Google Cloud Storage is a object storage API, it is not a filesystem. As a result, it isn't really designed to be "mounted" within a VM. It is designed to be highly durable and scalable to extraordinarily large objects (and large numbers of objects).
Though you can use gcsfuse to mount it as a filesystem, that method has pretty significant drawbacks. For example, it can be expensive in operation count to do even simple operations for a normal filesystem.
Likewise, there are many surprising behaviors that are a result of the fact that it is an object store. For example, you can't edit objects -- they are immutable. To give the illusion of writing to the middle of an object, the object is, in effect, deleted and recreated whenever a call to close() or fsync() happens.
The best way to use GCS is to design your application to use the API (or the S3 compatible API) directly. That way the semantics are well understood by the application, and you can optimize for them to get better performance and control your costs. Thus, to access it from your docker container, ensure your container has a way to authenticate through GCS (either through the credentials on the instance, or by deploying a key for a service account with the necessary permissions to access the bucket), then have the application call the API directly.
Finally, if what you need is actually a filesystem, and not specifically GCS, Google Cloud does offer at least 2 other options if you need a large mountable filesystem that is designed for that specific use case:
- Persistent Disk, which is the baseline filesystem that you get with a VM, but you can mount many of these devices on a single VM. However, you can't mount them read/write to multiple VMs at once -- if you need to mount to multiple VMs, the persistent disk must be read only for all instances they are mounted to.
- Cloud Filestore is a managed service that provides an NFS server in front of a persistent disk. Thus, the filesystem can be mounted read/write and shared across many VMs. However it is significantly more expensive (as of this writing, about $0.20/GB/month vs $0.04/GB/month in
us-central1) than PD, and there are minimum size requirements (1TB).
