protected void preDump(ErosaConnection connection) {
if (!(connection instanceof MysqlConnection)) {
throw new CanalParseException(
"Unsupported connection type : " + connection.getClass().getSimpleName());
}
// 开始启动心跳包
if (detectingEnable && StringUtils.isNotBlank(detectingSQL)) {
// fixed issue #56，避免重复创建heartbeat线程
if (mysqlHeartBeatTimeTask == null) {
logger.info("start heart beat.... ");
startHeartbeat((MysqlConnection) connection.fork());
}
}
if (binlogParser != null && binlogParser instanceof LogEventConvert) {
metaConnection = (MysqlConnection) connection.fork();
try {
metaConnection.connect();
} catch (IOException e) {
throw new CanalParseException(e);
}
tableMetaCache = new TableMetaCache(metaConnection);
((LogEventConvert) binlogParser).setTableMetaCache(tableMetaCache);
}
}
protected void afterDump(ErosaConnection connection) {
super.afterDump(connection);
if (!(connection instanceof MysqlConnection)) {
throw new CanalParseException(
"Unsupported connection type : " + connection.getClass().getSimpleName());
}
if (metaConnection != null) {
try {
metaConnection.disconnect();
} catch (IOException e) {
logger.error(
"ERROR # disconnect meta connection for address:{}",
metaConnection.getConnector().getAddress(),
e);
}
}
}
// 根据想要的position，可能这个position对应的记录为rowdata，需要找到事务头，避免丢数据
// 主要考虑一个事务执行时间可能会几秒种，如果仅仅按照timestamp相同，则可能会丢失事务的前半部分数据
private Long findTransactionBeginPosition(
ErosaConnection mysqlConnection, final EntryPosition entryPosition) throws IOException {
// 尝试找到一个合适的位置
final AtomicBoolean reDump = new AtomicBoolean(false);
mysqlConnection.reconnect();
mysqlConnection.seek(
entryPosition.getJournalName(),
entryPosition.getPosition(),
new SinkFunction<LogEvent>() {
private LogPosition lastPosition;
public boolean sink(LogEvent event) {
try {
CanalEntry.Entry entry = parseAndProfilingIfNecessary(event);
if (entry == null) {
return true;
}
// 直接查询第一条业务数据，确认是否为事务Begin/End
if (CanalEntry.EntryType.TRANSACTIONBEGIN == entry.getEntryType()
|| CanalEntry.EntryType.TRANSACTIONEND == entry.getEntryType()) {
lastPosition = buildLastPosition(entry);
return false;
} else {
reDump.set(true);
lastPosition = buildLastPosition(entry);
return false;
}
} catch (Exception e) {
// 上一次记录的poistion可能为一条update/insert/delete变更事件，直接进行dump的话，会缺少tableMap事件，导致tableId未进行解析
processError(
e, lastPosition, entryPosition.getJournalName(), entryPosition.getPosition());
reDump.set(true);
return false;
}
}
});
// 针对开始的第一条为非Begin记录，需要从该binlog扫描
if (reDump.get()) {
final AtomicLong preTransactionStartPosition = new AtomicLong(0L);
mysqlConnection.reconnect();
mysqlConnection.seek(
entryPosition.getJournalName(),
4L,
new SinkFunction<LogEvent>() {
private LogPosition lastPosition;
public boolean sink(LogEvent event) {
try {
CanalEntry.Entry entry = parseAndProfilingIfNecessary(event);
if (entry == null) {
return true;
}
// 直接查询第一条业务数据，确认是否为事务Begin
// 记录一下transaction begin position
if (entry.getEntryType() == CanalEntry.EntryType.TRANSACTIONBEGIN
&& entry.getHeader().getLogfileOffset() < entryPosition.getPosition()) {
preTransactionStartPosition.set(entry.getHeader().getLogfileOffset());
}
if (entry.getHeader().getLogfileOffset() >= entryPosition.getPosition()) {
return false; // 退出
}
lastPosition = buildLastPosition(entry);
} catch (Exception e) {
processError(
e, lastPosition, entryPosition.getJournalName(), entryPosition.getPosition());
return false;
}
return running;
}
});
// 判断一下找到的最接近position的事务头的位置
if (preTransactionStartPosition.get() > entryPosition.getPosition()) {
logger.error(
"preTransactionEndPosition greater than startPosition from zk or localconf, maybe lost data");
throw new CanalParseException(
"preTransactionStartPosition greater than startPosition from zk or localconf, maybe lost data");
}
return preTransactionStartPosition.get();
} else {
return entryPosition.getPosition();
}
}