Prometheus远端数据存储方案之PostgreSQL

Vecloud

今天看到德哥分享的基于postgresql的prometheus数据远端存储方案，于是有了本文的实验。

通常，prometheus的外置存储方案有好几种选择，例如influxdb，m3db， es，postgresql。
m3db一般在云原生环境下，用的更趁手些。
这里我们演示下postgresql的远端存储方案（可读可写），具体看下面的实验。

实验环境：

CentOS7.4
PG11-git-1921 编译安装版

参考文档：
88574693 编译安装 TimescaleDB 扩展
13522 远端存储的介绍
prometheus-postgresql-adapter prometheus-postgresql-adapter的官方文档介绍
官方文档
20191027_04.md 德哥blog
pg_prometheus pg_prometheus扩展的官方文档

1、安装llvm
yum install centos-release-scl-rhyum install llvm-toolset-7-clangyum install llvm5.0 yum install llvm5.0-libsyum install llvm5.0-develyum install clang

2、安装cmake-3.4以上的版本
cd /usr/local/wget https://github.com/Kitware/CMake/releases/download/v3.16.0-rc2/cmake-3.16.0-rc2-Linux-x86_64.shsh cmake-3.16.0-rc2-Linux-x86_64.sh即可在当前路径下安装cmake-3.16载入cmake-3.16到环境变量：export PATH=/usr/local/cmake-3.16.0-rc2-Linux-x86_64/binPATH

3、编译安装PG11带jit模块
su - postgrescd /home/postgres/wget yum localinstall epel-release-latest-7.noarch.rpmyum install llvm5.0 llvm5.0-devel clangcd /home/postgres/pg_sources/postgresql-11./configure --prefix=/usr/local/pgsql-11.5-jit-1921 \--with-python --with-perl --with-tcl --with-pam \--with-openssl --with-libxml --with-libxslt \--with-llvm LLVM_CONFIG='/usr/lib64/llvm5.0/bin/llvm-config'make make install 然后，还有些数据库的基础配置，这里就不细说了。

4、安装TimescaleDB扩展
su - postgrescd /home/postgres/cd timescaledb-1.4.2/export PATH=/usr/local/pgsql-11.5-jit-1921/binPATH./bootstrap 输入ycd ./build && makemake install 日志如下：[ 0%] Built target sqlfile[ 25%] Built target sqlupdatescripts[ 81%] Built target timescaledb[ 85%] Built target timescaledb-loader[100%] Built target timescaledb-tslInstall the project...-- Install configuration: "Release"-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb.control-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--1.4.1--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--1.4.1--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--1.4.0--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--1.3.2--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--1.3.1--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--1.3.0--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--1.2.2--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--1.2.1--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--1.2.0--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--1.1.1--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--1.1.0--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--1.0.1--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--1.0.0--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--1.0.0-rc3--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--1.0.0-rc2--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--1.0.0-rc1--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.12.1--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.12.0--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.11.0--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.10.1--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.10.0--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.9.2--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.9.1--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.9.0--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.8.0--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.7.1--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.7.0--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.6.1--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.6.0--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.5.0--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.4.2--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.4.1--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.4.0--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.3.0--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.2.0--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/share/extension/timescaledb--0.1.0--1.4.2.sql-- Installing: /usr/local/pgsql-11.5-jit-1921/lib/timescaledb-1.4.2.so-- Installing: /usr/local/pgsql-11.5-jit-1921/lib/timescaledb.so-- Installing: /usr/local/pgsql-11.5-jit-1921/lib/timescaledb-tsl-1.4.2.so即可完成timescaledb扩展的安装

编辑pg的配置文件，修改如下：
shared_preload_libraries = 'timescaledb'完成后重启PG进程

然后，登录到PG中，创建扩展：
postgres=# CREATE EXTENSION timescaledb;

5、安装pg_prometheus扩展
su - postgrescd /home/postgres/export PATH=/usr/local/pgsql-11.5-jit-1921/binPATHUSE_PGXS=1 make USE_PGXS=1 make install

编辑pg的配置文件，修改如下：
shared_preload_libraries = 'timescaledb,pg_prometheus'完成后重启PG进程

然后，登录到PG中，创建扩展：
postgres=# CREATE EXTENSION pg_prometheus ;postgres=# SELECT create_prometheus_table('metrics'); 或者使用 SELECT create_prometheus_table('metrics',use_timescaledb=>true);postgres=# INSERT INTO metrics VALUES ('cpu_usage{service="nginx",host="machine1"} 34.6 1494595898000'); postgres=# \d List of relations Schema | Name | Type | Owner --------+-----------------------+----------+---------- public | metrics | view | postgres public | metrics_copy | table | postgres public | metrics_labels | table | postgres public | metrics_labels_id_seq | sequence | postgres public | metrics_values | table | postgres(5 rows)

6、启动prometheus-postgresql-adapter
直接到prometheus-postgresql-adapter 下载解压prometheus-postgresql-adapter
./prometheus-postgresql-adapter -pg-port 1921 --pg-user postgres 即可在前台启动adapter进程

7、使用prometheus连接adapter端口：
vim /usr/local/prometheus/prometheus.yml 在最后加2个配置；
remote_write: - url: "http://192.168.2.4:9201/write" write_relabel_configs: - source_labels: [__name__] regex: 'go_.*' action: dropremote_read: - url: "http://192.168.2.4:9201/read" read_recent: false说明： 我这里设置的read_recent为false，表示查询prometheus近期数据不要到PG库里来捞数据，而是直接查prometheus本地缓存的数据，这样提高查询的速度并且能降低PG库的负载。

不足：
目前的配置来看，我们同事运行的prometheus和PG库， 存放同样历史周期的的metrics，PG库的体积远远超过了prometheus的体积。
PG库的metrics_values表已经 40 MB，此时的prometheus的data目录才 16MB 。 磁盘空间占用上，相差接近3倍。

优化方案待定：
调整remote_write 写入策略，通过drop操作来降低存储到PG的metrics的体积？