laotzi-demo

An LFE Demo of the Ten Thousand Things

Table of Contents

• Introduction
• Setup
  • Bypassing localhost Default
• Usage
• Under the Hood
• Ideas for Future Work

Introduction ↟

Steven Proctor emailed Robert and I about an interesting LFE demo. This is the demo that was born of that discussion.

Setup ↟

Just clone it:

$ git clone [email protected]:oubiwann/laotzi-demo.git

And then do :

$ make repl

This will download and compile all the dependencies, and then start the LFE REPL (also automatically starting the laotzi-demo application and the built-in web server).

Bypassing localhost Default ↟

If you'd like to run this demo's httpd server (which uses barista) on the non-loopback network interface, you'll need to update the lfe.config file and change the #(host "localhost") tuple to point to your preferred IP or hostname.

Usage ↟

From the REPL where the laotzi-demo application has been started, you can manually add children to the supervisor with the following:

> (laotzi-demo:add)
#(ok <0.60.0>)
> (laotzi-demo:add)
#(ok <0.62.0>)
> (laotzi-demo:add)
#(ok <0.64.0>)
> (laotzi-demo:add)
#(ok <0.66.0>)
> (laotzi-demo:add)
#(ok <0.68.0>)
> (laotzi-demo:add)
#(ok <0.70.0>)
> (laotzi-demo:add)
#(ok <0.72.0>)
> (laotzi-demo:add)
#(ok <0.74.0>)
> (laotzi-demo:get-children)
(#(undefined <0.64.0> worker (laotzi-demo-server))
 #(undefined <0.66.0> worker (laotzi-demo-server))
 #(undefined <0.68.0> worker (laotzi-demo-server))
 #(undefined <0.70.0> worker (laotzi-demo-server))
 #(undefined <0.72.0> worker (laotzi-demo-server))
 #(undefined <0.74.0> worker (laotzi-demo-server))
 #(undefined <0.60.0> worker (laotzi-demo-server))
 #(undefined <0.62.0> worker (laotzi-demo-server)))

You can add hundreds at a time with this function:

> (laotzi-demo:add 492)
ok

Or thousands:

> (laotzi-demo:add 2500)
ok
> (length (laotzi-demo:get-children))
3000

If you want to enable stats-gathering, do the following:

> (laotzi-demo:enable-stats)
ok

Let's make things interesting, and have the processes run code of varrying number of calls:

> (laotzi-demo:execute-tasks)
#(ok #(interval #Ref<0.0.0.9074>))

You can have the demo start tracking stats (in this case, repeatedly saving each process' number of reductions to ./www/data.json):

> (laotzi-demo:start-tracking)
#(ok #(interval #Ref<0.0.0.9079>))

With that done, we can now open http://localhost:5099/ in our browser, where we will be greeted with something like the following:

As time passes, you'll see that heatmap evolve along these lines:

This page has jquery AJAX polling set up, so you should see changes every 8 seconds or so. This will chew up your CPU, so don't leave it running :-)

Under the Hood ↟

Here are the interesting things that this demo applications does:

• Creates an OTP application, supervisor, and then thousands of worker processes.

• Enables stats-gathering for the OTP supervisor.

• Generates a JSON data file from process stats.

• Uses an early, development version of the lmug web server middleware framework (inspired by Clojure's Ring framework, which in turn was inspired by Python's WSGI).

• As part of the above point, it uses a built-in web server.

• Generates json with the ljson LFE library for parsing and creating JSON data.

• Makes use of the d3.js data visualization library.

Ideas for Future Work ↟

Setting aside the features that need to be added to the various nascent dependencies, here are some cool things to do:

• Add support for websockets and streaming monitoring data
• Update the d3.js heatmap data one cell at a time, based upon stream data (using websockets)
• Demonstrate swapping out YAWS, Cowboy, and native httpd
• Make the d3.js example more configurable so that changing total nodes created from 3000 to 500 or to 10,000 doesn't involve changing code
• Show more than just reductions
• Use additional visualization metaphors