[dart-misc] Parallel HTTP server via Isolate

[Michele Costa]

Hi all,

i maintain a micro-benchmark branch
<https://github.com/costajob/app-servers#dart-async> for different
languages, where i test the hypothetical max throughput of a plain "Hello
World" HTTP server by using the wrk <https://github.com/wg/wrk> tool.

I've added Dart 1.2.4 recently and noticed its throughput is not
disappointing, but nonetheless far from the Node.js one.
With Node i used the cluster library to allow pre-forking of multiple
processes, while Dart async implementation clearly does not run in parallel.

I've read that the Dart's Isolate library should support parallelism
through a multi-threading abstraction.
The API documentation
<https://api.dartlang.org/stable/1.24.2/dart-isolate/Isolate-class.html>
for Isolate was not so helpful, since it completely lacks concrete
implementation.

I've tried to extract the parallel server code used by the Techempower
benchmarks
<https://github.com/TechEmpower/FrameworkBenchmarks/blob/master/frameworks/Dart/dart-raw/server.dart>,
but i suspect something is broken here.
The Dart VM complains about the lack of a "reference" method, called to
pass the socket argument to the spawned isolates (line #30 of server.dart).

If you have any tips on how to implement a parallel server via the Isolate
library (or by using a pre-forking model like the one of Node.js) they will
be really appreciated.

Many thanks
Mike

PS - in case o pre-forking i do not want to rely on an external balancer, i
dare to use just standard library, like i didi for the other languages.