Add prometheus metric for server feature gate

[gangli113]

Fix #19324

Add a prometheus metric etcd_server_feature_enabled

Please read https://github.com/etcd-io/etcd/blob/main/CONTRIBUTING.md#contribution-flow.

[k8s-ci-robot]

Hi @gangli113. Thanks for your PR.

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[gangli113]

/cc @ahrtr

[gangli113]

sorry @ahrtr, assign to you by mistake. I was trying to add you to reviewer list.

[gangli113]

/cc @ahrtr

[ahrtr]

Overall looks good with just a minor comment. Thanks @gangli113 for the effort.

[ahrtr]

This is what I got. Should we remove AllAlpha and AllBeta? cc @fuweid @siyuanfoundation @ivanvc

F5WPP69Q7H:Downloads wachao$ curl http://127.0.0.1:2379/metrics | grep etcd_server_feature_enabled
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0# HELP etcd_server_feature_enabled Whether or not a feature is enabled. 1 is enabled, 0 is not.
# TYPE etcd_server_feature_enabled gauge
etcd_server_feature_enabled{name="AllAlpha",stage="ALPHA"} 0
etcd_server_feature_enabled{name="AllBeta",stage="BETA"} 0
etcd_server_feature_enabled{name="CompactHashCheck",stage="ALPHA"} 0
etcd_server_feature_enabled{name="DistributedTracing",stage="ALPHA"} 0
etcd_server_feature_enabled{name="InitialCorruptCheck",stage="ALPHA"} 0
etcd_server_feature_enabled{name="LeaseCheckpoint",stage="ALPHA"} 0
etcd_server_feature_enabled{name="LeaseCheckpointPersist",stage="ALPHA"} 0
etcd_server_feature_enabled{name="SetMemberLocalAddr",stage="ALPHA"} 0
etcd_server_feature_enabled{name="StopGRPCServiceOnDefrag",stage="ALPHA"} 0
etcd_server_feature_enabled{name="TxnModeWriteWithSharedBuffer",stage="BETA"} 1
100  155k    0  155k    0     0  49.5M      0 --:--:-- --:--:-- --:--:-- 75.9M

[ahrtr]

This is what I got. Should we remove AllAlpha and AllBeta? cc @fuweid @siyuanfoundation @ivanvc

To be clearer, I meant to remove AllAlpha and AllBeta from the metrics.

[fuweid]

To be clearer, I meant to remove AllAlpha and AllBeta from the metrics.

I think we should keep it because the user could set AllBeta=true to enable all the beta features.

[ahrtr]

I think we should keep it because the user could set AllBeta=true to enable all the beta features.

Valid point.

[ahrtr]

/ok-to-test

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ahrtr, fuweid, gangli113, siyuanfoundation

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[ahrtr]

/cherry-pick release-3.6

[k8s-infra-cherrypick-robot]

@ahrtr: new pull request created: #19495

In response to this:

/cherry-pick release-3.6

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