CODEWITHSUNDEEP
javaperformancenetty
WorM
WorM

Reputation: 1155

does slow connections effect netty performance?

CODE-1 

new NioServerSocketChannelFactory(Executors.newCachedThreadPool(), Executors.newCachedThreadPool(),WORKER_SIZE)

CODE-2

OrderedMemoryAwareThreadPoolExecutor executor = new OrderedMemoryAwareThreadPoolExecutor(48, 0, 0, 1, TimeUnit.SECONDS);
pipeline.addLast("executor", new ExecutionHandler(executor));

If IO worker thread pool size (default is 2*count of cpu) can be set from CODE-1, what is the purpose of adding executer (a thread pool) to pipeline in CODE-2 ?

IO operations are done from worker threads. Does that mean, a client with slow connection or bad network keeps IO worker thread busy until data is completely sent ? If so, increasing WORKER_SIZE would help me prevent latencies ?

Upvotes: 1

Views: 2721

Answers (2)

Jestan Nirojan
Jestan Nirojan

Reputation: 2486

Slow Connections does not affect Netty threads in NIO normally (check the update note).

Some points about Netty server internal threads

  • by default there will be only one Boss Thread per server port, and it will accept connection and handover the connection to worker thread.

  • to be precise: WORKER_SIZE is the maximum number of NioWorker runnables a server can have. for example If the server has only one connection, then there will be 1 worker thread. If number of connections are increasing and it can not be assigned to next worker (active connections > WORKER_SIZE), then connections will be assigned to a worker in a round robin fashion.

If IO worker thread pool size (default is 2*count of cpu) can be set from CODE-1, what is the purpose of adding executer (a thread pool) to pipeline in CODE-2 ?

If your upstream tasks are blocking then you should execute them in a separate thread pool using a execution handler. Otherwise Nio read/write will not work on time (latency?). I think having a execution handler will help to reduce the latency than setting big value to WORKER_SIZE.

IO operations are done from worker threads. Does that mean, a client with slow connection or bad network keeps IO worker thread busy until data is completely sent ? If so, increasing WORKER_SIZE would help me prevent latencies ?

Generally speaking, increasing the WORKER_SIZE >= number of cpu * 2 does not help because, NIO is non blocking and If I am not mistaken, its CPU intensive.For CPU intensive task CPU * 2 number of threads are chosen mostly.

Update:

NioWorker runs a loop with selector.select(500ms) to receive OP_READ, selector.select with timeout a blocking call and if most of the connections are slow, performance may reduce?. You can reduce the timeout in org.jboss.netty.channel.socket.nio.SelectorUtil.java and test.

Upvotes: 2

ClickerMonkey
ClickerMonkey

Reputation: 1931

The thread pool[s] you are adding in CODE-1 are for the boss threads, and worker threads. The boss threads accept connections and pass it on to worker thread to handle.

The executor you add in CODE-2 is for handling the messages read by the worker threads.

Slow connections will not affect performance since you are using a non-blocking architecture (NIO) - which is set in Netty to not block (it could if it wanted to)

Upvotes: 0

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