On Tue, 2010-08-17 at 12:18 -0700, Mike Boyers wrote:
> I've been a user of HttpClient 3 for several years and am now migrating to
> using HttpClient 4.
>
> With version 3, I wrapped (extended) the client in order to instrument it
> (via JMX). I kept track of the following pieces of information, per host:
> -Number of request (socket) timeouts
> -Number of connection timeouts
> -Number of timeouts while waiting for connection from pool
> -Total number of requests
> -Average Request duration
> -Maximum Request duration
> -Number of connections currently in pool
> -Max connections in pool
>
> With HttpClient version 4, I'd rather not extend the client and would instead
> like have developers use a pre-configured httpclient that was created with a
> ThreadSafeClientConnManager.
>
> I can see how to use a HttpRequestInterceptor and HttpResponseInterceptor
> to record things like number of transactions, request durations, etc.
>
> What I need help with is determining how I can record timeout information.
> When I'd recorded this in the past, I caught exceptions thrown by
> HttpClient's execute method in my extended class. It looks like when I call
> execute on HttpClient 4, if an exception is thrown, the
> HttpResponseInterceptor will not be called. I'm not sure where to intercept
> in this case.
HttpClient is an interface in 4.x, so instead of extending its default
implementation you should consider using the Decorator pattern in order
to introduce additional functionality.
>
> Another related question: I typically have a scheduled task that occasionally
> calls the connection manager's closeIdleConnections method. After I do this,
> when I want to learn how many connections are in each pool, I have to have
> kept track of each HttpRoute and then call the getConnectionsInPool(route)
> method for each route. Is there a way I can have the connection manager give
> me the list of routes so I don't have to keep track of them myself?
>
Presently not. It should be fairly easy to add, though, as the
ConnPoolByRoute class maintains a map of unique routes internally.
> And one final question: I'd like to consider the possibility of handing out
> an HttpClient that will not talk to any host unless it has been explicitly
> configured (to force developers to think about the proper max pool size so we
> fail fast when a remote source is having issues). What I'm thinking is
> something like:
> ConnPerRouteBean connPerRoute = new ConnPerRouteBean(0);
>
> // Then explicitly enable hosts as follows
> HttpHost localhost = new HttpHost("localhost", 8080);
> localhostRoute = new HttpRoute(localhost);
> connPerRoute.setMaxForRoute(localhostRoute, 10);
> ConnManagerParams.setMaxConnectionsPerRoute(params, connPerRoute);
>
> But I currently get an exception when instantiating ConnPerRouteBean with 0
> (needs to be a positive integer). Is there a different way to accomplish
> this other than the path I've outlined above?
>
We have not thought of this kind of situation so currently there is not
way to prevent the pooling connection manager from creating connections
to a particular target host by setting the per route limit to zero.
The only solution to the problem I can think of from the top of my head
is a custom connection manager that requires an explicit route
configuration before a connection for that particular route can be made.
Overall, I think you will be better off by developing a custom
connection manager given a fairly uncommon set of requirements that you
have.
Hope this helps
Oleg
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