fireproofsocks

fireproofsocks

Simple examples of distributed systems in Elixir?

I’m working to increase my understanding of how to build distributed systems as a way to leverage concurrency. I understand this is a broad topic, but I’m wondering if anyone has some examples of how to structure “work” across multiple nodes or multiple apps.

I admit I am not even sure I follow how things happen when you deploy a single app across multiple nodes (e.g. 1 app deployed to 2 EC2 instances)… that means there are 2 instances of the Erlang VM running. How is work delegated? E.g. if it’s a Phoenix app, does a multiple-server deployment assume that a load balancer is figuring out the “division of labor” and routing requests to different nodes? And does this assume that each node more or less has no awareness of the other nodes?

Or how about when you want to process a stream of inputs (e.g. using Task.async_stream/3)… do you have any way of routing the processing to different nodes? For this to work, wouldn’t each node need to know about the other nodes? Locally, this happens by specifying --sname and --remsh options when starting the app, e.g. something like

iex --sname app1@localhost -S mix
iex --sname app2 --remsh app1@localhost

What are good questions to ask when deciding how to break up work across multiple nodes/apps?

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viniciusmuller

viniciusmuller

Hey, have you checked the “Introduction to Mix” guide in the official documentation?
Although the name can be a bit misleading, this is the description of the guide:

In this guide, we will build a complete Elixir application, with its own supervision tree, configuration, tests, and more.

The application works as a distributed key-value store. We are going to organize key-value pairs into buckets and distribute those buckets across multiple nodes. We will also build a simple client that allows us to connect to any of those nodes and send requests

I think it might be helpful, it covers how nodes connect to each other using the configurations and shows some example of running code in a remote node and distributing work across nodes via sharding.

Overall the erlang runtime does no magic to help you and you still need to build your own mechanisms of distribution and load balancing in your application, but it provides all the building blocks you’ll need to do so.

apsori

apsori

I really need to get a copy of this book :slight_smile:

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