sbroker

ing out connections for the duration of the whole request, and you can leverage database caches more efficiently, effectively putting less pressure in the database. Not only that, proper connection pools can actually foresee when requests are not going to be served on time because the database is under high load and avoid sending the load to the database in the first place. We are using such implementation in our ad-serving Erlang system (https://github.com/fishcakez/sbroker) although there is a lot of interesting queue theory regarding sojourn times. Those requests would timeout anyway but the pool can foresee that with high precision and avoid making the database even slower. In other words, when you say "half of the time is spent in database", it is always worth asking how much of that time is a consequence of how you are interacting with the database in the first place. Another aspect to consider is if the language (or framework) you are using allow you to depend less on the database. For example, by processing jobs concurrently instead of storing them on Redis/DB, by building distributed clusters instead of pushing broadcasts to third party systems, etc.

if you do this you might as well ask yourself if you really need redis instead of keeping it all within your Elixir system. Deciding on which node this process lives is still up to you, but there are libraries like locks [3] that allow you to automatically determine a leader in your cluster. And once this is done you can start dealing with overload :) Of course this is just a simple and naive approach, there are a lot of really useful Erlang libraries to check out. Here's a list of libs that helped me when getting started by reading their docs and sources in no particular order: https://github.com/heroku/canal_lock - Erlang lock manager for concurrently variable resource numbers https://github.com/jlouis/safetyvalve - queueing facilities for tasks to be executed so their concurrency and rate can be limited on a running system https://github.com/fishcakez/sbroker - process broker for matchmaking between two groups of processes using sojourn time based active queue management to prevent congestion. https://github.com/ferd/backoff - exponential backoffs and timers to be used within OTP processes when dealing with cyclical events, such as reconnections, or generally retrying things https://github.com/jlouis/fuse - A Circuit Breaker for Erlang https://github.com/basho/sidejob - Parallel worker and capacity limiting library for Erlang https://github.com/pspdfkit-labs/sidetask - My humble Elixir wrapper for basho's sidejob [1] https://github.com/devinus/poolboy also used in Ecto, look through the Ecto sources if you want to see how it's used in Elixir. [2] http://erlang.org/doc/man/global.html [3] https://github.com/uwiger/locks and then https://github.com/uwiger/locks/blob/master/doc/locks_leader...