Add a hosting helper method for adding a persistent volume mount to containers

[DamianEdwards]

Related #974

As part of putting together the sample in dotnet/aspire-samples#52 it was suggested a new helper method could be added to Aspire.Hosting to make this scenario simpler, e.g.:

var database = builder.AddSqlServerContainer("sqlserver", "abcdefg123_78")
    .WithPersistentVolume("/var/opt/mssql")
    .AddDatabase("appdb");

The method WithPersistentVolume would be a shortcut to WithVolumeMount(string source, string target, VolumeMountType type, bool isReadOnly) with source being generated from the application name and resource name, e.g. $"{builder.Environment.ApplicationName}.{resourceName}.data", and type being VolumeMountType.Named and isReadOnly being false.

[mitchdenny]

Where would the volume mount be rooted? I like the idea generally, just need to figure out a few details.

[DamianEdwards]

When the volume mount is named, you don't specify where it's rooted AFAICT, it just becomes a named volume that's managed by the Docker host. See https://docs.docker.com/storage/volumes/

[DamianEdwards]

It makes me wonder whether the current shape of WithVolumeMount is actually confusing and conflating "Bind mounts" with "Volumes". Perhaps we should be revisiting that.

[josephaw1022]

Similar to #837 (comment)

[mitchdenny]

I think that there is an argument that volumes should be their own resource. In k8s volumes are a discrete resource often with a specific provider to get away from host specific volume mounts (e.g. ceph). In the cloud (using Azure as an example) you might use Azure Files or Azure Container Storage.

[DamianEdwards]

@mitchdenny as long as it doesn't complicate the really simple scenarios like the one this issue relates to.

[stbau04]

I created a seperate issure for splitting the current WithVolumeMount into two methods (one for bind mounts and one for named volumes): #1437

[DamianEdwards]

Now that #1437 is complete and we have separate WithBindMount and WithVolumeMount methods, I'm not sure there's anything left to do here. Folks who want a persistent volume on a container resource now do something like this:

var database = builder.AddSqlServerContainer("sqlserver", "abcdefg123_78")
    .WithVolumeMount("data", "/var/opt/mssql")
    .AddDatabase("appdb");

The only thing I can think that might be worth adding is that right now it's hard to name the volume based on the application/resource names, but that might be better left to more domain-specific helper methods like #837.

Thoughts @davidfowl @JamesNK?

[davidfowl]

Agreed, I think we follow the model that @mitchdenny introduced for emulators (UsePersistence()) though maybe we rename it 😄