Please check this page for your projects, and take whatever steps are necessary to move off of Stretch:
https://os-deprecation.toolforge.org/
Don't hesitate to reach out for help on IRC or mailing list if
you need help with this migration. You may find Cinder volumes
(https://wikitech.wikimedia.org/wiki/Help:Adding_Disk_Space_to_Cloud_VPS_instances#Cinder)
especially useful for transferring data between VMs. Note that we
do NOT recommend in-place OS upgrades of VMs; it is almost always
better to start with a fresh host and transfer workloads over.
Details about the what and why for this process can be found here:
https://wikitech.wikimedia.org/wiki/News/Stretch_deprecation
Here is the remaining deprecation timeline:
May 1, 2022: All active Stretch VMs will be shut down (but not deleted) by WMCS admins.
June 30, 2022: LTS support for Debian Stretch ends, all Stretch VMs will be deleted by WMCS admins