Things I like using it for:
- long running services
- doing anything w/ concurrency
- setting up cron-like processes that run every so often
- actor model anything
- stateful services
- web development using Phoenix & Ecto
- parsing
- encoding/decoding
Things I don't like are primarily related to it being a small enough community. That means libraries for third party services aren't always the best, and using it in the enterprise means that the smaller talent pool is less attractive when the company's priority is to use proven/boring tech for which you can hire tons of developers. I also don't think Elixir has a clear value proposition when you're writing small, single purpose functions for a serverless architecture (even though I really like writing it), or when you're company decides to go all in on Kafka for communication between micro services.
Just my two cents.
Being able to utilize erlang libraries means there are a ton of heavily production tested libraries you can easily drop into an elixir project.
I also encountered some pain with the AWS client for Elixir when our company implemented SSO. There was a lack of support for a certain flavor of environment variable if I recall correctly. It's not horrible, just a pain.
hard disagree on all but c++, .net and maybe python
I think people forget erlang has been around a long long time and I've written ruby for years and can speak with great confidence that the equivalent ruby libraries in elixir are typically much higher quality
The single unix process that BEAM uses is more conducive to some kinds of systems than some of the hackier-feeling solutions for the Rails ecosystem to tie different pieces together.
What's the issue with Kafka and Elixir?
AFAIK, any modernish language is good enough to get something up and running regardless of the task.
In the middle you will probably have a large number of problems that it's ok-ish at. But not really sure on what the distribution is here.
Can you give an examples? Respectfully, you were asked for tasks and instead gave a description of the category.
I can only think of real-time, or real performance limited software (example: rocket guidance software, aviation, etc). With these every modicum of performance per millisecond matters; but these constraints only apply in a few (relatively) small fields of software development.
In practice I haven't found the immutability of Elixir that useful for concurrency because data is deep copied when it goes across processes anyways. This is in comparison to Clojure where you can safely and perfomantly share immutable data across multiple threads.
To be clear, for NPCs it worked fine. But players are hoarders and in an RPG that can result in a ridiculous amount of data being attached to them.
Of course, maybe there's a generalized BEAM to C call library I'm not aware of? (I didn't think to search for one until now)
Also, honestly, it's a little easier to have a C daemon than an erlang daemon. Just call daemon() before the service loop vs setting up an app file. Of course, you have to build hotload yourself from dlopen and friends, and you lose out on a lot of features.
Elixir releases are built in and easy to use. You don't have to write an app file directly for instance.
I usually use ports for C interface (rather than NIFs). I have a little boilerplate C and Elixir that I recycle to do the ground work and then it's just your specific implementation detail.
I'm looking for the equivalent of Perl's h2xs, or something like that. (which incidentally, maybe I should be writing these things in perl ;)
A lot of languages that have more limited existing use have more gaps in their ecosystems. That means that to get something going quickly, you run into cases where you spend a lot more time building (or validating and tweaking existing but relatively rough) support infrastructure that you would just grab a well-tested, established library for in a language with a richer community and ecosystem. This is an area where the top tier ecosystems (Python, .NET, JVM) really shine over even second-tier popular ones like Ruby, and where both of those tower over things like BEAM, which has the additional problem that it has a fairly high impedance for incorporating C libraries, where many other platforms (some also with stronger ecosystems of their own) also more easily consume C libraries.
This extends both to broad application domains (e.g., scientific libraries) and to things like probability of having an idiomatic, language specific, well-supported client for a new service you want to tie in and incorporate.
If you're running a server—sure, BEAM me up.
In terms of what it's good at, we very successfully employed Erlang as the command and control language for some semi-embedded system medical devices. The runtime is predictable in terms of performance and memory, and fast enough for a lot of things. Where it wasn't, it's easy enough to talk to C. All the fault-tolerant bits are nice for a system like that where you want it to take note of a failure and restart the subsystem that failed. Lots of good logging, introspection and diagnostic tools exist.