209 lines
7 KiB
Markdown
209 lines
7 KiB
Markdown
# Exposing FastCGI Servers
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> **FastCGI** is a [binary protocol](https://en.wikipedia.org/wiki/Binary_protocol "Binary protocol") for interfacing interactive programs with a [web server](https://en.wikipedia.org/wiki/Web_server "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.
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>
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> — Wikipedia
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The _ingress-nginx_ ingress controller can be used to directly expose [FastCGI](https://en.wikipedia.org/wiki/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_.
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For most practical use-cases, php applications are a good example. PHP is not HTML so a FastCGI server like php-fpm processes a index.php script for the response to a request. See a working example below.
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This [post in a FactCGI feature issue](https://github.com/kubernetes/ingress-nginx/issues/8207#issuecomment-2161405468) describes a test for the FastCGI feature. The same test is described below here.
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## Example Objects to expose a FastCGI server pod
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### The FasctCGI server pod
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The _Pod_ object example below exposes port `9000`, which is the conventional FastCGI port.
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```yaml
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apiVersion: v1
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kind: Pod
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metadata:
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name: example-app
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labels:
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app: example-app
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spec:
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containers:
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- name: example-app
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image: php:fpm-alpine
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ports:
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- containerPort: 9000
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name: fastcgi
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```
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- For this example to work, a HTML response should be received from the FastCGI server being exposed
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- A HTTP request to the FastCGI server pod should be sent
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- The response should be generated by a php script as that is what we are demonstrating here
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The image we are using here `php:fpm-alpine` does not ship with a ready to use php script inside it. So we need to provide the image with a simple php-script for this example to work.
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- Use `kubectl exec` to get into the example-app pod
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- You will land at the path `/var/www/html`
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- Create a simple php script there at the path /var/www/html called index.php
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- Make the index.php file look like this
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```
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<!DOCTYPE html>
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<html>
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<head>
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<title>PHP Test</title>
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</head>
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<body>
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<?php echo '<p>FastCGI Test Worked!</p>'; ?>
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</body>
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</html>
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```
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- Save and exit from the shell in the pod
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- If you delete the pod, then you will have to recreate the file as this method is not persistent
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### The FastCGI service
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The _Service_ object example below matches port `9000` from the _Pod_ object above.
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```yaml
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apiVersion: v1
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kind: Service
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metadata:
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name: example-service
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spec:
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selector:
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app: example-app
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ports:
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- port: 9000
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targetPort: 9000
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name: fastcgi
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```
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### The configMap object and the ingress object
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The _Ingress_ and _ConfigMap_ objects below demonstrate the supported _FastCGI_ specific annotations.
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!!! Important
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NGINX actually has 50 [FastCGI directives](https://nginx.org/en/docs/http/ngx_http_fastcgi_module.html#directives)
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All of the nginx directives have not been exposed in the ingress yet
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### The ConfigMap object
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This configMap object is required to set the parameters of [FastCGI directives](https://nginx.org/en/docs/http/ngx_http_fastcgi_module.html#directives)
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!!! Attention
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- The _ConfigMap_ **must** be created before creating the ingress object
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- The _Ingress Controller_ needs to find the configMap when the _Ingress_ object with the FastCGI annotations is created
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- So create the configMap before the ingress
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- If the configMap is created after the ingress is created, then you will need to restart the _Ingress Controller_ pods.
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```yaml
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apiVersion: v1
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kind: ConfigMap
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metadata:
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name: example-cm
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data:
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SCRIPT_FILENAME: "/var/www/html/index.php"
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```
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### The ingress object
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- Do not create the ingress shown below until you have created the configMap seen above.
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- You can see that this ingress matches the service `example-service`, and the port named `fastcgi` from above.
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```
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apiVersion: networking.k8s.io/v1
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kind: Ingress
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metadata:
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annotations:
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nginx.ingress.kubernetes.io/backend-protocol: "FCGI"
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nginx.ingress.kubernetes.io/fastcgi-index: "index.php"
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nginx.ingress.kubernetes.io/fastcgi-params-configmap: "example-cm"
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name: example-app
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spec:
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ingressClassName: nginx
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rules:
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- host: app.example.com
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http:
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paths:
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- path: /
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pathType: Prefix
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backend:
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service:
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name: example-service
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port:
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name: fastcgi
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```
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## Send a request to the exposed FastCGI server
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You will have to look at the external-ip of the ingress or you have to send the HTTP request to the ClusterIP address of the ingress-nginx controller pod.
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```
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% curl 172.19.0.2 -H "Host: app.example.com" -vik
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* Trying 172.19.0.2:80...
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* Connected to 172.19.0.2 (172.19.0.2) port 80
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> GET / HTTP/1.1
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> Host: app.example.com
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> User-Agent: curl/8.6.0
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> Accept: */*
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>
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< HTTP/1.1 200 OK
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HTTP/1.1 200 OK
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< Date: Wed, 12 Jun 2024 07:11:59 GMT
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Date: Wed, 12 Jun 2024 07:11:59 GMT
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< Content-Type: text/html; charset=UTF-8
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Content-Type: text/html; charset=UTF-8
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< Transfer-Encoding: chunked
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Transfer-Encoding: chunked
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< Connection: keep-alive
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Connection: keep-alive
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< X-Powered-By: PHP/8.3.8
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X-Powered-By: PHP/8.3.8
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<
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<!DOCTYPE html>
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<html>
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<head>
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<title>PHP Test</title>
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</head>
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<body>
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<p>FastCGI Test Worked</p> </body>
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</html>
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```
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## FastCGI Ingress Annotations
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To enable FastCGI, the `nginx.ingress.kubernetes.io/backend-protocol` annotation needs to be set to `FCGI`, which overrides the default `HTTP` value.
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> `nginx.ingress.kubernetes.io/backend-protocol: "FCGI"`
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**This enables the _FastCGI_ mode for all paths defined in the _Ingress_ object**
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### The `nginx.ingress.kubernetes.io/fastcgi-index` Annotation
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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](https://nginx.org/en/docs/http/ngx_http_fastcgi_module.html#fastcgi_index).
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> `nginx.ingress.kubernetes.io/fastcgi-index: "index.php"`
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### The `nginx.ingress.kubernetes.io/fastcgi-params-configmap` Annotation
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To specify [_NGINX_ `fastcgi_param` directives](https://nginx.org/en/docs/http/ngx_http_fastcgi_module.html#fastcgi_param), 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.
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> `nginx.ingress.kubernetes.io/fastcgi-params-configmap: "example-configmap"`
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And the _ConfigMap_ object to specify the `SCRIPT_FILENAME` and `HTTP_PROXY` _NGINX's_ `fastcgi_param` directives will look like the following:
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```yaml
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apiVersion: v1
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kind: ConfigMap
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metadata:
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name: example-configmap
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data:
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SCRIPT_FILENAME: "/example/index.php"
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HTTP_PROXY: ""
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```
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Using the _namespace/_ prefix is also supported, for example:
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> `nginx.ingress.kubernetes.io/fastcgi-params-configmap: "example-namespace/example-configmap"`
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