聊聊maxwell的FileProducer

序

本文主要研究一下maxwell的FileProducer

FileProducer

maxwell-1.25.1/src/main/java/com/zendesk/maxwell/producer/FileProducer.java

public class FileProducer extends AbstractProducer {
    private final File file;
    private final FileWriter fileWriter;

    public FileProducer(MaxwellContext context, String filename) throws IOException {
        super(context);
        this.file = new File(filename);
        this.fileWriter = new FileWriter(this.file, true);
    }

    @Override
    public void push(RowMap r) throws Exception {
        String output = r.toJSON(outputConfig);

        if ( output != null ) {
            this.fileWriter.write(r.toJSON(outputConfig));
            this.fileWriter.write('\n');
            this.fileWriter.flush();
        }

        context.setPosition(r);
    }
}

• FileProducer继承了AbstractProducer，其构造器接收filename参数，然后创建FileWriter；其push方法写入json，然后执行context.setPosition(r)

RowMap

maxwell-1.25.1/src/main/java/com/zendesk/maxwell/row/RowMap.java

public class RowMap implements Serializable {

    //......

    public String toJSON(MaxwellOutputConfig outputConfig) throws Exception {
        MaxwellJson json = MaxwellJson.getInstance();
        JsonGenerator g = json.reset();

        g.writeStartObject(); // start of row {

        g.writeStringField(FieldNames.DATABASE, this.database);
        g.writeStringField(FieldNames.TABLE, this.table);

        if ( outputConfig.includesRowQuery && this.rowQuery != null) {
            g.writeStringField(FieldNames.QUERY, this.rowQuery);
        }

        g.writeStringField(FieldNames.TYPE, this.rowType);
        g.writeNumberField(FieldNames.TIMESTAMP, this.timestampSeconds);

        if ( outputConfig.includesCommitInfo ) {
            if ( this.xid != null )
                g.writeNumberField(FieldNames.TRANSACTION_ID, this.xid);

            if ( outputConfig.includesXOffset && this.xoffset != null && !this.txCommit )
                g.writeNumberField(FieldNames.TRANSACTION_OFFSET, this.xoffset);

            if ( this.txCommit )
                g.writeBooleanField(FieldNames.COMMIT, true);
        }

        if ( this.position != null ) {
            BinlogPosition binlogPosition = this.position.getBinlogPosition();
            if ( outputConfig.includesBinlogPosition )
                g.writeStringField(FieldNames.POSITION, binlogPosition.getFile() + ":" + binlogPosition.getOffset());

            if ( outputConfig.includesGtidPosition)
                g.writeStringField(FieldNames.GTID, binlogPosition.getGtid());
        }

        if ( outputConfig.includesServerId && this.serverId != null ) {
            g.writeNumberField(FieldNames.SERVER_ID, this.serverId);
        }

        if ( outputConfig.includesThreadId && this.threadId != null ) {
            g.writeNumberField(FieldNames.THREAD_ID, this.threadId);
        }

        if ( outputConfig.includesSchemaId && this.schemaId != null ) {
            g.writeNumberField(FieldNames.SCHEMA_ID, this.schemaId);
        }

        if ( this.comment != null ) {
            g.writeStringField(FieldNames.COMMENT, this.comment);
        }

        for ( Map.Entry entry : this.extraAttributes.entrySet() ) {
            g.writeObjectField(entry.getKey(), entry.getValue());
        }

        EncryptionContext encryptionContext = null;
        if (outputConfig.encryptionEnabled()) {
            encryptionContext = EncryptionContext.create(outputConfig.secretKey);
        }

        DataJsonGenerator dataWriter = outputConfig.encryptionMode == EncryptionMode.ENCRYPT_DATA
            ? json.getEncryptingGenerator()
            : json.getPlaintextGenerator();

        JsonGenerator dataGenerator = dataWriter.begin();
        if ( outputConfig.includesPrimaryKeys ) {
            List