Improvents on agent,user-custom thread pool.

[dennis]

Agent use two thread pools to execute actions,send use a fixed thread
pool (2+cpus threads),and send-off use a cached thread pool.These
pools are global in clojure system.

I think the Agent should allow users to customize the thread pool,
if no custom, then use the global thread pool.
Why do I need a custom thread pool?
First, the default thread pool is global, send use the thread pool
is a fixed size cpus +2, is likely to become the system bottleneck
sometime. Although you can use the send-off, use the cache thread
pool, but in a real world application, I can not use the cache thread
pool, which will introduce the risk of OutOfMemoryError, normally I
like to use a fixed-size thread pool.

Second, the actions which global thread pool execute are from a
variety of agents, the actions are not homogeneous, and can not
maximize the efficient use of the thread pool, we hope that you can
specify different agent to isolate a particular thread pool to
maximize the use of thread pool .

I think Agent could add two new functions:

(set-executor! agent (java.util.concurrent.Executors/
newFixedThreadPool 2))
(shutdown-agent agent)

set-executor! is to set the agent's custom thread pool,and shutdown-
agent to shutdown the agent's custom thread pool.

[Alex Miller]

Hey Dennis,

I suggested some of the same ideas here (http://tech.puredanger.com/
2010/06/08/clojure-agent-thread-pools/) and Rich said that these
seemed like good suggestions post-1.2. I think allowing you to modify
the agent thread pools after construction seems possibly dangerous
from a concurrency point of view, but maybe that would be ok.

Alex

[mnicky]

I just came across this thread (and also [1]) when I was googling for a way to customize the Clojure agents. Were any of these 'post 1.2' suggestions reconsidered since then? (I see they haven't been implemented yet).

Marek.

[1] https://groups.google.com/forum/?fromgroups#!topic/clojure-dev/qDfxSoesp4o