Running postgres command in pod definition doesnt work - postgresql

Question

I'm just adding the containers part of the spec. Everything is otherwise set up and working fine and values are hardcoded here. This is a simple Postgres pod that is part of a single replica deployment with its own PVC to persist state. But the problem is having nothing to do with my pod/deployment setup.
containers:
- name: postgres-container
image: postgres
imagePullPolicy: Always
volumeMounts:
- name: postgres-internal-volume
mountPath: /var/lib/postgresql/data
subPath: postgres
envFrom:
- configMapRef:
name: postgres-internal-cnf
ports:
- containerPort: 5432
command: ['psql']
args: [-U postgres -tc "SELECT 1 FROM pg_database WHERE datname = 'dominion'" | grep -q 1 || psql -h localhost -p 5432 -U postgres -c "CREATE DATABASE dominion"]
This command will create a database if it does not already exist. If I create the deployment and exec into the pod and run this command everything works fine. If I however run it here the pod fails to spin up and I get this error:
psql: error: could not connect to server: No such file or directory
Is the server running locally and accepting
connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
I was under the impression that this error comes from the default connection values being incorrect, but here I am hardcoding the localhost and the port number.

Answer 1

With your pod spec, you've replaced the default command -- which starts up the postgres server -- with your own command, so the server never starts. The proper way to perform initialization tasks with the official Postgres image is in the documentation.
You want to move your initialization commands into a ConfigMap, and then mount the scripts into /docker-entrypoint-initdb.d as described in those docs.
The docs have more details, but here's a short example. We want to run
CREATE DATABASE dominion when the postgres server starts (and only
if it is starting with an empty data directory). We can define a
simple SQL script in a ConfigMap:
apiVersion: v1
kind: ConfigMap
metadata:
name: postgres-init-scripts
data:
create-dominion-db.sql: |
CREATE DATABASE dominion
And then mount that script into the appropriate location in the pod
spec:
volumes:
- name: postgres-init-scripts
configMap:
name: postgres-init-scripts
containers:
- name: postgres-container
image: postgres
imagePullPolicy: Always
volumeMounts:
- name: postgres-internal-volume
mountPath: /var/lib/postgresql/data
subPath: postgres
- name: postgres-init-scripts
mountPath:
/docker-entrypoint-initdb.d/create-dominion-db.sql
subPath: create-dominion-db.sql
envFrom:
- configMapRef:
name: postgres-internal-cnf
ports:
- containerPort: 5432