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From "Dick Cavender (Jira)" <j...@apache.org>
Subject [jira] [Closed] (GEODE-6152) Client PROXY Regions may return the same Object instance on get(key) and cause Thread-safety issues
Date Thu, 26 Sep 2019 18:05:10 GMT

     [ https://issues.apache.org/jira/browse/GEODE-6152?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Dick Cavender closed GEODE-6152.
--------------------------------

> Client PROXY Regions may return the same Object instance on get(key) and cause Thread-safety
issues
> ---------------------------------------------------------------------------------------------------
>
>                 Key: GEODE-6152
>                 URL: https://issues.apache.org/jira/browse/GEODE-6152
>             Project: Geode
>          Issue Type: Bug
>          Components: client/server, regions
>    Affects Versions: 1.1.0, 1.1.1, 1.3.0, 1.2.1, 1.4.0, 1.5.0, 1.6.0, 1.7.0
>            Reporter: John Blum
>            Assignee: Anilkumar Gingade
>            Priority: Critical
>              Labels: SmallFeature
>             Fix For: 1.10.0
>
>          Time Spent: 2h 40m
>  Remaining Estimate: 0h
>
> According to Apache Geode's documentation (e.g. [Javadoc|http://geode.apache.org/releases/latest/javadoc/org/apache/geode/cache/client/ClientRegionShortcut.html#PROXY]),
client PROXY Regions are expected to return a new Object for each value on each {{Region.get(key)}}
invocation.
> The documentation states:
> {quote}
> A PROXY region has no local state and forwards all operations to a server.
> {quote}
> Given the client cache (i.e. Region) contains "no local state" and "all operations are
forwarded to a server", then this implies that the object, the Region's value mapped to the
key, is serialized when sent to a server and deserialized when received from a server.  The
act of de/serialization constitutes a new object every, single, time.
> However, in a highly concurrent application (e.g. a Web application), with multiple Threads
in the application potentially making concurrent data requests for the same "logical" domain
object stored in Apache Geode, it is possible for the same object reference to be returned,
even for a client {{PROXY}} Region.
> This is to be expected when using a {{CACHING_PROXY}}, since the client then has "local
state", but for a client {{PROXY}} Region, there is, or should be no "local state".
> It turns out that internally, Geode applies an optimization wherein, if 2 or more Threads
are concurrently making a data request for the same "logical" object, then only 1 Thread is
allowed to proceed with the request while the other Threads will wait for the response that
the permitted, requesting Thread received, thereby sharing the same object reference.
> This poses grave danger (race conditions due to lost updates, or incorrect decisions
made due to stale state) if the non-unique object type is not Thread-safe.  Under other conditions/configurations
(e.g. when sending {{Deltas}}), it is even possible to "lose data" due to competing and conflicting
data access operations, which results in a "_last-one-wins_" scenario.



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