Although Jersey
already have support for making asynchronous requests, it is
implemented by standard blocking way - every asynchronous request is
handled by one thread and that thread is released only after request is
completely processed. That is OK for lots of cases, but imagine how that
will work when you need
to do lots of parallel requests. Of course you
can limit (and its really wise thing
to do, you do want control your
resources) number of threads used for asynchronous requests, but you'll
get another maybe not pleasant consequence - obviously processing time
will incerase.
There are few projects which are trying
to deal
with that problem, commonly named as async http clients. I didn't want
to "re-implement a wheel" and I decided I'll use AHC - Async Http
Client made by Jeanfrancois Arcand. There is also interesting implementation from Apache - HttpAsyncClient, but it is still in "very early stages of development" and others haven't been in similar or better shape as AHC.
How
this works? Non-blocking clients allow users
to make same asynchronous
requests as we can do with standard approach but implementation is
different - threads are better utilized, they don't spend most of time
in idle state. Simply described - when you make a request (send it over
the network), you are waiting for reply from other
side. And there comes
main advantage of non-blocking approach - it uses these threads for
further work, like making other requests or processing responses etc..
Idle time is minimized and your resources (threads) will be far better
used.
Who should consider using this? Everyone
who is making lots of asynchronous requests. I haven't done proper
benchmark yet, but some simple dumb tests are showing huge improvement
in cases where lots of concurrent asynchronous requests are made in
short period.
Last but not least - this module is still
experimental, so if you don't like something or if you have ideas for
improvements/any feedback, feel free
to comment this blog post, send
mail
to [email protected] or contact me personally. All feedback is greatly appreciated!
maven dependency (will be present in java.net maven 2 repo by the end of the day):
link: http://download.java.net/maven/2/com/sun/jersey/experimental/jersey-non-blocking-client
<dependency>
<groupId>com.sun.jersey.experimental</groupId>
<artifactId>jersey-non-blocking-client</artifactId>
<version>1.9-SNAPSHOT</version>
</dependency>
code snippet:
ClientConfig cc = new DefaultNonBlockingClientConfig();
cc.getProperties().put(NonBlockingClientConfig.PROPERTY_THREADPOOL_SIZE, 10); // default value, feel free
to change
Client c = NonBlockingClient.create(cc);
AsyncWebResource awr = c.asyncResource("http://oracle.com");
Future<ClientResponse> responseFuture = awr.get(ClientResponse.class);
// or
awr.get(new TypeListener<ClientResponse>(ClientResponse.class) {
@Override
public void onComplete(Future<ClientResponse> f) throws InterruptedException {
...
}
});
javadoc (temporary location, won't be updated): http://anise.cz/~paja/jersey-non-blocking-client/
