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https://issues.apache.org/jira/browse/ZOOKEEPER-1246?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13142067#comment-13142067
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Hudson commented on ZOOKEEPER-1246:
-----------------------------------

Integrated in ZooKeeper-trunk #1352 (See 
[https://builds.apache.org/job/ZooKeeper-trunk/1352/])
    ZOOKEEPER-1246. Dead code in PrepRequestProcessor catch Exception block 
(camille)

camille : 
http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1196025
Files : 
* /zookeeper/trunk/CHANGES.txt
* 
/zookeeper/trunk/src/java/main/org/apache/zookeeper/server/PrepRequestProcessor.java
* 
/zookeeper/trunk/src/java/test/org/apache/zookeeper/server/PrepRequestProcessorTest.java

                
> Dead code in PrepRequestProcessor catch Exception block
> -------------------------------------------------------
>
>                 Key: ZOOKEEPER-1246
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1246
>             Project: ZooKeeper
>          Issue Type: Sub-task
>            Reporter: Thomas Koch
>            Assignee: Camille Fournier
>            Priority: Blocker
>             Fix For: 3.4.0, 3.5.0
>
>         Attachments: ZOOKEEPER-1246.patch, ZOOKEEPER-1246.patch, 
> ZOOKEEPER-1246_trunk.patch, ZOOKEEPER-1246_trunk.patch
>
>
> This is a regression introduced by ZOOKEEPER-965 (multi transactions). The 
> catch(Exception e) block in PrepRequestProcessor.pRequest contains an if 
> block with condition request.getHdr() != null. This condition will always 
> evaluate to false since the changes in ZOOKEEPER-965.
> This is caused by a change in sequence: Before ZK-965, the txnHeader was set 
> _before_ the deserialization of the request. Afterwards the deserialization 
> happens before request.setHdr is set. So the following RequestProcessors 
> won't see the request as a failed one but as a Read request, since it doesn't 
> have a hdr set.
> Notes:
> - it is very bad practice to catch Exception. The block should rather catch 
> IOException
> - The check whether the TxnHeader is set in the request is used at several 
> places to see whether the request is a read or write request. It isn't 
> obvious for a newby, what it means whether a request has a hdr set or not.
> - at the beginning of pRequest the hdr and txn of request are set to null. 
> However there is no chance that these fields could ever not be null at this 
> point. The code however suggests that this could be the case. There should 
> rather be an assertion that confirms that these fields are indeed null. The 
> practice of doing things "just in case", even if there is no chance that this 
> case could happen, is a very stinky code smell and means that the code isn't 
> understandable or trustworthy.
> - The multi transaction switch case block in pRequest is very hard to read, 
> because it missuses the request.{hdr|txn} fields as local variables.

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