[mysql] Optimize the checkpoint be optional under single parallelism (#365)

Co-authored-by: Leonard Xu <xbjtdcq@gmailcom>

flink-connector-mysql-cdc/src/main/java/com/ververica/cdc/connectors/mysql/source/MySqlParallelSource.java

@@ -130,10 +130,11 @@ public class MySqlParallelSource<T>
     public SplitEnumerator<MySqlSplit, PendingSplitsState> createEnumerator(
             SplitEnumeratorContext<MySqlSplit> enumContext) {
         MySqlValidator validator = new MySqlValidator(config);
+        final int currentParallelism = enumContext.currentParallelism();
 
         final MySqlSplitAssigner splitAssigner =
                 startupMode.equals("initial")
-                        ? new MySqlHybridSplitAssigner(config)
+                        ? new MySqlHybridSplitAssigner(config, currentParallelism)
                         : new MySqlBinlogSplitAssigner(config);
 
         return new MySqlSourceEnumerator(enumContext, splitAssigner, validator);
@@ -144,9 +145,11 @@ public class MySqlParallelSource<T>
             SplitEnumeratorContext<MySqlSplit> enumContext, PendingSplitsState checkpoint) {
         MySqlValidator validator = new MySqlValidator(config);
         final MySqlSplitAssigner splitAssigner;
+        final int currentParallelism = enumContext.currentParallelism();
         if (checkpoint instanceof HybridPendingSplitsState) {
             splitAssigner =
-                    new MySqlHybridSplitAssigner(config, (HybridPendingSplitsState) checkpoint);
+                    new MySqlHybridSplitAssigner(
+                            config, currentParallelism, (HybridPendingSplitsState) checkpoint);
         } else if (checkpoint instanceof BinlogPendingSplitsState) {
             splitAssigner =
                     new MySqlBinlogSplitAssigner(config, (BinlogPendingSplitsState) checkpoint);

flink-connector-mysql-cdc/src/main/java/com/ververica/cdc/connectors/mysql/source/assigners/MySqlHybridSplitAssigner.java

@@ -50,15 +50,17 @@ public class MySqlHybridSplitAssigner implements MySqlSplitAssigner {
 
     private final MySqlSnapshotSplitAssigner snapshotSplitAssigner;
 
-    public MySqlHybridSplitAssigner(Configuration configuration) {
-        this(new MySqlSnapshotSplitAssigner(configuration), false);
+    public MySqlHybridSplitAssigner(Configuration configuration, int currentParallelism) {
+        this(new MySqlSnapshotSplitAssigner(configuration, currentParallelism), false);
     }
 
     public MySqlHybridSplitAssigner(
-            Configuration configuration, HybridPendingSplitsState checkpoint) {
+            Configuration configuration,
+            int currentParallelism,
+            HybridPendingSplitsState checkpoint) {
         this(
                 new MySqlSnapshotSplitAssigner(
-                        configuration, checkpoint.getSnapshotPendingSplits()),
+                        configuration, currentParallelism, checkpoint.getSnapshotPendingSplits()),
                 checkpoint.isBinlogSplitAssigned());
     }
 

flink-connector-mysql-cdc/src/main/java/com/ververica/cdc/connectors/mysql/source/assigners/MySqlSnapshotSplitAssigner.java

@@ -69,6 +69,7 @@ public class MySqlSnapshotSplitAssigner implements MySqlSplitAssigner {
     private boolean assignerFinished;
 
     private final Configuration configuration;
+    private final int currentParallelism;
     private final LinkedList<TableId> remainingTables;
     private final RelationalTableFilters tableFilters;
     private final int chunkSize;
@@ -78,9 +79,10 @@ public class MySqlSnapshotSplitAssigner implements MySqlSplitAssigner {
 
     @Nullable private Long checkpointIdToFinish;
 
-    public MySqlSnapshotSplitAssigner(Configuration configuration) {
+    public MySqlSnapshotSplitAssigner(Configuration configuration, int currentParallelism) {
         this(
                 configuration,
+                currentParallelism,
                 new ArrayList<>(),
                 new ArrayList<>(),
                 new HashMap<>(),
@@ -89,9 +91,12 @@ public class MySqlSnapshotSplitAssigner implements MySqlSplitAssigner {
     }
 
     public MySqlSnapshotSplitAssigner(
-            Configuration configuration, SnapshotPendingSplitsState checkpoint) {
+            Configuration configuration,
+            int currentParallelism,
+            SnapshotPendingSplitsState checkpoint) {
         this(
                 configuration,
+                currentParallelism,
                 checkpoint.getAlreadyProcessedTables(),
                 checkpoint.getRemainingSplits(),
                 checkpoint.getAssignedSplits(),
@@ -101,12 +106,14 @@ public class MySqlSnapshotSplitAssigner implements MySqlSplitAssigner {
 
     private MySqlSnapshotSplitAssigner(
             Configuration configuration,
+            int currentParallelism,
             List<TableId> alreadyProcessedTables,
             List<MySqlSnapshotSplit> remainingSplits,
             Map<String, MySqlSnapshotSplit> assignedSplits,
             Map<String, BinlogOffset> splitFinishedOffsets,
             boolean assignerFinished) {
         this.configuration = configuration;
+        this.currentParallelism = currentParallelism;
         this.alreadyProcessedTables = alreadyProcessedTables;
         this.remainingSplits = remainingSplits;
         this.assignedSplits = assignedSplits;
@@ -166,8 +173,17 @@ public class MySqlSnapshotSplitAssigner implements MySqlSplitAssigner {
     public void onFinishedSplits(Map<String, BinlogOffset> splitFinishedOffsets) {
         this.splitFinishedOffsets.putAll(splitFinishedOffsets);
         if (allSplitsFinished()) {
-            LOG.info(
-                    "Snapshot split assigner received all splits finished, waiting for a complete checkpoint to mark the assigner finished.");
+            // Skip the waiting checkpoint when current parallelism is 1 which means we do not need
+            // to care about the global output data order of snapshot splits and binlog split.
+            if (currentParallelism == 1) {
+                assignerFinished = true;
+                LOG.info(
+                        "Snapshot split assigner received all splits finished and the job parallelism is 1, snapshot split assigner is turn into finished status.");
+
+            } else {
+                LOG.info(
+                        "Snapshot split assigner received all splits finished, waiting for a complete checkpoint to mark the assigner finished.");
+            }
         }
     }
 

flink-connector-mysql-cdc/src/test/java/com/ververica/cdc/connectors/mysql/debezium/reader/BinlogSplitReaderTest.java

@@ -75,6 +75,7 @@ import static org.junit.Assert.assertEquals;
 /** Tests for {@link BinlogSplitReader}. */
 public class BinlogSplitReaderTest extends MySqlTestBase {
 
+    private static final int currentParallelism = 4;
     private final UniqueDatabase customerDatabase =
             new UniqueDatabase(MYSQL_CONTAINER, "customer", "mysqluser", "mysqlpw");
 
@@ -586,7 +587,8 @@ public class BinlogSplitReaderTest extends MySqlTestBase {
     }
 
     private List<MySqlSnapshotSplit> getMySqlSplits(Configuration configuration, RowType pkType) {
-        final MySqlSnapshotSplitAssigner assigner = new MySqlSnapshotSplitAssigner(configuration);
+        final MySqlSnapshotSplitAssigner assigner =
+                new MySqlSnapshotSplitAssigner(configuration, currentParallelism);
         assigner.open();
         List<MySqlSnapshotSplit> mySqlSplits = new ArrayList<>();
         while (true) {

flink-connector-mysql-cdc/src/test/java/com/ververica/cdc/connectors/mysql/debezium/reader/SnapshotSplitReaderTest.java

@@ -60,6 +60,7 @@ import static org.junit.Assert.assertEquals;
 /** Tests for {@link SnapshotSplitReader}. */
 public class SnapshotSplitReaderTest extends MySqlTestBase {
 
+    private static final int currentParallelism = 4;
     private static final UniqueDatabase customerDatabase =
             new UniqueDatabase(MYSQL_CONTAINER, "customer", "mysqluser", "mysqlpw");
 
@@ -277,7 +278,8 @@ public class SnapshotSplitReaderTest extends MySqlTestBase {
     }
 
     private List<MySqlSplit> getMySqlSplits(Configuration configuration, RowType pkType) {
-        final MySqlSnapshotSplitAssigner assigner = new MySqlSnapshotSplitAssigner(configuration);
+        final MySqlSnapshotSplitAssigner assigner =
+                new MySqlSnapshotSplitAssigner(configuration, currentParallelism);
         assigner.open();
         List<MySqlSplit> mySqlSplitList = new ArrayList<>();
         while (true) {

flink-connector-mysql-cdc/src/test/java/com/ververica/cdc/connectors/mysql/source/assigners/MySqlHybridSplitAssignerTest.java

@@ -55,6 +55,7 @@ import static org.junit.Assert.assertEquals;
 /** Tests for {@link MySqlHybridSplitAssigner}. */
 public class MySqlHybridSplitAssignerTest extends MySqlTestBase {
 
+    private static final int currentParallelism = 4;
     private static final UniqueDatabase customerDatabase =
             new UniqueDatabase(MYSQL_CONTAINER, "customer", "mysqluser", "mysqlpw");
 
@@ -114,7 +115,7 @@ public class MySqlHybridSplitAssignerTest extends MySqlTestBase {
         HybridPendingSplitsState checkpoint =
                 new HybridPendingSplitsState(snapshotPendingSplitsState, false);
         final MySqlHybridSplitAssigner assigner =
-                new MySqlHybridSplitAssigner(configuration, checkpoint);
+                new MySqlHybridSplitAssigner(configuration, currentParallelism, checkpoint);
 
         // step 2. Get the MySqlBinlogSplit after all snapshot splits finished
         Optional<MySqlSplit> binlogSplit = assigner.getNext();

flink-connector-mysql-cdc/src/test/java/com/ververica/cdc/connectors/mysql/source/assigners/MySqlSnapshotSplitAssignerTest.java

@@ -48,6 +48,7 @@ import static org.junit.Assert.fail;
 /** Tests for {@link MySqlSnapshotSplitAssigner}. */
 public class MySqlSnapshotSplitAssignerTest extends MySqlTestBase {
 
+    private static final int currentParallelism = 4;
     private static final UniqueDatabase customerDatabase =
             new UniqueDatabase(MYSQL_CONTAINER, "customer", "mysqluser", "mysqlpw");
 
@@ -121,7 +122,8 @@ public class MySqlSnapshotSplitAssignerTest extends MySqlTestBase {
                         .collect(Collectors.toList());
         configuration.setString("table.whitelist", String.join(",", captureTableIds));
 
-        final MySqlSnapshotSplitAssigner assigner = new MySqlSnapshotSplitAssigner(configuration);
+        final MySqlSnapshotSplitAssigner assigner =
+                new MySqlSnapshotSplitAssigner(configuration, currentParallelism);
 
         assigner.open();
         List<MySqlSplit> sqlSplits = new ArrayList<>();

flink-connector-mysql-cdc/src/test/java/com/ververica/cdc/connectors/mysql/table/MySqlConnectorITCase.java

@@ -206,6 +206,94 @@ public class MySqlConnectorITCase extends MySqlTestBase {
         result.getJobClient().get().cancel().get();
     }
 
+    @Test
+    public void testCheckpointIsOptionalUnderSingleParallelism() throws Exception {
+        if (incrementalSnapshot) {
+            env.setParallelism(1);
+            // check the checkpoint is optional when parallelism is 1
+            env.getCheckpointConfig().disableCheckpointing();
+        } else {
+            return;
+        }
+        inventoryDatabase.createAndInitialize();
+        String sourceDDL =
+                String.format(
+                        "CREATE TABLE debezium_source ("
+                                + " `id` INT NOT NULL,"
+                                + " name STRING,"
+                                + " description STRING,"
+                                + " weight DECIMAL(10,3),"
+                                + " primary key (`id`) not enforced"
+                                + ") WITH ("
+                                + " 'connector' = 'mysql-cdc',"
+                                + " 'hostname' = '%s',"
+                                + " 'port' = '%s',"
+                                + " 'username' = '%s',"
+                                + " 'password' = '%s',"
+                                + " 'database-name' = '%s',"
+                                + " 'table-name' = '%s',"
+                                + " 'debezium.internal.implementation' = '%s',"
+                                + " 'scan.incremental.snapshot.enabled' = '%s',"
+                                + " 'server-id' = '%s',"
+                                + " 'scan.incremental.snapshot.chunk.size' = '%s'"
+                                + ")",
+                        MYSQL_CONTAINER.getHost(),
+                        MYSQL_CONTAINER.getDatabasePort(),
+                        inventoryDatabase.getUsername(),
+                        inventoryDatabase.getPassword(),
+                        inventoryDatabase.getDatabaseName(),
+                        "products",
+                        getDezImplementation(),
+                        incrementalSnapshot,
+                        getServerId(),
+                        getSplitSize());
+        tEnv.executeSql(sourceDDL);
+
+        // async submit job
+        TableResult result = tEnv.executeSql("SELECT * FROM debezium_source");
+        CloseableIterator<Row> iterator = result.collect();
+        String[] expectedSnapshot =
+                new String[] {
+                    "+I[101, scooter, Small 2-wheel scooter, 3.140]",
+                    "+I[102, car battery, 12V car battery, 8.100]",
+                    "+I[103, 12-pack drill bits, 12-pack of drill bits with sizes ranging from #40 to #3, 0.800]",
+                    "+I[104, hammer, 12oz carpenter's hammer, 0.750]",
+                    "+I[105, hammer, 14oz carpenter's hammer, 0.875]",
+                    "+I[106, hammer, 16oz carpenter's hammer, 1.000]",
+                    "+I[107, rocks, box of assorted rocks, 5.300]",
+                    "+I[108, jacket, water resistent black wind breaker, 0.100]",
+                    "+I[109, spare tire, 24 inch spare tire, 22.200]"
+                };
+        assertThat(
+                fetchRows(iterator, expectedSnapshot.length), containsInAnyOrder(expectedSnapshot));
+
+        try (Connection connection = inventoryDatabase.getJdbcConnection();
+                Statement statement = connection.createStatement()) {
+
+            statement.execute(
+                    "INSERT INTO products VALUES (default,'jacket','water resistent white wind breaker',0.2);"); // 110
+            statement.execute(
+                    "INSERT INTO products VALUES (default,'scooter','Big 2-wheel scooter ',5.18);");
+            statement.execute(
+                    "UPDATE products SET description='new water resistent white wind breaker', weight='0.5' WHERE id=110;");
+            statement.execute("UPDATE products SET weight='5.17' WHERE id=111;");
+            statement.execute("DELETE FROM products WHERE id=111;");
+        }
+
+        String[] expectedBinlog =
+                new String[] {
+                    "+I[110, jacket, water resistent white wind breaker, 0.200]",
+                    "+I[111, scooter, Big 2-wheel scooter , 5.180]",
+                    "-U[110, jacket, water resistent white wind breaker, 0.200]",
+                    "+U[110, jacket, new water resistent white wind breaker, 0.500]",
+                    "-U[111, scooter, Big 2-wheel scooter , 5.180]",
+                    "+U[111, scooter, Big 2-wheel scooter , 5.170]",
+                    "-D[111, scooter, Big 2-wheel scooter , 5.170]"
+                };
+        assertThat(fetchRows(iterator, expectedBinlog.length), containsInAnyOrder(expectedBinlog));
+        result.getJobClient().get().cancel().get();
+    }
+
     @Test
     public void testAllTypes() throws Throwable {
         fullTypesDatabase.createAndInitialize();