Running the Postgres CLI client from a Kubernetes jumpbox - postgresql

Question

I have setup a Postgres pod on my Kubernetes cluster, and I am trying to troubleshoot it a bit.
I would like to use the official Postgres image and deploy it to my Kubernetes cluster using kubectl. Given that my Postgres server connection details are:
host: mypostgres
port: 5432
username: postgres
password: 12345
And given that I think the command will be something like:
kubectl run -i --tty --rm debug --image=postgres --restart=Never -- sh
What do I need to do so that I can deploy this image to my cluster, connect to my Postgres server and start running SQL command against it (for troubleshooting purposes)?

Answer 1

If your primarily interested in troubleshooting, then you're probably looking for the kubectl port-forward command, which will expose a container port on your local host. First, you'll need to deploy the Postgres pod; you haven't shown what your pod manifest looks like, so I'm going to assume a Deployment like this:
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: postgres
name: postgres
namespace: sandbox
spec:
replicas: 1
selector:
matchLabels:
app: postgres
template:
metadata:
labels:
app: postgres
spec:
containers:
- env:
- name: POSTGRES_PASSWORD
value: secret
- name: POSTGRES_USER
value: example
- name: POSTGRES_DB
value: example
image: docker.io/postgres:13
name: postgres
ports:
- containerPort: 5432
name: postgres
protocol: TCP
volumeMounts:
- mountPath: /var/lib/postgresql
name: postgres-data
strategy: Recreate
volumes:
- emptyDir: {}
name: postgres-data
Once this is running, you can access postgres with the port-forward
command like this:
kubectl -n sandbox port-forward deploy/postgres 5432:5432
This should result in:
Forwarding from 127.0.0.1:5432 -> 5432
Forwarding from [::1]:5432 -> 5432
And now we can connect to Postgres using psql and run queries
against it:
$ psql -h localhost -U example example
psql (13.4)
Type "help" for help.
example=#
kubectl port-forward is only useful as a troubleshooting mechanism. If
you were trying to access your postgres pod from another pod, you
would create a Service and then use the service name as the hostname
for your client connections.
Update
If your goal is to deploy a client container so that you can log
into it and run psql, the easiest solution is just to kubectl rsh
into the postgres container itself. Assuming you were using the
Deployment shown earlier in this question, you could run:
kubectl rsh deploy/postgres
This would get you a shell prompt inside the postgres container. You
can run psql and not have to worry about authentication:
$ kubectl rsh deploy/postgres
$ psql -U example example
psql (13.4 (Debian 13.4-1.pgdg100+1))
Type "help" for help.
example=#
If you want to start up a separate container, you can use the kubectl debug command:
kubectl debug deploy/postgres
This gets you a root prompt in a debug pod. If you know the ip address
of the postgres pod, you can connect to it using psql. To get
the address of the pod, run this on your local host:
$ kubectl get pod/postgres-6df4c549f-p2892 -o jsonpath='{.status.podIP}'
10.130.0.11
And then inside the debug container:
root#postgres-debug:/# psql -h 10.130.0.11 -U example example
In this case you would have to provide an appropriate password,
because you are accessing postgres from "another machine", rather than
running directly inside the postgres pod.
Note that in the above answer I've used the shortcut
deploy/<deployment_name, which avoids having to know the name of the
pod created by the Deployment. You can replace that with
pod/<podname> in all cases.