- macros: fancy syntax and "magic" can be resolved at compile-time. Less work to do on runtime.
- templates: they get handled at compile-time, too, resulting in functions with blobs of binaries. This matters a lot, since a specific template-binary exists only once throughout the application and gets re-used whenever needed. This way you get near instant templating, instead of the usual string processing on every request.
- dispatching code like the routing that must be done on every request is like rails a DSL, but actually a macro, that gets compiled down to basic pattern matches, which is extremely fast.
- the concurrency model is extremely lightweight, handling more requests and/or doing more stuff per request is much more efficient hardware-wise. Indirect performance gain.
Just a few points that have a very noticeably impact, there are probably more. It boils down to the erlang vm's concurrency and pattern matching performance, plus elixir's compile-time macros and the fact that they treat strings as immutable binaries.
All well and good, but Erlang/beam code is not that fast.
> templates
Ruby's templates are parsed into code that stays in memory, too, so it's not like they're re-parsed each and every time.
> routing
Perhaps clever use of pattern matching helps here. But my point is: someone should dissect these things in a real-world-ish application to see what's actually true.
> concurrency
Yes, but let's be precise. Everyone knows Erlang's concurrency is way better than Ruby's. The claim was 'fast' though. As well as maintainable, which seems curious given that there are no really old Phoenix apps out there.
True, no doubt. You wanted a comparison why phoenix is faster than rails. And simply doing things at compile time reduces work at runtime. In Ruby, all Metaprogramming must be done at runtime, for example via method_missing trickery (been there, done that).
> Ruby's templates are parsed into code that stays in memory, too, so it's not like they're re-parsed each and every time.
This is actually not the same. A single immutable blob of binary (elixir strings) which is shared throughout the whole application can leverage hardware caching better. Jose could answer this probably better than I can do.
> someone should dissect these things in a real-world-ish application to see what's actually true.
Moz.com recently had fun with Elixir [1]. You may also have a look at https://www.youtube.com/watch?v=OxhTQdcieQE from latest RailsConf.
> The claim was 'fast' though
Well at least I know that BEAM processes are far lighter than eg: goroutines. Also there is a per-process GC, so no "stop the world", much smaller units for individual collects, and when a process finishes before the heap grows full, it can be discarded directly.
> maintainable, which seems curious given that there are no really old Phoenix apps out there
Fair enough.
Personally I'd not wait until a software stack is a decade old before even considering it. I have at least worked on Elixir/Phoenix projects for many months now on-off with multiple colleagues, and it was/is still pure joy. Aesthetically pleasing syntax helps (broken window syndrome I guess), plus functional programming style in general, plus phoenix' foundation in "plug" and the clear modularity. "Let it crash" with supervisors also is incredibly robust, and robustness in itself leads to less maintenance costs.
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Stuff like "Erlang processes are lighter" matters in some contexts, but not in a straight up speed contest. It matters a lot when you start trying to handle a bunch of concurrent connections, so maybe that's where we're getting some of the claims from.
Functional programming is not an 'antidote' to having to go back and read old code or necessarily understanding it easily.
It references this:
http://sorentwo.com/2016/02/02/caching-what-is-it-good-for.h...
Which is interesting, but I don't see source code. 1.5-2X is pretty believable, but quite a bit less than "12 times" - which someone quoted here.
Depends on what you're doing though. Seems to excel when having low CPU intensive workloads but high traffic pressure from my experience.
It could be a case of not yet being optimized for the tests, but I was expecting much more impressive numbers out of the box (particularly after the full-court press on the boards and blogs).
Chris McCord talks about it here https://www.reddit.com/r/elixir/comments/48ke69/any_reason_w...
I used Erlang at the last place I worked and like it a lot, but Rails is pretty good too in my book.
The one thing that comes to mind is that since each process has its own isolated memory space, Erlang's GC is not a "stop the universe" kind of thing, the GC can run in parallel with other processes.
(edit: again, this is just intuition on my part, I haven't remotely done the deep dive you're talking about)