My Erlang/OTP 20 Highlights

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Erlang Battleground

3 min readMay 30, 2017

While I was on vacation, Erlang/OTP 20 RC1 was released. As you can see in that page, these are the highlights according to the OTP team:

There are many great things there, but… being a thorough guy, I didn’t stop there and went for the README. And what a amazing thing! I found several other jewels there that are, at least from my perspective, much more worthy of highlight status than the ones listed above. So, here you have them…

Brujo’s Top 5 Unsung Highlights form OTP20-RC1

5. Compare and Swap for ETS

OTP-14319    Application(s): stdlib
               Related Id(s): PR-1076

               Add new function ets:select_replace/2 which performs
               atomic "compare-and-swap" operations for ETS objects
               using match specifications.

This one is something many of us were waiting for and working around in super-nasty ways for a long long time. A nice compare-and-swap for ETS is something I will certainly use in the future.

4. You can use ct_slave with rebar3 now

OTP-13806    Application(s): common_test

               The ct_slave modules now handle nodenames in the same
               way as nodenames passed to -sname. That means
               ct_slave:start('b@127.0.0.1'). will now work.

Another one that we have fought for a long time. As stated in this article (look for The Bad there), ct_slave and rebar3 weren’t friends. There was a workaround, of course, but it was super ugly and it basically involved not using ct_slave at all. That’s why this fix is more than welcomed.

3. Limit the logs backup on CT

OTP-14179    Application(s): common_test

               Added the new option, keep_logs. If setting the value
               for this option to an integer, N, common_test will
               remove all ct_run.* directories in the current log
               directory, except the N newest.

Besides making Loïc extra happy, this option will prevent me from starting every test run with rm -rf logs and then hating myself for not keeping track of previous runs 🤦‍♂️.

2. Write Pids and ports in the shell

OTP-14296    Application(s): debugger, stdlib

               The Erlang shell, qlc:string_to_handle(), and the
               Debugger (the Evaluator area and Edit variable window
               of the Bindings area) can parse pids, ports,
               references, and external funs, as long as they can be
               created in the running system.

I still have to try it (I use Erlang Solution’s OSX Installer and it doesn’t provide RCs), but if it means what I think it means (i.e. that erlang:is_process_alive(<0.1.0>). will work in the Erlang shell)… That would be the single most amazing feature of this release! I’ve been expecting this (particularly for ports, thanks Fred for recon:port_info/1,2!!! 😱) since my first encounter with an Erlang shell 10 years ago.

1. Drop all the Callback Boilerplate

OTP-13801    Application(s): stdlib

             Making code_change, terminate and handle_info callbacks
               optional in the OTP behaviours.

I honestly don’t know how this is not a highlight. Check the full conversation started by this tweet below…

So, these are my favorites (besides being able to use the atom ‘💩’, of course). What do you think? Did I miss any other hidden gem? Let me know in the comments below.

Erlang & Elixir Factory Lite Buenos Aires 2017

I want to finish this article with a little self-promotion, I hope you don’t mind…

I’m one of the organizers of the first South American Erlang & Elixir conference ever in Buenos Aires and I would like to invite you all to it.

The programme is already online and the list of talks is impressive. The BEAM community is growing fast and this will be a great place to start connecting all together. So, all my south-american readers: come join us! It will be awesome!