you don’t need to do anything - Discourse handles this automatically - sidekiq and redis will only run the job once, and sidekiq will only grab one of the web containers, but i don’t think you can be sure which one it is on any given backup if you are using local backups.
thus, you should use an external S3 bucket if you aren’t already, otherwise your backup files will likely be randomly stored across the local disks of both containers. using S3 bucket means your backup will always land in the same place.