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https://issues.apache.org/jira/browse/BEAM-702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15546300#comment-15546300
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Eugene Kirpichov commented on BEAM-702:
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Hmm, I didn't realize that we don't call finishBundle and teardown in case the
bundle fails. But yes, this makes a lot of sense.
I'm not sure whether I personally would prefer annotation-based closeables or
explicit calls (e.g. c.addCloseable(createDBWriter)). Explicit calls would make
it easier to open a dynamic set of resources (e.g. lazily open connections to
different shards of a database depending on the data). However that could be
encapsulated into a single Closeable object, making these styles equivalent.
> Simple pattern for per-bundle and per-DoFn Closeable resources
> --------------------------------------------------------------
>
> Key: BEAM-702
> URL: https://issues.apache.org/jira/browse/BEAM-702
> Project: Beam
> Issue Type: Improvement
> Reporter: Eugene Kirpichov
>
> Dealing with Closeable resources inside a processElement call is easy: simply
> use try-with-resources.
> However, bundle- or DoFn-scoped resources, such as long-lived database
> connections, are less convenient to deal with: you have to open them in
> startBundle and conditionally close in finishBundle (likewise
> setup/teardown), taking special care if there's multiple resources to close
> all of them.
> Perhaps we should provide something like Guava's Closer to DoFn's
> https://github.com/google/guava/wiki/ClosingResourcesExplained. Ideally, the
> user would need to only write a startBundle() or setup() method, but not
> write finishBundle() or teardown() - resources would be closed automatically.
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