> So HiPE is stable now?

I mean, it looks like HiPE has been shipped with OTP since 2001 (three years before work started on Dialyzer), and it certainly is enabled by default on all supported platforms (of which x86 and amd64 appear to be two). Now, you do have to pass the "native" option to the code compiler to make it compile to native code, but you don't need to jump through any more hoops than that.

For the software I've written, bytecode-compiled Erlang was fast enough for me, so I haven't much experience with HiPE. I'm pretty sure that none of the documentation on erlang.org indicates that HiPE is experimental or unstable. What was wrong with HiPE when you used it, and when did you use it?

> I understood that Erlang hot patching was only at a function level... No guarantees when the old code will be unloaded?

Yeah, it's hot patching at a whole function level. This level of granularity almost doesn't require any care at all, actually... far less than if you could patch at a statement level [0]. Read the first several paragraphs of [1] to get a high-level overview of how hot code swapping (and code unloading) works. (The prose from "There are ways to bind yourself" onwards is not relevant to your interests, so you can stop there.)

> Where do you find [hot code loading] beneficial?

Whenever I have a service whose code I need to upgrade, and won't need any complicated data migration as a result of the upgrade. Hot code loading is not absolutely critical, but it's another useful tool in Erlang's high-availability toolbox.

> I remember seeing someone porting OTP to Java or .Net.

That's cool! :D What parts of OTP did they not port? Mnesia? The Erlang stdlib? (There's lots more to OTP than gen_server and friends.) Did they also port single-assignment variables, transparent-to-application-code IPC, and distributed code loading-and-execution, or was this just an OTP-the-library port and not a "Let's port some of the nicer Erlang/OTP runtime features, as well as gen_server and friends." project?

> Personally, having to serialize everything and getting "transparent" scalability by moving stuff over the network doesn't appeal to me.

There's no need for scare quotes. Erlang process distribution is transparent to program code. And, like, anyone writing distributed software has to be aware that accessing off-node data is almost always more expensive than accessing on-node data. It's a law of physics. You can't ignore it.

Anyway. As an application writer, Erlang's process distribution is also incredibly nice (until measurements demonstrate that it's too slow for your application, and you have to do a bit of redesign).

For most web app backend services, and a lot of web infrastructure Erlang is more than fast enough, and gives you the tools to trivially scale to meet increasing demand.

> The main point seems to be that Ericsson made a good switch with it...

The point of that example is that over 1.5 million lines of Erlang were used in a piece of telecom hardware that provided 99.9999999% uptime. (That means that the switch was down for no more than 31 milliseconds per year.)

Erlang isn't good for every project. Only people who don't know what they're talking about make that claim. Erlang and OTP do provide you with the tools to relatively easily make fault-tolerant, scalable software. Is it the only toolset that does this? Fuck no. But it is a pretty-well-thought-out, battle-tested, actively maintained one.

What tools do you use when you must write highly-fault-tolerant, scalable software?

[0] If we assume a moderately complex function, there are certainly people alive who could keep all of the interactions between the first half of the currently-running-code and the second half of the to-be-switched-to-code in their head. I'm not one of them.

[1] http://learnyousomeerlang.com/designing-a-concurrent-applica... (You might need to reload the page after it is first loaded. Late image loading scrolled the page away from the intended anchor on my system.)