Migration on Plesk for Linux is stuck on the "Fetch configuration data from Plesk servers" step

Symptoms

• Migration process at Plesk > Tools & Settings > Migration and Transfer > 203.0.113.2 appears to be stuck at "Fetch configuration data from Plesk servers" step. The same information can be seen after pressing on the Logs tab.

• There is an active backup creation process ongoing on the source server, which can be seen Tools & Settings > Backup Manager.

• The CPU usage for this specific backup creation process is high:

  # top
  16836 root 39 19 117016 19932 9392 R 99.0 0.1 255:46.86 /opt/psa/admin/bin/pmm-ras --export-dump-as-file --session-path=/opt/psa/PMM/sessions/2020-08-13-041208.968 --volume-names=/

  As evident from the migration debug logs, the process hangs on the this step:

  # less /usr/local/psa/var/modules/panel-migrator/sessions/XXXXXXXXXXXXXX/debug.log
  ...
  +|2020-08-13_04:12:08,101|D|MT|core.runners.base||source|Execute command on the source server 'source': /opt/psa/bin/pleskbackup --domains-name --configuration --output-file /root/plesk_migrator/plesk_migrator-fdfdxz3e1g1grx9gpgbw4mupf3djhdtk/backup.tar -vvvvv --polling-interval 5 --from-file /root/plesk_migrator/plesk_migrator-fdfdxz3e1g1grx9gpgbw4mupf3djhdtk/filter.list

Cause

An ongoing backup process on the source server bottlenecks, which leaves very little to no resources for the migration process to proceed and it stalls until enough resources do become available.

Resolution