Some attachments fail to migrate silently when using CSV exports in CCMA

Issue Summary

When using the CSV export feature for migrating CCMA spaces, some attachments go missing in the Cloud. This feature is in GA for the following versions:

• CCMA 3.4.0 for PostGres dbs will now use CSV Export by default
• CCMA 3.4.5 for MySQL dbs GA
• CCMA 3.4.6 for Oracle dbs GA

Steps to Reproduce

• Use a version of CCMA with a database above to ensure spaces are exported to CSV during migration
• Migrate spaces with attachments

Expected Results

• All attachments are included if they exist on server
• If there are missing attachments on server, or CCMA can't access them, print error in the logs for missing attachment

Actual Results

Some attachments seem to be missed by CCMA. We have not been able to identify which attachments are not being picked up, and if there's a specific condition in which they will fail to migrate.

No errors are thrown in the atlassian-confluence.log or migration logs

The attachments appear to be accessible, but the following error is seen in the Cloud after migrating when trying to access missing attachments:

{"error":{"code":"NotFoundError","title":"Some resources were not found","href":"https://api.media.atlassian.com#NotFoundError"}}

Workaround

Disable CSV exports:

• Enable the following dark feature in Confluence from ${CONFLUENCE_URL}/admin/darkfeatures.action
• migration-assistant.enable.original-xml-export