[jira] [Updated] (CRUNCH-218) Add new Target.WriteMode to skip the write and continue pipeline if an output target exists

["Josh Wills (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CRUNCH-218?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Josh Wills updated CRUNCH-218:
------------------------------

    Attachment: CRUNCH-218.patch

What an elegant way to solve the checkpointing problem. Here's a patch for it.
                
> Add new Target.WriteMode to skip the write and continue pipeline if an output target exists
> -------------------------------------------------------------------------------------------
>
>                 Key: CRUNCH-218
>                 URL: https://issues.apache.org/jira/browse/CRUNCH-218
>             Project: Crunch
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 0.6.0
>            Reporter: Dave Beech
>            Assignee: Josh Wills
>            Priority: Minor
>         Attachments: CRUNCH-218.patch
>
>
> Quite often I write pipelines which persist data to the filesystem midway through the process, and then carry on doing further work. 
> If this intermediate data is already present, I think it would be good if I could set a write mode which skips over this first half of processing. This way I'd avoid running jobs unnecessarily and wasting cluster resources regenerating data I already have. 
> Example:
> PCollection<B> inter = pipeline.read(source).parallelDo(something).parallelDo(somethingElse);
> inter.write(At.sequenceFile('output'), WriteMode.SKIP_IF_EXISTS);
> PCollection<C> final = inter.parallelDo(moreWork);
>  

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