I'm new to k8s and need some direction on how to troubleshoot.

I have a postgres container and a graphql container. The graphql container is tries to connect to postgres on startup.

Problem

The graphql container can't connect to postgres. This is the error on startup:

{"internal":"could not connect to server: Connection refused\n\tIs the server running on host \"my-app\" (xxx.xx.xx.xxx) and accepting\n\tTCP/IP connections on port 5432?\n", "path":"

My understanding is that the graphql-container doesn't recognize the IP my-app (xxx.xx.xx.xxx). This is the actual Pod Host IP, so I'm confused as to why it doesn't recognize it. How do I troubleshoot errors like these?

What I tried

• Hardcoding the host in the connection uri in deployment.yaml to the actual pod host IP. Same error.

• Bashed into the graphql container and verified that it had the correct env values with the env command.

deployment.yaml

spec:
  selector:
    matchLabels:
      service: my-app
  template:
    metadata:
      labels:
        service: my-app
...
  - name: my-graphql-container
    image: image-name:latest
    env:
    - name: MY_POSTGRES_HOST
      value: my-app
    - name: MY_DATABASE
      value: db
    - name: MY_POSTGRES_DB_URL # the postgres connection url that the graphql container uses
      value: postgres://$(user):$(pw)@$(MY_POSTGRES_HOST):5432/$(MY_DATABASE)
...
  - name: my-postgres-db
    image: image-name:latest