The documentation for Google Filestore only makes specific reference to using it with "Google Compute Engine and Kubernetes Engine instances".
Following the instructions here I have been successfully able to mount a Filestore share in a Compute Engine instance.
Is it possible to mount a Filestore share in a custom runtime (Docker container) that is running in a Google App Engine Flexible instance and if so what would be the best way to do it ?
Thanks
Yes, you could do it. But as the App Engine environment says:
Flexible environment VM instances are restarted on a weekly basis. During restarts, Google's management services apply any necessary operating system and security updates.
You always have root access to Compute Engine VM instances. By default, SSH access to the VM instances in the flexible environment is disabled. If you choose, you can enable root access to your app's VM instances.
But, the disk is ephemeral. So, each week the VM is restarted, the disk get's deleted. Also, you could enable debug, SSH into the VM and mount the Filestore client but once you disable debug, the VM get's restarted as a fresh new VM.
You could try by editing the Dockerfile of the Flexible enviroment to achieve this.