mysql_cdc(test): add connection drop integration tests

[mmatczuk]

Summary

• Add 4 integration tests validating no data loss during MySQL CDC connection drops and reconnections
• Covers: mid-stream kill, binlog rotation + kill, snapshot-to-CDC transition + kill, and repeated rapid disconnections with fake rotate events
• All tests pass across MySQL 8.0, 9.0, and 9.1 with zero data loss

Context

Investigating a reported scenario where binlog rotation + connection drop + reconnect from cached checkpoint could theoretically cause data loss if old binlog files are purged. These tests confirm the canal reconnection logic correctly resumes from the cached position without losing events.

[claude]

Test pattern violation: silently discarded stream.Run error

The documented async stream.Run pattern for integration tests is:

go func() {
    if err := stream.Run(t.Context()); err != nil && !errors.Is(err, context.Canceled) {
        t.Error(err)
    }
}()

Discarding the error with _ = silently swallows genuine stream failures (e.g., config errors, connection issues unrelated to the test scenario), which could mask real bugs in these reconnection tests.

This applies to all 4 new test functions (TestIntegrationMySQLCDCConnectionDrop, TestIntegrationMySQLCDCConnectionDropWithBinlogRotation, TestIntegrationMySQLCDCConnectionDropAfterSnapshot, TestIntegrationMySQLCDCRepeatedConnectionDrops).

[claude]

Commits

LGTM

Review

Adds 4 well-structured MySQL CDC connection drop integration tests with shared helpers (killReplicationConnections, idCollector, buildCDCStream). Tests cover mid-stream kill, binlog rotation + kill, post-snapshot kill, and repeated kill cycles. Good use of integration.CheckSkip, assert.Eventually, mutex-protected collectors, and license.InjectTestService.

1. Silently discarded stream.Run error (integration_test.go L1265-L1267): All 4 new tests use _ = streamOut.Run(t.Context()) which silently swallows all stream errors. The documented pattern requires checking for non-context.Canceled errors via t.Error(err) to avoid masking genuine failures.

[claude]

Commits
LGTM

Review
Adds 4 well-structured integration tests for MySQL CDC connection drop resilience, with proper helpers (killReplicationConnections, idCollector, buildCDCStream). Code correctly follows existing file patterns: integration.CheckSkip(t), service.NewStreamBuilder with license.InjectTestService, assert.Eventually for polling, proper mutex synchronization in idCollector, and context.Canceled handling in background goroutines.

LGTM

[claude]

Commits
LGTM

Review
Adds 4 well-structured MySQL CDC connection drop integration tests with shared helpers (killReplicationConnections, idCollector, buildCDCStream). Tests correctly use integration.CheckSkip(t), license.InjectTestService, errors.Is(err, context.Canceled) in background goroutines, assert.Eventually for polling, and mutex-guarded state. Set-based assertions properly tolerate at-least-once delivery semantics. Arithmetic for inserted IDs is consistent across all test cases.

LGTM

[claude]

Commits
LGTM

Review
Adds 4 integration tests validating MySQL CDC connection drop and reconnection scenarios with supporting helpers (killReplicationConnections, idCollector, buildCDCStream). Tests properly use integration.CheckSkip(t), service.NewStreamBuilder(), license.InjectTestService(), assert.Eventually (no require inside), t.Context(), and errors.Is(err, context.Canceled) handling. Thread-safe ID collection via mutex is correctly encapsulated.

LGTM