Hi Raghav,
You cannot achieve this with the built in tools, but a simple custom
directive will do the trick. Something like this:
def createConcurrentLimiter(maxConcurrent: Int): Directive0 = {
// thread safe counter for connections
val concurrent = new AtomicInteger(0)
pass.tflatMap[Unit] { _ =>
if (concurrent.get() >= maxConcurrent) {
complete(StatusCodes.ServiceUnavailable)
} else {
concurrent.incrementAndGet()
mapResponse { response =>
concurrent.getAndDecrement()
response
}
}
}
}
// important to create once and reuse, so that the same atomic int is used
val maxOneConcurrent = createConcurrentLimiter(1)
val route = get {
extractRequest { req =>
maxOneConcurrent {
// never more than one in here
complete("ok")
}
}
}
--
Johan
Akka Team
On Mon, Sep 5, 2016 at 3:56 PM, 'Raghav Narula' via Akka User List <
[email protected]> wrote:
> I'm using akka-http to build one of my services which returns a chunked
> response that could be 10s of MBs big depending on the client's query. I've
> noticed that the memory required is proportional to the number of
> concurrent streams rather than the number of connections from clients, as
> idle connections seem to use hardly any resources at all.
>
> Is there any way to limit the number of responses being rendered? I can
> only see the akka.http.server.max-connections config variable which seems
> to limit the total number of connections, rather than in flight responses.
> With a low max-connections value clients could be denied service because of
> idle clients holding connections. With a high max-connections I get out of
> memory errors as there is potential for all the connections to make large
> requests.
>
> Ideally I'd like to be able to keep connections open so that clients can
> avoid the overhead of making new connections, but still limit the number of
> in flight responses to protect memory usage. Then if the client tries to
> make a request which can't be served, the connection is dropped with a 409
> maybe?
>
> Or is the common way to deal with this to just have a fast timeout so
> clients can't hold open connections for too long, and make them re-open
> connections frequently?
>
> --
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--
Akka Team
Lightbend <http://www.lightbend.com/> - Reactive apps on the JVM
Twitter: @akkateam
--
>>>>>>>>>> Read the docs: http://akka.io/docs/
>>>>>>>>>> Check the FAQ:
>>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html
>>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user
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