No, that seems like a fail-- at least, the part where it fails to let you
decide (based on the status of the job) whether/how to execute the
PipelineCallable. This seems tied to the idea that the Pipeline interface
should give you insight into the PipelineResult object for any
job/target/etc through its API-- does that make sense?
J
On Tue, Jan 26, 2016 at 8:50 AM, Igor Bernstein <igorbernstein@spotify.com>
wrote:
> Hi all,
>
> I was hoping someone can clarify how to handle errors in SequentialDos. I
> was really surprised to learn that SequentialDos get called for failed
> Jobs. See example below.
>
> From what I can tell, this happens because
> CrunchJobControl#executeReadySeqDoFns runs all PipelineCallables whose
> Targets are not "unfinished". CrunchJobControl#getUnfinishedTargets defines
> unfinished Targets as Targets that are not produced by waiting, running or
> ready Jobs. In other words: Targets that belong to failed Jobs are
> considered finished. Is this intentional?
>
> I can see this being useful in some scenarios, where my PipelineCallable
> can recover from a Job, but I don't see a clear way for my PipelineCallable
> to detect upstream failure.
>
> Anyone know if this is a bug and failed targets should be considered as
> unfinished or is this feature and I'm missing a way for me to check for
> upstream failure?
>
> Thanks in advance!
>
>
> Example Code
> class Main extends Configured implements Tool {
> @Override
> public int run(String[] args) throws Exception {
> MRPipeline pipeline = new MRPipeline(Main.class);
> PCollection<String> lines =
> pipeline.read(From.textFile("strings.txt"));
>
> lines
> .parallelDo(new BrokenMapper(), Writables.strings())
> .sequentialDo("input", new AfterBroken());
>
> return 0;
> }
>
> static class BrokenMapper extends MapFn<String, String> {
> @Override
> public String map(String input) {
> throw new RuntimeException("I'm broken");
> }
> }
>
> static class AfterBroken extends PipelineCallable<Void> {
> @Override
> protected Void getOutput(Pipeline pipeline) {
> return null;
> }
>
> @Override
> public Status call() throws Exception {
> System.out.println("I should not be called because I don't have a
> materialized collection");
>
> PCollection<String> lines = (PCollection<String>)
> getOnlyPCollection();
> // Surprise! collection hasn't been materialized
> Iterable<String> materialize = lines.materialize();
>
> return Status.SUCCESS;
> }
> }
>
> public static void main(String[] args) throws Exception {
> int rc = ToolRunner.run(new Main(), args);
> System.exit(rc);
> }
> }
>
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