Marcel Reutegger created OAK-1088:
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Summary: Thread safe MongoDocumentStore
Key: OAK-1088
URL: https://issues.apache.org/jira/browse/OAK-1088
Project: Jackrabbit Oak
Issue Type: Sub-task
Components: core, mongomk
Affects Versions: 0.10
Reporter: Marcel Reutegger
Assignee: Marcel Reutegger
In addition to relaxing synchronization in MongoMK we also need to look at
thread safety in {{MongoDocumentStore}}. AFAICS MemoryDocumentStore is
thread-safe and access to the store is consistent. This is currently not the
case for {{MongoDocumentStore}}. The main problem is maintaining the document
cache in {{MongoDocumentStore}}. Access to the cache is not coordinated between
multiple threads. I avoided the term synchronized, because the actual cache
implementation is thread-safe. What needs to be fixed is how
{{MongoDocumentStore}} interacts with the cache. E.g. {{findAndModify()}} sends
the update to MongoDB, gets the old document back, applies the updates to the
old document and then puts it into the cache. If this happens concurrently with
multiple threads it may happen that these operations overlap and a thread puts
an outdated document into the cache.
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