######################
Monitoring server load
######################

In this section we will present a simple way to monitor the load of a single application.  We will accomplish this by adding a route which will dump the active ``SpawnInfo`` objects from our ``Spawner``. Add the status method to your ``Spawner`` class:

.. code-block:: js

	status(req, res) {
	  let spawns = [];

	  this.activeSpawns.forEach((spawnInfo) => {
		spawns.push({
		  id: spawnInfo.spawnId,
		  port: spawnInfo.wsPort,
		  rendererType: spawnInfo.rendererType,
		  startTime: spawnInfo.startTime
		});
	  });

	  res.status(200).json(spawns);
	}

Next, bind the route to the status method in ``Spawner.start``:
	
.. code-block:: js

	this.expressApp.get("/status", this.status.bind(this));
	
Note that the ``status`` method is bound to a ``GET`` request as opposed to a ``POST`` request.
To quickly see this in action, restart your *Node.js* application and use the front end to create a few viewers.  Create a new browser tab and navigate to http://localhost:8082/status. You will see data for each one of your running instances.

The final task is to expose this data on our front end. We first will add a method in *index.html* to get the JSON data from our application server and instantiate an ``instance-template`` for each running instance:

.. code-block:: js

	async function updateServerStatus() {
	  let instanceJson = await $.getJSON("http://localhost:8082/status");

	  let $serverinstances = $("#server-instances");
	  $serverinstances.empty();

	  for (instance of instanceJson) {
		let templateText = $("#instance-template").html();
		templateText = templateText.replace(/{{id}}/g, instance.id)
		templateText = templateText.replace(/{{port}}/g, instance.port)
		templateText = templateText.replace(/{{rendererType}}/g, instance.rendererType)
		templateText = templateText.replace(/{{startTime}}/g, instance.startTime)

		$("#server-instances").append(templateText);
	  }
	}

For the purposes of our demo, we will call ``updateServerStatus`` at an interval of 1 second using the ``setInterval`` method when the page loads:

.. code-block:: js

	$(document).ready(() => { setInterval(updateServerStatus, 1000); });
	
When you reload the *index.html* page, you will see information about the running viewers populate the right column of the page as viewers are created and removed. If you want more granular updates you can reduce the interval time.
