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Posted to users@tomcat.apache.org by Saurav Sarkar <sa...@gmail.com> on 2017/10/11 12:56:17 UTC
Basic question related to NIO connector and Async servlet processing
Hi All,
I have got a basic question related to usage of Async servlet with tomcat
NIO connector.
I want to use Async servlet with Non Block I/O as per servlet spec
https://docs.oracle.com/javaee/7/tutorial/servlets013.htm?lipi=urn%3Ali%3Apage%3Ad_flagship3_pulse_read%3BmL0Q5Y7ESTy4lpYPU%2Br77w%3D%3D
Such that the http worker threads are released and the container threads
won't be sitting idle for I/O operations too.
I am on Tomcat 7. As i understand the default tomcat connector (BIO) is a
blocking one and is on a thread per connection model. I am not clear on
whether using async Non Blocking I/o in servlets won't suffice ? Won't the
http worker threads be released here or will it be held for the lifetime of
the connection ?
NIO connector will use request per threads or allocate threads when
processing is required .Will using NIO selector only release the http
worker threads if it is used in conjunction with
Asynchronous Non blocking I/O servlets ?
Best Regards,
Saurav
Re: Basic question related to NIO connector and Async servlet
processing
Posted by Christopher Schultz <ch...@christopherschultz.net>.
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Saurav,
On 10/11/17 8:56 AM, Saurav Sarkar wrote:
> I have got a basic question related to usage of Async servlet with
> tomcat NIO connector.
>
> I want to use Async servlet with Non Block I/O as per servlet spec
> https://docs.oracle.com/javaee/7/tutorial/servlets013.htm?lipi=urn%3Al
i%3Apage%3Ad_flagship3_pulse_read%3BmL0Q5Y7ESTy4lpYPU%2Br77w%3D%3D
>
> Such that the http worker threads are released and the container
> threads won't be sitting idle for I/O operations too.
>
> I am on Tomcat 7. As i understand the default tomcat connector
> (BIO) is a blocking one and is on a thread per connection model. I
> am not clear on whether using async Non Blocking I/o in servlets
> won't suffice ? Won't the http worker threads be released here or
> will it be held for the lifetime of the connection ?
You can't effectively use BIO with async, at least not the way you
actually want to use it. You should switch to NIO if you want to use
servlet-async.
> NIO connector will use request per threads or allocate threads
> when processing is required .Will using NIO selector only release
> the http worker threads if it is used in conjunction with
> Asynchronous Non blocking I/O servlets ?
That depends upon what you mean by "release" and, specifically, /when/
they are released.
With the BIO connector, HTTP keepalives can tie-up a connector up to
the keepAliveTimeout without accomplishing any useful work. This
happens ALL THE TIME -- clients make a keepalive request and then
never bother to close their connection cleanly. So the server wastes
thread-time waiting for another request which never comes.
The NIO connector (and APR connector) puts the connection into an I/O
selector and waits for an interrupt from the OS/JVM while the
request-processor thread goes back into the thread pool.
When doing servlet-async and Websocket, things get ... more complicated.
- -chris
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