背景

開了并行復制的半同步從庫SQL 線程報1032錯誤，異步復制從庫沒有報錯，偶爾會出現這種

版本

mysql 5.7.16

redhat 6.8

mysql> show variables like '%slave_para%';

+------------------------+---------------+

| Variable_name | Value |

+------------------------+---------------+

| slave_parallel_type | LOGICAL_CLOCK |

| slave_parallel_workers | 16 |

+------------------------+---------------+

分析

1、疑是對從庫執行了更新操作，導致更新的記錄不存在

2、查看error log發現

2018-04-03T10:11:47.720156+08:00 16 [ERROR] Slave SQL for channel '': **Worker 13** failed executing transaction **'a272bbcf-874f-11e7-a288-00505695b721:687871861**' at master log mysql-bin.004119, end_log_pos 376471678; **Could not execute Update_rows event** on table anytxn.seq_xxxx; Can't find record in 'seq_xxxx', Error_code: 1032; handler error HA_ERR_END_OF_FILE; the event's master log mysql-bin.004119, end_log_pos 376471678, Error_code: 1032

2018-04-03T10:11:47.720230+08:00 2 [Warning] Slave SQL for channel '': ... The slave coordinator and worker threads are stopped, possibly leaving data in inconsistent state. A restart should restore consistency automatically, although using non-transactional storage for data or info tables or DDL queries could lead to problems. In such cases you have to examine your data (see documentation for details). Error_code: 1756

2018-04-03T10:11:47.720959+08:00 2 [Note] Error reading relay log event for channel '': slave **SQL thread was killed**

3、從 SQL線程停止的position分析binlog發現

SET @@SESSION.GTID_NEXT= 'a272bbcf-874f-11e7-a288-00505695b721:687871861'/*!*/;

# at 376471694

#180403 10:11:47 server id 104073 end_log_pos 376471555 CRC32 0x1be91176 Querythread_id=2086049exec_time=0error_code=0

SET TIMESTAMP=1522721507/*!*/;

BEGIN

/*!*/;

# at 376471768

#180403 10:11:47 server id 104073 end_log_pos 376471616 CRC32 0x10644d77 Table_map: `anytxn`.`seq_xxxx` mapped to number 301

# at 376471829

#180403 10:11:47 server id 104073 end_log_pos 376471678 CRC32 0x871a9787 Update_rows: table id 301 flags: STMT_END_F

### UPDATE `anytxn`.`seq_xxxx`

### WHERE

### @1=7116088 /* LONGINT meta=0 nullable=0 is_null=0 */

### @2=1 /* INT meta=0 nullable=0 is_null=0 */

### SET

### @1=7116089 /* LONGINT meta=0 nullable=0 is_null=0 */

### @2=1 /* INT meta=0 nullable=0 is_null=0 */

# at 376471891

#180403 10:11:47 server id 104073 end_log_pos 376471709 CRC32 0x9eb59238 Xid = 22247621418

COMMIT/*!*/;

# at 376471922

#180403 10:11:47 server id 104073 end_log_pos 376471774 CRC32 0xf7b6ad5d GTIDlast_committed=641254sequence_number=641259

SET @@SESSION.GTID_NEXT= 'a272bbcf-874f-11e7-a288-00505695b721:687871862'/*!*/;

# at 376471987

#180403 10:11:47 server id 104073 end_log_pos 376471856 CRC32 0x6256de00 Querythread_id=2085350exec_time=0error_code=0

SET TIMESTAMP=1522721507/*!*/;

BEGIN

/*!*/;

# at 376472069

#180403 10:11:47 server id 104073 end_log_pos 376471979 CRC32 0x6c329578 Table_map: `anytxn`.`bm_cc_customer_address_info` mapped to number 1569

# at 376472192

#180403 10:11:47 server id 104073 end_log_pos 376472162 CRC32 0x834cc8b9 Write_rows: table id 1569 flags: STMT_END_F

### INSERT INTO `anytxn`.`bm_xxxxxxxxxxxxxx`

### SET

### @1=14480779 /* LONGINT meta=0 nullable=0 is_null=0 */

### @2='0000001002380654' /* STRING(96) meta=65120 nullable=0 is_null=0 */

### @3='B001' /* VARSTRING(30) meta=30 nullable=1 is_null=0 */

### @4=NULL /* STRING(12) meta=65036 nullable=1 is_null=1 */

### @5='10000010001202000000001' /* VARSTRING(96) meta=96 nullable=1 is_null=0 */

### @6='B00' /* STRING(9) meta=65033 nullable=1 is_null=0 */

### @7='xxxxxxxxxxx' /* VARSTRING(765) meta=765 nullable=1 is_null=0 */

### @8=NULL /* STRING(18) meta=65042 nullable=1 is_null=1 */

### @9=NULL /* STRING(18) meta=65042 nullable=1 is_null=1 */

### @10=NULL /* STRING(18) meta=65042 nullable=1 is_null=1 *

mysql@xxxxxx:/home/mysql> mysqlbinlog -v -v --start-datetime='2018-04-03 10:11:45' --stop-datetime='2018-04-03 10:11:48' /data/mysql/xxxxx-relay-bin.005477 | grep last_comm | grep 10:11:47 | grep 641254

#180403 10:11:47 server id 104073 end_log_pos 376469618 CRC32 0xb6dc6cef GTIDlast_committed=641227sequence_number=641254

#180403 10:11:47 server id 104073 end_log_pos 376471774 CRC32 0xf7b6ad5d GTIDlast_committed=641254sequence_number=641259

#180403 10:11:47 server id 104073 end_log_pos 376472258 CRC32 0x27cf3013 GTIDlast_committed=641254sequence_number=641260

從上面信息可以看出，發生更新記錄不存在是在更新anytxn.xxxx_id表的標識為7116088 的記錄

有兩個并發提交的事務last_committed=641254 ，與發現更新的記錄不存在的 GTID *.687871861 事務還有另一個并發提交的事務 sequence_number=641260(即insert另一張表的操作),難道是master有并發提交的事務，slave多個work線程去apply的時候出現了問題？

4、查看更新的記錄不存在的表和相關記錄

show create table seq_xxxx;

| seq_xxxx | CREATE TABLE seq_xxxx (

currentValue bigint(20) NOT NULL,

increment int(11) NOT NULL DEFAULT '1'

mysql> select * from seq_xxxx;

+--------------+-----------+

| currentValue | increment |

+--------------+-----------+

| 7116088 | 1 |

+--------------+-----------+

可以發現實際數據庫中是存在該記錄的

測試

mysql> select @@version;

+------------+

| @@version |

+------------+

| 5.7.19-log |

+------------+

1 row in set (0.00 sec)

mysql> show variables like '%para%';

+------------------------+---------------+

| Variable_name | Value |

+------------------------+---------------+

| slave_parallel_type | LOGICAL_CLOCK |

| slave_parallel_workers | 4 |

+------------------------+---------------+

sysbench /usr/share/sysbench/tests/include/oltp_legacy/oltp.lua --mysql-host=10.186.30.73 --mysql-socket=/opt/mysql/data/3307/mysqld.sock --mysql-port=3307 --db-driver=mysql --mysql-db=test --mysql-user=admin --mysql-password=admin --table_size=100000 --tables=5 --threads=100 --time=120 --report-interval=5 run

有并發提交的事務，但沒有模擬重現出更新的記錄不存在，但在庫中卻存在的情況

更新

slave_preserve_commit_order=1(default 0，MTS中有效)

確保事務以與在從服務器中繼日志中顯示的順序相同的順序在從服務器上apply，防止出現gaps。如果該值設置為0，slave并行apply事務可能會無序，檢查最近執行的事務并不能保證主服務器上的所有先前事務都已在從服務器上執行

開啟多線程復制后，這個參數推薦設置為1

總結

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