GenericObjectPool does per-resource work (e.g. validate) in a synchronized
context
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Key: POOL-108
URL: https://issues.apache.org/jira/browse/POOL-108
Project: Commons Pool
Issue Type: Improvement
Affects Versions: 1.3
Reporter: Matthew Moore
While using the pool library with DBCP, and load testing with simulated
failures, we noticed that a single bad connection can cause multiple threads to
block when the test on borrow flag is true. (Using "select 1" as a test query.)
Looking at the code, GenericObjectPool performs activation, passivation, and
validate on both borrow and return, inside of synchronized methods. This can
be a real problem, since any of these operations could conceivably block, in
which case all threads trying to obtain or release a resource will also block
for the duration. Some of these concerns are indirectly covered by POOL-93 in
2.0. Looking at revision 594226 I can see this has not yet been addressed.
Narrowing the synchronization scope via synchronized blocks, rather than
synchronizing the entire method, would deal with this easily enough. If I get
the time I'll work up a patch. This should be addressed - in the context of
DBCP it turns test on return / borrow into counter-intuitively dangerous
options.
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