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https://issues.apache.org/jira/browse/BEAM-88?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15298882#comment-15298882
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Ilya Ganelin commented on BEAM-88:
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I've spent some more time digging into this issue and it may actually be rather
tricky to fix. Because the method definitions are created in an interface, we
cannot define default values or behaviors for the methods. Even Java 8 default
methods won't solve this problem because tempLocation is defined in the base
PipelineOptions Interface and stagingLocation is defined within
DataflowPipelineOptions, thus while we could default from stagingLocation to
tempLocation, the reverse would not work.
Further, because these interfaces are never implemented explicitly but are
instead executed via a complex reflection mechanism based on defined
configuration properties, we don't even have the option of defining the correct
default behavior in classes that implement this interface.
The only way I could think of to get the right behavior is to create a specific
class that implements the DataflowPipelineOptions and have all classes that use
DataflowPipelineOptions use that class instead. However, because of the use of
multiple inheritance (via Interfaces) used throughout the project, that seems
like a non-starter.
I would love any insight as to how we could resolve this from those more
familiar with the project or perhaps from someone who has a deeper
understanding of the more advanced Java mechanisms.
> DataflowPipelineOptions.tempLocation doesn't really default to stagingLocation
> ------------------------------------------------------------------------------
>
> Key: BEAM-88
> URL: https://issues.apache.org/jira/browse/BEAM-88
> Project: Beam
> Issue Type: Bug
> Components: runner-dataflow
> Reporter: Eugene Kirpichov
> Priority: Trivial
>
> The documentation of DataflowPipelineOptions.tempLocation says: ..."defaults
> to using stagingLocation."...
> However calling .getTempLocation() when only --stagingLocation is specified
> on the command line gives null.
> The "defaulting" is really done in DataflowPipelineRunner.fromOptions():
> {code}
> if (Strings.isNullOrEmpty(dataflowOptions.getTempLocation())) {
> dataflowOptions.setTempLocation(dataflowOptions.getStagingLocation());
> {code}
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