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Daniel Westermann

Getting started with Ansible – Creating the PostgreSQL instance

In the last three posts we did the initial Ansible setup, installed the operating system packages, created the PostgreSQL group and user and downloaded, compiled and installed the PostgreSQL binaries from source. In this post we’ll look at how we can use Ansible to create our first PostgreSQL instance.

As a reminder this is our current playbook:

[ansible@ansiblecontrol ansible]$ pwd
/opt/ansible
[ansible@ansiblecontrol ansible]$ cat roles/postgresqldbserver/tasks/main.yml 
---
- name: Install PostgreSQL dependencies
  yum: name={{item}} state=present
  with_items:
   - gcc
   - openldap-devel
   - python-devel
   - readline-devel
   - openssl-devel
   - redhat-lsb
   - bison
   - flex
   - perl-ExtUtils-Embed
   - zlib-devel
   - crypto-utils
   - openssl-devel
   - pam-devel
   - libxml2-devel
   - libxslt-devel
   - tcl
   - tcl-devel
   - openssh-clients
   - bzip2
   - net-tools
   - wget
   - screen
   - ksh

- name: Add PostgreSQL operating system group
  group: name=postgressomegroup state=present

- name: Add PostgreSQL operating system user
  user: name=postgres comment="PostgreSQL binaries owner" group=postgres

- name: Download the PostgreSQL 9.5.3 sources
  get_url: url=https://ftp.postgresql.org/pub/source/v9.5.3/postgresql-9.5.3.tar.bz2 dest=/var/tmp mode=0755

- name: Copy PostgreSQL install script to targets
  copy: src=install_pg953.sh dest=/var/tmp/install_pg953.sh owner=root group=root mode="u=rwx"

- name: Compile and install PostgreSQL
  shell: /var/tmp/install_pg953.sh >> /var/tmp/install_pg_log
  args:
    executable: /usr/bin/bash

What we need now is an additional task which does the creation of the PostgreSQL cluster on disk. As with the installation from source we’ll need to do some scripting for this. Here is a very basic script for doing this:

#!/usr/bin/bash

PGUSER="postgres"
PGGROUP="postgres"
DATADIRECTORY="/u02/pgdata/PG1"
XLOGLOCATION="/u03/pgdata/PG1"
PGHOME="/u01/app/postgres/product/95/db_3/"
POSTGRESDBPASSWORD="postgres"

mkdir -p ${DATADIRECTORY}
mkdir -p ${XLOGLOCATION}
chown ${PGUSER}:${PGGROUP} ${DATADIRECTORY}
chown ${PGUSER}:${PGGROUP} ${XLOGLOCATION}

su - ${PGUSER} -c "echo ${POSTGRESDBPASSWORD} > /var/tmp/tmp_pwd"
su - ${PGUSER} -c "${PGHOME}/bin/initdb -D ${DATADIRECTORY} --pwfile=/var/tmp/tmp_pwd -X ${XLOGLOCATION} -k"

rm -f /var/tmp/tmp_pwd

su - ${PGUSER} -c "${PGHOME}/bin/pg_ctl -D ${DATADIRECTORY} start"

As with the PostgreSQL installation script we’ll put this into the “files” directory of our “postgresqldbserver” role:

[ansible@ansiblecontrol ansible]$ ls roles/postgresqldbserver/files/
create_pg953_cluster.sh  install_pg953.sh

We’ll use the same logic again and add two new tasks to our existing playbook:

- name: Copy the PostgreSQL cluster creation script to the targets
  copy: src=create_pg953_cluster.sh dest=/var/tmp/create_pg953_cluster.sh owner=root group=root mode="u=rwx"

- name: Create and start the PostgreSQL instance
  shell: /var/tmp/create_pg953_cluster.sh >> /var/tmp/create_pg_cluster.log
  args:
    executable: /usr/bin/bash

Once the playbook is executed again:

[ansible@ansiblecontrol ansible]$ ansible-playbook -i /opt/ansible/development /opt/ansible/roles/postgresqldbserver/site.yml

PLAY [postgresql-servers] ******************************************************

TASK [setup] *******************************************************************
ok: [192.168.22.171]
ok: [192.168.22.172]

TASK [postgresqldbserver : Install PostgreSQL dependencies] ********************
ok: [192.168.22.172] => (item=[u'gcc', u'openldap-devel', u'python-devel', u'readline-devel', u'openssl-devel', u'redhat-lsb', u'bison', u'flex', u'perl-ExtUtils-Embed', u'zlib-devel', u'crypto-utils', u'openssl-devel', u'pam-devel', u'libxml2-devel', u'libxslt-devel', u'tcl', u'tcl-devel', u'openssh-clients', u'bzip2', u'net-tools', u'wget', u'screen', u'ksh'])
ok: [192.168.22.171] => (item=[u'gcc', u'openldap-devel', u'python-devel', u'readline-devel', u'openssl-devel', u'redhat-lsb', u'bison', u'flex', u'perl-ExtUtils-Embed', u'zlib-devel', u'crypto-utils', u'openssl-devel', u'pam-devel', u'libxml2-devel', u'libxslt-devel', u'tcl', u'tcl-devel', u'openssh-clients', u'bzip2', u'net-tools', u'wget', u'screen', u'ksh'])

TASK [postgresqldbserver : Add PostgreSQL operating system group] **************
ok: [192.168.22.171]
ok: [192.168.22.172]

TASK [postgresqldbserver : Add PostgreSQL operating system user] ***************
ok: [192.168.22.172]
ok: [192.168.22.171]

TASK [postgresqldbserver : Download the PostgreSQL 9.5.3 sources] **************
ok: [192.168.22.172]
ok: [192.168.22.171]

TASK [postgresqldbserver : Copy PostgreSQL install script to targets] **********
changed: [192.168.22.171]
changed: [192.168.22.172]

TASK [postgresqldbserver : Compile and install PostgreSQL] *********************
changed: [192.168.22.172]
changed: [192.168.22.171]

TASK [postgresqldbserver : Copy the PostgreSQL cluster creation script to the targets] ***
ok: [192.168.22.171]
changed: [192.168.22.172]

TASK [postgresqldbserver : Create and start the PostgreSQL instance] ***********
changed: [192.168.22.172]
changed: [192.168.22.171]

PLAY RECAP *********************************************************************
192.168.22.171             : ok=9    changed=3    unreachable=0    failed=0   
192.168.22.172             : ok=9    changed=4    unreachable=0    failed=0   

… we should have a running PostgreSQL instance on both nodes, lets check:

[root@ansiblepg1 tmp]# ps -ef | grep postgres
postgres 17284     1  0 08:47 ?        00:00:00 /u01/app/postgres/product/95/db_3/bin/postgres -D /u02/pgdata/PG1
postgres 17288 17284  0 08:47 ?        00:00:00 postgres: checkpointer process   
postgres 17289 17284  0 08:47 ?        00:00:00 postgres: writer process   
postgres 17290 17284  0 08:47 ?        00:00:00 postgres: wal writer process   
postgres 17291 17284  0 08:47 ?        00:00:00 postgres: autovacuum launcher process   
postgres 17292 17284  0 08:47 ?        00:00:00 postgres: stats collector process   
root     17294 10223  0 08:47 pts/1    00:00:00 grep --color=auto postgres
[root@ansiblepg2 ~]# ps -ef | grep postgres
postgres 16951     1  0 08:47 ?        00:00:00 /u01/app/postgres/product/95/db_3/bin/postgres -D /u02/pgdata/PG1
postgres 16955 16951  0 08:47 ?        00:00:00 postgres: checkpointer process   
postgres 16956 16951  0 08:47 ?        00:00:00 postgres: writer process   
postgres 16957 16951  0 08:47 ?        00:00:00 postgres: wal writer process   
postgres 16958 16951  0 08:47 ?        00:00:00 postgres: autovacuum launcher process   
postgres 16959 16951  0 08:47 ?        00:00:00 postgres: stats collector process   
root     16985 16964  0 08:48 pts/0    00:00:00 grep --color=auto postgres

Isn’t that cool? Sure, there is much hard coding in here which needs to be extended by using variables. This is a topic for another post.

For your reference here is the complete playbook:

[ansible@ansiblecontrol ansible]$ cat /opt/ansible/roles/postgresqldbserver/tasks/main.yml 
---
- name: Install PostgreSQL dependencies
  yum: name={{item}} state=present
  with_items:
   - gcc
   - openldap-devel
   - python-devel
   - readline-devel
   - openssl-devel
   - redhat-lsb
   - bison
   - flex
   - perl-ExtUtils-Embed
   - zlib-devel
   - crypto-utils
   - openssl-devel
   - pam-devel
   - libxml2-devel
   - libxslt-devel
   - tcl
   - tcl-devel
   - openssh-clients
   - bzip2
   - net-tools
   - wget
   - screen
   - ksh

- name: Add PostgreSQL operating system group
  group: name=postgressomegroup state=present

- name: Add PostgreSQL operating system user
  user: name=postgres comment="PostgreSQL binaries owner" group=postgres

- name: Download the PostgreSQL 9.5.3 sources
  get_url: url=https://ftp.postgresql.org/pub/source/v9.5.3/postgresql-9.5.3.tar.bz2 dest=/var/tmp mode=0755

- name: Copy PostgreSQL install script to targets
  copy: src=install_pg953.sh dest=/var/tmp/install_pg953.sh owner=root group=root mode="u=rwx"

- name: Compile and install PostgreSQL
  shell: /var/tmp/install_pg953.sh >> /var/tmp/install_pg_log
  args:
    executable: /usr/bin/bash

- name: Copy the PostgreSQL cluster creation script to the targets
  copy: src=create_pg953_cluster.sh dest=/var/tmp/create_pg953_cluster.sh owner=root group=root mode="u=rwx"

- name: Create and start the PostgreSQL instance
  shell: /var/tmp/create_pg953_cluster.sh >> /var/tmp/create_pg_cluster.log
  args:
    executable: /usr/bin/bash

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Daniel Westermann
Daniel Westermann

Senior Consultant and Technology Leader Open Infrastructure