I would suggest that "getting" Erlang is more than that however and is important as code that does "something", but not necessarily in a good way, can be avoided by understanding the broader ideas you're dealing with. On that count I recommend Joe Armstrong's doctoral thesis: https://erlang.org/download/armstrong_thesis_2003.pdf. It's basically a detailed examination of what the language and runtime environment are trying to achieve: it answers "what?" and "why?". It's not a difficult or obscurely technical read and even though it's a couple hundred pages, you could probably get through it pretty easily in a couple of days depending on how fast you read.
I don't code Erlang myself, but I do a fair bit of Elixir work, and found it very enlightening for establishing the context from which all the details I do deal with using a BEAM language follow.
(Of course, if you need to deep dive into some Erlang code tomorrow, "Learn you some Erlang" or Joe's book. But do your Elixir.)
Also, https://ferd.ca/ , the guy behind Erlang in Anger and Learn you some Erlang, has a lot of very well thought-of contents.
It's not a programming tutorial, but it shows how to structure real world programs to make best use of what you get with Beam+OTP+Er{lang,lixir}. It's written as an Elixir book, but it's talking about architectural concepts that map directly and easily to Erlang.
[summary of the book: write as much as you possibly can in pure functional code, mostly because it's so easy to test. Then use GenServers (etc.) at the boundary to hold the state at the top of your stack of pure code]
Some helpful things about understanding Erlang: having familiarity with Prolog. While languages work differently, on a syntactical level they have quite a few things in common. Knowing one helps to anticipate how things may work in the other in terms of syntax. You would also benefit from familiarity with persistent data types. Often the way data can be accessed defines more high-level decisions within application. Coming from the world of mutable data structures it's easy to get trapped in situations where you realize something is impossible to do the "usual" way. There are, well... "patterns" that emerged in Erlang that might be quite unique (eg. ports), but I wouldn't know about a source that accumulates and catalogues such patterns. Just know that Erlang has quite a few of those. Sometimes the word describing a function or a module wouldn't make sense to a new programmer, because the jargon has changed (eg. ports, again), pay attention to those case, they usually describe some "super-structure" in the code.
Finally, one more thing that I found that makes you understand the language better: writing native extensions. In this way you get very intimate and "first-hand" understanding of how some mechanisms work that cannot be properly exposed in the language itself.
Otherwise, the books and references will help you get the syntax and maybe some of the otp system libraries, but the learning part is coming to terms with the core concept of a process as something with a bit of state that reads its message queue and responds. Each process should be fairly simple as it only manages its state and processes one request at a time. Sometimes business requirements make that processing complex. Sometimes processing that request means gathering information from other processes --- this can get complex if there's ordering or consistency requirements; in that case, the least complex option is to make sure all the requests that need consistency among themselves are handled by the same process. If only one process accesses the data and it only processes one message at a time, transactional concerns are easy to manage.
ETS works a little different under the hood, but think of each table as a process, if you want to read a key, you send it essentially { self(), read, Key} and it replies with the data. Same deal for writes, etc.
Mnesia is processes that you send messages to, and then that process does what you asked and sends the result back.
The beauty of an Erlang system is you can get a shell on it, and inspect all sorts of stuff. You can get a list of all the processes, and see how long their message queues are. If something has a long message queue, you can get a copy of the queue and inspect it. If it's a gen_server and it's not totally stuck, you can get a copy of its state.
You can look at the ETS tables. You can look at the Mnesia tables. You can look at the ETS or DETS tables underneath the ETS tables.
But you do have to be a little careful sometimes. If you are low on memory, and you get a copy of a big message queue, you could exhaust your memory and kill the whole VM. Many of the old footguns have been disarmed, but Erlang still gives you plenty of ammo to shoot yourself in the foot.
[0] https://chromewebstore.google.com/detail/rocky-ai/fdjoklehji...
Learn You Some Erlang has some useful discussion of OTP, and it was a big help to me to read through the OTP library source code. That of course will also get you more comfortable with Erlang itself.
Write a highly parallel web scraper / downloader as your first project, with workers and supervisors, there are plenty of examples how to do this with Erlang.
Then, learn the rest of the language, now that you know its raison d'être.
The actor model is a good idea, functional programming is a good idea... but the Erlang tooling experience is awful and many essential tools are dated. Hiring for an Erlang team is hard. Erlang projects can be an actor spaghetti.
And many people in the Erlang community really have to check their ego. If you want to assert that Erlang is the best language, trying other languages first is a good starting point.
Edit* Look, it showed me this same Ask HN post as a reference:
https://www.phind.com/search?cache=avz73b8uy17qz70rfoto0x8t
Also, here is an Awesome list concerning Erlang:
https://github.com/drobakowski/awesome-erlang
And Elixir's HexDocs section on ETS:
The syntax of erlang, while a little weird, is very small. I struggled the most with immutability.
Top 10 Resources For Getting Started with Erlang
These are the top ten resources that helped me when I started learning Erlang. I've not ordered them within the list because they complement each other. Your mileage may vary. Other Erlangers opinions may differ. These helped me greatly though. I cannot stress enough that there is no substitute for making. The below will help you much more if you start out trying to solve with Erlang some problem you know about. Decompose it into very small pieces and take each piece one at a time. For some more info on that see the post introducing the concept of Deliberate Practice.
1. Learn You Some Erlang I started learning Erlang back in 2009 at about the same time Learn You Some Erlang chapters started being posted by Fred Trottier-Hebert. This is the first place I'd recommend someone go when they are learning Erlang, especially if they have good prior software writing experience. I found LYWSE easy to understand and packed with detail. Sometimes it goes into too advanced details for a beginner, but you can skip these and come back to them when you are ready.
2. Joe Armstrong's Thesis Reading this thesis is drinking direct from the source. Joe Armstrong is one of the three fathers of Erlang. The other two are Bjarne Da ̈cker and Robert Virding. Reading A History of Erlang (PDF) by Joe Armstrong won't teach you Erlang, but it's a very interesting read.
3. The Erlang Web Site Erlang.org has some good examples, the OTP Design Principles User Guide, the Erlang Reference Manual, the documentation for the Erlang OTP libraries (Erlang's stdlib), and an online self-paced course.
4. The Erlang-Questions Mailing List The people on this list are very helpful. Chances are that your question has been asked before, so search the archives first. As with any mailing list it can take time to get an answer, so I tend to just use the archive. The FAQ, a link to the archives and instructions for subscribing are on their web site: http://erlang.org/mailman/listinfo/erlang-questions.
5. Free E-Books and Other Web Resources The following books are good to use for times when you don't have time to get into the coding zone, or when you want to deep dive into a particular topic. Concurrent Programming in Erlang, Part 1 Erlang For Skeptics - An old, but still useful, e-book that you'll need to build yourself from this project site. It's worth it though. TryErlang.org - A free hands-on web tutorial for Erlang I remember going through some others, but it's been a long time and I don't remember them. If you read this and know of a good (and legal) e-book link then please post it in the comments and I'll add it below here, with credit.
6. Commercial Books and Podcasts I bought some of the books on this list, borrowed others. They are all recommended, but in this economy it's important to stress you don't need them to learn Erlang, but they will make your learning Erlang easier. Erlang in Practice by Kevin Smith - From all accounts a very good series of screencasts on Erlang Erlang Programming by Francesco Cesarini and Simon Thompson Erlang and OTP in Action by Martin Logan, Eric Merritt, and Richard Carlsson Building Web Applications with Erlang: Working with REST and Web Sockets on Yaws
7. Online Q&A sites If you have a question while learning Erlang the chances are someone else has had it as well. It's also good when you don't have a specific question but you have some time to spend on learning. When that happens go to one of these Q&A sites and search for unanswered Erlang questions, pick one, and then research it until you have an answer. Once you have an answer you can go back to the question and post your answer if there isn't one yet.
Stackoverflow is probably the best known Q&A site. It is a great source for detailed Erlang information in their Erlang questions. They also have a decent number of unanswered Erlang questions at any one time.
Another less well-known site is Quora (requires login via Twitter or Facebook). They are getting more popular and are more focused on social connections than score, whereas StackOverflow is focused more on the score. They a tag so you can find Erlang questions, but I've not found a link for unanswered questions, only for open Erlang questions.
8. Twitter Twitter is always a great source for information, and for a dialogue with people that may be able to answer your questions. Feel free to follow me and tweet me if you have a problem. I also try to retweet anything on Erlang that I find interesting. My Twitter id is BillBarnhill.
9. Source Code The best way to learn a language is by making useful software using that language. The second best way is to read good code, trace how it runs, and re-read until you understand what it does. Often this will lead into writing code to get the software to scratch a particular itch you have. The best source code to read in my opinion is the OTP sources, for the sole reason that they will be what you interact with the most. The second best is the Github account of Basho and the repos in it, because these folks know their stuff.
10. Erlang Projects I Recommend This one isn't a resource as much as some recommendations from me on projects to learn about byt looking at the materials the developers publish, the source code, and building.
Web servers and frameworks
For web serving I recommend Cowboy. I started out on Yaws, then switched to Misultin for most things, Mochiweb for some others. When Misultin went away I switched to Cowboy and haven't looked back. There's some caveats though. Riak uses Webmachine and Mochiweb, and if you want to use Erlang professionally you need to know Riak. So you need to at least be comfortable with WebMachine and Mochiweb. The web framework Nitrogen lets you use Mochiweb or Yaws, and you should learn Nitrogen. Once you learn Nitrogen I suggest you learn Zotonic, which is a Content Management System (CMS) like Drupal and is built on top of Nitrogen. If you are coming from Rails, or want something that feels similar, then I suggest checking out the Chicago Boss web framework