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From: Alexandr Kuramshin <ein.nsk.ru@gmail.com>
Date: Wed, 15 Feb 2017 13:41:46 +0700
Message-ID: <CAAPGUBVXUCvfuhawPPgPo_OYivqJdmaANYxsbns3RCam-rdkJQ@mail.gmail.com>
Subject: Inaccurate documentation about transactions
To: dev@ignite.apache.org
Cc: Denis Magda <dmagda@apache.org>
Content-Type: multipart/alternative; boundary=001a11c0528483ad0205488bf903
archived-at: Wed, 15 Feb 2017 06:41:55 -0000

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After doing some tests with transactions I've found transactions work not
as expected after reading the documentation [1].

First of all, nowhere's written which methods of the cache are
transactional and which are not. Quite the contrary, after reading
documentation we get know that each TRANSACTIONAL cache is fully
ACID-compliant without exceptions.

Only after deep multi-thread testing, and consulting with other developers,
I get know that only get and put methods are running within transaction,
but iterator and query methods are running outside (in autonomous)
transaction with READ_COMMITTED isolation level.

Later I've understood that only methods throwing
TransactionTimeoutException/TransactionRollbackException/TransactionHeuristicException
are fully transactional. I think all methods on page [2] should be directly
described - are they transactional or not. Btw, why these exceptions are
not derived from the common base class, e.g. TransactionException?

Secondary, using the transactional get() method inside the READ_COMMITTED
transaction we expect to get the committed value, as the documentation [1]
claims:

* READ_COMMITTED - Data is read without a lock and is never cached in the
transaction itself.

Ok, but what about put()? After doing the put() a new value, we get
successive reads of the new value, that is actually DIRTY READ. Hence the
value is cached within transaction. It's not documented behavior.

[1] https://apacheignite.readme.io/docs/transactions

[2]
https://ignite.apache.org/releases/1.8.0/javadoc/org/apache/ignite/IgniteCache.html

-- 
Thanks,
Alexandr Kuramshin

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