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聊聊nifi的AbstractBinlogTableEventWriter

撸了今年阿里、腾讯和美团的面试,我有一个重要发现.......>>

本文主要研究一下nifi的AbstractBinlogTableEventWriter

AbstractBinlogTableEventWriter

nifi-1.11.4/nifi-nar-bundles/nifi-cdc/nifi-cdc-mysql-bundle/nifi-cdc-mysql-processors/src/main/java/org/apache/nifi/cdc/mysql/event/io/AbstractBinlogTableEventWriter.java

public abstract class AbstractBinlogTableEventWriter<T extends BinlogTableEventInfo> extends AbstractBinlogEventWriter<T> {

    protected void writeJson(T event) throws IOException {
        super.writeJson(event);
        if (event.getDatabaseName() != null) {
            jsonGenerator.writeStringField("database", event.getDatabaseName());
        } else {
            jsonGenerator.writeNullField("database");
        }
        if (event.getTableName() != null) {
            jsonGenerator.writeStringField("table_name", event.getTableName());
        } else {
            jsonGenerator.writeNullField("table_name");
        }
        if (event.getTableId() != null) {
            jsonGenerator.writeNumberField("table_id", event.getTableId());
        } else {
            jsonGenerator.writeNullField("table_id");
        }
    }

    // Default implementation for table-related binlog events
    @Override
    public long writeEvent(ProcessSession session, String transitUri, T eventInfo, long currentSequenceId, Relationship relationship) {
        FlowFile flowFile = session.create();
        flowFile = session.write(flowFile, (outputStream) -> {
            super.startJson(outputStream, eventInfo);
            writeJson(eventInfo);
            // Nothing in the body
            super.endJson();
        });
        flowFile = session.putAllAttributes(flowFile, getCommonAttributes(currentSequenceId, eventInfo));
        session.transfer(flowFile, relationship);
        session.getProvenanceReporter().receive(flowFile, transitUri);
        return currentSequenceId + 1;
    }
}
  • AbstractBinlogTableEventWriter继承了AbstractBinlogEventWriter,其泛型基类为BinlogTableEventInfo,它有四个子类,分别是DDLEventWriter、InsertRowsWriter、UpdateRowsWriter、DeleteRowsWriter

DDLEventWriter

nifi-1.11.4/nifi-nar-bundles/nifi-cdc/nifi-cdc-mysql-bundle/nifi-cdc-mysql-processors/src/main/java/org/apache/nifi/cdc/mysql/event/io/DDLEventWriter.java

public class DDLEventWriter extends AbstractBinlogTableEventWriter<DDLEventInfo> {

    @Override
    public long writeEvent(ProcessSession session, String transitUri, DDLEventInfo eventInfo, long currentSequenceId, Relationship relationship) {
        FlowFile flowFile = session.create();
        flowFile = session.write(flowFile, (outputStream) -> {
            super.startJson(outputStream, eventInfo);
            super.writeJson(eventInfo);
            jsonGenerator.writeStringField("query", eventInfo.getQuery());
            super.endJson();
        });
        flowFile = session.putAllAttributes(flowFile, getCommonAttributes(currentSequenceId, eventInfo));
        session.transfer(flowFile, relationship);
        session.getProvenanceReporter().receive(flowFile, transitUri);
        return currentSequenceId + 1;
    }
}
  • DDLEventWriter继承了AbstractBinlogTableEventWriter,其writeEvent方法写入DDLEventInfo

InsertRowsWriter

nifi-1.11.4/nifi-nar-bundles/nifi-cdc/nifi-cdc-mysql-bundle/nifi-cdc-mysql-processors/src/main/java/org/apache/nifi/cdc/mysql/event/io/InsertRowsWriter.java

public class InsertRowsWriter extends AbstractBinlogTableEventWriter<InsertRowsEventInfo> {

    /**
     * Creates and transfers a new flow file whose contents are the JSON-serialized value of the specified event, and the sequence ID attribute set
     *
     * @param session   A reference to a ProcessSession from which the flow file(s) will be created and transferred
     * @param eventInfo An event whose value will become the contents of the flow file
     * @return The next available CDC sequence ID for use by the CDC processor
     */
    @Override
    public long writeEvent(final ProcessSession session, String transitUri, final InsertRowsEventInfo eventInfo, final long currentSequenceId, Relationship relationship) {
        final AtomicLong seqId = new AtomicLong(currentSequenceId);
        for (Serializable[] row : eventInfo.getRows()) {

            FlowFile flowFile = session.create();
            flowFile = session.write(flowFile, outputStream -> {

                super.startJson(outputStream, eventInfo);
                super.writeJson(eventInfo);

                final BitSet bitSet = eventInfo.getIncludedColumns();
                writeRow(eventInfo, row, bitSet);

                super.endJson();
            });

            flowFile = session.putAllAttributes(flowFile, getCommonAttributes(seqId.get(), eventInfo));
            session.transfer(flowFile, relationship);
            session.getProvenanceReporter().receive(flowFile, transitUri);
            seqId.getAndIncrement();
        }
        return seqId.get();
    }

    protected void writeRow(InsertRowsEventInfo event, Serializable[] row, BitSet includedColumns) throws IOException {
        jsonGenerator.writeArrayFieldStart("columns");
        int i = includedColumns.nextSetBit(0);
        while (i != -1) {
            jsonGenerator.writeStartObject();
            jsonGenerator.writeNumberField("id", i + 1);
            ColumnDefinition columnDefinition = event.getColumnByIndex(i);
            Integer columnType = null;
            if (columnDefinition != null) {
                jsonGenerator.writeStringField("name", columnDefinition.getName());
                columnType = columnDefinition.getType();
                jsonGenerator.writeNumberField("column_type", columnType);
            }
            if (row[i] == null) {
                jsonGenerator.writeNullField("value");
            } else {
                jsonGenerator.writeObjectField("value", MySQLCDCUtils.getWritableObject(columnType, row[i]));
            }
            jsonGenerator.writeEndObject();
            i = includedColumns.nextSetBit(i + 1);
        }
        jsonGenerator.writeEndArray();
    }
}
  • InsertRowsWriter继承了AbstractBinlogTableEventWriter,其writeEvent方法写入InsertRowsEventInfo

UpdateRowsWriter

nifi-1.11.4/nifi-nar-bundles/nifi-cdc/nifi-cdc-mysql-bundle/nifi-cdc-mysql-processors/src/main/java/org/apache/nifi/cdc/mysql/event/io/UpdateRowsWriter.java

public class UpdateRowsWriter extends AbstractBinlogTableEventWriter<UpdateRowsEventInfo> {

    /**
     * Creates and transfers a new flow file whose contents are the JSON-serialized value of the specified event, and the sequence ID attribute set
     *
     * @param session   A reference to a ProcessSession from which the flow file(s) will be created and transferred
     * @param eventInfo An event whose value will become the contents of the flow file
     * @return The next available CDC sequence ID for use by the CDC processor
     */
    @Override
    public long writeEvent(final ProcessSession session, String transitUri, final UpdateRowsEventInfo eventInfo, final long currentSequenceId, Relationship relationship) {
        final AtomicLong seqId = new AtomicLong(currentSequenceId);
        for (Map.Entry<Serializable[], Serializable[]> row : eventInfo.getRows()) {

            FlowFile flowFile = session.create();
            flowFile = session.write(flowFile, outputStream -> {

                super.startJson(outputStream, eventInfo);
                super.writeJson(eventInfo);

                final BitSet bitSet = eventInfo.getIncludedColumns();
                writeRow(eventInfo, row, bitSet);

                super.endJson();
            });

            flowFile = session.putAllAttributes(flowFile, getCommonAttributes(seqId.get(), eventInfo));
            session.transfer(flowFile, relationship);
            session.getProvenanceReporter().receive(flowFile, transitUri);
            seqId.getAndIncrement();
        }
        return seqId.get();
    }

    protected void writeRow(UpdateRowsEventInfo event, Map.Entry<Serializable[], Serializable[]> row, BitSet includedColumns) throws IOException {

        jsonGenerator.writeArrayFieldStart("columns");
        int i = includedColumns.nextSetBit(0);
        while (i != -1) {
            jsonGenerator.writeStartObject();
            jsonGenerator.writeNumberField("id", i + 1);
            ColumnDefinition columnDefinition = event.getColumnByIndex(i);
            Integer columnType = null;
            if (columnDefinition != null) {
                jsonGenerator.writeStringField("name", columnDefinition.getName());
                columnType = columnDefinition.getType();
                jsonGenerator.writeNumberField("column_type", columnType);
            }
            Serializable[] oldRow = row.getKey();
            Serializable[] newRow = row.getValue();

            if (oldRow[i] == null) {
                jsonGenerator.writeNullField("last_value");
            } else {
                jsonGenerator.writeObjectField("last_value", MySQLCDCUtils.getWritableObject(columnType, oldRow[i]));
            }

            if (newRow[i] == null) {
                jsonGenerator.writeNullField("value");
            } else {
                jsonGenerator.writeObjectField("value", MySQLCDCUtils.getWritableObject(columnType, newRow[i]));
            }
            jsonGenerator.writeEndObject();
            i = includedColumns.nextSetBit(i + 1);
        }
        jsonGenerator.writeEndArray();
    }
}
  • UpdateRowsWriter继承了AbstractBinlogTableEventWriter,其writeEvent方法写入UpdateRowsEventInfo

DeleteRowsWriter

nifi-1.11.4/nifi-nar-bundles/nifi-cdc/nifi-cdc-mysql-bundle/nifi-cdc-mysql-processors/src/main/java/org/apache/nifi/cdc/mysql/event/io/DeleteRowsWriter.java

public class DeleteRowsWriter extends AbstractBinlogTableEventWriter<DeleteRowsEventInfo> {

    /**
     * Creates and transfers a new flow file whose contents are the JSON-serialized value of the specified event, and the sequence ID attribute set
     *
     * @param session   A reference to a ProcessSession from which the flow file(s) will be created and transferred
     * @param eventInfo An event whose value will become the contents of the flow file
     * @return The next available CDC sequence ID for use by the CDC processor
     */
    @Override
    public long writeEvent(final ProcessSession session, String transitUri, final DeleteRowsEventInfo eventInfo, final long currentSequenceId, Relationship relationship) {
        final AtomicLong seqId = new AtomicLong(currentSequenceId);
        for (Serializable[] row : eventInfo.getRows()) {

            FlowFile flowFile = session.create();
            flowFile = session.write(flowFile, outputStream -> {

                super.startJson(outputStream, eventInfo);
                super.writeJson(eventInfo);

                final BitSet bitSet = eventInfo.getIncludedColumns();
                writeRow(eventInfo, row, bitSet);

                super.endJson();
            });

            flowFile = session.putAllAttributes(flowFile, getCommonAttributes(seqId.get(), eventInfo));
            session.transfer(flowFile, relationship);
            session.getProvenanceReporter().receive(flowFile, transitUri);
            seqId.getAndIncrement();
        }
        return seqId.get();
    }

    protected void writeRow(DeleteRowsEventInfo event, Serializable[] row, BitSet includedColumns) throws IOException {
        jsonGenerator.writeArrayFieldStart("columns");
        int i = includedColumns.nextSetBit(0);
        while (i != -1) {
            jsonGenerator.writeStartObject();
            jsonGenerator.writeNumberField("id", i + 1);
            ColumnDefinition columnDefinition = event.getColumnByIndex(i);
            Integer columnType = null;
            if (columnDefinition != null) {
                jsonGenerator.writeStringField("name", columnDefinition.getName());
                columnType = columnDefinition.getType();
                jsonGenerator.writeNumberField("column_type", columnType);
            }
            if (row[i] == null) {
                jsonGenerator.writeNullField("value");
            } else {
                jsonGenerator.writeObjectField("value", MySQLCDCUtils.getWritableObject(columnType, row[i]));
            }
            jsonGenerator.writeEndObject();
            i = includedColumns.nextSetBit(i + 1);
        }
        jsonGenerator.writeEndArray();
    }
}
  • DeleteRowsWriter继承了AbstractBinlogTableEventWriter,其writeEvent方法写入DeleteRowsEventInfo

小结

AbstractBinlogTableEventWriter继承了AbstractBinlogEventWriter,其泛型基类为BinlogTableEventInfo,它有四个子类,分别是DDLEventWriter、InsertRowsWriter、UpdateRowsWriter、DeleteRowsWriter

doc


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