Multi-node setup on Ubuntu or Debian

This section describes the steps needed to set up a multi-node Citus cluster on your own Linux machines using deb packages.

Steps to be executed on all nodes

1. Add repository

# Add Citus repository for package manager
curl | sudo bash

2. Install PostgreSQL + Citus and initialize a database

# install the server and initialize db
sudo apt-get -y install postgresql-9.6-citus-6.2

# preload citus extension
sudo pg_conftool 9.6 main set shared_preload_libraries citus

This installs centralized configuration in /etc/postgresql/9.6/main, and creates a database in /var/lib/postgresql/9.6/main.

3. Configure connection and authentication

Before starting the database let’s change its access permissions. By default the database server listens only to clients on localhost. As a part of this step, we instruct it to listen on all IP interfaces, and then configure the client authentication file to allow all incoming connections from the local network.

sudo pg_conftool 9.6 main set listen_addresses '*'
sudo vi /etc/postgresql/9.6/main/pg_hba.conf
# Allow unrestricted access to nodes in the local network. The following ranges
# correspond to 24, 20, and 16-bit blocks in Private IPv4 address spaces.
host    all             all                 trust

# Also allow the host unrestricted access to connect to itself
host    all             all               trust
host    all             all             ::1/128                 trust


Your DNS settings may differ. Also these settings are too permissive for some environments, see our notes about Worker Security. The PostgreSQL manual explains how to make them more restrictive.

4. Start database servers, create Citus extension

# start the db server
sudo service postgresql restart
# and make it start automatically when computer does
sudo update-rc.d postgresql enable

You must add the Citus extension to every database you would like to use in a cluster. The following example adds the extension to the default database which is named postgres.

# add the citus extension
sudo -i -u postgres psql -c "CREATE EXTENSION citus;"

Steps to be executed on the coordinator node

The steps listed below must be executed only on the coordinator node after the previously mentioned steps have been executed.

1. Add worker node information

We need to inform the coordinator about its workers. To add this information, we call a UDF which adds the node information to the pg_dist_node catalog table. For our example, we assume that there are two workers (named worker-101, worker-102). Add the workers’ DNS names (or IP addresses) and server ports to the table.

sudo -i -u postgres psql -c "SELECT * from master_add_node('worker-101', 5432);"
sudo -i -u postgres psql -c "SELECT * from master_add_node('worker-102', 5432);"

2. Verify that installation has succeeded

To verify that the installation has succeeded, we check that the coordinator node has picked up the desired worker configuration. This command when run in the psql shell should output the worker nodes we added to the pg_dist_node table above.

sudo -i -u postgres psql -c "SELECT * FROM master_get_active_worker_nodes();"

Ready to use Citus

At this step, you have completed the installation process and are ready to use your Citus cluster. To help you get started, we have a tutorial which has instructions on setting up a Citus cluster with sample data in minutes.

Your new Citus database is accessible in psql through the postgres user:

sudo -i -u postgres psql