Loading JIRA gadget directory will cause CPU usage to spike, take long to load and all users will get affected

Summary

If a user tries to load JIRA gadget directory, the operation take a long time (up to a minute) to complete. It also causes a CPU usage spike, and affects the overall JIRA instance performance.

Steps to Reproduce

1. In a JIRA instance with multiple users, create or configure a dashboard.
2. Click Add gadget to display the gadget directory.

Expected Results

The gadget directory loads without issues and all gadgets are displayed.

Actual Results

The operation takes a long time, and consumes excessive CPU resources. This puts pressure on the whole instance, affecting other users that may be attempting to load other JIRA screens.
In some cases pages fail to load altogether with an error:

Page unavailable
The requested page failed to load. If the problem persists, please contact Atlassian Cloud Support.

Workaround

There is no workaround for this issue, although a later attempt to load the gadget directory may succeed if some of the data has been cached.