[jira] [Created] (TINKERPOP-2554) Extracting step metrics from ProfileStep throws NPE if the step was not triggered

["Saikiran Boga (Jira)" <ji...@apache.org>]

Saikiran Boga created TINKERPOP-2554:
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             Summary: Extracting step metrics from ProfileStep throws NPE if the step was not triggered
                 Key: TINKERPOP-2554
                 URL: https://issues.apache.org/jira/browse/TINKERPOP-2554
             Project: TinkerPop
          Issue Type: Bug
          Components: process
            Reporter: Saikiran Boga


When extracting step metrics from ProfileStep, this code block below[1] assumes that  step metrics is always initialized. But if a step does not invoke starts hasNext() or next() methods for any particular reason, this throws an NPE.

An example case where this could happen is if a step decides not to invoke any upstream step by halting at any other step:
{noformat}
step1 -> ProfileStep -> step2 -> ProfileStep -> step3 -> ProfileStep -> step4 -> ProfileStep{noformat}
In this case if say step3/4 decides not to get starts from previous step, then the step metrics on all the preceding ProfileStep are left uninitialized.

Sample trace:
{noformat}
java.lang.NullPointerException: null
at org.apache.tinkerpop.gremlin.process.traversal.util.DefaultTraversalMetrics.addTopLevelMetrics(DefaultTraversalMetrics.java:157)
at org.apache.tinkerpop.gremlin.process.traversal.util.DefaultTraversalMetrics.setMetrics(DefaultTraversalMetrics.java:143)
at org.apache.tinkerpop.gremlin.process.traversal.step.sideEffect.ProfileSideEffectStep.hasNext(ProfileSideEffectStep.java:75) 
at org.apache.tinkerpop.gremlin.process.traversal.step.util.ExpandableStepIterator.hasNext(ExpandableStepIterator.java:42)
...{noformat}
[1] https://github.com/apache/tinkerpop/blob/master/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/util/DefaultTraversalMetrics.java#L157



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