Memcached Replication (3)

This is the last article about Memcached Replication.If you missed previous two article, Read below article first for understanding.

1. http://seonguck.blogspot.kr/2014/06/memcached-replication-1.html

1. http://seonguck.blogspot.kr/2014/06/memcached-replication-2.html 

Install

Download KMC source first from GitHub.
https://github.com/kakao/mysql_5.6.14_kmc

To build KMC, you need to install basic library needed for MySQL 5.6.
Especially there's a lot of system which lack of libaio-devel and ncurses-devel and cmake.
And you need to install libmemcached library and development package.

libmemcached-1.0.4-1.el5.remi.x86_64.rpm
libmemcached-devel-1.0.4-1.el5.remi.x86_64.rpm

Now you can build KMC, you should run cmake with a few options.

# cd mysql-5.6.14_kmc
# mkdir Release
# cd Release
# cmake .. \
'-DBUILD_CONFIG=mysql_release' \
'-DCMAKE_INSTALL_PREFIX=/usr/local/mysql' \
'-DWITH_INNODB_MEMCACHED=ON' \
'-DENABLED_LOCAL_INFILE=OFF' \
'-DHAVE_QUERY_CACHE=OFF' \
'-DOPTIMIZER_TRACE=OFF' \
'-DENABLE_DEBUG_SYNC=OFF' \
'-DENABLED_PROFILING=OFF' \
'-DWITH_ARCHIVE_STORAGE_ENGINE=OFF' \
'-DWITH_EMBEDDED_SERVER=OFF' \
'-DENABLE_DTRACE=OFF'

Of course you don't need to all options, but you should put "DWITH_INNODB_MEMCACHED" for Memcached plugin of MySQL.
After cmake, just run make && make install. After installing you can find built MySQL executables in the directory you specified as INSTALL_PREFIX.
Before starting MySQL server, you should run $MYSQL_HOME/scripts/mysql_install_db script to create default dictionary schema as normal MySQL server.

Creating Memcached related schema.

After starting MySQL server, you should create Memcached related schema to activate Memcached plugin.
Initialization script is located in your MySQL home directory. Just run it.
Actually this procedure also need to original MySQL Memcached plugin not only for KMC. 

mysql> source $MYSQL_HOME/share/innodb_memcached_config.sql
mysql> use innodb_memcache
mysql> show tables

Check below three tables have created in innodb_memcache database.

• cache_policies
• config_options
• containers

Now we need to initialize KMC basic schema.

mysql> USE innodb_memcache;
mysql> INSERT INTO `containers` VALUES ('default','kmc','kmc_template','k','v','f','c','e','PRIMARY');

mysql> CREATE DATABASE kmc;
mysql> USE kmc;

mysql> DROP TABLE IF EXISTS `kmc_template`;
mysql> CREATE TABLE `kmc_template` (
  `k` varchar(255) CHARACTER SET latin1 COLLATE latin1_bin NOT NULL DEFAULT '',
  `v` mediumblob,
  `f` int(11) NOT NULL DEFAULT '0',
  `c` bigint(20) unsigned NOT NULL DEFAULT '0',
  `e` int(11) NOT NULL DEFAULT '0',
  PRIMARY KEY (`k`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 STATS_PERSISTENT=0;

## Don't need this default row anymore, But I am not sure.
mysql> INSERT INTO `kmc_template` VALUES ('1','DO-NOT-REMOVE',0,0,0);

On this procedure, table name must start with "kmc_" prefix.

Configurations

Lastly change my.cnf configuration file for KMC. Below options are not only for KMC but also memcached performance.
We don't use KMC as InnoDB or MyISAM engine together. So I changed InnoDB options minimally.
This is not so strict options(except kmc_connect_string and binlog-format), so you can change it for your system standardizations.

## InnoDB ------------------------
...
innodb_data_file_path = ibdata1:64M:autoextend
...
innodb_log_file_size = 32M
innodb_log_files_in_group = 2
innodb_log_buffer_size = 16M

## Memcached --------------------
daemon_memcached_option = '-m 20480 -p 11211 -c 80000 -t 8 -s /tmp/memcached.sock'
innodb_api_enable_binlog = 1
innodb_api_trx_level=0 ## READ-UNCOMMITTED
innodb_api_bk_commit_interval=1
daemon_memcached_r_batch_size=1
daemon_memcached_w_batch_size=1
innodb_api_enable_mdl=OFF

## Replication:Binary log -----------
server-id  = 1
## Replication query is always idempotent
slave_exec_mode = IDEMPOTENT
## Memcached connection string :: with socket file
kmc_connect_string = '--SOCKET="/tmp/memcached.sock" --BINARY-PROTOCOL --NOREPLY --TCP-NODELAY --TCP-KEEPALIVE'
binlog-checksum = NONE
sync_binlog = 0
master_info_repository = FILE
relay_log_info_repository = FILE
sync_master_info    = 0
sync_relay_log      = 0
sync_relay_log_info = 0
slave_checkpoint_group = 100000
slave_checkpoint_period = 1000
max_binlog_size = 100M
expire_logs_days=1
expire_max_log_files = 15
binlog-format = ROW

daemon_memcached_option is Memcached plugin startup options and kmc_connect_string option is for SQL thread of slave MySQL server.
Now starting MySQL server and check the basic function on.
And you can check replication setup and the way to check replication status out is same as original MySQL server.

Testing Memcached and Replication

MySQL Memcached plugin support both binary and text mode protocol, so we can simply test memcached operation with telnet program.

[root@matt001 ~]# telnet localhost 11211
Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.

set matt 0 0 9
Seong Uck
STORED

get matt
VALUE matt 0 9
Seong Uck
END

delete matt
DELETED

get matt
END

quit
Connection closed by foreign host.

If you want to check whether socket file(/tmp/memcached.sock) is working correctly, you can use netcat utility. In this case you can't use telnet.

[root@matt001 ~]# nc -U /tmp/memcached.sock
set matt 0 0 9
SEONG UCK
STORED

get matt
VALUE matt 0 9
SEONG UCK
END

quit
[root@matt001 ~]#

If you want to check the replicated data, run GET operation on slave memcached after run SET on master memcached.
Of course you can inspect the binary log file through mysqlbinlog utility.



Memcached replication feature(Added feature) does't have unit test yet. So you should be carefull.