聊聊debezium的RecordMakers

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本文主要研究一下debezium的RecordMakers

RecordMakers

debezium-v1.1.1.Final/debezium-connector-mysql/src/main/java/io/debezium/connector/mysql/RecordMakers.java

public class RecordMakers {

    private final Logger logger = LoggerFactory.getLogger(getClass());
    private final MySqlSchema schema;
    private final SourceInfo source;
    private final TopicSelector<TableId> topicSelector;
    private final boolean emitTombstoneOnDelete;
    private final Map<Long, Converter> convertersByTableNumber = new HashMap<>();
    private final Map<TableId, Long> tableNumbersByTableId = new HashMap<>();
    private final Map<Long, TableId> tableIdsByTableNumber = new HashMap<>();
    private final Schema schemaChangeKeySchema;
    private final Schema schemaChangeValueSchema;
    private final SchemaNameAdjuster schemaNameAdjuster = SchemaNameAdjuster.create(logger);
    private final Map<String, ?> restartOffset;

    //......

    public RecordMakers(MySqlSchema schema, SourceInfo source, TopicSelector<TableId> topicSelector,
                        boolean emitTombstoneOnDelete, Map<String, ?> restartOffset) {
        this.schema = schema;
        this.source = source;
        this.topicSelector = topicSelector;
        this.emitTombstoneOnDelete = emitTombstoneOnDelete;
        this.restartOffset = restartOffset;
        this.schemaChangeKeySchema = SchemaBuilder.struct()
                .name(schemaNameAdjuster.adjust("io.debezium.connector.mysql.SchemaChangeKey"))
                .field(Fields.DATABASE_NAME, Schema.STRING_SCHEMA)
                .build();
        this.schemaChangeValueSchema = SchemaBuilder.struct()
                .name(schemaNameAdjuster.adjust("io.debezium.connector.mysql.SchemaChangeValue"))
                .field(Fields.SOURCE, source.schema())
                .field(Fields.DATABASE_NAME, Schema.STRING_SCHEMA)
                .field(Fields.DDL_STATEMENTS, Schema.STRING_SCHEMA)
                .build();
    }

    public RecordsForTable forTable(TableId tableId, BitSet includedColumns, BlockingConsumer<SourceRecord> consumer) {
        Long tableNumber = tableNumbersByTableId.get(tableId);
        return tableNumber != null ? forTable(tableNumber, includedColumns, consumer) : null;
    }

    //......

}
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• RecordMakers提供了forTable方法，用于创建RecordsForTable

RecordsForTable

debezium-v1.1.1.Final/debezium-connector-mysql/src/main/java/io/debezium/connector/mysql/RecordMakers.java

    public final class RecordsForTable {
        private final BitSet includedColumns;
        private final Converter converter;
        private final BlockingConsumer<SourceRecord> consumer;

        protected RecordsForTable(Converter converter, BitSet includedColumns, BlockingConsumer<SourceRecord> consumer) {
            this.converter = converter;
            this.includedColumns = includedColumns;
            this.consumer = consumer;
        }

        public int read(Object[] row, Instant ts) throws InterruptedException {
            return read(row, ts, 0, 1);
        }

        public int read(Object[] row, Instant ts, int rowNumber, int numberOfRows) throws InterruptedException {
            return converter.read(source, row, rowNumber, numberOfRows, includedColumns, ts, consumer);
        }

        public int create(Object[] row, Instant ts) throws InterruptedException {
            return create(row, ts, 0, 1);
        }

        public int create(Object[] row, Instant ts, int rowNumber, int numberOfRows) throws InterruptedException {
            return converter.insert(source, row, rowNumber, numberOfRows, includedColumns, ts, consumer);
        }

        public int update(Object[] before, Object[] after, Instant ts) throws InterruptedException {
            return update(before, after, ts, 0, 1);
        }

        public int update(Object[] before, Object[] after, Instant ts, int rowNumber, int numberOfRows) throws InterruptedException {
            return converter.update(source, before, after, rowNumber, numberOfRows, includedColumns, ts, consumer);
        }

        public int delete(Object[] row, Instant ts) throws InterruptedException {
            return delete(row, ts, 0, 1);
        }

        public int delete(Object[] row, Instant ts, int rowNumber, int numberOfRows) throws InterruptedException {
            return converter.delete(source, row, rowNumber, numberOfRows, includedColumns, ts, consumer);
        }
    }
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• RecordsForTable提供了read、create、update、delete方法，它们都委托给converter的对应方法

Converter

debezium-v1.1.1.Final/debezium-connector-mysql/src/main/java/io/debezium/connector/mysql/RecordMakers.java

    protected static interface Converter {
        int read(SourceInfo source, Object[] row, int rowNumber, int numberOfRows, BitSet includedColumns, Instant ts,
                 BlockingConsumer<SourceRecord> consumer)
                throws InterruptedException;

        int insert(SourceInfo source, Object[] row, int rowNumber, int numberOfRows, BitSet includedColumns, Instant ts,
                   BlockingConsumer<SourceRecord> consumer)
                throws InterruptedException;

        int update(SourceInfo source, Object[] before, Object[] after, int rowNumber, int numberOfRows, BitSet includedColumns, Instant ts,
                   BlockingConsumer<SourceRecord> consumer)
                throws InterruptedException;

        int delete(SourceInfo source, Object[] row, int rowNumber, int numberOfRows, BitSet includedColumns, Instant ts,
                   BlockingConsumer<SourceRecord> consumer)
                throws InterruptedException;

    }
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• Converter接口定义了read、insert、update、delete方法

RecordMakers.Converter

debezium-v1.1.1.Final/debezium-connector-mysql/src/main/java/io/debezium/connector/mysql/RecordMakers.java

        Converter converter = new Converter() {

            @Override
            public int read(SourceInfo source, Object[] row, int rowNumber, int numberOfRows, BitSet includedColumns, Instant ts,
                            BlockingConsumer<SourceRecord> consumer)
                    throws InterruptedException {
                Object key = tableSchema.keyFromColumnData(row);
                Struct value = tableSchema.valueFromColumnData(row);
                if (value != null || key != null) {
                    Schema keySchema = tableSchema.keySchema();
                    Map<String, ?> partition = source.partition();
                    Map<String, Object> offset = source.offsetForRow(rowNumber, numberOfRows);
                    source.tableEvent(id);
                    Struct origin = source.struct();
                    SourceRecord record = new SourceRecord(partition, getSourceRecordOffset(offset), topicName, partitionNum,
                            keySchema, key, envelope.schema(), envelope.read(value, origin, ts));
                    consumer.accept(record);
                    return 1;
                }
                return 0;
            }

            @Override
            public int insert(SourceInfo source, Object[] row, int rowNumber, int numberOfRows, BitSet includedColumns, Instant ts,
                              BlockingConsumer<SourceRecord> consumer)
                    throws InterruptedException {
                validateColumnCount(tableSchema, row);
                Object key = tableSchema.keyFromColumnData(row);
                Struct value = tableSchema.valueFromColumnData(row);
                if (value != null || key != null) {
                    Schema keySchema = tableSchema.keySchema();
                    Map<String, ?> partition = source.partition();
                    Map<String, Object> offset = source.offsetForRow(rowNumber, numberOfRows);
                    source.tableEvent(id);
                    Struct origin = source.struct();
                    SourceRecord record = new SourceRecord(partition, getSourceRecordOffset(offset), topicName, partitionNum,
                            keySchema, key, envelope.schema(), envelope.create(value, origin, ts));
                    consumer.accept(record);
                    return 1;
                }
                return 0;
            }

            @Override
            public int update(SourceInfo source, Object[] before, Object[] after, int rowNumber, int numberOfRows, BitSet includedColumns,
                              Instant ts,
                              BlockingConsumer<SourceRecord> consumer)
                    throws InterruptedException {
                int count = 0;
                validateColumnCount(tableSchema, after);
                Object key = tableSchema.keyFromColumnData(after);
                Struct valueAfter = tableSchema.valueFromColumnData(after);
                if (valueAfter != null || key != null) {
                    Object oldKey = tableSchema.keyFromColumnData(before);
                    Struct valueBefore = tableSchema.valueFromColumnData(before);
                    Schema keySchema = tableSchema.keySchema();
                    Map<String, ?> partition = source.partition();
                    Map<String, Object> offset = source.offsetForRow(rowNumber, numberOfRows);
                    source.tableEvent(id);
                    Struct origin = source.struct();
                    if (key != null && !Objects.equals(key, oldKey)) {
                        // The key has changed, so we need to deal with both the new key and old key.
                        // Consumers may push the events into a system that won't allow both records to exist at the same time,
                        // so we first want to send the delete event for the old key...
                        SourceRecord record = new SourceRecord(partition, getSourceRecordOffset(offset), topicName, partitionNum,
                                keySchema, oldKey, envelope.schema(), envelope.delete(valueBefore, origin, ts));
                        consumer.accept(record);
                        ++count;

                        if (emitTombstoneOnDelete) {
                            // Next send a tombstone event for the old key ...
                            record = new SourceRecord(partition, getSourceRecordOffset(offset), topicName, partitionNum, keySchema, oldKey, null, null);
                            consumer.accept(record);
                            ++count;
                        }

                        // And finally send the create event ...
                        record = new SourceRecord(partition, getSourceRecordOffset(offset), topicName, partitionNum,
                                keySchema, key, envelope.schema(), envelope.create(valueAfter, origin, ts));
                        consumer.accept(record);
                        ++count;
                    }
                    else {
                        // The key has not changed, so a simple update is fine ...
                        SourceRecord record = new SourceRecord(partition, getSourceRecordOffset(offset), topicName, partitionNum,
                                keySchema, key, envelope.schema(), envelope.update(valueBefore, valueAfter, origin, ts));
                        consumer.accept(record);
                        ++count;
                    }
                }
                return count;
            }

            @Override
            public int delete(SourceInfo source, Object[] row, int rowNumber, int numberOfRows, BitSet includedColumns, Instant ts,
                              BlockingConsumer<SourceRecord> consumer)
                    throws InterruptedException {
                int count = 0;
                validateColumnCount(tableSchema, row);
                Object key = tableSchema.keyFromColumnData(row);
                Struct value = tableSchema.valueFromColumnData(row);
                if (value != null || key != null) {
                    Schema keySchema = tableSchema.keySchema();
                    Map<String, ?> partition = source.partition();
                    Map<String, Object> offset = source.offsetForRow(rowNumber, numberOfRows);
                    source.tableEvent(id);
                    Struct origin = source.struct();
                    // Send a delete message ...
                    SourceRecord record = new SourceRecord(partition, getSourceRecordOffset(offset), topicName, partitionNum,
                            keySchema, key, envelope.schema(), envelope.delete(value, origin, ts));
                    consumer.accept(record);
                    ++count;

                    // And send a tombstone ...
                    if (emitTombstoneOnDelete) {
                        record = new SourceRecord(partition, getSourceRecordOffset(offset), topicName, partitionNum,
                                keySchema, key, null, null);
                        consumer.accept(record);
                        ++count;
                    }
                }
                return count;
            }

            @Override
            public String toString() {
                return "RecordMaker.Converter(" + id + ")";
            }

            private void validateColumnCount(TableSchema tableSchema, Object[] row) {
                final int expectedColumnsCount = schema.tableFor(tableSchema.id()).columns().size();
                if (expectedColumnsCount != row.length) {
                    logger.error("Invalid number of columns, expected '{}' arrived '{}'", expectedColumnsCount, row.length);
                    throw new ConnectException(
                            "The binlog event does not contain expected number of columns; the internal schema representation is probably out of sync with the real database schema, or the binlog contains events recorded with binlog_row_image other than FULL or the table in question is an NDB table");
                }
            }
        };
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• RecordMakers创建了一个匿名Converter实现类，其实现方法基本是创建kafka connect的SourceRecord，然后执行consumer.accept(record)

小结

RecordMakers提供了forTable方法，用于创建RecordsForTable；RecordsForTable提供了read、create、update、delete方法，它们都委托给converter的对应方法

doc

• RecordMakers

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