Hacker News Reader

Comment by ha470 | Hacker News Reader

Sorry if this is a dumb question, but how do releases fit into the deployment story with containers so prevalent these days? (As in why is this a benefit when you can just package code into a single container to ship it?) Is it that it works with hot code updates? Or it’s a more Erlang-sanctioned way of deploying code?

View on HN

Fred Hebert was on the ElixirTalk podcast and mentioned speed of deploys as one advantage - no need to rebuild a bunch of VMs.

> From experience, we could deploy to a 70-node cluster in something like under 5 seconds by doing it in parallel. If you want to rotate your infrastructure... your deploy could be taking from 5 minutes to an hour depending on how fast the connection draining can be done.

https://soundcloud.com/elixirtalk/episode-145-feat-fred-hebe...

There's a good 'why releases' section of the article.

Even without the compilation and configuration stuff, it's easier to put the release bundle in something basic like an alpine image, rather than keep docker image versions and app in sync.

But the article says you have to run the release on the same OS/version that you built it on. So if you're running it on alpine, won't you need to build it on alpine, which suggests you'll need to configure your Dockerfile to compile it anyway?

With Distillery you can specify a directory for the ERTS so the release can be built on one OS and run on another. You just have to make sure ERTS was built on the OS that it will eventually run on.

That is correct. But that can be multiple stages, and therefore separated concerns.

Also, releases can be very small, after all the superfluous parts/symbols are stripped. Combine that with a fresh alpine image and you have quick-to-deploy containers.

You would have two images, one with all compile time dependencies, sources, etc, which you use to assemble the release, and another image with only the artifact (the release) and none of the rest. Hex (Elixir's package manager) is open source and uses this approach, which you can see here: https://github.com/hexpm/hexpm/blob/d015973e472af59644ee537f...

Building a container and building a release are quite similar in many respects, so if all you want to do to compile your Elixir app during a container build, a release might not give you very much. An Erlang/Elixir release has some goodies that you might be interested in, so I'd read up on those goodies to see if they are attractive to you.

Reply on news.ycombinator.com