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https://issues.apache.org/jira/browse/TEZ-1075?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14003570#comment-14003570
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Hitesh Shah commented on TEZ-1075:
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[~airbots]
bq. 2) In session mode, if there is a zero Vertex DAG in the middle between two
non-zero vertex DAGs;
What would a user do by running a zero vertex DAG? What is the point of running
such a DAG?
A zero-vertex DAG is legitimate - the question I have is in what scenario
should Tez allow someone to submit such a DAG and use up resources in the
cluster to run essentially nothing?
> 0 vertex dags should succeed
> ----------------------------
>
> Key: TEZ-1075
> URL: https://issues.apache.org/jira/browse/TEZ-1075
> Project: Apache Tez
> Issue Type: Bug
> Reporter: Bikas Saha
> Assignee: Chen He
> Labels: newbie++
> Attachments: TEZ-1075-v2.patch, TEZ-1075.patch
>
>
> Currently 0 vertex dags fail because of the following code in DAGImpl
> {code} if (numVertices == 0) {
> addDiagnostic("No vertices for dag");
> trySetTerminationCause(DAGTerminationCause.ZERO_VERTICES);
> if (event != null) {
> return DAGState.FAILED;
> }
> return finished(DAGState.FAILED);
> }
> {code}
> IMO a 0 vertex DAG is a legitimate construct and should just pass. Similar to
> a 0 task vertex. Its essentially a no-op operation.
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