idle object eviction-too coarse grained locking
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Key: POOL-165
URL: https://issues.apache.org/jira/browse/POOL-165
Project: Commons Pool
Issue Type: New Feature
Reporter: Mircea Markus
Fix For: 1.5.5
>From GenericKeyedObjectPoolFactory's javadoc:
"Optionally, one may configure the pool to examine and possibly evict objects
as they sit idle in the pool and to ensure that a minimum number of idle
objects is maintained for each key. This is performed by an "idle object
eviction" thread, which runs asynchronously. Caution should be used when
configuring this optional feature. Eviction runs require an exclusive
synchronization lock on the pool, so if they run too frequently and / or incur
excessive latency when creating, destroying or validating object instances,
performance issues may result. The idle object eviction thread may be
configured using the following attributes.."
This can be improved im the following manner:
- use an lock per object rather than per pool. Whenever borrowing an object
acquire a write lock for the time object is borrowed
- the "idle object eviction" will check if the object is locked and if so
ignore it - this is a best effort approach that should satisfy most of the
scenarios. Otherwise acquire a lock on it, and it won't be available for
clients.
Glad to help on this one!
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