RabbitMQ is IMHO probably the best open source example tackling a large, complicated real world problem with graceful degradation (e.g. if a queue keeps crashin

RabbitMQ is IMHO probably the best open source example tackling a large, complicated real world problem with graceful degradation (e.g. if a queue keeps crashing). Elixir has a lot of smaller but very high quality libraries to learn from. You may be interested in how Ecto & Postgrex manage DB connections, in particular how connection sockets are “borrowed” so data doesn’t get repeatedly messaged (read: copied) between processes. Bandit / Thousand Island also make interesting decisions for process structure in HTTP1.1 vs HTTP2. I think a common mistake is to create processes mimicking classic OOP structure, like an OrderProcessor, ShippingManager, etc. Processes in Erlang are a unit of fault tolerance, not code organization. This means more usually you’ll have one process per request, potentially calling code from many different modules; since requests are the things you want to fail separately from each other. In RabbitMQ’s case for instance connections and queues are processes, but exchanges are not. It would feel natural to model the problem as three processes with messages going Connection -> Exchange -> Queue, but in reality an exchange is a set of routing rules that can be applied by a connection directly, which avoids a lot of complexity and overhead. Last thing I’d note is supervision trees etc. are really about handling _unexpected_ errors (Joe uses the terms faults and errors with different meanings iirc). If you want a web request to be retried a few times with a delay, don’t use a supervisor for that, just loop with a sleep. Same for things like validating inputs from a form, usually you’d want to give the user a hint and not just crash. Some other useful links: - https://aosabook.org/en/v1/riak.html https://aosabook.org/en/v1/riak.html (bit old, but another large codebase) - https://ferd.ca/the-zen-of-erlang.html https://ferd.ca/the-zen-of-erlang.html - https://www.theerlangelist.com/article/spawn_or_not https://www.theerlangelist.com/article/spawn_or_not