How To Deploy PostgreSQL on Kubernetes

What is PostgreSQL?

PostgreSQL is a powerful, open source Relational Database Management System.

PostgreSQL is not controlled by any organization or any individual. Its source code is available free of charge. It is pronounced as "post-gress-Q-L".

PostgreSQL has earned a strong reputation for its reliability, data integrity, and correctness.

• It runs on all major operating systems, including Linux, UNIX (AIX, BSD, HP-UX, SGI IRIX, MacOS, Solaris, Tru64), and Windows.

• It is fully ACID compliant, has full support for foreign keys, joins, views, triggers, and stored procedures (in multiple languages)

• It includes most SQL:2008 data types, including INTEGER, NUMERIC, BOOLEAN, CHAR, VARCHAR, DATE, INTERVAL, and TIMESTAMP.

• It also supports storage of binary large objects, including pictures, sounds, or video.

• It has native programming interfaces for C/C++, Java, .Net, Perl, Python, Ruby, Tcl, ODBC, among others, and exceptional documentation.

Prerequisites

To follow this guide you need -

• Kubernetes Cluster

• GlusterFS Cluster

Step 1 - Create a PostgreSQL Container Image

Create a file name “Dockerfile” for PostgreSQL. This image contains our custom config dockerfile which will look like -

FROM ubuntu:latest
MAINTAINER XenonStack

RUN apt-key adv --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys B97B0AFCAA1A47F044F244A07FCC7D46ACCC4CF8

RUN echo "deb http://apt.postgresql.org/pub/repos/apt/ xenial-pgdg main" > /etc/apt/sources.list.d/pgdg.list

RUN apt-get update && apt-get install -y python-software-properties software-properties-common postgresql-9.6 postgresql-client-9.6 postgresql-contrib-9.6

RUN /etc/init.d/postgresql start &&\
 psql --command "CREATE USER root WITH SUPERUSER PASSWORD 'xenonstack';" &&\
 createdb -O root xenonstack

RUN echo "host all  all 0.0.0.0/0  md5" >> /etc/postgresql/9.6/main/pg_hba.conf

RUN echo "listen_addresses='*'" >> /etc/postgresql/9.6/main/postgresql.conf

# Expose the PostgreSQL port
EXPOSE 5432

# Add VOLUMEs to allow backup of databases
VOLUME  ["/var/lib/postgresql"]

# Set the default command to run when starting the container
CMD ["/usr/lib/postgresql/9.6/bin/postgres", "-D", "/var/lib/postgresql", "-c", "config_file=/etc/postgresql/9.6/main/postgresql.conf"]

This Postgres image has a base image of ubuntu xenial. After that, we create Super User and default databases. Exposing 5432 port will help external system to connect the PostgreSQL server.

Step 2 - Build PostgreSQL Docker Image

$ docker build -t dr.xenonstack.com:5050/postgres:v9.6

Step 3 - Create a Storage Volume (Using GlusterFS)

Using below-mentioned command create a volume in GlusterFS for PostgreSQL and start it.

As we don’t want to lose our PostgreSQL Database data just because a Gluster server dies in the cluster, so we put replica 2 or more for higher availability of data.

$ gluster volume create postgres-disk replica 2 transport tcp k8-master:/mnt/brick1/postgres-disk  k8-1:/mnt/brick1/postgres-disk
$ gluster volume start postgres-disk
$ gluster volume info postgres-disk

Step 4 - Deploy PostgreSQL on Kubernetes

Deploying PostgreSQL on Kubernetes have following prerequisites -

• Docker Image: We have created a Docker Image for Postgres in Step 2

• Persistent Shared Storage Volume: We have created a Persistent Shared Storage Volume in Step 3

• Deployment & Service Files: Next, we will create Deployment & Service Files

Create a file name “deployment.yml” for PostgreSQL. This deployment file will look like -

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: postgres
  namespace: production
spec:
  replicas: 1
  template:
 metadata:
   labels:
    k8s-app: postgres
 spec:
   containers:
   - name: postgres
     image: dr.xenonstack.com:5050/postgres:v9.6
     imagePullPolicy: "IfNotPresent"
     ports:
     - containerPort: 5432
     env:
     - name: POSTGRES_USER
       value: postgres
     - name: POSTGRES_PASSWORD
       value: superpostgres
     - name: PGDATA
       value: /var/lib/postgresql/data/pgdata
     volumeMounts:
        - mountPath: /var/lib/postgresql/data
          name: postgredb
   volumes:
     - name: postgredb
       glusterfs:
         endpoints: glusterfs-cluster
         path: postgres-disk
         readOnly: false

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