Elixir Clustering with Mix Releases and libcluster

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We finally have a Mix clustering guide to go with Phoenix deployment with Mix Releases.

Deploy an Elixir Cluster with Mix Releases and libcluster

The finished code for the guide is available at https://github.com/render-examples/elixir_cluster.

Meta: the Mix team has done a wonderful job learning from Distillery and making it even easier to cluster nodes, especially on platforms like Render (where I work) because we can auto-populate clustering variables for you.

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How are you keeping separate customer’s Erlang clusters. K8s network policies? It would be good to add TLS usage to the tutorial.

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Yes, firewalling through network policies. Regarding SSL, we terminate TLS at our L4 load balancer. Do you need e2e TLS?

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I mean TLS for distributed erlang so that all communication is encrypted. http://erlang.org/doc/apps/ssl/ssl_distribution.html

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Makes sense. We’ll add a guide for it.

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This is really great, anuragg! Say I have a horizontally distributed application with microservices sitting in other pods. To connect the main application to the microservices, would I just add multiple topologies for them to connect to each other?

If so, as Render uses IP instead of FQDN for the DNS resolution, how would I send messages to and from the different topologies? Since the IP isn’t guaranteed to be the same each time a service goes up and down, I can’t quite call :rpc.call(node_name, :"Module", :function, [:"args"]) or Node.spawn(:"servicename@127.0.0.1", :"Module", fun, args).

How would you recommend passing messages between topologies in this situation?

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Each Render service gets a unique internal-only URL of the type service-slug:port. You will see it on the dashboard once the service is deployed. You can connect to this URL from other services in your account; think of it as a built-in automatic VPC with preconfigured DNS. It sounds like this will work for your use case.

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