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Exposing FastCGI Servers

FastCGI is a binary protocol for interfacing interactive programs with a web server. [...] (It's) aim is to reduce the overhead related to interfacing between web server and CGI programs, allowing a server to handle more web page requests per unit of time.

— Wikipedia

The ingress-nginx ingress controller can be used to directly expose FastCGI servers. Enabling FastCGI in your Ingress only requires setting the backend-protocol annotation to FCGI, and with a couple more annotations you can customize the way ingress-nginx handles the communication with your FastCGI server.

Example Objects to Expose a FastCGI Pod

The Pod example object below exposes port 9000, which is the conventional FastCGI port.

apiVersion: v1
kind: Pod
metadata:
  name: example-app
labels:
  app: example-app
spec:
  containers:
  - name: example-app
    image: example-app:1.0
    ports:
    - containerPort: 9000
      name: fastcgi

The Service object example below matches port 9000 from the Pod object above.

apiVersion: v1
kind: Service
metadata:
  name: example-service
spec:
  selector:
    app: example-app
  ports:
  - port: 9000
    targetPort: 9000
    name: fastcgi

And the Ingress and ConfigMap objects below demonstrates the supported FastCGI specific annotations (NGINX actually has 50 FastCGI directives, all of which have not been exposed in the ingress yet), and matches the service example-service, and the port named fastcgi from above. The ConfigMap must be created first for the Ingress Controller to be able to find it when the Ingress object is created, otherwise you will need to restart the Ingress Controller pods.

# The ConfigMap MUST be created first for the ingress controller to be able to
# find it when the Ingress object is created.

apiVersion: v1
kind: ConfigMap
metadata:
  name: example-cm
data:
  SCRIPT_FILENAME: "/example/index.php"

---

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    nginx.ingress.kubernetes.io/backend-protocol: "FCGI"
    nginx.ingress.kubernetes.io/fastcgi-index: "index.php"
    nginx.ingress.kubernetes.io/fastcgi-params-configmap: "example-cm"
  name: example-app
spec:
  ingressClassName: nginx
  rules:
  - host: app.example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: example-service
            port:
              name: fastcgi

FastCGI Ingress Annotations

To enable FastCGI, the nginx.ingress.kubernetes.io/backend-protocol annotation needs to be set to FCGI, which overrides the default HTTP value.

nginx.ingress.kubernetes.io/backend-protocol: "FCGI"

This enables the FastCGI mode for all paths defined in the Ingress object

The nginx.ingress.kubernetes.io/fastcgi-index Annotation

To specify an index file, the fastcgi-index annotation value can optionally be set. In the example below, the value is set to index.php. This annotation corresponds to the NGINX fastcgi_index directive.

nginx.ingress.kubernetes.io/fastcgi-index: "index.php"

The nginx.ingress.kubernetes.io/fastcgi-params-configmap Annotation

To specify NGINX fastcgi_param directives, the fastcgi-params-configmap annotation is used, which in turn must lead to a ConfigMap object containing the NGINX fastcgi_param directives as key/values.

nginx.ingress.kubernetes.io/fastcgi-params-configmap: "example-configmap"

And the ConfigMap object to specify the SCRIPT_FILENAME and HTTP_PROXY NGINX's fastcgi_param directives will look like the following:

apiVersion: v1
kind: ConfigMap
metadata:
  name: example-configmap
data:
  SCRIPT_FILENAME: "/example/index.php"
  HTTP_PROXY: ""
Using the namespace/ prefix is also supported, for example:

nginx.ingress.kubernetes.io/fastcgi-params-configmap: "example-namespace/example-configmap"