Backup to AWS storage fails in Plesk: Unable to create the remote backup: Transport error: Extension transport: ext://s3-backup/server/: 100 Continue

Symptoms

• Plesk Obsidian running on a Linux-based server and using the Amazon S3 Backup extension for Plesk

• Backup from Plesk to AWS S3 fails with an error that is similar to the following:

  Unable to create the remote backup: Transport error: Extension transport: ext://s3-backup/server/: 100 Continue

• With enabled debug mode in Plesk, the following error appears in the /var/log/plesk/PMM/backup-202301010000/backup.log:

  S3Exception caught: Error executing "UploadPart" on "https://w3m7.la.idrivee2-18.com/platinum-server/backup_202301010000.tar?uploadId=m6b0p2k6-747b-4153-a0a3-80b565b3b4b5&partNumber=792"; AWS HTTP error: cURL error 56: TCP connection reset by peer (see http://curl.haxx.se/libcurl/c/libcurl-errors.html) (server): 100 Continue -
  DEBUG (7) [extension/s3-backup]: Rethrow exception because total maximum number of failures exceeded.
  DEBUG (7) [extension/s3-backup]: uploadPart error: 100 Continue
  DEBUG (7) [extension/s3-backup]: abortMultipartUpload request:

Cause

Intermittent networking issues between the Plesk server and AWS s3 storage are preventing the backup upload process from finishing successfully.

Resolution

1. Log into Plesk

2. Edit the /usr/local/psa/admin/conf/panel.ini

3. Set the following values in the [ext-s3-backup] section of the panel.ini file (create the section if necessary):

   [ext-s3-backup]
   MaxResumeAttempts = 30
   MaxResumeFailures = 30

These values will increase the number of possible resume attempts that the extension will make while uploading the backup. You may increase the value for the number of allowed attempts further if necessary.