F5 iRules Data Plane Programmability > 5. NGINX programmability Source | Edit on

5.4. Lab 3 - Injecting HTTP header using stream proxy¶

Start an NGINX docker instance with the inject_header app by running the following commands: This places the inject_header.conf file and inject_header.js files into the running NGINX instance.

EXAMPLE=inject_header
docker run --rm --name njs_example  -v $(pwd)/conf/$EXAMPLE.conf:/etc/nginx/nginx.conf:ro  -v $(pwd)/njs/$EXAMPLE.js:/etc/nginx/example.js:ro -p 80:80 -p 8090:8090 -d nginx

The nginx.conf will be as follows, notice it includes the njs script and calls the inject_header function for every request:

 ...

 stream {
    js_include example.js;

 server {
    listen 80;

    proxy_pass 127.0.0.1:8080;
    js_filter inject_header;
    }
}

 ...

The njs code adds an HTTP header called Foo with a value of my_foo:

function inject_header(s) {
    inject_my_header(s, 'Foo: my_foo');
}

function inject_my_header(s, header) {
     var req = '';

 s.on('upload', function(data, flags) {
    req += data;
    var n = req.search('\n');
    if (n != -1) {
      var rest = req.substr(n + 1);
      req = req.substr(0, n + 1);
      s.send(req + header + '\r\n' + rest, flags);
      s.off('upload');
    }
 });
}

To validate that it is working run the following commands:
```
curl http://localhost/
my_foo

docker stop njs_example
```

Previous Next