fix thread Local metrics (#1621)

[singhravidutt]

No description provided.

[singhravidutt]

/gcbrun

[gemini-code-assist]

Summary of Changes

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This pull request resolves an issue where thread-local metrics were not being properly accounted for in scenarios involving multi-threaded operations, specifically during vectored reads. The changes introduce a robust system for collecting and consolidating these metrics from individual worker threads, ensuring that the overall statistics accurately reflect the complete I/O activity. This enhancement improves the reliability and completeness of performance monitoring for concurrent file system operations.

Highlights

• Thread-Local Metric Aggregation: Implemented a mechanism to correctly aggregate thread-local metrics from worker threads involved in vectored read operations into the main thread's statistics. This ensures accurate reporting of metrics for concurrent I/O.
• Enhanced Metric Management: Added functionality to GhfsThreadLocalStatistics to increment metrics by their string name and to look up Metric enum values by name, improving flexibility in metric handling.
• Vectored Read Statistics Integration: Introduced a ConcurrentHashMap in GoogleHadoopFSInputStream to temporarily store thread-local statistics during vectored reads, which are then merged into the global statistics upon stream closure.
• Worker Thread Statistic Control: Added explicit calls within VectoredIOImpl to reset thread-local statistics before a worker thread processes a new range and to capture/merge these statistics after the range processing is complete (both success and failure paths).
• New Integration Test: A new integration test was added to GoogleHadoopFSInputStreamIntegrationTest to validate the correct aggregation of thread-local metrics during vectored read operations.

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Changelog

• gcs/src/main/java/com/google/cloud/hadoop/fs/gcs/GhfsThreadLocalStatistics.java
  • Added a new increment method that accepts a metric name as a string.
  • Implemented a static getMetricByName method within the Metric enum to retrieve metrics by their string label.
  • Introduced a BY_LABEL map in the Metric enum for efficient lookup of metrics by name.
• gcs/src/main/java/com/google/cloud/hadoop/fs/gcs/GoogleHadoopFSInputStream.java
  • Declared a ConcurrentHashMap named rangeReadThreadStats to store thread-local statistics for vectored reads.
  • Modified the readVectored method to pass the rangeReadThreadStats map to the VectoredIOImpl.
  • Added calls to mergeRangeReadThreadStats() and rangeReadThreadStats.clear() within the close() method to aggregate and reset statistics.
  • Implemented the mergeRangeReadThreadStats() private method to transfer collected range read statistics to the main thread's local statistics.
• gcs/src/main/java/com/google/cloud/hadoop/fs/gcs/VectoredIOImpl.java
  • Updated the readVectored method signature and VectoredReadChannel constructor to accept a ConcurrentHashMap for range read statistics.
  • Added captureAndResetThreadLocalStats() to collect and merge thread-local statistics from worker threads into the shared map.
  • Introduced resetThreadLocalStats() to clear thread-local statistics for worker threads before processing new ranges.
  • Integrated calls to resetThreadLocalStats() and captureAndResetThreadLocalStats() at appropriate points within the readVectored and readCombinedRange methods.
• gcs/src/test/java/com/google/cloud/hadoop/fs/gcs/GhfsThreadLocalStatisticsTest.java
  • Updated map initialization in getInitMetrics to use Map.ofEntries for clarity and consistency.
• gcs/src/test/java/com/google/cloud/hadoop/fs/gcs/GoogleHadoopFSInputStreamIntegrationTest.java
  • Added a new integration test fs_operation_threadLocalMetric_tests to verify the correct aggregation of thread-local metrics during vectored reads.
• gcs/src/test/java/com/google/cloud/hadoop/fs/gcs/VectoredIOImplTest.java
  • Modified test methods to pass and manage the new rangeReadThreadStats ConcurrentHashMap.

Activity

• No specific activity (comments, reviews, or progress updates) was provided in the context for this pull request.

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[gemini-code-assist]

Code Review

This pull request aims to fix thread-local metrics collection for vectored reads by introducing a mechanism to aggregate stats from worker threads and merge them into the main thread's statistics. While the overall approach is sound and correctly handles single-range vectored reads, I've identified a critical issue in how statistics are collected for combined (merged) ranges. This bug will result in incorrect metrics being reported.

[gemini-code-assist]

The call to captureAndResetThreadLocalStats() is incorrectly placed inside the loop over child ranges and, more importantly, before updateBytesRead(). This will lead to incorrect metrics.

Specifically:

1. The statistics from the GCS API call (e.g., GCS_GET_MEDIA_REQUEST) will only be captured for the first child range and then reset, being lost for subsequent child ranges in the same combined block.
2. The STREAM_READ_BYTES statistic, which is updated in updateBytesRead(), will not be captured at all because captureAndResetThreadLocalStats() is called before it.

To fix this, captureAndResetThreadLocalStats() should be moved out of the for loop and placed after it, but before combinedFileRange.getData().complete(readContent). This ensures all statistics for the combined read are accumulated before being captured.

[codecov]

Codecov Report

❌ Patch coverage is 97.43590% with 1 line in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (branch-3.1.x@4d5f49a). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
...cloud/hadoop/fs/gcs/GhfsThreadLocalStatistics.java	88.88%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##             branch-3.1.x    #1647   +/-   ##
===============================================
  Coverage                ?   82.65%           
  Complexity              ?     2344           
===============================================
  Files                   ?      124           
  Lines                   ?    10359           
  Branches                ?     1256           
===============================================
  Hits                    ?     8562           
  Misses                  ?     1277           
  Partials                ?      520           

Flag	Coverage Δ
integrationtest	68.10% <94.87%> (?)
unittest	73.19% <97.43%> (?)

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[mudit-97]

LGTM (cherry pick)