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使用pgpool-II进行postgresql的replication

最近一直研究postgresql,也想做一个像mysql一样的replication。 毕竟单台postgresql无论性能如何,总有撑不下去的时候。

网上查了下关于postgresql的一些资料,发现pg本身不带replication这个功能,master-slave也没有,但是一些第三方的软件可以支持这些,一开始发现slony似乎看着不错,但是配了一天发现这个东西配置实在是太复杂了,需要手动增加相关的库,以后增加新的也比较麻烦,而功能也比较单一。

后来问了下公司里来自yahoo的同事,发现yahoo是使用pgpool-II来实现的。找了下资料发现这个配置比较简单,基本是单个配置文件就可以搞定,而且有不同的conf.sample提供出来,有master-slave的config sample和replication的config sample.这样就节省了大量的时间了。

说下安装过程,还是比较简单。 安装时候需要指定一下postgresql的安装路径就可以了,其它没有特别的。

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 --with-pgsql= --with-pgsql-includedir= --with-pgsql-ibdir= 
```

安装完成后在安装目录的etc下有几个实例文件。里面说明的也比较清楚。下面修改的一个是监听端口,由于我不想改程序,所以就让pgpoo-II直接监听5432端口,这个也是postgresql的默认端口。另外一个是relication_mode=yes,这个一定要这样选。load_balance_mode = true 这个就随意了,这个就是把select查询分配到2个不同的机器上。

```c
# # pgpool-II configuration file sample # $Header: /cvsroot/pgpool/pgpool-II/pgpool.conf.sample,v 1.26 2009/02/15 05:26:28 t-ishii Exp $ # Host name or IP address to listen on: '*' for all, '' for no TCP/IP # connections listen_addresses = '192.168.100.1' # Port number for pgpool port = 5432 # Port number for pgpool communication manager pcp_port = 9898 # Unix domain socket path.  (The Debian package defaults to # /var/run/postgresql.) socket_dir = '/tmp' # Unix domain socket path for pgpool communication manager. # (Debian package defaults to /var/run/postgresql) pcp_socket_dir = '/tmp' # Unix domain socket path for the backend. Debian package defaults to /var/run/postgresql! backend_socket_dir = '/tmp' # pgpool communication manager timeout. 0 means no timeout, but strongly not recommended! pcp_timeout = 5 # number of pre-forked child process num_init_children = 32 # Number of connection pools allowed for a child process max_pool = 10 # If idle for this many seconds, child exits.  0 means no timeout. child_life_time = 300 # If idle for this many seconds, connection to PostgreSQL closes. # 0 means no timeout. connection_life_time = 0 # If child_max_connections connections were received, child exits. # 0 means no exit. child_max_connections = 0 # If client_idle_limit is n (n > 0), the client is forced to be # disconnected whenever after n seconds idle (even inside an explicit # transactions!) # 0 means no disconnect. client_idle_limit = 0 # Maximum time in seconds to complete client authentication. # 0 means no timeout. authentication_timeout = 10 # Logging directory logdir = '/tmp' # pid file name pid_file_name = '/tmp/pgpool.pid' # Replication mode replication_mode = true # Load balancing mode, i.e., all SELECTs are load balanced. # This is ignored if replication_mode is false. load_balance_mode = true # if there's a data mismatch between master and secondary # start degeneration to stop replication mode replication_stop_on_mismatch = false # If true, replicate SELECT statement when load balancing is disabled. # If false, it is only sent to the master node. replicate_select = false # Semicolon separated list of queries to be issued at the end of a session reset_query_list = 'ABORT; RESET ALL; SET SESSION AUTHORIZATION DEFAULT' # for 8.3 or newer PostgreSQL versions DISCARD ALL can be used as # follows. However beware that DISCARD ALL holds exclusive lock on # pg_listener so it will be a serious performance problem if there are # lots of concurrent sessions. # reset_query_list = 'ABORT; DISCARD ALL' # If true print timestamp on each log line. print_timestamp = true # If true, operate in master/slave mode. master_slave_mode = false # If true, cache connection pool. connection_cache = true # Health check timeout.  0 means no timeout. health_check_timeout = 20 # Health check period.  0 means no health check. health_check_period = 0 # Health check user health_check_user = 'nobody' # Execute command by failover. # special values:  %d = node id #                  %h = host name #                  %p = port number #                  %D = database cluster path #                  %m = new master node id #                  %M = old master node id #                  %% = '%' character # failover_command = '' # Execute command by failback. # special values:  %d = node id #                  %h = host name #                  %p = port number #                  %D = database cluster path #                  %m = new master node id #                  %M = old master node id #                  %% = '%' character # failback_command = '' # If true, automatically locks a table with INSERT statements to keep # SERIAL data consistency.  If the data does not have SERIAL data # type, no lock will be issued. An /\*INSERT LOCK\*/ comment has the # same effect.  A /NO INSERT LOCK*/ comment disables the effect. insert_lock = true # If true, ignore leading white spaces of each query while pgpool judges # whether the query is a SELECT so that it can be load balanced.  This # is useful for certain APIs such as DBI/DBD which is known to adding an # extra leading white space. ignore_leading_white_space = true # If true, print all statements to the log.  Like the log_statement option # to PostgreSQL, this allows for observing queries without engaging in full # debugging. log_statement = true # If true, incoming connections will be printed to the log. log_connections = true # If true, hostname will be shown in ps status. Also shown in # connection log if log_connections = true. # Be warned that this feature will add overhead to look up hostname. log_hostname = true # if non 0, run in parallel query mode parallel_mode = false # if non 0, use query cache enable_query_cache = false #set pgpool2 hostname pgpool2_hostname = '' # system DB info system_db_hostname = '192.168.100.1' system_db_port = 5433 system_db_dbname = 'pgpool' system_db_schema = 'pgpool_catalog' system_db_user = 'pgpool' system_db_password = '' # backend_hostname, backend_port, backend_weight # here are examples backend_hostname0 = '192.168.100.1' backend_port0 = 5433 backend_weight0 = 1 #backend_data_directory0 = '/data' backend_hostname1 = '192.168.100.2' backend_port1 = 5432 backend_weight1 = 1 #backend_data_directory1 = '/data1' # - HBA - # If true, use pool_hba.conf for client authentication. In pgpool-II # 1.1, the default value is false. The default value will be true in # 1.2. enable_pool_hba = false # - online recovery - # online recovery user recovery_user = 'nobody' # online recovery password recovery_password = '' # execute a command in first stage. recovery_1st_stage_command = '' # execute a command in second stage. recovery_2nd_stage_command = '' # maximum time in seconds to wait for the recovering node's postmaster # start-up. 0 means no wait. # this is also used as a timer waiting for clients disconnected before # starting 2nd stage recovery_timeout = 90 # If client_idle_limit_in_recovery is n (n > 0), the client is forced # to be disconnected whenever after n seconds idle (even inside an # explicit transactions!)  0 means no disconnect. This parameter only # takes effect in recovery 2nd stage. client_idle_limit_in_recovery = 0
```

启动也简单

```c
pgpool -n -d > /tmp/pgpool.log 2>&1
```

关闭也很容易

```c
pgpool stop
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