Add failing test for retry + abort issue

Author: ggilder

go/logic/migrator_test.go

@@ -1210,3 +1210,102 @@ func TestCheckAbort_DetectsContextCancellation(t *testing.T) {
 		t.Fatal("Expected checkAbort to return error when context is cancelled")
 	}
 }
+
+func (suite *MigratorTestSuite) TestPanicOnWarningsDuplicateDuringCutoverWithHighRetries() {
+	ctx := context.Background()
+
+	// Create table with email column (no unique constraint initially)
+	_, err := suite.db.ExecContext(ctx, fmt.Sprintf("CREATE TABLE %s (id INT PRIMARY KEY AUTO_INCREMENT, email VARCHAR(100))", getTestTableName()))
+	suite.Require().NoError(err)
+
+	// Insert initial rows with unique email values - passes pre-flight validation
+	_, err = suite.db.ExecContext(ctx, fmt.Sprintf("INSERT INTO %s (email) VALUES ('user1@example.com')", getTestTableName()))
+	suite.Require().NoError(err)
+	_, err = suite.db.ExecContext(ctx, fmt.Sprintf("INSERT INTO %s (email) VALUES ('user2@example.com')", getTestTableName()))
+	suite.Require().NoError(err)
+	_, err = suite.db.ExecContext(ctx, fmt.Sprintf("INSERT INTO %s (email) VALUES ('user3@example.com')", getTestTableName()))
+	suite.Require().NoError(err)
+
+	// Verify we have 3 rows
+	var count int
+	err = suite.db.QueryRowContext(ctx, fmt.Sprintf("SELECT COUNT(*) FROM %s", getTestTableName())).Scan(&count)
+	suite.Require().NoError(err)
+	suite.Require().Equal(3, count)
+
+	// Create postpone flag file
+	tmpDir, err := os.MkdirTemp("", "gh-ost-postpone-test")
+	suite.Require().NoError(err)
+	defer os.RemoveAll(tmpDir)
+	postponeFlagFile := filepath.Join(tmpDir, "postpone.flag")
+	err = os.WriteFile(postponeFlagFile, []byte{}, 0644)
+	suite.Require().NoError(err)
+
+	// Start migration in goroutine
+	done := make(chan error, 1)
+	go func() {
+		connectionConfig, err := getTestConnectionConfig(ctx, suite.mysqlContainer)
+		if err != nil {
+			done <- err
+			return
+		}
+
+		migrationContext := newTestMigrationContext()
+		migrationContext.ApplierConnectionConfig = connectionConfig
+		migrationContext.InspectorConnectionConfig = connectionConfig
+		migrationContext.SetConnectionConfig("innodb")
+		migrationContext.AlterStatementOptions = "ADD UNIQUE KEY unique_email_idx (email)"
+		migrationContext.HeartbeatIntervalMilliseconds = 100
+		migrationContext.PostponeCutOverFlagFile = postponeFlagFile
+		migrationContext.PanicOnWarnings = true
+
+		// High retry count + exponential backoff means retries will take a long time and fail the test if not properly aborted
+		migrationContext.SetDefaultNumRetries(30)
+		migrationContext.CutOverExponentialBackoff = true
+		migrationContext.SetExponentialBackoffMaxInterval(128)
+
+		migrator := NewMigrator(migrationContext, "0.0.0")
+
+		//nolint:contextcheck
+		done <- migrator.Migrate()
+	}()
+
+	// Wait for migration to reach postponed state
+	// TODO replace this with an actual check for postponed state
+	time.Sleep(3 * time.Second)
+
+	// Now insert a duplicate email value while migration is postponed
+	// This simulates data arriving during migration that would violate the unique constraint
+	_, err = suite.db.ExecContext(ctx, fmt.Sprintf("INSERT INTO %s (email) VALUES ('user1@example.com')", getTestTableName()))
+	suite.Require().NoError(err)
+
+	// Verify we now have 4 rows (including the duplicate)
+	err = suite.db.QueryRowContext(ctx, fmt.Sprintf("SELECT COUNT(*) FROM %s", getTestTableName())).Scan(&count)
+	suite.Require().NoError(err)
+	suite.Require().Equal(4, count)
+
+	// Unpostpone the migration - gh-ost will now try to apply binlog events with the duplicate
+	err = os.Remove(postponeFlagFile)
+	suite.Require().NoError(err)
+
+	// Wait for Migrate() to return - with timeout to detect if it hangs
+	select {
+	case migrateErr := <-done:
+		// Success - Migrate() returned
+		// It should return an error due to the duplicate
+		suite.Require().Error(migrateErr, "Expected migration to fail due to duplicate key violation")
+		suite.Require().Contains(migrateErr.Error(), "Duplicate entry", "Error should mention duplicate entry")
+	case <-time.After(5 * time.Minute):
+		suite.FailNow("Migrate() hung and did not return within 5 minutes - failure to abort on warnings in retry loop")
+	}
+
+	// Verify all 4 rows are still in the original table (no silent data loss)
+	err = suite.db.QueryRowContext(ctx, fmt.Sprintf("SELECT COUNT(*) FROM %s", getTestTableName())).Scan(&count)
+	suite.Require().NoError(err)
+	suite.Require().Equal(4, count, "Original table should still have all 4 rows")
+
+	// Verify both user1@example.com entries still exist
+	var duplicateCount int
+	err = suite.db.QueryRowContext(ctx, fmt.Sprintf("SELECT COUNT(*) FROM %s WHERE email = 'user1@example.com'", getTestTableName())).Scan(&duplicateCount)
+	suite.Require().NoError(err)
+	suite.Require().Equal(2, duplicateCount, "Should have 2 duplicate email entries")
+}