Hi Mike,
[snip]
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.
Yes - I will use the decorator pattern to achieve this.
I was wondering if there was a wider interest in the type of
instrumentation I mentioned? I know when I implemented it for
HttpClient 3, it was invaluable in being proactive about tracking
problems. I'm using some other packages (ehCache, logback) that
support JMX out of the box (made optional via configuration if you
don't want it). Is there any community interest for doing so in
HttpClient or is it considered out of scope?
I've needed something along these lines, though much simpler - e.g. a
way to monitor fetch rate and bytes read, and terminate upon various
limits being hit (too slow, too big).
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.
FWIW, I need a way to abort active connections, which was discussed on
this list a few weeks back. This feels related, in case you're into
extending the connection manager API :)
-- Ken
--------------------------------------------
<http://ken-blog.krugler.org>
+1 530-265-2225
--------------------------------------------
Ken Krugler
+1 530-210-6378
http://bixolabs.com
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