[DRAFT] feat: added client side metric instrumentation to read_rows and mutate_rows

[daniel-sanche]

Builds off of #1188 to add instrumentation to read_rows and mutate_rows, along with the mutation batcher

[gemini-code-assist]

Summary of Changes

Hello @daniel-sanche, 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 Bigtable client library by integrating robust client-side metric instrumentation. It provides granular insights into the performance and behavior of read_rows and mutate_rows operations, including those handled by the mutation batcher. This allows developers to better understand latency, retry patterns, and resource utilization at both the operation and individual attempt levels, facilitating performance optimization and debugging.

Highlights

• Client-Side Metric Instrumentation: Introduced client-side metric instrumentation for read_rows and mutate_rows operations, including the mutation batcher, to capture detailed performance data.
• Metric Tracking for Operations and Attempts: Operations now track overall duration, final status, streaming status, cluster/zone information, and flow throttling time. Individual attempts within an operation track duration, end status, backoff time, GFE latency, and application blocking time.
• Integration with Retry Logic: The new tracked_retry mechanism wraps existing retry logic to seamlessly integrate metric collection for each attempt and the overall operation.
• Comprehensive Test Coverage: Added extensive system and unit tests to validate metric collection for various scenarios, including successful operations, retries, timeouts, unauthorized access, and mid-stream failures for both synchronous and asynchronous clients.

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[gemini-code-assist]

Code Review

This pull request introduces client-side metric instrumentation for read_rows and mutate_rows operations, which is a valuable addition for monitoring and performance analysis. The changes are well-structured, using a tracked_retry wrapper to cleanly inject metrics logic into existing retry mechanisms. The refactoring of read_row and row_exists methods in the client is a good improvement, enhancing code reuse and ensuring consistent metric coverage. The new system tests are comprehensive and cover a wide range of success and failure scenarios, which is excellent. I have a couple of minor suggestions to improve code clarity by removing a type: ignore directive. Overall, this is a solid contribution.

[gemini-code-assist]

To improve readability and avoid the type: ignore, you could introduce a local variable for self._operation_metric.active_attempt. This helps the type checker understand that the object is not None within the conditional block.

active_attempt = self._operation_metric.active_attempt
if active_attempt is not None:
    active_attempt.application_blocking_time_ns += (
        time.monotonic_ns() - block_time
    )

[gemini-code-assist]

For consistency and improved readability, you could introduce a local variable for self._operation_metric.active_attempt here as well. This makes the logic clearer and aligns it with the suggested change in the async version of this file.

active_attempt = self._operation_metric.active_attempt
if active_attempt is not None:
    active_attempt.application_blocking_time_ns += (
        time.monotonic_ns() - block_time
    )