ConfigAdmin implementation is not thread-safe
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Key: FELIX-1477
URL: https://issues.apache.org/jira/browse/FELIX-1477
Project: Felix
Issue Type: Bug
Components: Configuration Admin
Affects Versions: configadmin-1.0.10
Reporter: Andy Wilkinson
I've been doing some work with ConfigAdmin in a multi-threaded environment and
have come across a number of issues caused by thread safety problems. The
symptoms are typically either an IllegalStateException from
ConfiguationAdapter.checkDeleted when, in fact, the Configuration has not been
deleted, or a NPE, where PersistenceManager is checked once for being non-null,
and the used again without re-checking for it having been nulled out, e.g. due
to concurrent invocations of delete and update.
I tracked down a common cause of the IllegalStateException from checkDeleted to
FilePersistenceManager's exists method. If exists is called on one thread while
store (for an update) is being run on another, the rename can cause exists to
incorrectly return false. synchronizing on this in exists appears to resolve
this problem.
I've produced a patch that goes someway to improve the thread-safety, although
I does not make the implementation completely thread-safe. Without the patch in
place I was seeing a failure about one run in three. Since applying the patch I
have yet to see a failure after more than 100 runs.
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