1.1.1. If a crash happens thisconfiguration does not guarantee that the relay log info will be consistent
【環境描述】
msyql5.6.14
【報錯信息】
mysql的slave啟動時，error.log中出現Warning警告：
[Warning] Slave SQL: If a crash happensthis configuration does not guarantee that the relay log info will beconsistent, Error_code: 0
這條Warning信息對Mysql和MySQL復制功能沒有任何影響。
【報錯原因】
MySQL5.6版本開始支持把master.info和relay-log.info的內容寫入到mysql庫的表中，
master.info--> mysql.slave_master_info
relay-log.info--> mysql. slave_relay_log_info
同時在MySQL5.6版本中，增加了 Slave crash-safe replication功能，為了保證mysql的replication能夠crash-safe，slave_master_info和slave_relay_log_info表必須使用事務型的存儲引擎（InnoDB），不要嘗試去手動修改這兩張表的內容。同時，Slave還要開啟relay_log_recovery功能。
【解決方法】
設置master_info_repository和relay_log_info_repository的值為TABLE，同時開啟relay_log_recovery功能。
修改/etc/my.cnf配置文件，添加以下3項：
master-info-repository=table # 可以使用set global 動態修改
relay-log-info-repository=table # 可以使用setglobal 動態修改
relay-log-recovery=1 # 只讀參數，必須修改my.cnf重啟mysql
然後重啟mysql實例。
【參考資料】
l master.info和relay-log.info日志
在復制的Slave節點上會創建兩個日志，分別是master.infor和relay-log.info，位於datadir目錄中。在MySQL5.6和後續的版本中，可以通過設置master-info-file和relay-log-info-file參數來指定寫入到mysql的表中或者寫入文件。
這兩個文件中包含一些類似showslave status輸出的信息，當slave啟動的時候會讀取master.info和relay-log.info文件來確定從master讀取binary log和讀取relay log的信息。
Slave的I/O線程負責更新維護master.info文件，
master.info
mysql.slave_master_info
SHOW SLAVE STATUS Column
Description
1
Number_of_lines
[None]
Number of lines in the file
2
Master_log_name
Master_Log_File
The name of the master binary log currently being read from the master
3
Master_log_pos
Read_Master_Log_Pos
The current position within the master binary log that have been read from the master
4
Host
Master_Host
The host name of the master
5
User
Master_User
The user name used to connect to the master
6
User_password
Password (not shown by SHOW SLAVE STATUS)
The password used to connect to the master
7
Port
Master_Port
The network port used to connect to the master
8
Connect_retry
Connect_Retry
The period (in seconds) that the slave will wait before trying to reconnect to the master
9
Enabled_ssl
Master_SSL_Allowed
Indicates whether the server supports SSL connections
10
Ssl_ca
Master_SSL_CA_File
The file used for the Certificate Authority (CA) certificate
11
Ssl_capath
Master_SSL_CA_Path
The path to the Certificate Authority (CA) certificates
12
Ssl_cert
Master_SSL_Cert
The name of the SSL certificate file
13
Ssl_cipher
Master_SSL_Cipher
The list of possible ciphers used in the handshake for the SSL connection
14
Ssl_key
Master_SSL_Key
The name of the SSL key file
15
Ssl_verify_server_cert
Master_SSL_Verify_Server_Cert
Whether to verify the server certificate
16
Heartbeat
[None]
Interval between replication heartbeats, in seconds
17
Bind
Master_Bind
Which of the slave's network interfaces should be used for connecting to the master
18
Ignored_server_ids
Replicate_Ignore_Server_Ids
The number of server IDs to be ignored, followed by the actual server IDs
19
Uuid
Master_UUID
The master's unique ID
20
Retry_count
Master_Retry_Count
Maximum number of reconnection attempts permitted Added in MySQL 5.6.1)
Slave的SQL線程負責維護relay-log.info文件，在MySQL5.6中relay-log.info包含文件中的記錄數和復制延遲的秒數。
relaylog.info
slave_relay_log_info
SHOW SLAVE STATUS
Description
1
Number_of_lines
[None]
Number of lines in the file or rows in the table
2
Relay_log_name
Relay_Log_File
The name of the current relay log file
3
Relay_log_pos
Relay_Log_Pos
The current position within the relay log file; events up to this position have been executed on the slave database
4
Master_log_name
Relay_Master_Log_File
The name of the master binary log file from which the events in the relay log file were read
5
Master_log_pos
Exec_Master_Log_Pos
The equivalent position within the master's binary log file of events that have already been executed
6
Sql_delay
SQL_Delay
The number of seconds that the slave must lag the master
設置master_info_repository和relay_log_info_repository參數：
SQL> stop slave;
SQL> set global master_info_repository=table;
SQL> set global relay_log_info_repository=table;
SQL> show variables like '%repository';
+--------------------------------------+---------+
| Variable_name | Value |
+--------------------------------------+---------+
| master_info_repository | TABLE |
| relay_log_info_repository | TABLE |
+--------------------------------------+----------+
查看向Master讀取日志的情況：
SQL> select * from slave_master_info;
查看Slave的Relay日志應用情況：
SQL> select * from slave_relay_log_info;
注意：
master.info和relay-log.info內的數據會有一定的延遲，取決於mysql把slave信息刷到硬盤的時間，如果要獲得slave的實時信息，可以查詢slave_master_info和slave_relay_log_info表，或者執行show slave status查看。
l master-info-repository
master-info-repository={ FILE | TABLE }，默認值是FILE，這個參數用於設置Slave節點上把master的信息寫入到物理文件中還是寫入到mysql. slave_master_info表中。
如果設置為FILE，也是mysql的默認設置，Slave會在datadir/master.info文件中記錄master的信息，從MySQL5.6版本開始，建議使用TABLE模式。
l relay-log-info-reposity
relay-log-info-reposity=file|table，默認值是FILE，這個參數用於設置slave節點上把relay-log.info的信息寫入到datadir/relay-log.info文件或者mysql. slave_relay_log_info表。
如果設置為FILE，也是mysql的默認設置，Slave會在datadir/master.info文件中記錄master的信息，從MySQL5.6版本開始，建議使用TABLE模式。
l relay-log-recovery
relay-log-recover=0|1，默認值是0不開啟，該參數用於設置是否開啟relay log的自動恢復功能。當開啟relay_log_recovery功能，slave數據庫在啟動的時候，會忽略未被執行的relay log，它會重新連接master獲取relay log來進行恢復。
當slave發生宕機的時候，建議開啟該功能，可以有效避免slave執行了relay log裡面的訛誤記錄。
如果開啟relay_log_recovery功能，必須同時把relay_log_info_reposity設置為TABLE模式。
