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# Accommodation for JWT

JWT (short for Json Web Token) is an authentication method widely used. Basically an authentication server generates a JWT and you then use this token in every request you make to a backend service. The JWT can be quite big and is present in every http headers. This means you may have to adapt the max-header size of your nginx-ingress in order to support it.

## Symptoms

If you use JWT and you get http 502 error from your ingress, it may be a sign that the buffer size is not big enough.

To be 100% sure look at the logs of the `ingress-nginx-controller` pod, you should see something like this:

    upstream sent too big header while reading response header from upstream...

## Increase buffer size for headers

In nginx, we want to modify the property `proxy-buffer-size`. The size is arbitrary. It depends on your needs. Be aware that a high value can lower the performance of your ingress proxy. In general a value of 16k should get you covered.

### Using helm

If you're using helm you can simply use the `config` properties.

     # -- Will add custom configuration options to Nginx https://kubernetes.github.io/ingress-nginx/user-guide/nginx-configuration/configmap/
      config:
        proxy-buffer-size: 16k

## Manually in kubernetes config files

If you use an already generated config from for a provider, you will have to change the `controller-configmap.yaml`

    ---
    # Source: ingress-nginx/templates/controller-configmap.yaml
    apiVersion: v1
    kind: ConfigMap
    # ...
    data:
      #...
      proxy-buffer-size: "16k"

References: * Custom Configuration