[PDFBOX-845] Lockup in PDDocument.load() --> PDFParser.parseObject() with 6 threads

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Cannot Reproduce
• Affects Version/s: 1.2.1
• Component/s: Parsing

Environment

Linux lxdev01 2.6.32-24-generic #42-Ubuntu SMP Fri Aug 20 14:24:04 UTC 2010 i686 GNU/Linux

java version "1.6.0_20"
Java(TM) SE Runtime Environment (build 1.6.0_20-b02)
Java HotSpot(TM) Server VM (build 16.3-b01, mixed mode)

testng 5.11
running under maven-surefire plugin v2.5 with parallel=methods and threadCount=6

• Assignee: Unassigned
• Reporter: Larry West
• Created: 29/Sep/10 19:49
• Updated: 04/Aug/14 18:29
• Resolved: 04/Aug/14 18:29

Description

This is a TestNG unit test suite, with each test loading a different PDF via PDDocument.load(). I just switched TestNG to parallel=methods (had been serial) and it locked up first time. "jstack -l" output will be attached, but I'm putting the pdfbox portions here (just below).

In looking at the code, it's not clear what's being waited on, except that four of the threads are stuck in BaseParser.parseDirObject(), apparently waiting on the (synchronized) toString() method of a [local] StringBuffer. (StringBuffer is used in BaseParser.java where a StringBuilder is clearly preferable – this is probably true for every local instance of a StringBuffer.)

I don't know why that would cause the thread to sit waiting, though (JVM problem? 1.6.0_20 on Linux), and the other two threads appear to be waiting on COSObjectKey.getNumber() [perhaps], and I see no synchronized objects or methods there.

Finding the cause of the lockup would be preferable, but replacing StringBuffer with StringBuilder whereever they are used locally (possibly including any private non-static members) would be an improvement in performance if nothing else.

Threads 1, 2, 4, & 6:
at org.apache.pdfbox.pdfparser.BaseParser.parseDirObject(BaseParser.java:1013)
at org.apache.pdfbox.pdfparser.BaseParser.parseCOSDictionaryValue(BaseParser.java:157)
at org.apache.pdfbox.pdfparser.BaseParser.parseCOSDictionary(BaseParser.java:233)
at org.apache.pdfbox.pdfparser.BaseParser.parseDirObject(BaseParser.java:929)
at org.apache.pdfbox.pdfparser.PDFParser.parseObject(PDFParser.java:519)
at org.apache.pdfbox.pdfparser.PDFParser.parse(PDFParser.java:179)

Threads 3 & 5:
at org.apache.pdfbox.cos.COSDocument.getObjectFromPool(COSDocument.java:481)
at org.apache.pdfbox.pdfparser.PDFParser.parseObject(PDFParser.java:540)
at org.apache.pdfbox.pdfparser.PDFParser.parse(PDFParser.java:179)

I should add: these same tests, using the same files, have run literally hundreds of times on various machines (Windows, Mac, Linux) using PDFBox 1.2.1 without any lockup.

Clearly I can back off parallelizing my tests for now, but there is no obvious reason why PDDocument.load() can't be called in parallel, and so it concerns me that this will be a real problem.

Issue Links

• relates to: PDFBOX-353 org.pdfbox.pdfparser.BaseParser.parseDirObject