A question about your HttpClient example and beyond

[Frederic Bregier]

Hi,

I will not talk about the specific Http part of Netty but about its main interest, the NIO of Netty.
Of course, Trustin or others can be more precised than me. It is just my general comprehension.

To compare to a standard Blocking IO, Netty uses less threads to manage the same behaviour.
For instance, if you think about Apache or Tomcat, one connection will be handled by at least one thread through the full life of the connection. So if you have 1000 connections, you will have at least 1000 threads.
In Netty, a thread will be active when data arrives into the server (the general idea is greatly simplified here, it is not to take it as the reality). For instance, for those 1000 connections, maybe at most 100 are really sending something on the same time to the server, so around 100 threads will be used. Netty does something like reusing threads, whatever the connection is.

Another point of course is the non blocking way. Once you send something, you have the choice to continue the job without waiting that the data is really sent (of course, you have to take care about it for instance before closing the channel). So you can overlap sending data with other computations (for instance for next packet to be sent).
Compares to blocking IO, of course, there you wait for the data to be really sent (or at least buffered).

So in many points, Netty approach should have more performance than blocking IO. I said "should" since there exist some counter examples where blocking IO are faster, since NIO introduces some extra computing comparing to blocking IO. However most of the time, these extra are masked by the implementation of Netty and are quicker than blocking IO. But I recall some examples however.

Also, Netty can have different kind of transport (nio, oio, ...), so the behaviour can be different according to one or another low network transport framework.

This is not the full idea of Netty, but a start of answer to your question.
For more information, either other people can continue this thread (or correct where I a wrong), and of course you can read the examples that are in Netty (even those not about Http) and the documentation of Netty.

HTH,
Cheers,
Frederic
  ----- Original Message ----- 
  From: J. Mi (via Nabble) 
  To: Frederic Bregier 
  Sent: Wednesday, September 02, 2009 9:12 PM
  Subject: A question about your HttpClient example and beyond


  Hi folks,
  Â 
  Currently, my application's process flow logic is like this:
  Â 
  -> A controlling process receives one request for data which will be fetched from multiple online sources.
  -> The controlling process spawns multiple threads. Each of these threads will (1) use Apache synchronous commons httpclient to fetch the data; (2) parse the data; and (3)
  Â Â Â Â return the data to the controlling process.
  -> The controlling process joins all threads and return the combined data to the requestor.
  Â 
  So basically, each thread uses a synchronous httpclient to fetch the data and then parse it.
  Â 
  In reading org.jboss.netty.example.http.snoop package, I have the following question:
  If I just replace the Apache's synchronous httpclient with Nettty's org.jboss.netty.handler.codec.http.* as the example does, will I be benefited performance-wise? I heard something about blocking I/O hurts multi-threading. If so, should Netty's package work better for me?
  Â 
  Or should I actually get ride of the existing multi-threading by using Netty's framework? If so, which of your examples can be better referenced for my purpose?
  Â 
  Thanks for your in advance,
  Jason
  Â 
  Â 

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