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https://issues.apache.org/jira/browse/IGNITE-2426?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Denis Magda closed IGNITE-2426.
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> Document optimisitic (deadlock-free) transactions on readme.io
> --------------------------------------------------------------
>
> Key: IGNITE-2426
> URL: https://issues.apache.org/jira/browse/IGNITE-2426
> Project: Ignite
> Issue Type: Bug
> Affects Versions: 1.5.0.final
> Reporter: Denis Magda
> Priority: Critical
> Labels: important
> Fix For: 1.6
>
> Attachments: TransactionTest.java
>
>
> There is a lack of documentation on how optimistic & serializable
> transactions work.
> Basic documentation has to be added covering some specific cases in addition.
> As an example, the test attached demonstrates the following.
> Both tasks update cache with put operations only without reading and keeping
> entries's versions cause there is no any cache.get/getAll calls as a part of
> the transaction.
> Each transaction has it's unique ID. So at the commit time when one
> transaction B tries to update an entry locking it before and sees that the
> entry is locked by some transaction A, started earlier (have smaller
> transaction ID), then transaction B will just wait until the lock is released
> and can proceed with the commit later. If this repeats for every entry of
> transactions and we haven't detected any conflict then both transactions
> succeeds. This is exactly what happens sometimes in your test.
> However, if the transactions were using cache.get or related operations then
> during the commit time both transactions would be checking entry versions in
> addition before proceeding with the commit. In general if an entry version at
> commit time is different to the entry version at get time then a transaction
> fails. To see this in practice use cache.getAndPut() instead of cache.put()
> in the code. After applying this modification one of the transactions will
> always fail.
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