Page include macro fails to render and page load hangs

Summary

When a page contains a page include macro in Confluence, even if it is just nested one level deep the page fill fail to render and load indefinitely. CPU usage also goes up to 100%

Environment

• Confluence 5.9.1-OD-2015.39.1-0001
• MySQL 5.6

Tested on PostgreSQL 9.2 and could not replicate this issue.

Steps to Reproduce

1. Create one page with simple text
2. Create a second page which includes the previous page

OR

1. Download and restore the space export attached to this ticket
2. Try to access the 'Include one deep' page

Expected Results

Page loads normally with the included text from the other page

Actual Results

I don't see any exceptions in the logs, but there are multiple blocking HTTP threads (one per page load) and CPU usage is ~100%

Notes

Although this is just an error caused by the page include macro, the CPU usage could cause a outages in production environments.

Workaround

Copy the text from included pages directly and disable the page include macro.