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From "Alessandro Presta (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (GIRAPH-556) Race condition in EdgeStore
Date Fri, 08 Mar 2013 07:12:13 GMT

     [ https://issues.apache.org/jira/browse/GIRAPH-556?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Alessandro Presta updated GIRAPH-556:
-------------------------------------

    Attachment: GIRAPH-556.patch

Fixes the bug by always initializing a newly-created VertexEdges before inserting it.

At the same time, I also remove some leftover checks for null pointer in VertexEdges#initialize()
implementations: we never (and should never) call initialize with a null Iterable (what I
originally thought was the cause of this bug).
                
> Race condition in EdgeStore
> ---------------------------
>
>                 Key: GIRAPH-556
>                 URL: https://issues.apache.org/jira/browse/GIRAPH-556
>             Project: Giraph
>          Issue Type: Bug
>            Reporter: Alessandro Presta
>            Priority: Critical
>         Attachments: GIRAPH-556.patch
>
>
> In EdgeStore#addPartitionEdges(), when there is no VertexEdges data structure for a vertex,
we try to insert a newly-created one. If the insertion is successful, we initialize it and
later insert an edge in the synchronized block.
> It can happen that, between creation and initialization, another thread acquires the
lock and tries to add an edge, leading to a NullPointerException for many implementations
of VertexEdges.
> The fix is to create and initialize the structure before we try to insert it.

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