Start Demo Cluster¶
To do the tutorials you’ll need a single-machine Citus cluster with a master and two worker PostgreSQL instances. Follow these instructions to create a temporary installation which is quick to try and easy to remove.
1. Download the package
Download and unzip it into a directory of your choosing. Then, enter that directory:
2. Initialize the cluster
Citus has two kinds of components, the master and the workers. The master coordinates queries and maintains metadata on where in the cluster each row of data is. The workers hold your data and respond to queries.
Let’s create directories for those nodes to store their data in:
bin/initdb -D data/master bin/initdb -D data/worker
The above commands will give you warnings about trust authentication. Those will become important when you’re setting up a production instance of Citus but for now you can safely ignore them.
The master needs to know where it can find the worker. To tell it you can run:
echo "localhost 9701" >> data/master/pg_worker_list.conf
We assume that ports 9700 (for the master) and 9701 (for the worker) are available on your machine. Feel free to use different ports if they are in use.
Citus is a Postgres extension. To tell Postgres to use this extension,
you’ll need to add it to a configuration variable called
echo "shared_preload_libraries = 'citus'" >> data/master/postgresql.conf echo "shared_preload_libraries = 'citus'" >> data/worker/postgresql.conf
3. Start the master and worker
Let’s start the databases:
bin/pg_ctl -D data/master -o "-p 9700" -l master_logfile start bin/pg_ctl -D data/worker -o "-p 9701" -l worker_logfile start
And initialize them:
bin/createdb -p 9700 $(whoami) bin/createdb -p 9701 $(whoami)
Above you added Citus to
shared_preload_libraries. That lets it hook into some
deep parts of Postgres, swapping out the query planner and executor. Here, we
load the user-facing side of Citus (such as the functions you’ll soon call):
bin/psql -p 9700 -c "CREATE EXTENSION citus;" bin/psql -p 9701 -c "CREATE EXTENSION citus;"
4. Ready for the tutorials!
Your cluster is running and eagerly awaiting data. Proceed to the sharding tutorial to begin learning how to use Citus.