https://bz.apache.org/bugzilla/show_bug.cgi?id=63240
Bug ID: 63240
Summary: Use of synchronized in
DocumentHelper.newDocumentBuilder
Product: POI
Version: unspecified
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P2
Component: POI Overall
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
We are procesing XLSF files in parallel and faced a performance bottleneck.
Investigating the issue, it turns out that all threads wait on the synchronized
DocumentHelper.newDocumentBuilder().
It was introduced in this commit:
https://github.com/apache/poi/commit/eabb6a924be24abb879372d0bc967e0d316b2cf8?diff=split
Related Bug:
https://bz.apache.org/bugzilla/show_bug.cgi?id=56814#c10
It seems that the synchronized was added because it does not have any impact on
single-threaded applications, as it will get optimized away. When working
multi-threaded, all threads are waiting for the mehtod to finish.
This is the related code section:
https://github.com/apache/poi/blame/trunk/src/ooxml/java/org/apache/poi/ooxml/util/DocumentHelper.java#L89-L98
The newDocumentBuilder does not seem to mutate any global state as it only
creates a local variable which is returned afterwards.
Is there any special reason for this synchronized? Can this be removed? Are
there workarounds we can use with the current version of POI?
This is the thread dump/call stack:
> "thread-2" - Thread t@845
> java.lang.Thread.State: BLOCKED
> at
> org.apache.poi.util.DocumentHelper.newDocumentBuilder(DocumentHelper.java:87)
> - waiting to lock <246a71d6> (a java.lang.Class) owned by "thead-1"
> t@806
> at
> org.apache.poi.util.DocumentHelper.readDocument(DocumentHelper.java:140)
> at
> org.apache.poi.openxml4j.opc.PackageRelationshipCollection.parseRelationshipsPart(PackageRelationshipCollection.java:308)
> at
> org.apache.poi.openxml4j.opc.PackageRelationshipCollection.<init>(PackageRelationshipCollection.java:167)
> at
> org.apache.poi.openxml4j.opc.PackageRelationshipCollection.<init>(PackageRelationshipCollection.java:135)
> at
> org.apache.poi.openxml4j.opc.PackagePart.loadRelationships(PackagePart.java:565)
> at org.apache.poi.openxml4j.opc.PackagePart.<init>(PackagePart.java:111)
> at org.apache.poi.openxml4j.opc.PackagePart.<init>(PackagePart.java:82)
> at org.apache.poi.openxml4j.opc.PackagePart.<init>(PackagePart.java:127)
> at
> org.apache.poi.openxml4j.opc.ZipPackagePart.<init>(ZipPackagePart.java:79)
> at
> org.apache.poi.openxml4j.opc.ZipPackage.getPartsImpl(ZipPackage.java:335)
> at org.apache.poi.openxml4j.opc.OPCPackage.getParts(OPCPackage.java:756)
> at org.apache.poi.openxml4j.opc.OPCPackage.open(OPCPackage.java:327)
> at
> org.apache.poi.ss.usermodel.WorkbookFactory.create(WorkbookFactory.java:184)
> at
> org.apache.poi.ss.usermodel.WorkbookFactory.create(WorkbookFactory.java:149)
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