I fixed the entity cache issues in revision 1476296. The fix does not
include the distributed cache system, but that should be easy to fix by
duplicating the fixes to the local cache.
I found some flaws in the entity engine that I will discuss in another
thread.
-Adrian
On 4/22/2013 9:45 AM, Adrian Crum wrote:
Thanks Jacopo. I haven't looked into the entity cache implementation
thoroughly, but I was under the impression that it can be configured
to be distributed.
I have the fix working on my local copy. As you can see, I have made
some related changes already and will be making some more, but I won't
commit the fix until next weekend - to give everyone a chance to respond.
-Adrian
On 4/22/2013 9:33 AM, Jacopo Cappellato wrote:
It seems actually to be an issue rather than a feature (I can't think
of a use case where this behavior would be useful); I have created a
few test cases (similar to the one you have provided in the other
thread) that further analyze your discovery but they don't add much
to what you found (apart from confirming the risk of getting stale
data).
However, when we start design/implement a refactoring of this part of
the system, I would suggest that we also consider how to deal with
similar scenarios in a clustered deployment (in fact many of the
production deployment are based on clusters); the simplest use case
could be: in a cluster, we have two OFBiz instances connected to the
same database; in one instance the list is cached, in the other
instance one of the generic values (that are part of the selection)
is updated. A distributed cache system may help here.
Jacopo
On Apr 21, 2013, at 10:54 AM, Adrian Crum
<adrian.c...@sandglass-software.com> wrote:
Last week I discovered a flaw in the EntityListCache implementation:
http://mail-archives.apache.org/mod_mbox/incubator-ofbiz-dev/201304.mbox/%3c516ac7b4.2020...@sandglass-software.com%3E
To summarize: Entity conditions that are cached become stale when
any member of the cached list is changed - making the cache contents
invalid. In addition, GenericValues in the cached list are mutable -
which is inconsistent with the primary key cache, where
GenericValues from the cache are immutable.
I would like to fix this, but I think we should discuss it first.
One change would be to make the list member GenericValues immutable.
This will make the GenericValues retrieved from the entity list
cache consistent with the GenericValues retrieved from the primary
key cache, but it won't prevent an invalid cache (because the list
member GenericValue can be cloned and modified). Also, this change
will likely break a lot of code, because it is common to retrieve a
list of GenericValues from the cache and then make changes to the
list members. We could create a "transitional" GenericValue that
would warn developers when they modify a cached list member, and
then switch to an immutable GenericValue some time in the future.
To fix the stale cache problem, the cache instance can be made a
GenericValue listener in all of its list members - so any time a
list member is modified the cache will be cleared. This will keep
the cache valid, but there might be a performance hit. I'm open to
other solutions to this problem.
Any thoughts?
-Adrian
