Postgres Running with WAL

Postgres master and slave (standby) servers working with Docker.

To run this project follow steps below:

Prerequisites

sudo apt install -y git
sudo apt install -y postgresql postgresql-contrib postgresql-client-common
sudo /etc/init.d/postgresql stop

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Install Docker

sudo apt install -y apt-transport-https ca-certificates curl software-properties-common
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable"
sudo apt update
apt-cache policy docker-ce
sudo apt install -y docker-ce
sudo usermod -aG docker ${USER}
su - ${USER}
id -nG
sudo usermod -aG docker username

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Install Docker-Compose

sudo curl -L "https://github.com/docker/compose/releases/download/1.25.0/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
sudo chmod +x /usr/local/bin/docker-compose
sudo ln -s /usr/local/bin/docker-compose /usr/bin/docker-compose
docker-compose --version

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Run script to start the magic

# make script executable
sudo chmod +x initializer.sh
# run this script
./initializer.sh

Password for user docker is docker

After script finish, add line below into ./master_volume/postgres/postgresql.conf

sudo vi ./master_volume/postgres/postgresql.conf
max_replication_slots = 1

Restart master docker restart master

Then access remotely master server to create replication slot to avoid problem if slave serve go down and lost some WAL position, and then REDO from this replication slot.

psql -h 127.0.0.1 -p 5432 -U docker
select * from pg_replication_slots;

Expected result:

slot_name	plugin	slot_type	datoid	database	active	active_pid	xmin	catalog_xmin	restart_lsn

Create slot on master: select * from pg_create_physical_replication_slot('standby_replication_slot');

Expected result:

slot_name	xlog_position
standby_replication_slot

After some seconds run command below to check if everything is fine. select * from pg_replication_slots;

Expected result:

slot_name	plugin	slot_type	datoid	database	active	active_pid	xmin	catalog_xmin	restart_lsn
standby_replication_slot		physical			t	44			0/3000108

To test

You can download script: Dummy data