背景
PolarDB 的云原生存算分离架构, 具备低廉的数据存储、高效扩展弹性、高速多机并行计算能力、高速数据搜索和处理; PolarDB与计算算法结合, 将实现双剑合璧, 推动业务数据的价值产出, 将数据变成生产力.
本文将介绍PolarDB 开源版 使用pgpool-II实现透明读写分离.
pgpool-II是PostgreSQL读写分离中间件, 由于PolarDB是计算存储分离架构, 和aws aurora一样, 只需要配置pgpool的负载均衡, 不需要配置它ha功能.
ha功能建议采用polardb开源生态产品, 例如乘数科技的集群管理软件, 配置pgpool时使用rw, ro节点对应的vip即可(vip由乘数的集群管理软件来管理).
测试环境为macOS+docker, PolarDB部署请参考如何用 PolarDB 证明巴菲特的投资理念 - 包括PolarDB简单部署。
部署pgpool-II
cd ~
wget https://www.pgpool.net/mediawiki/download.php?f=pgpool-II-4.4.1.tar.gz -O pgpool-II-4.4.1.tar.gz
tar -zxvf pgpool-II-4.4.1.tar.gz
cd pgpool-II-4.4.1
./configure --prefix=/usr/local/pgpool4.4.1 --with-openssl
make -j 8
sudo make install 配置动态库和默认路径
sudo vi /etc/ld.so.conf
# addd
/usr/local/pgpool4.4.1/lib
sudo ldconfig
vi ~/.bash_profile
# add
export PATH=/usr/local/pgpool4.4.1/bin:$PATH
. ~/.bash_profile 配置pgpool-II
polardb 3节点配置如下:
[postgres@1373488a35ab ~]$ netstat -anp|grep LISTEN
tcp 0 0 0.0.0.0:5434 0.0.0.0:* LISTEN 72/postgres
tcp 0 0 0.0.0.0:5432 0.0.0.0:* LISTEN 9/postgres
tcp 0 0 0.0.0.0:5433 0.0.0.0:* LISTEN 33/postgres
tcp6 0 0 :::5434 :::* LISTEN 72/postgres
tcp6 0 0 :::5432 :::* LISTEN 9/postgres
tcp6 0 0 :::5433 :::* LISTEN 33/postgres
unix 2 [ ACC ] STREAM LISTENING 22905 9/postgres ./.s.PGSQL.5432
unix 2 [ ACC ] STREAM LISTENING 18212 33/postgres ./.s.PGSQL.5433
unix 2 [ ACC ] STREAM LISTENING 24071 72/postgres ./.s.PGSQL.5434
[postgres@1373488a35ab ~]$ psql -p 5432 -c "select pg_is_in_recovery();"
pg_is_in_recovery
-------------------
f
(1 row)
[postgres@1373488a35ab ~]$ psql -p 5433 -c "select pg_is_in_recovery();"
pg_is_in_recovery
-------------------
t
(1 row)
[postgres@1373488a35ab ~]$ psql -p 5434 -c "select pg_is_in_recovery();"
pg_is_in_recovery
-------------------
t
(1 row) polardb与aurora类似, 共享存储集群模式, 无需pgpool来管理HA.
https://www.pgpool.net/docs/latest/en/html/example-aurora.html
配置pgpool.conf
cd /usr/local/pgpool4.4.1/etc
sudo vi pgpool.conf
listen_addresses = '0.0.0.0'
port = 9999
unix_socket_directories = '/tmp'
pcp_listen_addresses = 'localhost'
pcp_port = 9898
pcp_socket_dir = '/tmp'
log_destination = 'stderr'
logging_collector = on
log_directory = '/tmp/pgpool_logs'
pid_file_name = '/var/run/pgpool/pgpool.pid'
logdir = '/tmp'
backend_clustering_mode = 'streaming_replication'
load_balance_mode = on
sr_check_period = 0
health_check_period = 0
failover_on_backend_shutdown=off
failover_on_backend_error=off
enable_pool_hba = on
backend_hostname0 = '127.0.0.1'
backend_port0 = '5432'
backend_weight0 = 1
backend_application_name0 = 'polardb_primray'
backend_flag0 = 'ALWAYS_PRIMARY|DISALLOW_TO_FAILOVER'
backend_hostname1 = '127.0.0.1'
backend_port1 = '5433'
backend_weight1 = 2
backend_application_name1 = 'polardb_reader1'
backend_flag1 = 'DISALLOW_TO_FAILOVER'
backend_hostname2 = '127.0.0.1'
backend_port2 = '5434'
backend_weight2 = 2
backend_application_name2 = 'polardb_reader2'
backend_flag2 = 'DISALLOW_TO_FAILOVER' 配置pool_hba.conf
sudo vi pool_hba.conf
# add
host all all 0.0.0.0/0 md5 配置pgpool数据库用户密码文件pool_passwd
[postgres@1373488a35ab etc]$ sudo pg_md5 --md5auth --username=digoal pwd123
[postgres@1373488a35ab etc]$ cat /usr/local/pgpool4.4.1/etc/pool_passwd
digoal:md531a770cec82aa37e217bb6e46c3f9d55
-- 实际上就是pwd+username的md5值
postgres=# select md5('pwd123digoal');
md5
----------------------------------
31a770cec82aa37e217bb6e46c3f9d55
(1 row) 在数据库中创建相应用户
postgres=# create user digoal superuser encrypted password 'pwd123' login;
CREATE ROLE 配置pcp管理用户密码文件pcp.conf
postgres=# select md5('pwd123');
md5
----------------------------------
45cb41b32dcfb917ccd8614f1536d6da
(1 row)
cd /usr/local/pgpool4.4.1/etc
sudo vi pcp.conf
pcpadm:45cb41b32dcfb917ccd8614f1536d6da 准备pgpool运行时pid文件目录和日志目录
sudo mkdir /var/run/pgpool
sudo mkdir /tmp/pgpool_logs 启动pgpool
sudo pgpool 查看pgpool监听
[postgres@1373488a35ab pgpool_logs]$ netstat -anp|grep LISTE
(Not all processes could be identified, non-owned process info
will not be shown, you would have to be root to see it all.)
tcp 0 0 0.0.0.0:9999 0.0.0.0:* LISTEN -
tcp 0 0 0.0.0.0:5434 0.0.0.0:* LISTEN 72/postgres
tcp 0 0 0.0.0.0:5432 0.0.0.0:* LISTEN 9/postgres
tcp 0 0 0.0.0.0:5433 0.0.0.0:* LISTEN 33/postgres
tcp 0 0 127.0.0.1:9898 0.0.0.0:* LISTEN -
tcp6 0 0 :::5434 :::* LISTEN 72/postgres
tcp6 0 0 :::5432 :::* LISTEN 9/postgres
tcp6 0 0 :::5433 :::* LISTEN 33/postgres
unix 2 [ ACC ] STREAM LISTENING 22905 9/postgres ./.s.PGSQL.5432
unix 2 [ ACC ] STREAM LISTENING 18212 33/postgres ./.s.PGSQL.5433
unix 2 [ ACC ] STREAM LISTENING 24071 72/postgres ./.s.PGSQL.5434
unix 2 [ ACC ] STREAM LISTENING 30964 - /tmp/.s.PGSQL.9999
unix 2 [ ACC ] STREAM LISTENING 30967 - /tmp/.s.PGSQL.9898 使用pcp管理命令查看pgpool中间件状态
pcp_node_info -U pcpadm -p 9898
Password:
127.0.0.1 5432 2 0.200000 up unknown primary unknown 0 none none 2023-01-02 03:44:20
127.0.0.1 5433 2 0.400000 up unknown standby unknown 0 none none 2023-01-02 03:44:20
127.0.0.1 5434 2 0.400000 up unknown standby unknown 0 none none 2023-01-02 03:44:20 [postgres@1373488a35ab etc]$ pcp_node_count -U pcpadm -p 9898
Password:
3 pcp_pool_status -U pcpadm -h localhost -p 9898
Password:
...
name : backend_application_name1
value: polardb_reader1
desc : application_name for backend #1
name : backend_hostname2
value: 127.0.0.1
desc : backend #2 hostname
name : backend_port2
value: 5434
desc : backend #2 port number
name : backend_weight2
value: 0.400000
desc : weight of backend #2
name : backend_flag2
value: DISALLOW_TO_FAILOVER
desc : backend #2 flag
... 使用pgpool代理链接polardb
export PGPASSWORD=pwd123
export PGDATABASE=postgres
psql -p 9999 -U digoal -c "select * from pg_stat_activity where pid=pg_backend_pid();" 测试pgpool读写分离
pgbench -i -s 1 -h 127.0.0.1 -p 9999 -U digoal postgres pgbench -n -r -P 1 -c 8 -j 8 -T 10 -S -h 127.0.0.1 -p 9999 -U digoal postgres
[postgres@1373488a35ab ~]$ psql -p 5432 -c "select count(*) from pg_stat_activity where application_name='pgbench';"
count
-------
8
(1 row)
[postgres@1373488a35ab ~]$ psql -p 5433 -c "select count(*) from pg_stat_activity where application_name='pgbench';"
count
-------
8
(1 row)
[postgres@1373488a35ab ~]$ psql -p 5434 -c "select count(*) from pg_stat_activity where application_name='pgbench';"
count
-------
8
(1 row) 
