Preview of some PowerPoint files fail to render

Summary

After attaching certain PowerPoint files on a Confluence page and publishing it, the preview keeps loading indefinitely and eventually shows the error "There was a problem converting this attachment".

Environment

Confluence Server or Data Center

Diagnosis

1. While the preview fails, the file can be downloaded successfully.

2. The following error is seen in the application logs:

   atlassian-confluence.log

   2020-08-22 12:20:41,807 ERROR [DefaultSlideCacheManager:thread-1] [com.benryan.conversion.AbstractSlideConversionTask] call problem while converting test.pptx -- referer: https://example.site.com/display/AA/Test+Page | url: /plugins/servlet/pptslide | traceId: d153768c7837eeb8 | userName: user1 java.lang.IllegalArgumentException: image == null!

Cause

The preview is timing out for certain PowerPoint files as Confluence is not able to perform the document conversion within the default configured time of 30 seconds.

Solution

1. Shutdown Confluence

2. Add the following properties to <Confluence-Install>/bin/setenv.sh (when using Linux) or setenv.bat (when using .bat file in Windows). In case you are running Confluence as service in Windows, refer to Configuring System Properties (under Windows service)

   ⚠️The process is different between Data Center and Server installations of Confluence:

   Data Center

   Data Center has separate Sandbox processes to do conversions. We need to use conversion.sandbox.java.options (Recognized System Properties) to pass the required parameters to external processes. For further information kindly review the Document conversion for Confluence Data Center KB article.

   ℹ️ To ensure each Sandbox system property is recognized correctly, please separate them with commas.

   • setenv.sh - Linux

     CATALINA_OPTS="-Dconversion.sandbox.java.options=-Dconfluence.document.conversion.slides.convert.timeout=120,-Dconfluence.document.conversion.imaging.convert.timeout=120 ${CATALINA_OPTS}"

   • setenv.bat - Windows

     set CATALINA_OPTS=-Dconversion.sandbox.java.options=-Dconfluence.document.conversion.slides.convert.timeout=120,-Dconfluence.document.conversion.imaging.convert.timeout=120 %CATALINA_OPTS%

   Server

   • setenv.sh - Linux

     CATALINA_OPTS="-Dconfluence.document.conversion.threads=3 ${CATALINA_OPTS}" CATALINA_OPTS="-Dconfluence.document.conversion.slides.convert.timeout=120 ${CATALINA_OPTS}" CATALINA_OPTS="-Dconfluence.document.conversion.imaging.convert.timeout=120 ${CATALINA_OPTS}"

   • setenv.bat - Windows

     set CATALINA_OPTS=-Dconfluence.document.conversion.threads=3 %CATALINA_OPTS% set CATALINA_OPTS=-Dconfluence.document.conversion.slides.convert.timeout=120 %CATALINA_OPTS% set CATALINA_OPTS=-Dconfluence.document.conversion.imaging.convert.timeout=120 %CATALINA_OPTS%

3. Delete the contents from inside the folder <Confluence-Home>/viewfile/

4. ℹ️ For Data Center instances, also delete the contents inside:

   <Confluence-Home>/shared-home/dcl-document/

   <Confluence-Home>/shared-home/dcl-document_hd/

5. Clear Confluence plugins cache

6. Startup Confluence

Verification

After completing the steps above and restarting Confluence, navigate to the page containing the previously-failing PowerPoint attachment. Because the preview cache was cleared, Confluence will perform a fresh conversion using the new timeout values. Allow a few minutes for the conversion to complete, then confirm the preview renders successfully instead of showing "There was a problem converting this attachment.