mysql的XA事務恢復過程

mysql數據庫開機報錯：
InnoDB: The log sequence number in ibdata files does not match
InnoDB: the log sequence number in the ib_logfiles!
100224 12:24:20 InnoDB: Database was not shut down normally!
InnoDB: Starting crash recovery.
InnoDB: Reading tablespace information from the .ibd files...
InnoDB: Restoring possible half-written data pages from the doublewrite
InnoDB: buffer...
InnoDB: Transaction 0 4497755 was in the XA prepared state.
InnoDB: Transaction 0 4468551 was in the XA prepared state.
InnoDB: Transaction 0 4468140 was in the XA prepared state.
InnoDB: 3 transaction(s) which must be rolled back or cleaned up
InnoDB: in total 0 row operations to undo
InnoDB: Trx id counter is 0 5312768
InnoDB: Starting in background the rollback of uncommitted transactions
100224 12:24:20 InnoDB: Rollback of non-prepared transactions completed
100224 12:24:20 InnoDB: Started; log sequence number 0 3805002509
100224 12:24:20 InnoDB: Starting recovery for XA transactions...
100224 12:24:20 InnoDB: Transaction 0 4497755 in prepared state after recovery
100224 12:24:20 InnoDB: Transaction contains changes to 8 rows
100224 12:24:20 InnoDB: Transaction 0 4468551 in prepared state after recovery
100224 12:24:20 InnoDB: Transaction contains changes to 1 rows
100224 12:24:20 InnoDB: Transaction 0 4468140 in prepared state after recovery
100224 12:24:20 InnoDB: Transaction contains changes to 1 rows
100224 12:24:20 InnoDB: 3 transactions in prepared state after recovery
100224 12:24:20 [Note] Found 3 prepared transaction(s) in InnoDB
100224 12:24:20 [Warning] Found 3 prepared XA transactions
100224 12:24:20 [Note] Event Scheduler: Loaded 0 events
100224 12:24:20 [Note] /opt/mysql/bin/mysqld: ready for connections.
Version: '5.1.39' socket: '/tmp/mysql.sock' port: 3306 MySQL Community Server (GPL)
意味著有三個XA的事務沒有提交或回滾。
登錄到mysql
mysql> xa recover;
+----------+--------------+--------------+------------------------------------------------------------+
| formatID | gtrid_length | bqual_length | data |
+----------+--------------+--------------+------------------------------------------------------------+
| 131075 | 30 | 28 | 1-7f000001:bae5:4b6928eb:f06397f000001:bae5:4b6928eb:f0650 |
| 131075 | 30 | 28 | 1-7f000001:bae5:4b6928eb:fb5c37f000001:bae5:4b6928eb:fb5cd |
| 131075 | 30 | 28 | 1-7f000001:bae5:4b6928eb:f03ea7f000001:bae5:4b6928eb:f0400 |
+----------+--------------+--------------+------------------------------------------------------------+
數據表示信息如下：
formatIDis the formatIDpart of the transaction xid
gtrid_lengthis the length in bytes of the gtridpart of the xid
bqual_lengthis the length in bytes of the bqualpart of the xid
datais the concatenation of the gtridand bqualparts of the xid
這是三個XA事務的信息，准備直接回滾。
mysql> xa rollback '1-7f000001:bae5:4b6928eb:fb5c3','7f000001:bae5:4b6928eb:fb5cd',131075;
Query OK, 0 rows affected (0.41 sec)
再啟動就正常了。

MySQL XA
I.5. 對XA事務的限制
XA事務支持限於InnoDB存儲引擎。
MySQL XA實施是針對外部XA的，其中，MySQL服務器作為資源管理器，而客戶端程序作為事務管理器。未實施“內部XA”。這樣，就允許MySQL服務器內的單獨存儲引擎作為RM（資源管理器），而服務器本身作為TM（事務管理器）。處理包含1個以上存儲引擎的XA事務時，需要內部XA。內部XA的實施是不完整的，這是因為，它要求存儲引擎在表處理程序層面上支持兩階段提交，目前僅對InnoDB實現了該特性。
對於XA START，不支持JOIN和RESUME子句。

對於XA END，不支持SUSPEND [FOR MIGRATE]子句。
在全局事務內，對於每個XA事務，xid值的bqual部分應是不同的，該要求是對當前MySQL XA實施的限制。它不是XA規范的組成部分。

如果XA事務達到PREPARED狀態而且MySQL服務器宕機，當服務器重啟後，能夠繼續處理事務。就像原本應當的那樣。但是，如果客戶端連接中止而服務器繼續運行，服務器將回滾任何未完成的XA事務，即使該事務已達到PREPARED狀態也同樣。它應能提交或回滾PREPARED XA事務，但在不更改二進制日志機制的情況下不能這樣。