本文主要研究一下rocketmq-mysql的BinlogPositionManager
BinlogPositionManager
rocketmq-externals/rocketmq-mysql/src/main/java/org/apache/rocketmq/mysql/position/BinlogPositionManager.java
public class BinlogPositionManager {
private Logger logger = LoggerFactory.getLogger(BinlogPositionManager.class);
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private DataSource dataSource;
private Config config;
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private String binlogFilename;
private Long nextPosition;
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public BinlogPositionManager(Config config, DataSource dataSource) {
this.config = config;
this.dataSource = dataSource;
}
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public void initBeginPosition() throws Exception {
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if (config.startType == null || config.startType.equals("DEFAULT")) {
initPositionDefault();
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} else if (config.startType.equals("NEW_EVENT")) {
initPositionFromBinlogTail();
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} else if (config.startType.equals("LAST_PROCESSED")) {
initPositionFromMqTail();
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} else if (config.startType.equals("SPECIFIED")) {
binlogFilename = config.binlogFilename;
nextPosition = config.nextPosition;
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}
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if (binlogFilename == null || nextPosition == null) {
throw new Exception("binlogFilename | nextPosition is null.");
}
}
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//......
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public String getBinlogFilename() {
return binlogFilename;
}
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public Long getPosition() {
return nextPosition;
}
}
- BinlogPositionManager提供了initBeginPosition、getBinlogFilename、getPosition方法；其中initBeginPosition方法根据config.startType的类型来执行不同逻辑，DEFAULT的是执行initPositionDefault，NEW_EVENT是执行initPositionFromBinlogTail，LAST_PROCESSED是执行initPositionFromMqTail，SPECIFIED是设置指定的binlogFilename及nextPosition
initPositionDefault
rocketmq-externals/rocketmq-mysql/src/main/java/org/apache/rocketmq/mysql/position/BinlogPositionManager.java
public class BinlogPositionManager {
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//......
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private void initPositionDefault() throws Exception {
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try {
initPositionFromMqTail();
} catch (Exception e) {
logger.error("Init position from mq error.", e);
}
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if (binlogFilename == null || nextPosition == null) {
initPositionFromBinlogTail();
}
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}
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//......
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}
- initPositionDefault执行的是initPositionFromMqTail方法，在binlogFilename或者nextPosition为null时还会执行initPositionFromBinlogTail
initPositionFromBinlogTail
rocketmq-externals/rocketmq-mysql/src/main/java/org/apache/rocketmq/mysql/position/BinlogPositionManager.java
public class BinlogPositionManager {
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//......
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private void initPositionFromBinlogTail() throws SQLException {
String sql = "SHOW MASTER STATUS";
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Connection conn = null;
ResultSet rs = null;
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try {
Connection connection = dataSource.getConnection();
rs = connection.createStatement().executeQuery(sql);
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while (rs.next()) {
binlogFilename = rs.getString("File");
nextPosition = rs.getLong("Position");
}
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} finally {
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if (conn != null) {
conn.close();
}
if (rs != null) {
rs.close();
}
}
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}
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//......
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}
- initPositionFromBinlogTail方法通过SHOW MASTER STATUS来获取最新的binlogFilename及nextPosition
initPositionFromMqTail
rocketmq-externals/rocketmq-mysql/src/main/java/org/apache/rocketmq/mysql/position/BinlogPositionManager.java
public class BinlogPositionManager {
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//......
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private void initPositionFromMqTail() throws Exception {
DefaultMQPullConsumer consumer = new DefaultMQPullConsumer("BINLOG_CONSUMER_GROUP");
consumer.setNamesrvAddr(config.mqNamesrvAddr);
consumer.setMessageModel(MessageModel.valueOf("BROADCASTING"));
consumer.start();
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Set<MessageQueue> queues = consumer.fetchSubscribeMessageQueues(config.mqTopic);
MessageQueue queue = queues.iterator().next();
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if (queue != null) {
Long offset = consumer.maxOffset(queue);
if (offset > 0)
offset--;
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PullResult pullResult = consumer.pull(queue, "*", offset, 100);
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if (pullResult.getPullStatus() == PullStatus.FOUND) {
MessageExt msg = pullResult.getMsgFoundList().get(0);
String json = new String(msg.getBody(), "UTF-8");
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JSONObject js = JSON.parseObject(json);
binlogFilename = (String) js.get("binlogFilename");
nextPosition = js.getLong("nextPosition");
}
}
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}
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//......
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}
- initPositionFromMqTail方法创建DefaultMQPullConsumer，然后从指定的topic拉取MessageQueue，然后通过consumer.maxOffset(queue)获取offset，再执行pull，找到第一个msg，然后设置binlogFilename及nextPosition
小结
BinlogPositionManager提供了initBeginPosition、getBinlogFilename、getPosition方法；其中initBeginPosition方法根据config.startType的类型来执行不同逻辑，DEFAULT的是执行initPositionDefault，NEW_EVENT是执行initPositionFromBinlogTail，LAST_PROCESSED是执行initPositionFromMqTail，SPECIFIED是设置指定的binlogFilename及nextPosition
doc
- BinlogPositionManager