GODRIVER-3659 Filter CMAP/SDAM events for awaitMinPoolSizeMS

[prestonvasquez]

GODRIVER-3659

Summary

This PR implements event filtering for awaitMinPoolSizeMS in the unified test runner, as specified in the unified test format specification.

A naive implementation would clear specific event arrays after initialization:

client.pooled = nil
client.serverDescriptionChanged = nil
client.serverHeartbeatStartedEvent = nil
// ... clear each SDAM event type

However, if we add a new CMAP or SDAM event type in the future, we must remember to update this clearing block. Forgetting to do so means initialization events leak into test assertions, causing false failures.

The eventSequencer assigns a monotonically increasing sequence number to each CMAP and SDAM event as it's recorded. After pool initialization completes, we capture the current sequence as a cutoff. When verifying test expectations, we filter out any events with sequence numbers at or below the cutoff. This approach is future-proof because new event types automatically participate in filtering as long as they call the appropriate recording method in their event processor.

Background & Motivation

PR #2196 added support for awaitMinPoolSizeMS to the unified test runner, but was merged before the specification PR mongodb/specifications#1834 was finalized. As a result, the initial implementation used a simplified approach that doesn't match the final specification requirements.

Per the spec, when awaitMinPoolSizeMS is specified:

Any CMAP and SDAM event/log listeners configured on the client should ignore any events that occur before the pool is being populated.

[Copilot]

Pull Request Overview

This PR implements event filtering for awaitMinPoolSizeMS in the unified test runner to comply with the specification requirement that CMAP and SDAM events occurring during connection pool initialization should be ignored. The implementation uses a sequence-based filtering approach where events are assigned monotonically increasing sequence numbers, and a cutoff is set after pool initialization completes.

Key Changes:

• Replaced boolean awaitMinPoolSize field with awaitMinPoolSizeMS integer field to specify timeout duration
• Introduced eventSequencer to track event ordering via sequence numbers and filter events below a cutoff threshold
• Modified event processing functions to record sequence numbers for all CMAP and SDAM events

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
internal/integration/unified/entity.go	Updated entityOptions to use awaitMinPoolSizeMS with timeout duration instead of boolean flag
internal/integration/unified/client_entity.go	Added eventSequencer type and filtering logic; updated awaitMinimumPoolSize to accept timeout parameter and set cutoff after pool initialization
internal/integration/unified/event_verification.go	Modified event verification functions to use filterEventsBySeq for filtering CMAP and SDAM events
internal/integration/unified/client_entity_test.go	Added comprehensive unit tests for eventSequencer functionality

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[mongodb-drivers-pr-bot]

🧪 Performance Results

Commit SHA: 57c3818

The following benchmark tests for version 69127df7bedfbd0007c55290 had statistically significant changes (i.e., |z-score| > 1.96):

Benchmark	Measurement	% Change	Patch Value	Stable Region	H-Score	Z-Score
BenchmarkBSONDeepDocumentEncoding	ops_per_second_min	-32.2247	2278.0029	Avg: 3361.1109 Med: 3401.2631 Stdev: 510.6022	0.7568	-2.1212
BenchmarkBSONDeepDocumentDecoding	ops_per_second_min	18.7094	2375.5565	Avg: 2001.1528 Med: 2006.4528 Stdev: 169.0134	0.7768	2.2152
BenchmarkMultiInsertLargeDocument	total_mem_allocs	11.9970	1988.0000	Avg: 1775.0476 Med: 1800.0000 Stdev: 106.3117	0.7279	2.0031
BenchmarkMultiFindMany	total_mem_allocs	10.7965	518495.0000	Avg: 467970.6111 Med: 469972.5000 Stdev: 22195.9290	0.7594	2.2763
BenchmarkMultiFindMany	total_bytes_allocated	10.5783	840501240.0000	Avg: 760096146.2222 Med: 763743356.0000 Stdev: 36028084.7754	0.7558	2.2317
BenchmarkMultiInsertLargeDocument	allocated_bytes_per_op	-6.9672	26026403.0000	Avg: 27975509.9429 Med: 27920426.0000 Stdev: 645517.9504	0.8187	-3.0194
BenchmarkMultiInsertSmallDocument	ns_per_op	-5.2620	6244.0000	Avg: 6590.8111 Med: 6581.5000 Stdev: 171.3524	0.7360	-2.0240
BenchmarkSmallDocInsertOne	allocated_bytes_per_op	-0.2812	5673.0000	Avg: 5689.0000 Med: 5689.0000 Stdev: 4.1633	0.8750	-3.8431

For a comprehensive view of all microbenchmark results for this PR's commit, please check out the Evergreen perf task for this patch.

[mongodb-drivers-pr-bot]

API Change Report

No changes found!