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From Shawn Weeks <>
Subject Re: Revision Source for AtomicDistributedMapCacheClient
Date Wed, 20 Nov 2019 14:23:58 GMT
Thanks I realized this morning that it's up to the AtomicDistributedMapCache implementation
to manage the revision not whatever it's using it. I'm going to just have an integer column
and +1 the revision during a replace if the current revision matches the one already stored
in the entry.


On 11/19/19, 8:13 AM, "Bryan Bende" <> wrote:

    There are two methods in AtomicDistributedMapCache, one is fetch which
    returns an AtomicCacheEntry which has <K,V,R>, the second is replace
    which takes an updated entry and will replace if the revision in the
    updated entry matches the revision stored in the cache (i.e. no one
    else has updated it).
    In WaitNotifyProtocol, getSignal calls fetch and replace signal calls replace.
    For a relational database you will need some kind of revision column
    on the table, and typically you would issue an update statement with a
    where clause that has "REVISION = ?" and if no rows are updated from
    the statement then you know the revision no longer matches.
    Here is an example of how we implemented optimistic locking for
    registry which is similar:
    On Tue, Nov 19, 2019 at 9:01 AM Shawn Weeks <> wrote:
    > Where does the value from revision come from on the call to replace in AtomicDistributedMapCacheClient?
What should it be set to on a call to replace if a revision isn’t provided? I’m looking
at the WaitNotifyProtocol class and it looks like revision isn’t even used. If that’s
the case then the changes I did a while back to add support for AtomicDistributedMapCacheClient
to HBase doesn’t actually work with Wait Notify as the values in the call to replace will
never work. I think that means that Wait Notify isn’t updating the cache in an atomic way
either but I may be missing something.
    > Thanks
    > Shawn

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