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From "Siddharth Wagle (JIRA)" <j...@apache.org>
Subject [jira] [Created] (AMBARI-2142) Unecessary use of @Transactional on all DAO methods
Date Thu, 16 May 2013 17:09:16 GMT
Siddharth Wagle created AMBARI-2142:
---------------------------------------

             Summary: Unecessary use of @Transactional on all DAO methods
                 Key: AMBARI-2142
                 URL: https://issues.apache.org/jira/browse/AMBARI-2142
             Project: Ambari
          Issue Type: Bug
          Components: controller
    Affects Versions: 1.3.0
            Reporter: Siddharth Wagle
            Assignee: Siddharth Wagle
             Fix For: 1.3.0
         Attachments: AMBARI-2142.patch

Most of the DAO objects in Ambari are annotated with @Transactional.  (see org.apache.ambari.server.orm.dao.HostRoleCommandDAO).

{quote}
 Any method or class marked with this annotation will be considered for transactionality.
Consult the documentation on http://code.google.com/p/google-guice for detailed semantics.
Marking a method @Transactional will start a new transaction before the method executes and
commit it after the method returns.

If the method throws an exception, the transaction will be rolled back unless you have specifically
requested not to in the #ignore() clause.

Similarly, the set of exceptions that will trigger a rollback can be defined in the #rollbackOn()
clause. By default, only unchecked exceptions trigger a rollback.
{quote}

I think that marking simple getter methods as transactional may be introducing unnecessary
overhead.  I don't think that a non-mutating method that does not require read consistency
needs to be marked transactional.

Profiling a service start on a 200 node cluster shows that about 1/3 of the time is spent
in almost 3000 JDBC commit() and over 1400 setAutoCommit() calls. 


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