Migration or Site import fails: Unable to add database user: Database user name is invalid

Symptoms

• Unable to migrate a database in Tools & Settings > Migration & Transfer Manager > source server or via Site import extension, when a database username has more than 16 characters:

  PLESK_ERROR: Unable to create database user 'usernamewith16characters' in subscription 'example.com': Command execution failed on the local server with non-zero exit code.
  command: /usr/local/psa/bin/database --create-dbuser usernamewith16characters -passwd '' -domain example.com -any-database -type mysql -server localhost:3306 -ignore-nonexistent-options
  exit code: 1
  stdout:
  stderr: Unable to add database user: Database user name is invalid.

• On the target server limit for length of a database username in MariaDB 5.6 was increased, MariaDB 10.2, MySQL 5.7 are used.

Cause

Currently database usernames longer than 16 characters is not supported. The issue is consider as a Plesk bug with id #PPM-1889 which is planned to be fixed in future products updates.

Resolution

As a workaround:

1. Connect to the server via SSH;

2. Upload the attached patched file and extract it:

   # wget https://support.plesk.com/hc/en-us/article_attachments/115000725194/Checker.zip
   # unzip Checker.zip

3. Backup original file:

   # mv /usr/local/psa/admin/plib/Checker.php{,.bak}

4. Replace original file with the fixed one:

   # mv Checker.php /usr/local/psa/admin/plib/

5. Re-migrate databases.

   NOTE: The fix works only for site import. It still will not be possible to create database user with the name containing more than 16 characters.