Caching leaves room for potential race condition

[Felix Gilcher <mailing_lists@…>]

Currently, the AgaviExecution? filter calls checkCache() to see wether an action has been cached and then readCache() to retrieve the cached values. However, no checking is done on the return value of readCache() so that in multithreaded environements a clearCache() call from another thread might happen inbetween the check and the read, leading to an error.

Solution: check the result of the readCache operation and act accordingly (if fail, treat action as not cached).

[david]

Should be fixed as part of the 1.0 storage rewrite

[david]

(In [2169]) more graceful handling of potential race conditions on cache read, closes #608

[david]

(In [2170]) error suppression, otherwise [2169] would be pretty pointless, refs #608