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

5.5. Lab 4 - Subrequests join¶

Combining the results of several subrequests asynchronously into a single JSON reply.

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

EXAMPLE=join_subrequests
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 for the /join url it calls the njs with a join command:

  ...

  http {
     js_include example.js;

     server {
        listen 80;

        location /join {
            js_content join;
        }

        location /foo {
            proxy_pass http://localhost:8080;
        }

        location /bar {
            proxy_pass http://localhost:8090;
        }
     }
  }

The njs code joins the responses of the two other requests into a single output:

 .. code-block:: js

    function join(r) {
        join_subrequests(r, ['/foo', '/bar']);
    }

    function join_subrequests(r, subs) {
        var parts = [];

    function done(reply) {
         parts.push({ uri:  reply.uri,
                   code: reply.status,
                   body: reply.responseBody });

      if (parts.length == subs.length) {
          r.return(200, JSON.stringify(parts));
      }
    }

     for (var i in subs) {
        r.subrequest(subs[i], done);
        }
     }

To show this run the following commands:

curl http://localhost/join
[{"uri":"/foo","code":200,"body":"FOO"},{"uri":"/bar","code":200,"body":"BAR"}]

docker stop njs_example

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