feat: block time duration for SLOs

[auricom]

Overview

[gemini-code-assist]

Summary of Changes

Hello @auricom, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the system's monitoring capabilities by introducing a new Prometheus Summary metric specifically for tracking block time durations. This addition allows for more granular analysis of block processing times through percentiles over a rolling window, which is essential for accurately defining and monitoring Service Level Objectives (SLOs) related to block production and reception.

Highlights

• New Metric Introduction: A new Prometheus Summary metric, BlockTimeSummary, has been added to the Metrics struct to track block time durations.
• Metric Configuration: The BlockTimeSummary is configured to capture percentiles (0.5, 0.9, 0.95, 0.99) over a 60-second rolling window, providing detailed insights into block time distribution.
• Data Recording Integration: The RecordBlockTime function has been updated to observe block durations using the newly introduced BlockTimeSummary metric, ensuring it is populated with real-time data.

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[gemini-code-assist]

Code Review

This pull request introduces a new Prometheus summary metric, BlockTimeSummary, to track block time percentiles over a rolling window, likely for SLO monitoring. The changes include adding the metric definition, initializing it, and observing it when new block times are recorded.

My review includes two main points:

1. A suggestion to clarify the purpose of the new summary metric in its help text, as summaries with a short MaxAge are better suited for real-time monitoring than long-term SLO tracking, for which histograms are generally preferred.
2. A recommendation to add unit tests for the RecordBlockTime function, which is modified in this PR but currently lacks test coverage.

Overall, the changes are straightforward, but addressing these points will improve the clarity and robustness of the metrics implementation.

[gemini-code-assist]

The RecordBlockTime function is modified here, but it appears to lack unit tests. To ensure the logic is correct and prevent future regressions, it would be beneficial to add tests in pkg/metrics/metrics_test.go.

Test cases could cover:

• The first call for a given chainID only sets the arrival time and does not record a metric.
• A subsequent call with a later arrivalTime correctly records observations for both BlockTime and BlockTimeSummary.
• A call with an earlier or identical arrivalTime does not record any metric observation.

[chatton]

LGTM 👍