AWS Kubernetes RDS connection

Question

I'm having some trouble with my AWS Kubernetes instance.

I'm trying to get my django instances to connect to the RDS service via the DB endpoint.

DATABASES = {
    'default': {
        'ENGINE': 'django.contrib.gis.db.backends.postgis',
        'NAME': os.environ['NAME'],
        'USER': os.environ['USER'],
        'PASSWORD': os.environ['PASSWORD'],
        'HOST': os.environ['HOST'],
        'PORT': os.environ['PORT']
    }
}

The host string would resemble this service.key.region.rds.amazonaws.com and is being passed to the container via env in the deploy.yml

containers:
  - name: service
    env:
      - name: HOST
        value: service.key.region.rds.amazonaws.com

This set up works locally in kubernetes but not when I put it in the cluster I have on AWS. It returns the following error instead:

django.db.utils.OperationalError: could not translate host name

Any suggestions or am I missing something in how AWS likes handling things?

Is there any chance your manage.py file is reading the wrong settings file? Asking because I saw [this SO thread](https://stackoverflow.com/questions/41573313/docker-compose-with-django-could-not-translate-host-name-db-to-address-name-o) that feels possibly related to your issue, despite being about Docker. — ingernet, Mar 10 '18 at 17:52
No rolling my own with kubeadm, 1 master 1 node. Attempting to learn the hard-ish way. — macintoshPrime, Mar 10 '18 at 17:53
@ingernet I just double checked my settings files and by base.py doesn't hold any DB configs. I changed some things and rebuilt the image just to be sure and I still get the same error. Good thought though, thanks for the suggestions. — macintoshPrime, Mar 10 '18 at 18:08
Never thought to check that. I can psql into the RDS service with no issue. Hmm might be a django issue... — macintoshPrime, Mar 10 '18 at 18:33
I would still guess it's more Kubernetes, as it has it's own DNS service. — the4thv, Mar 10 '18 at 18:49

score 4 · Accepted Answer · answered Mar 10 '18 at 18:04

4

Assuming your AWS deployment is now in the same VPC as your RDS, then you will need to change your host to use the private IP.

answered Mar 10 '18 at 18:04

the4thv

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1

Pardon my ignorance but where do I find the private ip of the RDS, the closest I can find in the RDS dashboard is the endpoint. – macintoshPrime Mar 10 '18 at 18:15
1

OK, before I decide this is absolutely wrong, try pinging the RDS end point to get the private IP address. Then use that in your deployment. – the4thv Mar 10 '18 at 18:34
Awesome! I think that it's related to Kubernetes internal routing: https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/ – the4thv Mar 10 '18 at 18:52
1

Thanks for the help and the link. Much appreciated – macintoshPrime Mar 10 '18 at 18:57
what if you're in a different VPC, different account, different region? – szeitlin Sep 21 '18 at 15:58

AWS Kubernetes RDS connection

1 Answers1