[jira] [Closed] (BEAM-381) OffsetBasedReader should construct sources before updating the range tracker

["Daniel Halperin (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/BEAM-381?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Daniel Halperin closed BEAM-381.
--------------------------------

> OffsetBasedReader should construct sources before updating the range tracker
> ----------------------------------------------------------------------------
>
>                 Key: BEAM-381
>                 URL: https://issues.apache.org/jira/browse/BEAM-381
>             Project: Beam
>          Issue Type: Bug
>          Components: sdk-java-core
>    Affects Versions: 0.1.0-incubating, 0.2.0-incubating
>            Reporter: Daniel Halperin
>            Assignee: Daniel Halperin
>             Fix For: 0.2.0-incubating
>
>
> OffsetBasedReader has the following code:
> {code}
>       if (!rangeTracker.trySplitAtPosition(splitOffset)) {
>         return null;
>       }
>       long start = source.getStartOffset();
>       long end = source.getEndOffset();
>       OffsetBasedSource<T> primary = source.createSourceForSubrange(start, splitOffset);
>       OffsetBasedSource<T> residual = source.createSourceForSubrange(splitOffset, end);
>       this.source = primary;
>       return residual;
> {code}
> The first line is the line that updates the range of this source. However, subsequent lines might throw (specifically, in source.createSourceForSubrange). We should construct the sources first, and then catch exceptions and return null if they fail. This way, the splitAtFraction call will not throw (so work is not wasted) and the range tracker will not be updated if either the primary or (more likely) the residual could not be created.



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