adaptive connection pool sizing
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Key: HTTPCLIENT-1101
URL: https://issues.apache.org/jira/browse/HTTPCLIENT-1101
Project: HttpComponents HttpClient
Issue Type: New Feature
Components: HttpClient
Affects Versions: Future
Reporter: Jon Moore
Assignee: Jon Moore
I'm currently working on a patch (wrote most of it on a cross-country flight)
that will adapt the size of a per-route connection pool based on the
interactions we see from that particular host. There's a sample implementation
that does TCP-style additive increase/multiplicative decrease (AIMD) adaptation
of the per-route pool where successful requests allow probing for more
connections, but socket timeouts, connection timeouts, and 503s all result in
backoffs.
I'm hoping to hook this up for a demo to show multiple clients hitting a server
with a fixed capacity where we can kill one client and the others then increase
their pool sizes to take advantage of the unused server capacity. We can then
restart the client and see things rebalance again. This would enable folks to
use HttpClient e.g. in an application server cluster setting, where we wouldn't
have to precompute or adjust the connection pool sizes as we add/remove nodes
from the cluster (whether intentionally or via failures).
Once I get that proof of concept working I'll post a patch for review. Roughly
the patch hooks into AbstractHttpClient to look either for an HttpResponse or
to catch an Exception, then hands those events off to another object to decide
whether to backoff or not. In turn, we dynamically manage a ConnPerRouteBean to
adjust the maxPerRoute to allow for the pool to grow or shrink naturally with
TSSCM. Default implementations are all backwards compatible and don't change
behavior.
Thoughts?
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