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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[Copilot]

Potential index out of bounds panic if seqSlice length doesn't match events length. Add a length check before the loop or validate that i < len(seqSlice) in the loop condition.

[Copilot]

Potential index out of bounds panic if the index is beyond the slice length. Add bounds checking before accessing es.seqByEventType[eventType][index].

Suggested change

	return es.seqByEventType[eventType][index] <= es.cutoff
	seqs, ok := es.seqByEventType[eventType]
	if !ok || index < 0 || index >= len(seqs) {
	return false
	}
	return seqs[index] <= es.cutoff

[mongodb-drivers-pr-bot]

🧪 Performance Results

Commit SHA: 95e4d63

The following benchmark tests for version 690e89e64dcf7a0007e61054 had statistically significant changes (i.e., |z-score| > 1.96):

Benchmark	Measurement	% Change	Patch Value	Stable Region	H-Score	Z-Score
BenchmarkBSONFlatDocumentDecoding	ops_per_second_min	-41.4294	1295.6187	Avg: 2212.0622 Med: 2257.7594 Stdev: 308.0519	0.8254	-2.9750
BenchmarkBSONDeepDocumentDecoding	ops_per_second_min	20.1159	2403.7017	Avg: 2001.1528 Med: 2006.4528 Stdev: 169.0134	0.7919	2.3818
BenchmarkMultiFindMany	total_bytes_allocated	-10.1039	683296536.0000	Avg: 760096146.2222 Med: 763743356.0000 Stdev: 36028084.7754	0.7443	-2.1317
BenchmarkMultiFindMany	total_mem_allocs	-9.8681	421791.0000	Avg: 467970.6111 Med: 469972.5000 Stdev: 22195.9290	0.7368	-2.0805

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!