PostgreSQL DBA(1) - 数据库参数设置#1

本节简单介绍了可用于诊断PostgreSQL数据库参数设置的工具：postgresqltuner,包括该工具的安装和基本使用。

一、安装

在REHL系列下安装：

#该工具基于Perl语言开发,首先安装Perl相关的开发包
#yum -y install perl-DBD-Pg
#获取工具包
#cd /tmp
#wget -O postgresqltuner.pl https://postgresqltuner.pl
#chmod +x postgresqltuner.pl

二、基本使用

在数据库主机上执行:

[xdb@localhost bin]$ /tmp/postgresqltuner.pl --host=localhost --user xdb --database testdb
postgresqltuner.pl version 1.0.0
Connecting to localhost:5432 database testdb with user xdb...
Argument "11beta2" isn't numeric in numeric gt (>) at /tmp/postgresqltuner.pl line 818.
[OK]      User used for report have super rights
=====  OS information  =====
[INFO]    OS: linux Version: 3.10.0-514.16.1.el7.x86_64 Arch: x86_64-linux-thread-multi
[INFO]    OS total memory: 732.52 MB
[BAD]     Memory overcommitment is allowed on the system. This can lead to OOM Killer killing some PostgreSQL process, which will cause a PostgreSQL server restart (crash recovery)
[INFO]    sysctl vm.overcommit_ratio=50
[BAD]     vm.overcommit_ratio is too small, you will not be able to use more than 50*RAM+SWAP for applications
[INFO]    Currently used I/O scheduler(s) : deadline
=====  General instance informations  =====
-----  Version  -----
Argument "11beta2" isn't numeric in numeric gt (>) at /tmp/postgresqltuner.pl line 818.
[OK]      You are using last 11beta2
-----  Uptime  -----
[INFO]    Service uptime :  09m 53s
[WARN]    Uptime is less than 1 day. postgresqltuner.pl result may not be accurate
-----  Databases  -----
[INFO]    Database count (except templates): 2
[INFO]    Database list (except templates): postgres testdb
-----  Extensions  -----
[INFO]    Number of activated extensions : 1
[INFO]    Activated extensions : plpgsql
[WARN]    Extensions pg_stat_statements is disabled
-----  Users  -----
[OK]      No user account will expire in less than 7 days
[OK]      No user with password=username
[OK]      Password encryption is enabled
-----  Connection information  -----
[INFO]    max_connections: 100
[INFO]    current used connections: 6 (6.00%)
[INFO]    3 are reserved for super user (3.00%)
[INFO]    Average connection age :  08m 14s
[WARN]    Average connection age is less than 10 minutes. Use a connection pooler to limit new connection/seconds
-----  Memory usage  -----
[INFO]    configured work_mem: 4.00 MB
[INFO]    Using an average ratio of work_mem buffers by connection of 150% (use --wmp to change it)
[INFO]    total work_mem (per connection): 6.00 MB
[INFO]    shared_buffers: 128.00 MB
Argument "11beta2" isn't numeric in numeric gt (>) at /tmp/postgresqltuner.pl line 818.
[INFO]    Track activity reserved size : 0.00 B
[WARN]    maintenance_work_mem is less or equal default value. Increase it to reduce maintenance tasks time
[INFO]    Max memory usage :
      shared_buffers (128.00 MB)
    + max_connections * work_mem * average_work_mem_buffers_per_connection (100 * 4.00 MB * 150 / 100 = 600.00 MB)
    + autovacuum_max_workers * maintenance_work_mem (3 * 64.00 MB = 192.00 MB)
    + track activity size (0.00 B)
    = 920.00 MB
[INFO]    effective_cache_size: 4.00 GB
[INFO]    Size of all databases : 33.19 MB
[WARN]    shared_buffer is too big for the total databases size, memory is lost
[INFO]    PostgreSQL maximum memory usage: 125.59% of system RAM
[BAD]     Max possible memory usage for PostgreSQL is more than system total RAM. Add more RAM or reduce PostgreSQL memory
[INFO]    max memory+effective_cache_size is 684.76% of total RAM
[WARN]    the sum of max_memory and effective_cache_size is too high, the planer can find bad plans if system cache is smaller than expected
-----  Logs  -----
[OK]      log_hostname is off : no reverse DNS lookup latency
[WARN]    log of long queries is desactivated. It will be more difficult to optimize query performances
[OK]      log_statement=none
-----  Two phase commit  -----
Argument "11beta2" isn't numeric in numeric gt (>) at /tmp/postgresqltuner.pl line 818.
[OK]      Currently no two phase commit transactions
-----  Autovacuum  -----
[OK]      autovacuum is activated.
[INFO]    autovacuum_max_workers: 3
-----  Checkpoint  -----
[WARN]    checkpoint_completion_target(0.5) is low
-----  Disk access  -----
[OK]      fsync is on
[OK]      synchronize_seqscans is on
-----  WAL  -----
Argument "11beta2" isn't numeric in numeric gt (>) at /tmp/postgresqltuner.pl line 818.
-----  Planner  -----
[OK]      costs settings are defaults
[BAD]     some plan features are disabled : enable_partitionwise_aggregate,enable_partitionwise_join
=====  Database information for database testdb  =====
-----  Database size  -----
[INFO]    Database testdb total size : 11.44 MB
Argument "11beta2" isn't numeric in numeric gt (>) at /tmp/postgresqltuner.pl line 818.
[INFO]    Database testdb tables size : 8.38 MB (73.22%)
[INFO]    Database testdb indexes size : 3.06 MB (26.78%)
-----  Tablespace location  -----
Argument "11beta2" isn't numeric in numeric gt (>) at /tmp/postgresqltuner.pl line 818.
[OK]      No tablespace in PGDATA
-----  Shared buffer hit rate  -----
[INFO]    shared_buffer_heap_hit_rate: 99.03%
[INFO]    shared_buffer_toast_hit_rate: 0.00%
[INFO]    shared_buffer_tidx_hit_rate: 28.57%
[INFO]    shared_buffer_idx_hit_rate: 98.43%
[OK]      Shared buffer idx hit rate is very good
-----  Indexes  -----
[OK]      No invalid indexes
Argument "11beta2" isn't numeric in numeric gt (>) at /tmp/postgresqltuner.pl line 818.
[OK]      No unused indexes
-----  Procedures  -----
[OK]      No procedures with default costs

=====  Configuration advices  =====
-----  checkpoint  -----
[MEDIUM] Your checkpoint completion target is too low. Put something nearest from 0.8/0.9 to balance your writes better during the checkpoint interval
-----  extension  -----
[LOW] Enable pg_stat_statements to collect statistics on all queries (not only queries longer than log_min_duration_statement in logs)
-----  sysctl  -----
[URGENT] set vm.overcommit_memory=2 in /etc/sysctl.conf and run sysctl -p to reload it. This will disable memory overcommitment and avoid postgresql killed by OOM killer.

执行完毕,该工具会输出一系列的参数调整建议.这些参数的含义和为何如此调整,下节讨论.

三、小结

本节简单介绍了postgresqltuner.pl工具的安装和基本使用,有兴趣的可以查看该工具postgresqltuner的源码并进行改进.