apollo_committer: add per-block commit latency histogram metric

[itamar-starkware]

No description provided.

[reviewable-StarkWare]

This change is 

[itamar-starkware]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• apollo_batcher: debug-log compressed byte size of committer-returned commitment infos #14891
• apollo_dashboard: alert on committer block number lag and block commit latency #14890
• apollo_committer: add per-block commit latency histogram metric #14889 👈 (View in Graphite)
• apollo_committer,apollo_committer_config: warn when block commit exceeds duration threshold #14888
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[cursor]

PR Summary

Low Risk
Observability-only change; no commit logic, storage, or API behavior is modified.

Overview
Adds a Prometheus histogram committer_block_commit_latency so operators can see per-block end-to-end commit latency (seconds), not only cumulative millisecond counters.

Each successful block path that already calls update_metrics now also records durations.block into that histogram. The metric description notes this applies to commits and reverts alike.

Registration happens in register_metrics alongside existing committer gauges/counters. A new integration test wires a local Prometheus recorder, runs commit_block, and asserts the histogram has count 1 and a positive sum.

^{Reviewed by Cursor Bugbot for commit 6b3efac. Bugbot is set up for automated code reviews on this repo. Configure here.}

[yoavGrs]

@yoavGrs made 1 comment.
Reviewable status: 0 of 5 files reviewed, 1 unresolved discussion (waiting on itamar-starkware).

---

crates/apollo_committer/src/committer.rs line 683 at r1 (raw file):

) {
    BLOCKS_COMMITTED.increment(1);
    TOTAL_BLOCK_DURATION.increment((durations.block * 1000.0) as u64);

I see we already have the TOTAL_BLOCK_DURATION metric.

[itamar-starkware]

crates/apollo_committer/src/committer.rs line 683 at r1 (raw file):

Previously, yoavGrs wrote…

I see we already have the TOTAL_BLOCK_DURATION metric.

You are right. The new metric gives you full distubition p50/p95/p99 and not only a mean over a window. I think it gives extra info, I also want to identify a peak easily.
I can remove the old metric if you want.

[yoavGrs]

@yoavGrs reviewed 5 files and all commit messages, and made 1 comment.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on itamar-starkware).

---

crates/apollo_committer/src/committer.rs line 683 at r1 (raw file):

Previously, itamar-starkware wrote…

You are right. The new metric gives you full distubition p50/p95/p99 and not only a mean over a window. I think it gives extra info, I also want to identify a peak easily.
I can remove the old metric if you want.

If you think it's redundant, please remove it in a following PR.