Here is a summary of what I'm trying to do:

enter image description here

I can get my flask app to respond without HTTPS/SSL. But am receiving a '503 Service Unavailable' when I am trying to use SSL. My understanding is since the load balancer has the Cloudflare origin certificate installed, it will SSL terminate so the flask app does not need modifications for SSL.

Here is my Kubernetes yaml for the load balancer and flask app service:

apiVersion: v1
kind: Service
  name: flask-service
    run: flask-service
    service.beta.kubernetes.io/do-loadbalancer-tls-ports: "443"
    service.beta.kubernetes.io/do-loadbalancer-certificate-id: "68e1d971-1a7c-40d2-8f33-aed797a9535d"        
    app: flask
  - name: tcp
    protocol: "TCP"
    port: 5000
    targetPort: 5000
  - name: https
    protocol: TCP
    port: 443
    targetPort: 5000
  type: LoadBalancer
apiVersion: apps/v1
kind: Deployment
  name: flask
      app: flask  
  replicas: 1
        app: flask
      - name: flask
        imagePullPolicy: Always
        image: gcr.io/xxxxyyyyyy/flask:staging
        - containerPort: 5000
            memory: 8000Mi
            memory: 4000Mi

I would appreciate any suggestions as I have been looking at this problem for the past few days with no luck.

1 Answer 1


In the company I'm working for, we are just have a lot of same issues with Cloudflare and Docker Swarm. We are hitting a lots of 503 Error and we are running both node, php and python application.

What we discovered is when you are create a single connection between Cloudflare and your Cluster its some buffering and keep a live settings you did not have control over, and this 503 Error keep coming.

We discovered this with Cloudflare service, HA Proxy, Load Balance from Digital ocean and with default NGINX settings.

We dive deep into it and try to search on what happen, first of all cloudflare give us around 1-300ms more ping time for every single request, the secound is NGINX enable proxy buffering and this 2 things to getter is not working pretty well I think.

So what I can recommend and its working for us is setup a NGINX server as proxy layer, disable proxy buffering and then use Letsencrypt (certbot) to generate your own SSL - don't dot it on production, create a test setup first.

That's my best shoot to tell you what's going on here, its sound a lot like the issue we fight with in months before we discovered this issue about the connection drops between client and the Docker Swarm service containers.

If you test my answer of, late me know about its help you.

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