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https://issues.apache.org/jira/browse/FOP-2874?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
simon steiner reassigned FOP-2874:
----------------------------------
Assignee: simon steiner
> [PATCH] FOP conserve memory policy fails in multi-threaded environment
> ----------------------------------------------------------------------
>
> Key: FOP-2874
> URL: https://issues.apache.org/jira/browse/FOP-2874
> Project: FOP
> Issue Type: Bug
> Affects Versions: 2.2, 2.3
> Reporter: Piyush Khandelwal
> Assignee: simon steiner
> Priority: Critical
> Attachments: cached-model.patch
>
> Original Estimate: 48h
> Remaining Estimate: 48h
>
> When conserve memory policy is enabled
> Code Snippet 1:
> {code:java}
> foUserAgent.setConserveMemoryPolicy(true);
> {code}
> in multi-threaded environment, it throws following exception
> {code:java}
> SEVERE: Error while serializing page 154. Reason: java.io.IOException:
> \tmp\fop-page-153.ser5056538250865196860.fop.tmp has been already created for
> /fop-page-153.ser
> java.io.IOException: \tmp\fop-page-153.ser5056538250865196860.fop.tmp has
> been already created for /fop-page-153.ser
> at
> org.apache.fop.apps.io.ResourceResolverFactory$DefaultTempResourceResolver.createTempFile(ResourceResolverFactory.java:187)
> at
> org.apache.fop.apps.io.ResourceResolverFactory$DefaultTempResourceResolver.getOutputStream(ResourceResolverFactory.java:199)
> at
> org.apache.fop.apps.io.ResourceResolverFactory$TempAwareResourceResolver.getOutputStream(ResourceResolverFactory.java:159)
> at
> org.apache.fop.apps.io.ResourceResolverFactory$DefaultResourceResolver.getOutputStream(ResourceResolverFactory.java:126)
> at
> org.apache.fop.apps.io.InternalResourceResolver.getOutputStream(InternalResourceResolver.java:103)
> at
> org.apache.fop.area.CachedRenderPagesModel.savePage(CachedRenderPagesModel.java:132)
> at
> org.apache.fop.area.CachedRenderPagesModel.checkPreparedPages(CachedRenderPagesModel.java:112)
> at
> org.apache.fop.area.RenderPagesModel.addPage(RenderPagesModel.java:146)
> at
> org.apache.fop.layoutmgr.AbstractPageSequenceLayoutManager.finishPage(AbstractPageSequenceLayoutManager.java:316)
> at
> org.apache.fop.layoutmgr.PageSequenceLayoutManager.finishPage(PageSequenceLayoutManager.java:243)
> at
> org.apache.fop.layoutmgr.AbstractPageSequenceLayoutManager.makeNewPage(AbstractPageSequenceLayoutManager.java:287)
> at
> org.apache.fop.layoutmgr.PageSequenceLayoutManager.makeNewPage(PageSequenceLayoutManager.java:192)
> at
> org.apache.fop.layoutmgr.PageBreaker.handleBreakTrait(PageBreaker.java:633)
> at org.apache.fop.layoutmgr.PageBreaker.startPart(PageBreaker.java:511)
> at
> org.apache.fop.layoutmgr.AbstractBreaker.addAreas(AbstractBreaker.java:659)
> at
> org.apache.fop.layoutmgr.AbstractBreaker.addAreas(AbstractBreaker.java:604)
> at
> org.apache.fop.layoutmgr.AbstractBreaker.addAreas(AbstractBreaker.java:599)
> at org.apache.fop.layoutmgr.PageBreaker.doPhase3(PageBreaker.java:338)
> at
> org.apache.fop.layoutmgr.AbstractBreaker.doLayout(AbstractBreaker.java:458)
> at org.apache.fop.layoutmgr.PageBreaker.doLayout(PageBreaker.java:112)
> at
> org.apache.fop.layoutmgr.PageSequenceLayoutManager.activateLayout(PageSequenceLayoutManager.java:143)
> at
> org.apache.fop.area.AreaTreeHandler.endPageSequence(AreaTreeHandler.java:267)
> at
> org.apache.fop.fo.pagination.PageSequence.endOfNode(PageSequence.java:130)
> at
> org.apache.fop.fo.FOTreeBuilder$MainFOHandler.endElement(FOTreeBuilder.java:360)
> at org.apache.fop.fo.FOTreeBuilder.endElement(FOTreeBuilder.java:190)
> at
> org.apache.xalan.transformer.TransformerIdentityImpl.endElement(TransformerIdentityImpl.java:1102)
> at
> com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(AbstractSAXParser.java:609)
> at
> com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanEndElement(XMLDocumentFragmentScannerImpl.java:1782)
> at
> com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2967)
> at
> com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:602)
> at
> com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:112)
> at
> com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:505)
> at
> com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:841)
> at
> com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:770)
> at
> com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
> at
> com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1213)
> at
> org.apache.xalan.transformer.TransformerIdentityImpl.transform(TransformerIdentityImpl.java:485)
> at
> java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
> at java.util.concurrent.FutureTask.run(FutureTask.java:266)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
> at java.lang.Thread.run(Thread.java:748)
> {code}
> *Cause:*
> CachedRenderPagesModel.java creates URIs using following code:
> Code Snippet 2:
> {code:java}
> String fname = "fop-page-" + page.getPageIndex() + ".ser";
> URI tempURI = tempBaseURI.resolve(fname);
> {code}
> CachedRenderPagesModel.java uses createTempFile method inside
> ResourceResolverFactory.java to create serialized PageViewport objects in the
> tmp directory.
> Code Snippet 3:
> {code:java}
> private File createTempFile(String path) throws IOException {
> File tempFile = File.createTempFile(path, ".fop.tmp");
> File oldFile = (File)this.tempFiles.put(path, tempFile);
> if (oldFile != null) {
> String errorMsg = oldFile.getAbsolutePath() + " has been
> already created for " + path;
> boolean newTempDeleted = tempFile.delete();
> if (!newTempDeleted) {
> errorMsg = errorMsg + ". " + tempFile.getAbsolutePath() +
> " was not deleted.";
> }
> throw new IOException(errorMsg);
> } else {
> return tempFile;
> }
> }
> {code}
> Here the code is using a concurrent HashMap to map the URI path created in
> Code Snippet 2 with the temp file created and if it get replaced while
> storing, it throws an exception.
> In multi threaded environment, different threads can create same path in code
> snippet 2 and will always replace the entry created in map in code snippet 3,
> and will throw the exception.
> *Solution:*
> There are multiple ways we can make the URI (being used as key in the map)
> unique.
> # We can use SecureRandom to generate a radom number and append it to the
> URI.
> # Append thread name to the URI
> # Use combination of above two solutions i.e., append both in the URI
>
> This will make sure that we get an unique path as key for the map across
> multiple threads and avoid this exception.
> The patch uses a SecureRandom to make this path unique across different
> threads in code snippet 2.
> {code:java}
> String fname = "fop-page-" + page.getPageIndex() + "-" + sr.nextLong() +
> ".ser";
> URI tempURI = tempBaseURI.resolve(fname);
> {code}
> Here sr is secure random object.
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