Perf Optimisation: Use EEX Template for SVG Rendering

[nelsonic]

At present we have a 511 Byte template.svg file which we are manually String.replace-ing the {count} in:

 String.replace(svg_badge_template(), ~r/{count}/, to_string(count))

This does not take advantage of Phoenix's template compilation for faster rendering.

Todo

• refactor template to badge.svg.eex
• render using render(conn, "badge.svg", count)
• apply gzip compression for even faster rendering

Note: rendering is not currently a "bottleneck" in the app,
the DB query is orders of magnitude slower than String.replace.
This optimisation should be considered after ETS is implemented for caching the count.

[nelsonic]

Using the String.replace method, the response time on localhost is around 500µs:

That's µs not ms ... 500 microseconds ... 500 millionths of a second.

We can definitely speed this up, and it would be good to do a more scientific benchmark of response times ... but I don't think any one is going to complain about this response time. 😉

Still if you have time to help refactor this, please dive in! 💻