[jira] [Commented] (TEZ-1247) Method verify() of DAG can't been called multiples times in some cases

[Jeff Zhang (JIRA)]

    [ 
https://issues.apache.org/jira/browse/TEZ-1247?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14048673#comment-14048673
 ] 

Jeff Zhang commented on TEZ-1247:
---------------------------------

The verify method of DAG has a piece of code which would change the DAG, and 
this piece of code would cause exception if called multiple times. IMHO, the 
verify method should not have side effect on DAG, otherwise it will confuse 
users. 

Have some thinking on change of DAG
*  use builder pattern to construct the DAG, and in the build method to verify 
the DAG rather than making the verify method public. 
*  move the add* method which as side effect to the DAGBuilder, otherwise even 
after user verify a correct DAG, he could still call the add* method to change 
the DAG. All the side-effect operation and verify logic should be in 
DAGBuilder. 

{code}
  public void verify(boolean restricted) throws IllegalStateException {
    if (vertices.isEmpty()) {
      throw new IllegalStateException("Invalid dag containing 0 vertices");
    }

    processEdgesAndGroups();     // has side-effect on DAG
{code}


> Method verify() of DAG can't been called multiples times in some cases
> ----------------------------------------------------------------------
>
>                 Key: TEZ-1247
>                 URL: https://issues.apache.org/jira/browse/TEZ-1247
>             Project: Apache Tez
>          Issue Type: Bug
>    Affects Versions: 0.4.0
>            Reporter: Jeff Zhang
>            Assignee: Jeff Zhang
>




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