Sharded Cluster Local connection using postgres-util

Local Connection to the database has to be through the postgres-utils sidecar. This sidecar has all PostgreSQL binaries that are not present in the main container called patroni like the psql command.

This main container only have the required binaries and utilities to be able to configure the postgres sharded cluster and the HA configuration.

Access to postgres-util sidecar

First we’ll check the if the container is present in the pods, for these example we have a sharded cluster named stackgres, composed of three pods and installed in the default namespace:

kubectl get pods -n default -l app=StackGresShardedCluster,stackgres.io/shardedcluster=true

output:

NAME                READY   STATUS    RESTARTS   AGE
stackgres-coord-0   5/5     Running   0          12m
stackgres-shard0-0  5/5     Running   0          12m
stackgres-shard1-0  5/5     Running   0          11m

As you can see in the list we have 5/5 containers (sidecars) ready. To check the list of these containers we can run the next command:

kubectl get pods stackgres-coord-0 -n default -o jsonpath='{.spec.containers[*].name}*'

output:

patroni envoy pgbouncer postgres-util prometheus-postgres-exporter

At this point we already checked that sidecar postgres-util is up and running. Now, to access the postgres instance through this sidecar you can either connect via a terminal and then access the psql, or execute the psql command directly:

Directly via psql:

$ kubectl exec -it stackgres-coord-0 -c postgres-util -- psql
psql (14.6 OnGres Inc.)
Type "help" for help.

postgres=#

Or in a bash console:

$ kubectl exec -it stackgres-coord-0 -c postgres-util -- bash
bash-4.4$ psql
psql (14.6 OnGres Inc.)
Type "help" for help.

postgres=#

The psql command connects via unix socket directly and doesn’t require a password. Alternatively, you could specify the port 6432 and then the connection goes through the connection pooling tool (PgBouncer), and you will be prompted for the postgres password.