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https://issues.apache.org/jira/browse/TEZ-1075?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14005480#comment-14005480
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Bikas Saha commented on TEZ-1075:
---------------------------------
Ideally it shouldn't need to. The DAG is saved upon submission and then upon
completion that fact is saved. If the AM dies in between then I would expect
the original saved DAG to be executed from scratch since it did not make any
further action (identical to an non-empty dag that got saved just before the AM
died). Upon starting from scratch it should again realize that its empty and
succeed immediately.
However, if changes are need in recovery code for this then we should make that
change.
> 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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