Dart: handle incoming HTTP requests in parallel

Question

I am trying to write an HTTP server in Dart that can handle multiple requests in parallel. I have been unsuccessful at achieving the \"parallel\" part thus far.

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Answer 1

I wrote a library called dart-isoserver to do this a while back. It's severely bit rotted now, but you can see the approach.

https://code.google.com/p/dart-isoserver/

What I did was proxy HttpRequest and HttpResponse via isolate ports, since you cannot send them directly. It worked, though there were a few caveats:

1. I/O on the request and response went though the main isolate, so that part was not parallel. Other work done in the worker isolate didn't block the main isolate though. What really should happen is that a socket connection should be transferrable between isolates.
2. Exceptions in the isolate would bring down the whole server. spawnFunction() now has an uncaught exception handler parameter, so this is somewhat fixable, but spawnUri() doesn't. dart-isoserver used spawnUri() to implement hot-loading, so that would have to be removed.
3. Isolates are a little slow to start up, and you probably don't want one per connection for the thousands of concurrent connection use cases that nginx and node.js target. An isolate pool with work queues would probably perform better, though that would eliminate the nice feature you could use blocking I/O in a worker.

A note about your first code example. That definitely won't run in parallel, as you noticed, because Dart is single-threaded. No Dart code in the same isolate ever runs concurrently.