操作系統：CentOS7

Postgresql版本：10.10
Pgpool-II版本：4.0.6

端口
??9999：對外提供服務
??9000：watch_dog
??9898：pcp
??9694：watch_dog心跳檢查

備注：下文的安裝步驟中，【】包圍的部分需根據自己的環境來配置

背景

??項目上有實現數據庫高可用的需求，Postgresql本身支持數據同步和手動failover。即，一個雙機熱備的Postgresql集群，主節點宕機時，整個集群只能對外提供讀服務，而無法提供寫服務，只有手動執行promote命令晉升備節點為主節點，才能恢復數據庫服務的正常。以下是Postgresql官方文檔的引文:

PostgreSQL does not provide the system software required to identify a
failure on the primary and notify the standby database server.

??Pgpool通過其WatchDog的虛擬IP和健康檢查功能實現了自動故障切換。本文使用master-slave模式搭建集群，不使用replication_mode的原因是該模式下的online recovery存在限制，Pgpool官網引文如下：

There is a restriction in the online recovery in replication_mode. If
Pgpool-II itself is installed on multiple hosts, online recovery does
not work correctly, because Pgpool-II has to stop all the clients
during the 2nd stage of online recovery. If there are several
Pgpool-II hosts, only one of them will have received the online
recovery command and will block the connections from clients.

??為實現分區容錯，本文使用3個節點搭建集群，每個節點安裝Pgpool-II和Postgresql數據庫，數據庫為1主2備。
??注意：Pgpool-II和Postgresql集群對于主節點使用的術語不同，Pgpool-II的主節點稱為Master，Postgresql的主節點稱為Primary；備節點使用的術語相同，都為standby。

步驟

1 安裝并配置PostgreSQL
??在所有節點安裝PostgreSQL，但僅需要在節點1配置并啟動PostgreSQL，然后使用pcp_recovery_node功能初始化并啟動節點2、3上的Postgresql服務，注意不要讓PostgreSQL開機自啟。參考PG數據庫安裝。

2 配置/etc/hosts
??增加DNS配置，供recovery_1st_stage使用

【節點1的IP】 【節點1的主機名】 【節點2的IP】 【節點2的主機名】 【節點3的IP】 【節點3的主機名】

3 配置ssh免密通信
??Pgpool的failover配置中使用的failover.sh、follow_master.sh，以及online recovery配置中使用的recovery_1st_stage、pgpool_remote_start腳本中，都涉及通過ssh進行遠程操作。
??需要配置root用戶到postgres用戶（包括本機的postgres用戶）的單向，以及postgres用戶之間的雙向免密通信。
3.1 設置postgres用戶的密碼

su passwd postgres

3.2 在當前節點執行以下語句，生成密鑰
??注意不要設置passphrase

su 【當前用戶】 ssh-keygen -t rsa

3.3 將公鑰發送到其他節點

ssh-copy-id -i ~/.ssh/id_rsa.pub 【用戶名】@【IP】

3.4 測試ssh

ssh 【用戶名】@【IP】

4 修改ssh配置（可選，默認10個一般夠）

vi /etc/ssh/sshd_config

修改

MaxSessions 100

重啟sshd

systemctl restart sshd

5 配置系統日志
??創建日志文件，應創建在/var/log路徑下，否則syslog無法寫入文件（除非關閉或配置SELinux）。

mkdir /var/log/pgpool touch /var/log/pgpool/pgpool_run.log

修改syslog配置

vi /etc/rsyslog.conf

修改

*.info;mail.none;authpriv.none;cron.none;LOCAL1.none /var/log/messages LOCAL1.* /var/log/pgpool/pgpool_run.log

重啟

systemctl restart rsyslog

6 配置pgpass
??為了允許數據庫的postgres用戶無需為流復制和在線恢復指定密碼，對于每個節點，在操作系統的postgres用戶的主目錄中創建.pgpass文件，權限改為600。

su postgres vi ~/.pgpass

編輯

# hostname:port:database:username:password # In a standby server, a database field of replication matches streaming replication connections made to the master server. 【節點1的IP】:5432:postgres:postgres:123456 【節點2的IP】:5432:postgres:postgres:123456 【節點3的IP】:5432:postgres:postgres:123456

授權

chmod 600 ~/.pgpass

7 安裝Pgpool
??root用戶執行，在所有節點安裝和配置Pgpool；為了使用在線恢復功能，需要pgpool_recovery、pgpool_remote_start、pgpool_switch_xlog等函數，因此需要安裝pgpool_recovery。
??注意：安裝pgpool_recovery需要先安裝postgresql-devel。

mkdir /usr/local/pgpool cd /usr/local/pgpool tar -zxvf pgpool-II-4.0.6.tar.gz cd /usr/local/pgpool/pgpool-II-4.0.6 ./configure --with-pgsql=/usr/local/pgsql make && make install cd /usr/local/pgpool/pgpool-II-4.0.6/src/sql/pgpool-recovery chown -R postgres /usr/local/pgsql make && make install cp /usr/local/etc/pgpool.conf.sample-stream /usr/local/etc/pgpool.conf

8 在節點1的Postgresql上安裝pgpool_recovery擴展
??使用PG創建數據庫時，實際上是通過復制一個現有的數據庫來工作的。默認情況下，它復制名為template1的標準系統數據庫。

psql template1 -c "CREATE EXTENSION pgpool_recovery" psql postgres -c "CREATE EXTENSION pgpool_recovery"

9 編寫failover腳本
在所有節點上新建配置文件，并賦予執行權限

vi /usr/local/pgpool/failover_stream.sh

編輯腳本（注意和pgpool.conf中failover_command參數的聯系），如果primary宕機，晉升standby；如果standby宕機，僅記錄日志。

#!/bin/bash # This script is run by failover_command.set -o xtrace logger -i -p local1.info failover_command begin# 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 # %% = '%' characterFAILED_NODE_ID="$1" FAILED_NODE_HOST="$2" FAILED_NODE_PORT="$3" FAILED_NODE_PGDATA="$4" NEW_MASTER_NODE_ID="$5" NEW_MASTER_NODE_HOST="$6" OLD_MASTER_NODE_ID="$7" OLD_PRIMARY_NODE_ID="$8" NEW_MASTER_NODE_PORT="$9" NEW_MASTER_NODE_PGDATA="${10}"PGHOME=/usr/local/pgsqllogger -i -p local1.info failover.sh: start: failed_node_id=${FAILED_NODE_ID} old_primary_node_id=${OLD_PRIMARY_NODE_ID} \failed_host=${FAILED_NODE_HOST} new_master_host=${NEW_MASTER_NODE_HOST}## Test passwrodless SSH ssh -T -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null postgres@${NEW_MASTER_NODE_HOST} -i ~/.ssh/id_rsa ls /tmp > /dev/nullif [ $? -ne 0 ]; thenlogger -i -p local1.error failover.sh: passwrodless SSH to postgres@${NEW_MASTER_NODE_HOST} failed. Please setup passwrodless SSH.exit 1 fi# If standby node is down, skip failover. if [ ${FAILED_NODE_ID} -ne ${OLD_PRIMARY_NODE_ID} ]; thenlogger -i -p local1.info failover.sh: Standby node is down. Skipping failover.exit 0 fi# Promote standby node. logger -i -p local1.info failover.sh: Primary node is down, promote standby node PostgreSQL@${NEW_MASTER_NODE_HOST}.ssh -T -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null \ postgres@${NEW_MASTER_NODE_HOST} -i ~/.ssh/id_rsa ${PGHOME}/bin/pg_ctl -D ${NEW_MASTER_NODE_PGDATA} -w promoteif [ $? -ne 0 ]; thenlogger -i -p local1.error failover.sh: new_master_host=${NEW_MASTER_NODE_HOST} promote failedexit 1 filogger -i -p local1.info failover.sh: end: new_master_node_id=$NEW_MASTER_NODE_ID started as the primary node exit 0

授權

chmod +x /usr/local/pgpool/failover_stream.sh

10 編寫follow_master腳本
??使仍在運行的standby從新的primary上同步數據，三個及以上節點數量時，需要設置此腳本

vi /usr/local/pgpool/follow_master.sh

編輯腳本

#!/bin/bash # This script is run after failover_command to synchronize the Standby with the new Primary.set -o xtrace logger -i -p local1.info follow_master begin# 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 # %H = new master node host name # %P = old primary node id # %R = new master database cluster path # %r = new master port number # %% = '%' character FAILED_NODE_ID="$1" FAILED_NODE_HOST="$2" FAILED_NODE_PORT="$3" FAILED_NODE_PGDATA="$4" NEW_MASTER_NODE_ID="$5" NEW_MASTER_NODE_HOST="$6" OLD_MASTER_NODE_ID="$7" OLD_PRIMARY_NODE_ID="$8" NEW_MASTER_NODE_PORT="$9" NEW_MASTER_NODE_PGDATA="${10}"PGHOME=/usr/local/pgsql ARCHIVEDIR=/home/pg/data/archivedir REPL_USER=postgres PCP_USER=postgres PGPOOL_PATH=/usr/local/bin PCP_PORT=9898# Recovery the slave from the new primary logger -i -p local1.info follow_master.sh: start: synchronize the Standby node PostgreSQL@${FAILED_NODE_HOST} with the new Primary node PostgreSQL@${NEW_MASTER_NODE_HOST}## Test passwrodless SSH ssh -T -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null postgres@${NEW_MASTER_NODE_HOST} -i ~/.ssh/id_rsa ls /tmp > /dev/nullif [ $? -ne 0 ]; thenlogger -i -p local1.error follow_master.sh: passwrodless SSH to postgres@${NEW_MASTER_NODE_HOST} failed. Please setup passwrodless SSH.exit 1 fi## Get PostgreSQL major version PGVERSION=`${PGHOME}/bin/initdb -V | awk '{print $3}' | sed 's/\..*//' | sed 's/\([0-9]*\)[a-zA-Z].*/\1/'`if [ ${PGVERSION} -ge 12 ]; thenRECOVERYCONF=${FAILED_NODE_PGDATA}/myrecovery.conf elseRECOVERYCONF=${FAILED_NODE_PGDATA}/recovery.conf fi# Check the status of standby ssh -T -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null \postgres@${FAILED_NODE_HOST} -i ~/.ssh/id_rsa ${PGHOME}/bin/pg_ctl -w -D ${FAILED_NODE_PGDATA} status## If Standby is running, run pg_basebackup. if [ $? -eq 0 ]; then# Execute pg_basebackupssh -T -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null postgres@${FAILED_NODE_HOST} -i ~/.ssh/id_rsa "set -o errexit${PGHOME}/bin/pg_ctl -w -m f -D ${FAILED_NODE_PGDATA} stoprm -rf ${FAILED_NODE_PGDATA}rm -rf ${ARCHIVEDIR}/*${PGHOME}/bin/pg_basebackup -h ${NEW_MASTER_NODE_HOST} -U ${REPL_USER} -p ${NEW_MASTER_NODE_PORT} -D ${FAILED_NODE_PGDATA} -X streamif [ ${PGVERSION} -ge 12 ]; thensed -i -e \"\\\$ainclude_if_exists = '$(echo ${RECOVERYCONF} | sed -e 's/\//\\\//g')'\" \-e \"/^include_if_exists = '$(echo ${RECOVERYCONF} | sed -e 's/\//\\\//g')'/d\" ${FAILED_NODE_PGDATA}/postgresql.confficat > ${RECOVERYCONF} << EOT primary_conninfo = 'host=${NEW_MASTER_NODE_HOST} port=${NEW_MASTER_NODE_PORT} user=${REPL_USER} passfile=''/home/postgres/.pgpass''' recovery_target_timeline = 'latest' restore_command = 'scp ${NEW_MASTER_NODE_HOST}:${ARCHIVEDIR}/%f %p' EOTif [ ${PGVERSION} -ge 12 ]; thentouch ${FAILED_NODE_PGDATA}/standby.signalelseecho \"standby_mode = 'on'\" >> ${RECOVERYCONF}fi"if [ $? -ne 0 ]; thenlogger -i -p local1.error follow_master.sh: end: pg_basebackup failedexit 1fi# start Standby node on ${FAILED_NODE_HOST}ssh -T -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null \postgres@${FAILED_NODE_HOST} -i ~/.ssh/id_rsa $PGHOME/bin/pg_ctl -l /dev/null -w -D ${FAILED_NODE_PGDATA} start# If start Standby successfully, attach this nodeif [ $? -eq 0 ]; then# Run pcp_attact_node to attach Standby node to Pgpool-II.${PGPOOL_PATH}/pcp_attach_node -w -h localhost -U $PCP_USER -p ${PCP_PORT} -n ${FAILED_NODE_ID}if [ $? -ne 0 ]; thenlogger -i -p local1.error follow_master.sh: end: pcp_attach_node failedexit 1fi# If start Standby failed, drop replication slot "${FAILED_NODE_HOST}"elselogger -i -p local1.error follow_master.sh: end: follow master command failedexit 1fielselogger -i -p local1.info follow_master.sh: failed_nod_id=${FAILED_NODE_ID} is not running. skipping follow master commandexit 0 filogger -i -p local1.info follow_master.sh: end: follow master command complete exit 0

授權

chmod +x /usr/local/pgpool/follow_master.sh

11 編寫recovery_1st_stage腳本
??pcp_recovery_node會用到recovery_1st_stage和pgpool_remote_start。
??recovery_1st_stage會使用pg_basebackup從現存的主節點同步數據，初始化數據庫，更新recovery配置文件。

vi /home/pg/data/recovery_1st_stage.sh

編輯

#!/bin/bash # This script is executed by "recovery_1st_stage" to recovery a Standby node.set -o xtrace logger -i -p local1.info recovery_1st_stage beginPRIMARY_NODE_PGDATA="$1" DEST_NODE_HOST="$2" DEST_NODE_PGDATA="$3" PRIMARY_NODE_PORT="$4" DEST_NODE_PORT=5432# 這里是hostname變量，所以需要配置DNS PRIMARY_NODE_HOST=$(hostname) PGHOME=/usr/local/pgsql ARCHIVEDIR=/home/pg/data/archivedir REPL_USER=postgreslogger -i -p local1.info recovery_1st_stage: start: pg_basebackup for Standby node PostgreSQL@{$DEST_NODE_HOST}## Test passwrodless SSH ssh -T -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null postgres@${DEST_NODE_HOST} -i ~/.ssh/id_rsa ls /tmp > /dev/nullif [ $? -ne 0 ]; thenlogger -i -p local1.error recovery_1st_stage: passwrodless SSH to postgres@${DEST_NODE_HOST} failed. Please setup passwrodless SSH.exit 1 fi## Get PostgreSQL major version PGVERSION=`${PGHOME}/bin/initdb -V | awk '{print $3}' | sed 's/\..*//' | sed 's/\([0-9]*\)[a-zA-Z].*/\1/'` if [ $PGVERSION -ge 12 ]; thenRECOVERYCONF=${DEST_NODE_PGDATA}/myrecovery.conf elseRECOVERYCONF=${DEST_NODE_PGDATA}/recovery.conf fi## Execute pg_basebackup to recovery Standby node ssh -T -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null postgres@$DEST_NODE_HOST -i ~/.ssh/id_rsa "set -o errexitrm -rf $DEST_NODE_PGDATArm -rf $ARCHIVEDIR/*${PGHOME}/bin/pg_basebackup -h ${PRIMARY_NODE_HOST} -U ${REPL_USER} -p ${PRIMARY_NODE_PORT} -D ${DEST_NODE_PGDATA} -X streamif [ ${PGVERSION} -ge 12 ]; thensed -i -e \"\\\$ainclude_if_exists = '$(echo ${RECOVERYCONF} | sed -e 's/\//\\\//g')'\" \-e \"/^include_if_exists = '$(echo ${RECOVERYCONF} | sed -e 's/\//\\\//g')'/d\" ${DEST_NODE_PGDATA}/postgresql.confficat > ${RECOVERYCONF} << EOT primary_conninfo = 'host=${PRIMARY_NODE_HOST} port=${PRIMARY_NODE_PORT} user=${REPL_USER} passfile=''/home/postgres/.pgpass''' recovery_target_timeline = 'latest' restore_command = 'scp ${PRIMARY_NODE_HOST}:${ARCHIVEDIR}/%f %p' EOTif [ ${PGVERSION} -ge 12 ]; thentouch ${DEST_NODE_PGDATA}/standby.signalelseecho \"standby_mode = 'on'\" >> ${RECOVERYCONF}fised -i \"s/#*port = .*/port = ${DEST_NODE_PORT}/\" ${DEST_NODE_PGDATA}/postgresql.conf "if [ $? -ne 0 ]; thenlogger -i -p local1.error recovery_1st_stage: end: pg_basebackup failed. online recovery failedexit 1 filogger -i -p local1.info recovery_1st_stage: end: recovery_1st_stage complete exit 0

授權

chmod +x /home/pg/data/recovery_1st_stage.sh

12 編寫pgpool_remote_start腳本（注意沒有sh擴展名）
pgpool_remote_start負責啟動數據庫

vi /home/pg/data/pgpool_remote_start

編輯

#!/bin/bash # This script is run after recovery_1st_stage to start Standby node.set -o xtrace logger -i -p local1.info pgpool_remote_start beginPGHOME=/usr/local/pgsql DEST_NODE_HOST="$1" DEST_NODE_PGDATA="$2"logger -i -p local1.info pgpool_remote_start: start: remote start Standby node PostgreSQL@$DEST_NODE_HOST## Test passwrodless SSH ssh -T -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null postgres@${DEST_NODE_HOST} -i ~/.ssh/id_rsa ls /tmp > /dev/nullif [ $? -ne 0 ]; thenlogger -i -p local1.error pgpool_remote_start: passwrodless SSH to postgres@${DEST_NODE_HOST} failed. Please setup passwrodless SSH.exit 1 fi## Start Standby node ssh -T -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null postgres@$DEST_NODE_HOST -i ~/.ssh/id_rsa " $PGHOME/bin/pg_ctl -l /dev/null -w -D $DEST_NODE_PGDATA start "if [ $? -ne 0 ]; thenlogger -i -p local1.error pgpool_remote_start: PostgreSQL@$DEST_NODE_HOST start failed.exit 1 filogger -i -p local1.info pgpool_remote_start: end: PostgreSQL@$DEST_NODE_HOST started successfully. exit 0

授權

chmod +x /home/pg/data/pgpool_remote_start.sh

13 配置pgpool.conf
復制Pgpool配置模板文件

cp /usr/local/etc/pgpool.conf.sample-stream /usr/local/etc/pgpool.conf vi /usr/local/etc/pgpool.conf

修改

#CONNECTIONS listen_addresses = '*' port = 9999 pcp_listen_addresses = '*' pcp_port = 9898#- Backend Connection Settings -backend_hostname0 ='【集群內第1個節點的IP，多個節點配置一致】' backend_port0 = 5432 backend_weight0 = 1 backend_data_directory0 = '/home/pg/data' backend_flag0 = ‘ALLOW_TO_FAILOVER’backend_hostname1 ='【集群內第2個節點的IP，多個節點配置一致】' backend_port1 = 5432 backend_weight1 = 1 backend_data_directory1 = '/home/pg/data' backend_flag1 = 'ALLOW_TO_FAILOVER'backend_hostname2 ='【集群內第3個節點的IP，多個節點配置一致】' backend_port2 = 5432 backend_weight2 = 1 backend_data_directory2 = '/home/pg/data' backend_flag2 = 'ALLOW_TO_FAILOVER'#- Authentication - enable_pool_hba = on pool_passwd ='pool_passwd'#------------------------------------------------------------------------------ # POOLS #------------------------------------------------------------------------------# - Concurrent session and pool size -num_init_children = 400 max_pool = 4#------------------------------------------------------------------------------ # LOGS #------------------------------------------------------------------------------ log_destination = 'syslog' syslog_facility = 'LOCAL1'#------------------------------------------------------------------------------ # FILE LOCATIONS #------------------------------------------------------------------------------pid_file_name = '/usr/local/pgpool/pgpool.pid'#------------------------------------------------------------------------------ # REPLICATION MODE #------------------------------------------------------------------------------ replication_mode = off #------------------------------------------------------------------------------ # LOAD BALANCING MODE #------------------------------------------------------------------------------ load_balance_mode = on #------------------------------------------------------------------------------ # MASTER/SLAVE MODE #------------------------------------------------------------------------------ master_slave_mode = on master_slave_sub_mode = 'stream' # - Streaming - sr_check_period = 5 sr_check_user = 'postgres' sr_check_password ='123456' sr_check_database = 'postgres' follow_master_command = '/usr/local/pgpool/follow_master.sh %d %h %p %D %m %H %M %P %r %R' #------------------------------------------------------------------------------ #HEALTH CHECK #------------------------------------------------------------------------------health_check_period = 10 health_check_timeout = 20 health_check_user = 'postgres' health_check_password ='123456' health_check_database = 'postgres'#------------------------------------------------------------------------------ #FAILOVER AND FAILBACK #------------------------------------------------------------------------------ # 注意failover_stream.sh后的參數，要與failover_stream.sh中的腳本匹配 failover_command = '/usr/local/pgpool/failover_stream.sh %d %h %p %D %m %H %M %P %r %R'#------------------------------------------------------------------------------ #WATCHDOG #------------------------------------------------------------------------------ use_watchdog = on wd_hostname = '【本機IP】' wd_port = 9000 delegate_IP = '【虛擬IP】' if_cmd_path = '/sbin' if_up_cmd = 'ip addr add $_IP_$/24 dev 【網卡名稱（通過ip addr查看）】 label 【網卡名稱（通過ip addr查看）】:0' if_down_cmd = 'ip addr del $_IP_$/24 dev 【網卡名稱（通過ip addr查看）】' arping_path = '/usr/sbin' arping_cmd = 'arping -U $_IP_$ -w 1' wd_heartbeat_port = 9694 wd_heartbeat_keepalive = 2 wd_heartbeat_deadtime = 30 heartbeat_destination0 = '【其他節點1的IP】' heartbeat_destination_port0 = 9694 heartbeat_device0 = '【網卡名稱（通過ip addr查看）】' heartbeat_destination1 = '【其他節點2的IP】' heartbeat_destination_port1 = 9694 heartbeat_device1 = '【網卡名稱（通過ip addr查看）】'#------------------------------------------------------------------------------ # ONLINE RECOVERY #------------------------------------------------------------------------------recovery_user = 'postgres' recovery_password = '123456' recovery_1st_stage_command = 'recovery_1st_stage.sh' #- Other pgpool Connection Settings -other_pgpool_hostname0 ='【其他節點1的IP】' other_pgpool_port0 = 9999 other_wd_port0 = 9000 other_pgpool_hostname1 ='【其他節點2的IP】' other_pgpool_port1 = 9999 other_wd_port1 = 9000

14 生成pool_passwd

/usr/local/bin/pg_md5 -p --md5auth --username=postgres pool_passwd chown postgres:postgres /usr/local/etc/pool_passwd

操作完成后，在/usr/local/etc目錄下會生成一個pool_passwd文件，該文件在pgpool.conf中通過“pool_passwd”選項配置。

15 配置pool_hba.conf
??客戶端認證配置文件，在pgpool.conf中配置“enable_pool_hba = on”時，將使用該文件認證客戶端連接。
root用戶執行

cp /usr/local/etc/pool_hba.conf.sample /usr/local/etc/pool_hba.conf chown postgres:postgres /usr/local/etc/pool_hba.conf vi /usr/local/etc/pool_hba.conf

修改

local all all md5 host all all 0.0.0.0/0 md5 host all all 0/0 md5

16 配置pcp.conf
??Pgpool-II為管理員提供了執行管理操作的接口，例如獲取Pgpool-II狀態或遠程終止Pgpool-II進程。pcp.conf是此接口用于身份驗證的用戶名/密碼文件。所有操作模式都需要設置pcp.conf文件。數據庫中使用PCP進行健康檢測和復制延遲檢測的用戶，其用戶名和密碼必須在pcp.conf中聲明。
16.1 生成密碼摘要

/usr/local/bin/pg_md5 【密碼】

16.2 生成和配置文件

cp /usr/local/etc/pcp.conf.sample /usr/local/etc/pcp.conf vi /usr/local/etc/pcp.conf

編輯

# Example: postgres:【上一步生成的密碼摘要】

17 設置PCP密碼配置文件
??由于follow_master_command腳本必須在不輸入密碼的情況下執行PCP命令，所以我們在Pgpool-II啟動用戶的主目錄中創建.pcppass。

echo 'localhost:9898:【數據庫用戶名稱】:【數據庫用戶密碼】' > ~/.pcppass chmod 600 ~/.pcppass

18 允許postgres用戶以root身份執行相關命令
root用戶執行

chmod u+s /sbin/ip chmod u+s /sbin/arping

19 配置開機自啟

vi /etc/systemd/system/pgpool.service

編輯

[Unit] Description=Pgpool-II After=syslog.target network.target[Service] Type=forkingUser=rootExecStart=/usr/local/bin/pgpool -C -D ExecStop=/usr/local/bin/pgpool -m fast stop ExecReload=/usr/local/bin/pgpool reload LimitNOFILE=65536 KillMode=process KillSignal=SIGINT Restart=on-abnormal RestartSec=30s TimeoutSec=0[Install] WantedBy=multi-user.target

開機自啟

systemctl enable pgpool

20 在所有節點啟動pgpool

systemctl start pgpool

21 通過pcp_recovery_node初始化備節點數據庫
??pcp_recovery_node會先在primary節點執行SELECT pgpool_recovery(‘recovery_1st_stage’, ‘【需要啟動的standby的IP】’, ‘【數據目錄】’, ‘5432’, 【節點編號】)，可以通過查詢PG日志查看異常信息；然后執行recovery_1st_stage.sh和pgpool_remote_start.sh

pcp_recovery_node -h 【主節點的IP】 -p 9898 -U 【PCP用戶名（數據庫）】 -n 【node-id】

22 查看節點狀態
22.1 Pgpool節點狀態

pcp_watchdog_info -h 【虛擬IP】 -p 9898 -U 【Pgpool用戶】

22.2 數據庫節點狀態
通過虛擬IP的9999端口開啟PostgreSQL數據庫命令行，執行

show pool_nodes;

注意：如果使用navicat的命令行功能，可能需要關閉并重啟命令行界面（建立新的session）才能看到正確的節點狀態
23 高可用測試
23.1 Pgpool 高可用測試

• master停止pgpool服務，某個standby接管master服務
• 重啟之前停止的master的pgpool服務，節點狀態變為standby
• standby停止pgpool服務，節點狀態變為shutdown
• 重啟standby，節點狀態恢復為standby

23.2 數據庫高可用測試

• primary停止數據庫服務，某個standby晉升為primary，其他standby執行follow
  master，從新的primary同步數據
• 執行pcp_recovery_node，將之前停止服務的primary重啟
• standby停止數據庫服務，其他節點無變化
• 執行pcp_recovery_node，將之前停止服務的standby重啟

24 負載均衡測試
??使用pgbench進行負載均衡測試
24.1 數據初始化

pgbench -i -h 【主節點IP】 -p 5432 postgres 24.2 測試 ```shell pgbench -c 【客戶端數量】 -T 【持續時間（秒）】 -h 【集群虛擬IP】 postgres -p 9999 -U postgres -S（表示只讀測試）

24.3 使用show pool_nodes查看查詢請求在各節點的負載
25 非正常關閉pgpool后的故障恢復

• 非正常關閉pgpool，要清理緩存文件：

rm /tmp/.s.PGSQL.9999 rm /tmp/.s.PGPOOLWD_CMD.9000 rm /tmp/.s.PGSQL.9898

• 如果啟動第一個節點狀態為standby，重啟pgpool并使用
  pcp_attach_node加入該節點

總結

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