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From "Stefan Bodewig (JIRA)" <>
Subject [jira] [Commented] (COMPRESS-446) Resource Leak in ParallelScatterZipCreator#writeTo(ZipArchiveOutputStream)
Date Sat, 10 Nov 2018 05:20:00 GMT


Stefan Bodewig commented on COMPRESS-446:

The one you are currently using implicitly is

By using the two-arg constructor of {{ParallelScatterZipCreator}} you can plug in your own
{{ScatterGatherBackingStoreSupplier}} which has a single method that is responsible for creating
a new {{ScatterGatherBackingStore}}. This is assuming you are creating {{ParallelScatterZipCreator}}
yourself and not using a third-party library that abstracts that away from you.

> Resource Leak in ParallelScatterZipCreator#writeTo(ZipArchiveOutputStream)
> --------------------------------------------------------------------------
>                 Key: COMPRESS-446
>                 URL:
>             Project: Commons Compress
>          Issue Type: Bug
>          Components: Archivers
>    Affects Versions: 1.16.1
>         Environment: The application was running inside a Docker container, the JVM had
about 1.7 GByte heap space.
>            Reporter: Christoph Ludwig
>            Priority: Major
>              Labels: zip
>             Fix For: 1.17
> Before it does anything else, {{ParallelScatterZipCreator#writeTo(ZipArchiveOutputStream)}}
loops over all futures returned by the creator`s executor service and calls {{Future#get()}}.
This will block until the future's computation is completed, respectively - i.e., until all
entries have been written to the thread-local scatter streams.
> However, if the computation of a future fails, then {{Future#get()}} can also throw an
exception. This exception escapes {{ParallelScatterZipCreator#writeTo(ZipArchiveOutputStream)}}
before the executor service is shut down. The latter means that also the thread-local variables
in the executor service's threads and all objects referenced by them continue to exist and
cannot be reclaimed by the GC.
> I encountered this situation when - while processing an archive with 130,000 documents
- the JVM threw an {{OutOfMemoryError}}. The application was not able to recover from this
OOM error because most of the heap was occupied by objects reachable from the executor service's
> Of course, the OOM is mostly the fault of my own code; I will be able to work around
the "leaked" executor service because I supply it in the first place and can therefore shut
it down if I detect an error situation.  
> The effect would be the same, though, if, say, {{Future#get()}} throws an {{InterruptedException}}.
Therefore, {{ParallelScatterZipCreator#writeTo(ZipArchiveOutputStream)}}  should either shut
down and release all resources if it cannot complete its task due to an Exception thrown by
a future or it should offer a reasonable recovery strategy. 

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