// 2. 执行dump前的准备工作
preDump(erosaConnection);
erosaConnection.connect();// 链接
// 3. 获取最后的位置信息
final EntryPosition startPosition = findStartPosition(erosaConnection);
if (startPosition == null) {
throw new CanalParseException("can't find start position for " + destination);
}
logger.info("find start position : {}", startPosition.toString());
// 重新链接，因为在找position过程中可能有状态，需要断开后重建
erosaConnection.reconnect();
// 4. 启动一个心跳线程
startHeartBeat(erosaConnection);
final SinkFunction sinkHandler = new SinkFunction<EVENT>() {
private LogPosition lastPosition;
public boolean sink(EVENT event) {
try {
CanalEntry.Entry entry = parseAndProfilingIfNecessary(event);
if (!running) {
return false;
}
if (entry != null) {
exception = null; // 有正常数据流过，清空exception
transactionBuffer.add(entry);
// 记录一下对应的positions
this.lastPosition = buildLastPosition(entry);
// 记录一下最后一次有数据的时间
lastEntryTime = System.currentTimeMillis();
}
return running;
} catch (TableIdNotFoundException e) {
throw e;
} catch (Exception e) {
// 记录一下，出错的位点信息
processError(e,
this.lastPosition,
startPosition.getJournalName(),
startPosition.getPosition());
throw new CanalParseException(e); // 继续抛出异常，让上层统一感知
}
}
};
// 4. 开始dump数据
if (StringUtils.isEmpty(startPosition.getJournalName()) && startPosition.getTimestamp() != null) {
erosaConnection.dump(startPosition.getTimestamp(), sinkHandler);
} else {
erosaConnection.dump(startPosition.getJournalName(),
startPosition.getPosition(),
sinkHandler);
}
} catch (TableIdNotFoundException e) {
exception = e;