What can I only do in Erlang?

1. Binaries: this isn't really an issue. We ship the JVM with anything that we do in Java. Unzip, run, done. Go is probably ideal there but it doesn't support embedded resources without some hideous hacks so you're still going to be deploying more than just a single binary in a lot of cases. CLR is pretty good at this as well.

2. Sockets: 0MQ/WCF/JMS/any stream abstraction wired up correctly.

3. ASN.1: Everything has ASN.1 libraries these days. I've never had to use one in the real world in any of the sectors I've worked in.

3. Let it crash: we do this. In fact we force threads to crash if they do anything bad by throwing an exception that isn't caught. All threads are designed to be idempotent, restartable and transaction aware. This is true in JVM/CLR at least.

4. Supervision: New thread, new state, no shared state. Not hard. PHP does this...

5. Inspection: I've seen the Erlang toolchain and it's pretty good but I'm not joking but inspecting and debugging the state of a system is better when there is lots of pooled knowledge (google) and lots of diverse tools. JVM wins there every time.

7. Messaging is not RPC: It's not in JMS either or WCF. It abstracts the transport away. In fact we have inproc transports in some cases that use concurrent collections to throw messages around.

8. Dialyzer: compiler, static typing (Java is less strong here to be honest than say C#).

I really like the idea of Erlang but the worse is better mantra applies here. It's easier to get staff, the knowledge when something goes pop is available, we benefit from the reuse of billions of lines of code written and tested by others if we pick a JVM. If we have to think a bit or throw some more kit at it, so be it.

Edit: just to add, I'm not knocking Erlang and quite like it in principle (I spent 2 months disassembling CouchDB to see if we could maintain it so it's not a foreign language to me), but the justifications in the reply aren't particularly unique ones nor are they major advantages.

http://www.erlang.org/doc/efficiency_guide/binaryhandling.ht...

http://www.erlang.org/doc/programming_examples/bit_syntax.ht...

Erlang is really strong for that.

As to Java, sure, you can do anything with it, and do a decent job of it. But sometimes, as a startup, you are resource constrained, so if you can do more with less because you have a good grasp of a tool like Rails, or Erlang or Lua or whatever, that might make the difference. For a large company, Java is definitely a safe pick - no one ever got fired for choosing it: you'll be able to get whatever you need done, and "If we have to think a bit or throw some more kit at it, so be it." For a group like WhatsApp, Erlang seems to have been a good pick.

Yes it is far superior from a representation point of view at least there. I have no doubts about that.

3. it's not only letting it crash, it's supervisors, restarts, cascading crashes when the parents retried enought times. Yes you can do it in other languages, but in erlang it's already done and battle tested.

4. that's not supervision

7. in erlang sending a message to a process in the same cpu and in another server has the same syntax and it's the common way of building software, in other languages calling a method and doing a jms message are two different things that you have to deal differently.

8. I would add quick check to the mix, but yes, dialyzer is just a kind of progressive typing