PostgreSQL的HA解决方案-2负载均衡（load balance）
一.部署说明
1.1 实施环境
本文档实验环境如下：
PGSQL主机: 192.168.1.45
PGSQL备机: 192.168.1.50
软件和系统版本
Pgsql 版本: pgsql 9.2.4
Linux 版本: Redhat 5.8
pgpool版本：pgpool-II version 3.3.4 (tokakiboshi)
1.2 文档说明
在postgresql 的stream replication配置一文我们实现了postgresql的stream replication，实现了postgresql的热备。而实际生产中集群的目的之一就是负载均衡。那我们系统为例，刚开始java程序需要修改数据源，将查询的压力分担给从机，对数据的修改设置为主机。但是这种方式不灵活，负载不能均衡，并且比较麻烦。所以如果此时有一个路由控制器多好，可以根据请求将请求分发给不同的数据库。刚好，pgpoool就是这么一个中间件，负责与数据库集群交互，对外提供统一的访问接口，使得程序对数据库的访问变得简单，提高整个系统的性能。本文主要配置pgpool的负载均衡，是在上篇博文：PostgreSQL的HA解决方案-1主从和备份（master/slave and backup） 的基础之上配置的。
为了试验减少不必要的麻烦，本系列试验中，各个主机之间的通信，都是设置为无密码访问，且关闭主从的防火墙，但对于实际生产，需要根据实际需要，配置密码，增强集群的安全性。
二.配置步骤
1.1 源码安装pgpool。参考中文手册：http://pgpool.projects.pgfoundry.org/pgpool-II/doc/pgpool-zh_cn.html#install。
1.2 安装pgpool中提供的工具。安装 pgpool_regclass。注意 pgpool_regclass是在你解压pgpool后的目录中的sql目录下，而不是你的安装目录。
pgpool_regclass主要作用是，方便在数据库查询中，查询关于pgpool的的配置参数，监控信息等，请仔细阅读中文手册。应在在每台通过 pgpool-II 访问的数据库中执行 pgpool-regclass.sql。你不需要在你执行“psql -f pgpool-regclass.sql template1”后建立的数据库中这么做，因为这个模板数据库将被克隆成新建的数据库。
- cd pgpool-II-x.x.x/sql/pgpool-regclass
- make
- make install
- psql -f pgpool-regclass.sql template1
安装之后，再在/usr/local/pgsql/share/extension/目录下多出如下文件：
- -rw-r--r-- root root Sep : pgpool_regclass.control
- -rw-r--r-- root root Sep : pgpool_regclass--1.0.sql
- -rw-r--r-- root root Sep : pgpool-regclass.sql
1.3 配置pgpool的配置文件。
主要配置：
- listen_addresses="*"
- port=
- backend_hostname0="localhost"
- backend_port0=""
- backend_weight0=
- backend_hostname1="192.168.57.175"
- backend_port1=""
- backend_weight1=
- replication_mode=off
- load_balance_mode=on
- master_slave_mode=on
- master_save_sub_mode="stream"
- parallel_mode=off
详细配置：
- # ----------------------------
- # pgPool-II configuration file
- # ----------------------------
- #
- # This file consists of lines of the form:
- #
- # name = value
- #
- # Whitespace may be used. Comments are introduced with "#" anywhere on a line.
- # The complete list of parameter names and allowed values can be found in the
- # pgPool-II documentation.
- #
- # This file is read on server startup and when the server receives a SIGHUP
- # signal. If you edit the file on a running system, you have to SIGHUP the
- # server for the changes to take effect, or use "pgpool reload". Some
- # parameters, which are marked below, require a server shutdown and restart to
- # take effect.
- #
- #------------------------------------------------------------------------------
- # CONNECTIONS
- #------------------------------------------------------------------------------
- # - pgpool Connection Settings -
- #listen_addresses = 'localhost'
- listen_addresses = '*'
- # Host name or IP address to listen on:
- # '*' for all, '' for no TCP/IP connections
- # (change requires restart)
- port =
- # Port number
- # (change requires restart)
- socket_dir = '/tmp'
- # Unix domain socket path
- # The Debian package defaults to
- # /var/run/postgresql
- # (change requires restart)
- # - pgpool Communication Manager Connection Settings -
- pcp_port =
- # Port number for pcp
- # (change requires restart)
- pcp_socket_dir = '/tmp'
- # Unix domain socket path for pcp
- # The Debian package defaults to
- # /var/run/postgresql
- # (change requires restart)
- # - Backend Connection Settings -
- #backend_hostname0 = 'host1'
- backend_hostname0 = '192.168.1.45'
- # Host name or IP address to connect to for backend
- backend_port0 =
- # Port number for backend
- backend_weight0 =
- # Weight for backend (only in load balancing mode)
- #backend_data_directory0 = '/data'
- # Data directory for backend
- backend_flag0 = 'ALLOW_TO_FAILOVER'
- # Controls various backend behavior
- # ALLOW_TO_FAILOVER or DISALLOW_TO_FAILOVER
- backend_hostname1 = '192.168.1.50'
- backend_port1 =
- backend_weight1 =
- #backend_data_directory1 = '/data1'
- backend_flag1 = 'ALLOW_TO_FAILOVER'
- # - Authentication -
- enable_pool_hba = on
- # Use pool_hba.conf for client authentication
- pool_passwd = 'pool_passwd'
- # File name of pool_passwd for md5 authentication.
- # "" disables pool_passwd.
- # (change requires restart)
- authentication_timeout =
- # Delay in seconds to complete client authentication
- # means no timeout.
- # - SSL Connections -
- ssl = off
- # Enable SSL support
- # (change requires restart)
- #ssl_key = './server.key'
- # Path to the SSL private key file
- # (change requires restart)
- #ssl_cert = './server.cert'
- # Path to the SSL public certificate file
- # (change requires restart)
- #ssl_ca_cert = ''
- # Path to a single PEM format file
- # containing CA root certificate(s)
- # (change requires restart)
- #ssl_ca_cert_dir = ''
- # Directory containing CA root certificate(s)
- # (change requires restart)
- #------------------------------------------------------------------------------
- # POOLS
- #------------------------------------------------------------------------------
- # - Pool size -
- num_init_children =
- # Number of pools
- # (change requires restart)
- max_pool =
- # Number of connections per pool
- # (change requires restart)
- # - Life time -
- child_life_time =
- # Pool exits after being idle for this many seconds
- child_max_connections =
- # Pool exits after receiving that many connections
- # means no exit
- connection_life_time =
- # Connection to backend closes after being idle for this many seconds
- # means no close
- client_idle_limit =
- # Client is disconnected after being idle for that many seconds
- # (even inside an explicit transactions!)
- # means no disconnection
- #------------------------------------------------------------------------------
- # LOGS
- #------------------------------------------------------------------------------
- # - Where to log -
- log_destination = 'stderr'
- # Where to log
- # Valid values are combinations of stderr,
- # and syslog. Default to stderr.
- # - What to log -
- print_timestamp = on
- # Print timestamp on each line
- # (change requires restart)
- log_connections = on
- # Log connections
- log_hostname = on
- # Hostname will be shown in ps status
- # and in logs if connections are logged
- log_statement = on
- # Log all statements
- log_per_node_statement = off
- # Log all statements
- # with node and backend informations
- log_standby_delay = 'none'
- # Log standby delay
- # Valid values are combinations of always,
- # if_over_threshold, none
- # - Syslog specific -
- syslog_facility = 'LOCAL0'
- # Syslog local facility. Default to LOCAL0
- syslog_ident = 'pgpool'
- # Syslog program identification string
- # Default to 'pgpool'
- # - Debug -
- debug_level =
- # Debug message verbosity level
- # means no message, or more mean verbose
- #------------------------------------------------------------------------------
- # FILE LOCATIONS
- #------------------------------------------------------------------------------
- pid_file_name = '/var/run/pgpool/pgpool.pid'
- # PID file name
- # (change requires restart)
- logdir = '/tmp'
- # Directory of pgPool status file
- # (change requires restart)
- #------------------------------------------------------------------------------
- # CONNECTION POOLING
- #------------------------------------------------------------------------------
- connection_cache = on
- # Activate connection pools
- # (change requires restart)
- # Semicolon separated list of queries
- # to be issued at the end of a session
- # The default is for 8.3 and later
- reset_query_list = 'ABORT; DISCARD ALL'
- # The following one is for 8.2 and before
- #reset_query_list = 'ABORT; RESET ALL; SET SESSION AUTHORIZATION DEFAULT'
- #------------------------------------------------------------------------------
- # REPLICATION MODE
- #------------------------------------------------------------------------------
- replication_mode = off
- # Activate replication mode
- # (change requires restart)
- replicate_select = off
- # Replicate SELECT statements
- # when in replication or parallel mode
- # replicate_select is higher priority than
- # load_balance_mode.
- insert_lock = on
- # Automatically locks a dummy row or a table
- # with INSERT statements to keep SERIAL data
- # consistency
- # Without SERIAL, no lock will be issued
- lobj_lock_table = ''
- # When rewriting lo_creat command in
- # replication mode, specify table name to
- # lock
- # - Degenerate handling -
- replication_stop_on_mismatch = off
- # On disagreement with the packet kind
- # sent from backend, degenerate the node
- # which is most likely "minority"
- # If off, just force to exit this session
- failover_if_affected_tuples_mismatch = off
- # On disagreement with the number of affected
- # tuples in UPDATE/DELETE queries, then
- # degenerate the node which is most likely
- # "minority".
- # If off, just abort the transaction to
- # keep the consistency
- #------------------------------------------------------------------------------
- # LOAD BALANCING MODE
- #------------------------------------------------------------------------------
- load_balance_mode = on
- # Activate load balancing mode
- # (change requires restart)
- ignore_leading_white_space = on
- # Ignore leading white spaces of each query
- white_function_list = ''
- # Comma separated list of function names
- # that don't write to database
- # Regexp are accepted
- black_function_list = 'nextval,setval'
- # Comma separated list of function names
- # that write to database
- # Regexp are accepted
- #------------------------------------------------------------------------------
- # MASTER/SLAVE MODE
- #------------------------------------------------------------------------------
- master_slave_mode = on
- # Activate master/slave mode
- # (change requires restart)
- master_slave_sub_mode = 'stream'
- # Master/slave sub mode
- # Valid values are combinations slony or
- # stream. Default is slony.
- # (change requires restart)
- # - Streaming -
- #sr_check_period =
- sr_check_period =
- # Streaming replication check period
- # Disabled () by default
- sr_check_user = 'postgres'
- # Streaming replication check user
- # This is necessary even if you disable
- # streaming replication delay check with
- # sr_check_period =
- sr_check_password = 'postgres123'
- # Password for streaming replication check user
- delay_threshold =
- # Threshold before not dispatching query to standby node
- # Unit is in bytes
- # Disabled () by default
- # - Special commands -
- follow_master_command = ''
- # Executes this command after master failover
- # Special values:
- # %d = node id
- # %h = host name
- # %p = port number
- # %D = database cluster path
- # %m = new master node id
- # %H = hostname of the new master node
- # %M = old master node id
- # %P = old primary node id
- # %r = new master port number
- # %R = new master database cluster path
- # %% = '%' character
- #------------------------------------------------------------------------------
- # PARALLEL MODE
- #------------------------------------------------------------------------------
- parallel_mode = off
- # Activates parallel query mode
- # (change requires restart)
- pgpool2_hostname = ''
- # Set pgpool2 hostname
- # (change requires restart)
- # - System DB info -
- system_db_hostname = 'localhost'
- # (change requires restart)
- system_db_port =
- # (change requires restart)
- system_db_dbname = 'pgpool'
- # (change requires restart)
- system_db_schema = 'pgpool_catalog'
- # (change requires restart)
- system_db_user = 'pgpool'
- # (change requires restart)
- system_db_password = ''
- # (change requires restart)
- #------------------------------------------------------------------------------
- # HEALTH CHECK
- #------------------------------------------------------------------------------
- #health_check_period =
- health_check_period =
- # Health check period
- # Disabled () by default
- health_check_timeout =
- # Health check timeout
- # means no timeout
- health_check_user = 'postgres'
- # Health check user
- health_check_password = 'postgres123'
- # Password for health check user
- health_check_max_retries =
- # Maximum number of times to retry a failed health check before giving up.
- health_check_retry_delay =
- # Amount of time to wait (in seconds) between retries.
- #------------------------------------------------------------------------------
- # FAILOVER AND FAILBACK
- #------------------------------------------------------------------------------
- failover_command = '/home/postgres/scripts/failover_stream.sh %d %H /usr/local/pgsql/data/postgresql.trigger.5432'
- # Executes this command at failover
- # Special values:
- # %d = node id
- # %h = host name
- # %p = port number
- # %D = database cluster path
- # %m = new master node id
- # %H = hostname of the new master node
- # %M = old master node id
- # %P = old primary node id
- # %r = new master port number
- # %R = new master database cluster path
- # %% = '%' character
- failback_command = ''
- # Executes this command at failback.
- # Special values:
- # %d = node id
- # %h = host name
- # %p = port number
- # %D = database cluster path
- # %m = new master node id
- # %H = hostname of the new master node
- # %M = old master node id
- # %P = old primary node id
- # %r = new master port number
- # %R = new master database cluster path
- # %% = '%' character
- fail_over_on_backend_error = on
- # Initiates failover when reading/writing to the
- # backend communication socket fails
- # If set to off, pgpool will report an
- # error and disconnect the session.
- search_primary_node_timeout =
- # Timeout in seconds to search for the
- # primary node when a failover occurs.
- # means no timeout, keep searching
- # for a primary node forever.
- #------------------------------------------------------------------------------
- # ONLINE RECOVERY
- #------------------------------------------------------------------------------
- recovery_user = 'postgres'
- # Online recovery user
- recovery_password = 'postgres123'
- # Online recovery password
- recovery_1st_stage_command = ''
- # Executes a command in first stage
- recovery_2nd_stage_command = ''
- # Executes a command in second stage
- recovery_timeout =
- # Timeout in seconds to wait for the
- # recovering node's postmaster to start up
- # means no wait
- client_idle_limit_in_recovery =
- # Client is disconnected after being idle
- # for that many seconds in the second stage
- # of online recovery
- # means no disconnection
- # - means immediate disconnection
- #------------------------------------------------------------------------------
- # WATCHDOG
- #------------------------------------------------------------------------------
- # - Enabling -
- use_watchdog = off
- # Activates watchdog
- # (change requires restart)
- # -Connection to up stream servers -
- trusted_servers = ''
- # trusted server list which are used
- # to confirm network connection
- # (hostA,hostB,hostC,...)
- # (change requires restart)
- ping_path = '/bin'
- # ping command path
- # (change requires restart)
- # - Watchdog communication Settings -
- wd_hostname = ''
- # Host name or IP address of this watchdog
- # (change requires restart)
- wd_port =
- # port number for watchdog service
- # (change requires restart)
- wd_authkey = ''
- # Authentication key for watchdog communication
- # (change requires restart)
- # - Virtual IP control Setting -
- delegate_IP = ''
- # delegate IP address
- # If this is empty, virtual IP never bring up.
- # (change requires restart)
- ifconfig_path = '/sbin'
- # ifconfig command path
- # (change requires restart)
- if_up_cmd = 'ifconfig eth0:0 inet $_IP_$ netmask 255.255.255.0'
- # startup delegate IP command
- # (change requires restart)
- if_down_cmd = 'ifconfig eth0:0 down'
- # shutdown delegate IP command
- # (change requires restart)
- arping_path = '/usr/sbin' # arping command path
- # (change requires restart)
- arping_cmd = 'arping -U $_IP_$ -w 1'
- # arping command
- # (change requires restart)
- # - Behaivor on escalation Setting -
- clear_memqcache_on_escalation = on
- # Clear all the query cache on shared memory
- # when standby pgpool escalate to active pgpool
- # (= virtual IP holder).
- # This should be off if client connects to pgpool
- # not using virtual IP.
- # (change requires restart)
- wd_escalation_command = ''
- # Executes this command at escalation on new active pgpool.
- # (change requires restart)
- # - Lifecheck Setting -
- # -- common --
- wd_lifecheck_method = 'heartbeat'
- # Method of watchdog lifecheck ('heartbeat' or 'query')
- # (change requires restart)
- wd_interval =
- # lifecheck interval (sec) >
- # (change requires restart)
- # -- heartbeat mode --
- wd_heartbeat_port =
- # Port number for receiving heartbeat signal
- # (change requires restart)
- wd_heartbeat_keepalive =
- # Interval time of sending heartbeat signal (sec)
- # (change requires restart)
- wd_heartbeat_deadtime =
- # Deadtime interval for heartbeat signal (sec)
- # (change requires restart)
- heartbeat_destination0 = 'db2'
- # Host name or IP address of destination
- # for sending heartbeat signal.
- # (change requires restart)
- heartbeat_destination_port0 =
- # Port number of destination for sending
- # heartbeat signal. Usually this is the
- # same as wd_heartbeat_port.
- # (change requires restart)
- heartbeat_device0 = ''
- # Name of NIC device (such like 'eth0')
- # used for sending/receiving heartbeat
- # signal to/from destination .
- # This works only when this is not empty
- # and pgpool has root privilege.
- # (change requires restart)
- #heartbeat_destination1 = 'host0_ip2'
- #heartbeat_destination_port1 =
- #heartbeat_device1 = ''
- # -- query mode --
- wd_life_point =
- # lifecheck retry times
- # (change requires restart)
- wd_lifecheck_query = 'SELECT 1'
- # lifecheck query to pgpool from watchdog
- # (change requires restart)
- wd_lifecheck_dbname = 'template1'
- # Database name connected for lifecheck
- # (change requires restart)
- wd_lifecheck_user = 'nobody'
- # watchdog user monitoring pgpools in lifecheck
- # (change requires restart)
- wd_lifecheck_password = ''
- # Password for watchdog user in lifecheck
- # (change requires restart)
- # - Other pgpool Connection Settings -
- #other_pgpool_hostname0 = 'host0'
- # Host name or IP address to connect to for other pgpool
- # (change requires restart)
- #other_pgpool_port0 =
- # Port number for othet pgpool
- # (change requires restart)
- #other_wd_port0 =
- # Port number for othet watchdog
- # (change requires restart)
- #other_pgpool_hostname1 = 'host1'
- #other_pgpool_port1 =
- #other_wd_port1 =
- #------------------------------------------------------------------------------
- # OTHERS
- #------------------------------------------------------------------------------
- relcache_expire =
- # Life time of relation cache in seconds.
- # means no cache expiration(the default).
- # The relation cache is used for cache the
- # query result against PostgreSQL system
- # catalog to obtain various information
- # including table structures or if it's a
- # temporary table or not. The cache is
- # maintained in a pgpool child local memory
- # and being kept as long as it survives.
- # If someone modify the table by using
- # ALTER TABLE or some such, the relcache is
- # not consistent anymore.
- # For this purpose, cache_expiration
- # controls the life time of the cache.
- relcache_size =
- # Number of relation cache
- # entry. If you see frequently:
- # "pool_search_relcache: cache replacement happend"
- # in the pgpool log, you might want to increate this number.
- check_temp_table = on
- # If on, enable temporary table check in SELECT statements.
- # This initiates queries against system catalog of primary/master
- # thus increases load of master.
- # If you are absolutely sure that your system never uses temporary tables
- # and you want to save access to primary/master, you could turn this off.
- # Default is on.
- #------------------------------------------------------------------------------
- # ON MEMORY QUERY MEMORY CACHE
- #------------------------------------------------------------------------------
- memory_cache_enabled = off
- # If on, use the memory cache functionality, off by default
- memqcache_method = 'shmem'
- # Cache storage method. either 'shmem'(shared memory) or
- # 'memcached'. 'shmem' by default
- # (change requires restart)
- memqcache_memcached_host = 'localhost'
- # Memcached host name or IP address. Mandatory if
- # memqcache_method = 'memcached'.
- # Defaults to localhost.
- # (change requires restart)
- memqcache_memcached_port =
- # Memcached port number. Mondatory if memqcache_method = 'memcached'.
- # Defaults to .
- # (change requires restart)
- memqcache_total_size =
- # Total memory size in bytes for storing memory cache.
- # Mandatory if memqcache_method = 'shmem'.
- # Defaults to 64MB.
- # (change requires restart)
- memqcache_max_num_cache =
- # Total number of cache entries. Mandatory
- # if memqcache_method = 'shmem'.
- # Each cache entry consumes bytes on shared memory.
- # Defaults to ,,(.8MB).
- # (change requires restart)
- memqcache_expire =
- # Memory cache entry life time specified in seconds.
- # means infinite life time. by default.
- # (change requires restart)
- memqcache_auto_cache_invalidation = on
- # If on, invalidation of query cache is triggered by corresponding
- # DDL/DML/DCL(and memqcache_expire). If off, it is only triggered
- # by memqcache_expire. on by default.
- # (change requires restart)
- memqcache_maxcache =
- # Maximum SELECT result size in bytes.
- # Must be smaller than memqcache_cache_block_size. Defaults to 400KB.
- # (change requires restart)
- memqcache_cache_block_size =
- # Cache block size in bytes. Mandatory if memqcache_method = 'shmem'.
- # Defaults to 1MB.
- # (change requires restart)
- memqcache_oiddir = '/var/log/pgpool/oiddir'
- # Temporary work directory to record table oids
- # (change requires restart)
- white_memqcache_table_list = ''
- # Comma separated list of table names to memcache
- # that don't write to database
- # Regexp are accepted
- black_memqcache_table_list = ''
- # Comma separated list of table names not to memcache
- # that don't write to database
- # Regexp are accepted
1.4 启动pgpool：pgpool -dn 以非守护进程，调试模式运行pgpool，因为如果默认是守护进程，待会想停止就麻烦了。其他参数--help.
注意观察调试信息。如果有错误，请重新查看配置文件。如果没有法相错误，使用命令：psql -p 9999 ，通过pgpool进入数据库。如果可以进入就说明pgpool监听的9999正常，且成功连接数据库。
此时使用如下命令查看监听的数据库信息：当发现status为3时，使用ping、telnet、psql -h进行测试网络连通性。关闭防火墙。
- postgres=# show pool_nodes;
- node_id | hostname | port | status | lb_weight | role
- ---------+--------------+------+--------+-----------+---------
- | 192.168.1.45 | | | 0.500000 | primary
- | 192.168.1.50 | | | 0.500000 | standby
当然，可以启动主从数据库的日志级别为 all。那么对数据的一切操作，都可以查看到。此时可以使用脚本测试一下。就可以查看主从的日志。看看是否都有日志记录。
- for i in {..}; do echo $i; psql -p -U postgres -h 192.168.1.45 -d postgres -c "select * from test"; done
1.5 查看pgpool的状态。参考手册：http://pgpool.projects.pgfoundry.org/pgpool-II/doc/pgpool-zh_cn.html#show-commands
之前安装的regclass就是通过psql查看pgpool状态的工具。可以运行下列命令查看：
- pgpool-II 通过 SHOW 命令提供一些信息。SHOW 是一个真实的 SQL 语句, 但是如果该命令查询 pgpool-II 信息的话，pgpool-II 解释了该命令。可选项如下:
- pool_status, 获取配置
- pool_nodes, 获取节点信息
- pool_processes, 获取pgPool-II 进程信息
- pool_pools, 获取pgPool-II 所有的连接池信息
- pool_version, 获取pgPool_II 版本信息
比如：pool_processes。查看进程池的情况。可以根据需要修改pgpool中的设置。
- postgres=# show pool_processes;
- pool_pid | start_time | database | username | create_time | pool_counter
- ----------+---------------------+----------+----------+---------------------+--------------
- | -- :: | postgres | postgres | -- :: |
- | -- :: | | | |
- | -- :: | | | |
- | -- :: | | | |
- | -- :: | | | |
- | -- :: | | | |
- | -- :: | | | |
- | -- :: | | | |
- | -- :: | | | |
- | -- :: | | | |
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