag for watch notify interval

[jingyih]

Make watch progress notify configurable via flag --experimental-watch-progress-notify-interval.

[jingyih]

cc @jpbetz

[codecov-io]

Codecov Report

Merging #11463 into master will decrease coverage by 0.25%.
The diff coverage is 95.83%.

@@            Coverage Diff             @@
##           master   #11463      +/-   ##
==========================================
- Coverage   64.21%   63.96%   -0.26%     
==========================================
  Files         403      403              
  Lines       38079    38083       +4     
==========================================
- Hits        24453    24358      -95     
- Misses      11993    12066      +73     
- Partials     1633     1659      +26

Impacted Files	Coverage Δ
etcdserver/config.go	79.51% <ø> (ø)	⬆️
embed/config.go	50.84% <ø> (ø)	⬆️
etcdserver/api/v3rpc/watch.go	76.94% <0%> (-2.8%)	⬇️
etcdmain/config.go	84% <100%> (+0.07%)	⬆️
embed/etcd.go	68.23% <100%> (+0.06%)	⬆️
client/client.go	53.26% <0%> (-30.72%)	⬇️
client/members.go	51.61% <0%> (-13.71%)	⬇️
auth/simple_token.go	65.85% <0%> (-11.39%)	⬇️
pkg/netutil/netutil.go	63.11% <0%> (-7.38%)	⬇️
clientv3/namespace/watch.go	87.87% <0%> (-6.07%)	⬇️
... and 24 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 5770a6d...e628ced. Read the comment docs.

[xiang90]

shall we make this a global flag? or a per watch configuration?

[xiang90]

my initial thought is to support global min value (do not overload server if user sets a very small value at per watcher level) and a per watcher value.

[jingyih]

my initial thought is to support global min value (do not overload server if user sets a very small value at per watcher level) and a per watcher value.

This sounds good to me. So the global min value would be configured as a server flag, and the per watcher value is configured via an optional field in watch create request?

[xiang90]

This sounds good to me. So the global min value would be configured as a server flag, and the per watcher value is configured via an optional field in watch create request?

yes. we can do this in two steps though.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[jingyih]

Reopening this PR (just rebased). It seems useful to make the watch progress notify interval configurable. For example, see https://github.com/kubernetes/enhancements/tree/master/keps/sig-api-machinery/1904-efficient-watch-resumption

cc @xiang90 @gyuho @wojtek-t @ptabor

[jingyih]

I cannot reopen this PR... Let me create a new one.