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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。
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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：
https://blog.csdn.net/qq_43303221/article/details/88574693#cmake_34_50 编译安装 TimescaleDB 扩展
https://studygolang.com/articles/13522?fr=sidebar 远端存储的介绍
https://github.com/timescale/prometheus-postgresql-adapter prometheus-postgresql-adapter的官方文档介绍
https://prometheus.io/docs/prometheus/latest/configuration/configuration/#remote_write 官方文档
https://github.com/digoal/blog/blob/master/201910/20191027_04.md 德哥blog
https://github.com/timescale/pg_prometheus pg_prometheus扩展的官方文档
1、安装llvm
yum install centos-release-scl-rh yum install llvm-toolset-7-clang yum install llvm5.0 yum install llvm5.0-libs yum install llvm5.0-devel yum 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.sh sh 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/bin:$PATH
3、编译安装PG11带jit模块
su - postgres cd /home/postgres/ wget yum localinstall epel-release-latest-7.noarch.rpm yum install llvm5.0 llvm5.0-devel clang cd /home/postgres/pg_sources/postgresql-11 ./configure --prefix=/usr/local/pgsql-11.5-jit-1921 \ --with-python --with-perl --with-tcl --with-pam \ --with-openssl --with-libxml --with-libxslt \ --with-llvm LLVM_CONFIG='/usr/lib64/llvm5.0/bin/llvm-config' make make install 然后，还有些数据库的基础配置，这里就不细说了。
4、安装TimescaleDB扩展
su - postgres cd /home/postgres/ cd timescaledb-1.4.2/ export PATH=/usr/local/pgsql-11.5-jit-1921/bin:$PATH ./bootstrap 输入y cd ./build && make make 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-tsl Install 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 - postgres cd /home/postgres/ export PATH=/usr/local/pgsql-11.5-jit-1921/bin:$PATH USE_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https://github.com/timescale/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: drop remote_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？