PPTX File Conversion Service causes Sustained CPU Spike, OOME if the file contain charts

Summary

Uploading some PPTX files to Confluence can cause OutOfMemory error while generating preview.

Steps to Reproduce

1. Upload a Powerpoint file with 300 pages containing graphs/pictures to Confluence (attached, 9.87MB)
2. Open file in preview window several times

Expected Results

Confluence should pre-calculate the resource commitment before previewing the document. Similar to CONFSERVER-45209

Actual Results

Confluence became unresponsive. The below exception is thrown in the catalina.out file:

11-Jan-2018 14:19:12.170 SEVERE [http-nio-8090-ClientPoller-1] org.apache.tomcat.util.net.NioEndpoint$Poller.run
 java.lang.OutOfMemoryError: Java heap spaceException in thread "C3P0PooledConnectionPoolManager[identityToken->1bqxcmo9s1qzxzgfaa24s0|4be2e790]-HelperThread-#1" java.lang.OutOfMemoryError: Java heap space

11-Jan-2018 14:20:25.883 SEVERE [http-nio-8090-ClientPoller-0] org.apache.tomcat.util.net.NioEndpoint$Poller.run
 java.lang.OutOfMemoryError: Java heap space

Heap Dump Analysis

Workaround

Upgrade the Document Conversion add-on with the latest version, below

• Download the right document-conversion-library-x.x.xx.jar

  Confluence version	Document Library  Version
  6.0 - 6.4	Document conversion 1.2.25 (mirror)
  after 6.4	Document conversion 2.0.2.1

• Install the add on by file upload, as per installing plugins 

STEP TO REPLICATE

1. Create a PPTX files and include multiple charts in the PPTX file.
2. Attach the file in the Confluence page.
3. Preview the file.

EXPECTED BEHAVIOUR

• The thumbnails for the PPTX file will load correctly.
• The file will preview correctly in Confluence.

ACTUAL BEHAVIOUR

• Thumbnails for the file will not load.
• The preview will take sometime depending on the number and complexity of the Charts inside the file.
• Noticed a CPU SPIKE while previewing the file:
  
• The following conversion thread found in the thread dump:

  "conversion-thread-0-internal" #192 daemon prio=5 tid=0x00007f06e81f0000 nid=0x39cb runnable [0x00007f066bbbd000]
     java.lang.Thread.State: RUNNABLE
  	at java.util.Vector.indexOf(Vector.java:382)
  	at java.text.AttributedString.addAttributeRunData(AttributedString.java:532)
  	at java.text.AttributedString.addAttributes(AttributedString.java:398)
  	at com.aspose.slides.ms.pbdb106a0.p6a2feef8.pa5e0ff62.r.do(Unknown Source)
  	at com.aspose.slides.ms.pbdb106a0.p6a2feef8.pa5e0ff62.r.break(Unknown Source)
  	at com.aspose.slides.ms.pbdb106a0.p6a2feef8.aw.do(Unknown Source)
  	at com.aspose.slides.ms.pbdb106a0.p6a2feef8.aw.do(Unknown Source)
  	at com.aspose.slides.ms.pbdb106a0.p6a2feef8.aw.do(Unknown Source)
  	at com.aspose.slides.p6a2feef8.af.do(Unknown Source)
  	- locked <0x00000007bac1a908> (a java.lang.Object)
  	at com.aspose.slides.hc.do(Unknown Source)
  	at com.aspose.slides.bvq.if(Unknown Source)
  	at com.aspose.slides.bvq.do(Unknown Source)
  	at com.aspose.slides.bvq.do(Unknown Source)
  	at com.aspose.slides.bvq.do(Unknown Source)
  	at com.aspose.slides.bvq.do(Unknown Source)
  	at com.aspose.slides.bvq.do(Unknown Source)
  	at com.aspose.slides.bvq.do(Unknown Source)
  	at com.aspose.slides.bvq.do(Unknown Source)
  	at com.aspose.slides.bvq.do(Unknown Source)
  	at com.aspose.slides.bvq. (Unknown Source)
  	at com.aspose.slides.TextFrame.do(Unknown Source)
  	at com.aspose.slides.TextFrame.do(Unknown Source)
  	at com.aspose.slides.TextFrame.else(Unknown Source)
  	at com.aspose.slides.buy.do(Unknown Source)
  	at com.aspose.slides.blj.int(Unknown Source)
  	at com.aspose.slides.rk.byte(Unknown Source)
  	at com.aspose.slides.aht.do(Unknown Source)
  	at com.aspose.slides.ta.int(Unknown Source)
  	at com.aspose.slides.ta.else(Unknown Source)
  	at com.aspose.slides.os.int(Unknown Source)
  	at com.aspose.slides.os.do(Unknown Source)
  	at com.aspose.slides.ta.int(Unknown Source)
  	at com.aspose.slides.ta.else(Unknown Source)
  	at com.aspose.slides.mu.do(Unknown Source)
  	at com.aspose.slides.ta.int(Unknown Source)
  	at com.aspose.slides.ta.else(Unknown Source)
  	at com.aspose.slides.it.int(Unknown Source)
  	at com.aspose.slides.Chart.do(Unknown Source)
  	at com.aspose.slides.GroupShape.do(Unknown Source)
  	at com.aspose.slides.Slide.for(Unknown Source)
  	at com.aspose.slides.Slide.do(Unknown Source)
  	at com.aspose.slides.Slide.do(Unknown Source)
  	at com.aspose.slides.bgv.do(Unknown Source)
  	at com.aspose.slides.bgv.if(Unknown Source)
  	at com.aspose.slides.Presentation.do(Unknown Source)
  	at com.aspose.slides.Presentation.if(Unknown Source)
  	at com.aspose.slides.Presentation.save(Unknown Source)
  	at com.atlassian.plugins.conversion.convert.image.SlidesConverter.convertDocDirect(SlidesConverter.java:83)
  	at com.atlassian.confluence.plugins.conversion.impl.runnable.JVMConversionRunnable.doWork(JVMConversionRunnable.java:83)
  	at com.atlassian.confluence.plugins.conversion.impl.runnable.ConversionRunnable.run(ConversionRunnable.java:36)
  	at com.atlassian.confluence.plugins.conversion.impl.runnable.JVMConversionRunnable.run(JVMConversionRunnable.java:22)
  	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
  	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
  	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
  	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
  	at java.lang.Thread.run(Thread.java:745)
     Locked ownable synchronizers:
  	- 0x00000006e2064818> (a java.util.concurrent.ThreadPoolExecutor$Worker)
  

UPD: investigation details here: https://bulldogwiki.internal.atlassian.com/wiki/display/CSE/Document+Conversion%3A+PSR-62