Beating the C10k Problem

Traditional Thread-Based HTTP Servers

Single threaded server

Traditional applications are inherently limited to a couple thousand connections，even built on top of modern servlet containers

Nonblocking HTTP Server with Netty and RxNetty

Netty is entirely event-driven;we never block waiting for data to be sent ir received.Instead,raw bytes in the form of ByteBuf instances are pushed to our processing pipeline.Whenever a few bytes arrive to our application,Netty will notify our handler.Whenever we send few bytes,we get a ChannelFuture without blocking.

Netty uses just a handful of threads to process possibly thousands of connections.We do not keep any heavyweight data structures or threads per each connection.

Observable server with RxNetty

HttpServer .newServer(8080) .start((req,resp)) -> { String amountStr = req.getDecodedPath().substring(1); BigDecimal amount = new BigDecimal(amountStr); Observable<String> response = Observable .just(amount) .map(eur -> eur.multiply(RATE)) .map(usd -> "{\"EUR\": " + amount +"," + "\"USD\": " + isd + "}"); return resp.writeString(response); }) .awaitShutdown();

This implementation can easily withstand thousands of concurrent connections,and vertical scalability is limited only by the amount of traffic it must handle,not the number of more-or-less idle connections.

Reactive HTTP Servers Tour

Http Client Code

A TCP/IP connection is actually quite lightweight.The operating system must keep a socket descriptor for each open connection (around one kb) and that is pretty much it.When a packet (messages) arrives,the kernel dispatches it to the appropriate process,like JVM.One kb is quite a small memory footprint compared to the roughly one mb consumed by the stack of each thread blocked on a socket.

Nonblocking HTTP Client with RxNetty

RxNetty goes a bit futrher compared to other nonblocking HTTP clients and does not simply notify us when the entrie response arrives.Instead,we get a stream of ByteBuf messages,optionally followed by Observable completion when the server decides to drop the connection.

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