Replication Tips & Tricks

Program Agenda  Replication setup and status checking  Binary log analysis  Crash-safe slaves  Multi-source replication  Slave fail-over using GTID3 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

About the Presentation This presentation will introduce you to some replication features and also briefly show tips and tricks on how to work with replication. The focus is on short ideas and each item does not go deeper into details.4 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Reading Slave Status Understanding the fields of SHOW SLAVE STATUS ● I/O Thread Status ● SQL Thread Status – Slave_IO_Running – Slave_SQL_Running – Last_IO_Errno – Last_SQL_Errno – Last_IO_Error – Last_SQL_Error – Last_IO_Error_Timestamp – Last_SQL_Error_Timestamp ● Master being replicated from – Master_Host – Master_Port6 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Reading Slave Status Understanding the fields of SHOW SLAVE STATUS ● Next event to execute – in master log coordinates – Relay_Master_Log_File + Exec_Master_Log_Pos ● Next event to execute – in relay log coordinates Relay_Log_File + Relay_Log_Pos ● Next event to read from master Master_Log_File + Read_Master_Log_Pos7 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Reading the Binary Log Decoding the binary log ● Use mysqlbinlog --hexdump Show hex dump of event as comment --start-position Start dumping at a position --stop-position Stop dumping after this position # at 275 175 =373 16 10 #120927 23:11:58 server id 3 end_log_pos 373 # Position Timestamp Type Master ID Size Master Pos Flags # 113 1e c1 64 50 02 03 00 00 00 62 00 00 00 75 01 00 00 00 00 Little-endian Query8 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Reading the Binary Log Decoding the binary log # at 275 #120927 23:11:58 server id 3 end_log_pos 373 # Position Timestamp Type Master ID Size Master Pos Flags # 113 1e c1 64 50 02 03 00 00 00 62 00 00 00 75 01 00 00 00 00 # 126 c5 03 00 00 00 00 00 00 04 00 00 1a 00 00 00 00 |................| # 136 00 00 01 00 00 00 00 00 00 00 00 06 03 73 74 64 |.............std| # 146 04 21 00 21 00 08 00 74 65 73 74 00 69 6e 73 65 |.......test.inse| # 156 72 74 20 69 6e 74 6f 20 74 32 20 76 61 6c 75 65 |rt.into.t2.value| # 166 73 20 28 31 2c 27 74 65 73 74 69 6e 67 27 29 |s..1..testing..| # Query thread_id=965 exec_time=0 error_code=0 SET TIMESTAMP=1348780318/*!*/; insert into t2 values (1,testing) /*!*/;9 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Reading the Binary Log Decode row events ● Use mysqlbinlog --verbose Decode row events into pseudo-SQL # at 849 # at 893 #120928 15:19:24 server id 3 end_log_pos 893 Table_map: `test`.`t2` mapped to number 48 #120928 15:19:24 server id 3 end_log_pos 941 Write_rows: table id 48 flags: STMT_END_F BINLOG 3KNlUBMDAAAALAAAAH0DAAAAADAAAAAAAAEABHRlc3QAAnQyAAIDDwIoAAM= 3KNlUBcDAAAAMAAAAK0DAAAAADAAAAAAAAEAAv/8AwAAAA1yb3dzIGFyZSBjb29s /*!*/;10 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Reading the Binary Log Decode row events ● Use mysqlbinlog --verbose Decode row events into pseudo-SQL # at 849 # at 893 #120928 15:19:24 server id 3 end_log_pos 893 Table_map: `test`.`t2` mapped to number 48 #120928 15:19:24 server id 3 end_log_pos 941 Write_rows: table id 48 flags: STMT_END_F BINLOG 3KNlUBMDAAAALAAAAH0DAAAAADAAAAAAAAEABHRlc3QAAnQyAAIDDwIoAAM= 3KNlUBcDAAAAMAAAAK0DAAAAADAAAAAAAAEAAv/8AwAAAA1yb3dzIGFyZSBjb29s /*!*/; ### INSERT INTO test.t2 ### SET ### @1=3 ### @2=rows are cool11 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Cloning a Slave Creating a slave image 1. Stop the slave 2. Write down where slave has stopped – SHOW SLAVE STATUS – Relay_Master_Log_File + Exec_Master_Log_Pos 3. Backup slave – mysqldump – slow but safe – Physical file copy – fast but you need to shut down the server12 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Cloning a Slave Setting up the new slave 4. Restore backup on new slave 5. Direct the slave to the master – CHANGE MASTER – Master_Host + Master_Port – Relay_Master_Log_File + Exec_Master_Log_Pos 6. Start slave – START SLAVE13 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Cloning a Slave The easy way – using MySQL Utilities ● Using mysqldbcopy mysqldbcopy replication=slave locking=snapshot source=root:pass@master.example.com destination=root:pass@slave.example.com database ...14 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Cloning a Slave The easy way – using MySQL Utilities ● Using mysqldbcopy mysqldbcopy replication=slave locking=lockall source=root:pass@master.example.com destination=root:pass@slave.example.com database ...15 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Point in time recovery ● Use mysqlbinlog --to-datetime Stop reading when reaching date ● Example mysqlbinlog --read-from-remote-server e --host=master -uroot --position=192 ar ! --to-datetime=”2009-04-11 12:36:56” ps ing am reas st master-bin.00002[2-4] | e nc mysql -uroot --host=slave tim lly i : a ing ic r n ot on W a on m not16 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Using Relay Servers ● Relieve master server by creating relay slaves ● Just keep binary logs ● Do not store data in tables – Use BLACKHOLE engine – --log-slave-updates SET STORAGE_ENGINE = BLACKHOLE ALTER TABLE table ENGINE = BLACKHOLE17 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Using Relay Servers replicate-wild-do-table-wild=*.%_east replicate-wild-do-table-wild=*.%_west ● Filtering replication stream ● Filtering done on relay servers ● replicatewild*table – Work with cross-database queries18 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Write Your Own Library Write your own utility library ● Create a utility library to easier work with replication ● Common functions to manage replication: – Start/stop slave – Change master – Fetch master position – Fetch slave execute/read position – Fetch master host information19 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Write Your Own Library Basic functions using Bourne shell # Usage: mysql_exec socket sql ... # Usage: stop_slave socket [ thread ] mysql_exec () { stop_slave () { sock=$1 mysql_exec $1 STOP SLAVE $2 shift 1 } mysql uroot vertical batch skipcolumnnames # Usage: start_slave socket [ thread ] socket="$sock" start_slave () { exec "$*" mysql_exec $1 START SLAVE $2 } }20 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Write Your Own Library Basic functions using Bourne shell # Usage: change_master socket [ host [ port [ file [ pos ] ] ] ] change_master () { host=${2:+MASTER_HOST=$2} port=${3:+,MASTER_PORT=$3} file=${4:+,MASTER_LOG_FILE=$4} pos=${5:+,MASTER_LOG_POS=$5} mysql_exec $1 CHANGE MASTER TO $host $port $file $pos } # Usage: fetch_master_pos socket fetch_master_pos () { mysql_exec $1 SHOW MASTER STATUS | grep <File|<Pos | cut f2 d: }21 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Write Your Own Library Basic functions using Bourne shell # Usage: fetch_slave_exec_pos socket fetch_slave_exec_pos () { mysql_exec $1 SHOW SLAVE STATUS | grep <Relay_Master_Log_File|<Exec_Master_Log_Pos | cut f2 d: } # Usage: fetch_slave_read_pos socket fetch_slave_read_pos () { mysql_exec $1 SHOW SLAVE STATUS | grep <Master_Log_File|<Read_Master_Log_Pos | cut f2 d: }22 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

master1.example.com master2.example.com Round-Robin Replication ● Slave can only replicate from single master at a time ● Use time sharing to replicate from several masters Stop Switcher Start Save slave1.example.com Restore23 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Round-Robin Replication A version using Bourne Shell # Usage: fetch_host_and_pos socket fetch_host_and_pos () { mysql_exec $1 SHOW SLAVE STATUS | grep <Master_(Host|Port|Log_File)|<Read_Master_Log_Pos | cut -f2 -d: } # Usage: stop_and_save socket stop_and_save () { sock="/var/run/mysqld/$1.sock" stop_slave $socket fetch_host_and_pos $sock >$1.savepos }24 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Round-Robin Replication A version using Bourne Shell restore_and_start () { cnt=1 socket="/var/run/mysqld/$1.sock" while true cat $1.savepos | { do read host stop_and_save mysqld.$cnt read port cnt=`expr $cnt % 5 + 1` read file restore_and_start mysqld.$cnt read pos sleep 60 change_master $socket done $host $port $file $pos start_slave $socket } }25 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Crash-safe Slaves Keeping replication information in sync with data FILE TABLE ● Traditional Replication – Position stored in file – Update after transaction – Crash can lose update ● Transactional Replication ● Repository location FILE or TABLE – Positions stored in table master_info_repository – Update part of transaction relay_log_info_repository – Crash-safe26 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Crash-safe Slaves Steps to set up crash-safe slaves ● Direct server to use table-based repository – Defaults to FILE master_info_repository=TABLE relay_log_info_repository=TABLE ● Ensure that a transactional engine is used – InnoDB default since 5.6.6 – Before 5.6.6: set the storage engine ALTER TABLE slave_master_info ENGINE = InnoDB ALTER TABLE slave_relay_log_info ENGINE = InnoDB27 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Round-Robin Replication A version using pure SQL CREATE TABLE my_masters ( CREATE TABLE current_master ( idx INT PRIMARY KEY, idx INT host CHAR(50) NOT NULL, ) ENGINE=InnoDB port INT NOT NULL DEFAULT 3306, log_file CHAR(50), log_pos LONG, UNIQUE INDEX (host,port,user) ) ENGINE=InnoDB CREATE PROCEDURE save_position() BEGIN DECLARE l_idx INT UNSIGNED; UPDATE my_masters AS mi, mysql.slave_relay_log_info AS rli SET mi.log_pos = rli.master_log_pos, mi.log_file = rli.master_log_name WHERE idx = (SELECT idx FROM current_master); END28 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Round-Robin Replication In pure SQL CREATE PROCEDURE fetch_next_master(OUT p_host CHAR(50), OUT p_port INT UNSIGNED, OUT p_file CHAR(50), OUT p_pos BIGINT) BEGIN DECLARE l_next_idx INT DEFAULT 1; SELECT idx INTO l_next_idx FROM my_masters Select next index, WHERE idx > (SELECT idx FROM current_master) if there is one ORDER BY idx LIMIT 1; SELECT idx INTO l_next_idx FROM my_masters Select the first index, if WHERE idx >= l_next_idx ORDER BY idx LIMIT 1; there were no next index UPDATE current_master SET idx = l_next_idx; SELECT host, port, log_file, log_pos Fetch master info using INTO p_host, p_port, p_file, p_pos FROM my_masters WHERE idx = l_next_idx; the index END29 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Round-Robin Replication In pure SQL CREATE EVENT multi_source ON SCHEDULE EVERY 10 SECOND DO BEGIN DECLARE l_host CHAR(50); DECLARE l_port INT UNSIGNED; DECLARE l_file CHAR(50); DECLARE l_pos BIGINT; SET SQL_LOG_BIN = 0; STOP SLAVE; START TRANSACTION; CALL save_current_position(); CALL fetch_next_master(l_host, l_port, l_file, l_pos); CALL change_master(l_host, l_port, repl_user, xyzzy, l_file, l_pos); COMMIT; START SLAVE; END30 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Different Tables on Master and Slave ● Upgrading – Example: Upgrading a topology without downtime ● Saving space – Not keeping big columns on slave ● Hiding data – Keeping data away from users – Note: still available in binary log and relay log – just not applied to table ● Debugging and Auditing – Adding data for auditing31 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Different Tables on Master and Slave More columns on slave CREATE TABLE employee ( name CHAR(40), Master CREATE TABLE employee ( name CHAR(40), Slave email CHAR(40) email CHAR(40), changed TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP ) ) ● Same initial columns ● Statement-based or row-based replication32 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Different Tables on Master and Slave More columns on master CREATE TABLE employee ( CREATE TABLE employee ( name CHAR(40), name CHAR(40), email CHAR(40), email CHAR(40), password CHAR(40) password CHAR(40) ) Master ) Slave ● Same initial columns ● Row-based replication only33 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Different Tables on Master and Slave Different types of columns on master and slave CREATE TABLE employee ( CREATE TABLE employee ( emp_id INT, emp_id TINYINT, name CHAR(40), name CHAR(40), email CHAR(40) email CHAR(40) ) Master ) Slave ● Table definitions are identical … except that some column type are different34 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Different Tables on Master and Slave Slave type conversions CREATE TABLE employee ( CREATE TABLE employee ( emp_id INT, emp_id TINYINT, name CHAR(40), name CHAR(40), email CHAR(40) email CHAR(40) ) Master ) Slave ● Consider this statement: St at em INSERT INTO employee VALUES Re ent Works fine (1, Bob, bob@example.com), pl -b ica a (500, Alice, alice@example.com) tio sed Fails silently! n35 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Different Tables on Master and Slave Slave type conversions CREATE TABLE employee ( CREATE TABLE employee ( emp_id TINYINT, emp_id INT, name CHAR(40), name CHAR(40), email CHAR(40) email CHAR(40) ) Master ) Slave ● Consider this statement: Ro w Re -ba pl INSERT INTO employee VALUES ica sed tio Throws an error! (1, Bob, bob@example.com), n (100, Alice, alice@example.com)36 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Different Tables on Master and Slave Slave type conversions ● @@GLOBAL.SLAVE_TYPE_CONVERSIONS – Type: SET(ALL_LOSSY, ALL_NON_LOSSY) – Require slave restart ● Lossy conversions ● Non-lossy conversions – INT → TINYINT – TINYINT → INT – CHAR(64) → VARCHAR(32) – VARCHAR(32) → CHAR(64) – DOUBLE → FLOAT – FLOAT → DOUBLE37 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Different Tables on Master and Slave Slave type conversions ● Conversions within same domain possible – INT, TINYINT, SMALLINT, MEDIUMINT, BIGINT – CHAR(n), VARCHAR(n), TINYTEXT, TEXT, … – DECIMAL(n,m), DOUBLE, FLOAT ● ALL_NON_LOSSY in SLAVE_TYPE_CONVERSIONS – Conversion to larger domains allowed ● ALL_LOSSY in SLAVE_TYPE_CONVERSIONS – Conversion to smaller domains allowed (truncation/rounding may occur)38 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Different Tables on Master and Slave Slave type conversions CREATE TABLE employee ( CREATE TABLE employee ( emp_id TINYINT, emp_id INT, name VARCHAR(40), name VARCHAR(40), email VARCHAR(40) email VARCHAR(40) ) Master ) Slave ● Consider this statement: Ro w Re -ba pl ica sed INSERT INTO employee VALUES (1, Bob, bob@example.com), tio Works fine! (100, Alice, alice@example.com) n SLAVE_TYPE_CONVERSIONS = ALL_NON_LOSSY39 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Different Tables on Master and Slave Slave type conversions CREATE TABLE employee ( CREATE TABLE employee ( emp_id INT, emp_id TINYINT, name VARCHAR(40), name VARCHAR(40), email VARCHAR(40) email VARCHAR(40) ) Master ) Slave ● Consider this statement: Ro w Re -ba pl ica sed INSERT INTO employee VALUES (1, Bob, bob@example.com), tio Throws an error! (100, Alice, alice@example.com) n SLAVE_TYPE_CONVERSIONS = ALL_NON_LOSSY40 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Master and Slave out of sync ● Slave stopped with a strange error ERROR 1062 (23000): Duplicate entry 3 for key PRIMARY ● Compare two databases using mysqldbcompare mysqldbcompare --server1=root@master.example.com --server2=root@slave1.example.com employee41 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Master and Slave out of sync Comparing two databases and finding the differences $ mysqldbcompare --quiet --server1=root@localhost:3309 --server2=root@localhost:3310 world # Checking databases world on server1 and world on server2 # # # Data differences found among rows: --- world.City +++ world.City @@ -1,5 +1,5 @@ -+-------+------------+--------------+-----------+-------------+ -| ID | Name | CountryCode | District | Population | -+-------+------------+--------------+-----------+-------------+ -| 3048 | Stockholm | SWE | Lisboa | 750348 | -+-------+------------+--------------+-----------+-------------+ ++-------+-----------+--------------+-----------+-------------+ +| ID | Name | CountryCode | District | Population | ++-------+-----------+--------------+-----------+-------------+ +| 3048 | Helsinki | SWE | Lisboa | 750348 | ++-------+-----------+--------------+-----------+-------------+42 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Master and Slave out of sync Synchronizing master and slave databases $ mysqldbcompare --quiet --difftype=sql --changes-for=server2 > --server1=root@master.example.com --server2=root@slave1.example.com > world # Checking databases world on server1 and world on server2 # # # Transformation for --changes-for=server2: # # Data differences found among rows: UPDATE world.City SET Name = Stockholm WHERE ID = 3048;43 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Master and Slave out of sync Synchronizing master and slave databases $ mysqldbcompare --quiet --difftype=sql --changes-for=server1 > --server1=root@master.example.com --server2=root@slave1.example.com > world # Checking databases world on server1 and world on server2 # # # Transformation for --changes-for=server1: # # Data differences found among rows: UPDATE world.City SET Name = Helsinki WHERE ID = 3048;44 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Replication Event Checksums Configurations and options ● Controlling checksum generation (default is CRC32 since 5.6.6) SET GLOBAL BINLOG_CHECKSUM = CRC32 ● Enable verification on events read by dump thread SET GLOBAL MASTER_VERIFY_CHECKSUM = ON ● Enable verification on events read by SQL thread SET GLOBAL SLAVE_SQL_VERIFY_CHECKSUM = ON46 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Using Global Transaction ID for Fail-over Handling positions in MySQL 5.5 ● Binary log positions manually handled ● Each server has its own position ● Failing over slaves to new masters difficult – What is the position to fail over to? CHANGE MASTER TO MASTER_HOST=master1.example.com, MASTER_PORT=3306, MASTER_USER=repl_user, MASTER_PASSWORD=xyzzy, MASTER_LOG_FILE=master-bin.00001, MASTER_LOG_POS=22145; Different for different servers47 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Using Global Transaction ID for Fail-over Enabling Global Transaction IDs ● MySQL 5.6 has Global Transaction ID [mysqld] – Positions independent of server … gtid-mode=on ● GTID handshake disable-gtid-unsafe-statements – Done on connection with master log-bin=master-bin – Negotiate position automatically log-slave-updates CHANGE MASTER TO MASTER_HOST=master1.example.com, MASTER_PORT=3306, MASTER_USER=repl_user, MASTER_PASSWORD=xyzzy, MASTER_LOG_FILE=master-bin.00001, MASTER_LOG_POS=22145; MASTER_AUTO_POSITION=1;48 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Using Global Transaction ID for Fail-over Failing over to a new master ● Failing over slave to another master – Switch over – old master server is online – Fail over – old master server is down ● GTID handshake – Automatically done when changing master STOP SLAVE; CHANGE MASTER TO MASTER_HOST=master2.example.com, MASTER_PORT=3306; START SLAVE;49 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

The preceding is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle.50 Copyright © 2012, Oracle and/or its affiliates. All rights reserved.

Replication Tips & Tricks

by Mats Kindahl on Sep 30, 2012

Accessibility

Categories

Upload Details

Usage Rights

1 Embed 1

Statistics

Replication Tips & Tricks Presentation Transcript