Summary

When changing an Issue Type Scheme on a project, if some of the issue types of issues in the project are no longer covered by the new scheme, then a migration of issue types will occur. If there's a very large number of these issues, then the operation can take a large amount of time, which will cause gateway timeouts when using a reverse proxy.

Steps to Reproduce

1. Find a project with the order of 100000s of issues in one issue type
2. Create an issue type scheme that does not include that issue type
3. Change that project's issue type scheme to the new one not including that issue type, and go through the migration steps

Expected Results

Issue types are migrated without issue.

Actual Results

The URL takes so long to load that it causes gateway timeouts at the proxy server.

Workaround

This workaround may require increasing the maximum number of issues in a bulk operation with the system property jira.bulk.edit.limit.issue.count - note that you may need to test in a staging environment to ensure that the resources consumed by this increase do not cause problems. You may need to perform this in batches rather than all at once, depending on how large the set of issues are that need to be changed.

1. Create an issue type scheme that contains the full set of issue types from both your original and desired destination state
2. Assign that issue type scheme to the project
3. Use a bulk move operation to change the issue type of the affected issues
4. Now assign the new issue type scheme to the project, without needing to run through the migration