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https://issues.apache.org/jira/browse/FOP-2211?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13583091#comment-13583091
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Chris Bowditch commented on FOP-2211:
-------------------------------------

Hi Alexios.

A Virtual File System is a really useful tool in a cloud environment as 
different components running on different physical machines can talk to each 
other and read/write data to shared resources, without having to rely on shared 
drives.

It may be unlikely that a temp file written by tenant A can be read by tenant 
B, but compliance dictates that we should put safeguards in place to esnure 0% 
risk of such an occurance, We have the virtual file system which is partitioned 
by tenant so why not use that? Just need an interface in FOP to allow temp 
files to be handled in a way other than temp files. Of course that interface 
should not prevent temporary data still being handled in temp files, so we will 
look to make the necessary revisions to ensure both use cases are possible.

Thanks,

Chris
                
> [PATCH] Fix & improve the handling of temporary files using the new URI 
> resource resolvers
> ------------------------------------------------------------------------------------------
>
>                 Key: FOP-2211
>                 URL: https://issues.apache.org/jira/browse/FOP-2211
>             Project: Fop
>          Issue Type: Bug
>          Components: general
>    Affects Versions: trunk
>            Reporter: Alexios Giotis
>             Fix For: trunk
>
>         Attachments: fop.patch, xgc.patch
>
>
> As written in http://markmail.org/message/zelumstxxsdyvkcz , after the merge 
> of the Temp_URI_Resolution branch (Sept 2012), the actual pattern of using 
> temp files has changed from:
> {code}
> File tmpFile = File.createTempFile(....);
> // Write and read from the file
> tmpFile.delete();
> {code}
> to:
> {code}
> File tmpFile = new File(System.getProperty("java.io.tmpdir"), 
> counterStartingFrom1AsString);
> tmpFile.deleteOnExit();
> // Write and read from the file
> {code}
> This is fine when FOP is executed from the command line (which I guess this 
> is how most people use it) but it introduces a number of bad side effects for 
> long running processes that use FOP embedded.
>  
> 1. Different FOP processes can't be executed in parallel on the same system 
> because creating the same temp file fails.
> 2. If the JVM is not normally terminated, the temp files are never deleted 
> and the next invocation of the JVM fails to run.
> 3. deleteOnExit() keeps for the life of the JVM an unknown number of temp 
> files both on disk and a reference in memory.
> There should not be a need to implement a custom resource resolver when using 
> FOP embedded in order to fix those issues. The default implementation should 
> work at least as good as it worked in FOP 1.1 or earlier. 
> Attached are 2 patches, one for XGC and one for FOP that should fix and 
> improve the handling of at least the temporary files.
> For reference, [1] lists some reasons for implementing the new URI resource 
> resolvers.
> [1] http://wiki.apache.org/xmlgraphics-fop/URIResolution

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