High CPU usage and preview keeps loading for PDF macro or Powerpoint macro

Summary

When we use the PDF macro or Powerpoint macro to display files the preview keeps loading.
We also observe high CPU usage on Confluence server

Environment

Windows , this could not be replicated on linux
Confluence 5.10.x

Steps to Reproduce

1. Create a page
2. Attach a PDF file
3. Add the pdf macro , you can use { then type pdf
4. Try to save the macro after selecting the file and save the page

Expected Results

The macro should load in time and no impact on CPU .

Actual Results

1. The below exception is thrown in the atlassian-confluence.log file:
   (This will appear only if the macro does not load at all)

   2016-09-12 13:47:10,243 WARN [DefaultSlideCacheManager:thread-1] [persistence.dao.filesystem.TrackingAttachmentDataFileSystem] getAttachmentData Unexpected exception getting fileStoreId - cannot log metrics of operation
    -- referer: http://xxx/display/xx/xxx+xxx | url: /plugins/servlet/pptslide | traceId: 37a8bcd860ea045c | userName: admin
   net.sf.hibernate.LazyInitializationException: Failed to lazily initialize a collection - no session or session was closed
   	at net.sf.hibernate.collection.PersistentCollection.initialize(PersistentCollection.java:209)
   	at net.sf.hibernate.collection.PersistentCollection.read(PersistentCollection.java:71)
   	at net.sf.hibernate.collection.Bag.iterator(Bag.java:256)
   	at com.atlassian.confluence.content.ContentProperties.find(ContentProperties.java:112)
   	at com.atlassian.confluence.content.ContentProperties.getStringProperty(ContentProperties.java:73)
   	at com.atlassian.confluence.pages.Attachment.getFileStoreId(Attachment.java:208)
   	at com.atlassian.confluence.pages.persistence.dao.filesystem.TrackingAttachmentDataFileSystem.getAttachmentData(TrackingAttachmentDataFileSystem.java:80)
   	at com.atlassian.confluence.pages.persistence.dao.filesystem.FileSystemAttachmentDataDao.getDataForAttachment(FileSystemAttachmentDataDao.java:63)
   	at com.atlassian.confluence.pages.persistence.dao.hibernate.AbstractHibernateAttachmentDao.getAttachmentData(AbstractHibernateAttachmentDao.java:237)
   	at com.atlassian.confluence.pages.attachments.CachingAttachmentDao.getAttachmentData(CachingAttachmentDao.java:174)
   	at com.atlassian.confluence.pages.DefaultAttachmentManager.getAttachmentData(DefaultAttachmentManager.java:231)
   	at com.atlassian.confluence.pages.DefaultAttachmentManager.getAttachmentData(DefaultAttachmentManager.java:225)
   	at com.atlassian.confluence.pages.DelegatorAttachmentManager.getAttachmentData(DelegatorAttachmentManager.java:114)
   	at com.atlassian.confluence.pages.CachingAttachmentManager.getAttachmentData(CachingAttachmentManager.java:87)
   

2. CPU is high for most of the time . You can see the high CPU when the macro keeps loading
3. In browser consolve we see a 404 status for this request : http://10.60.3.192:8510/plugins/servlet/pptslide?attachment=xyz.pdf&attachmentId=950274&attachmentVer=1&pageId=950275&slide=1 and the response is * {"error": "converting"}

   *

Notes

We also observe the same when viewing powerpoint macro

We can disable the Office connector macro system add-on from General Configuration >> Manage add-ons >> Sytem Add-ons which has these macros. This way we can avoid the High CPU.