feat(anvil): be able to specify a prefix path for temp disk storage

[kahuang]

Component

Anvil

Describe the feature you would like

When anvil state grows, it persists it temporarily to disk. I'd like to be able to specify a prefix path for the directory that gets created by anvil for this state.

Additional context

I am running Anvil in the cloud, and want to attach a persistent disk to the instance and mount it at the path anvil will use for storing state. Because it's a random directory each time, there's no way for me to programatically mount my disk at that location before anvil starts.

[gakonst]

@mattsse PTAL^

[mattsse]

Does this also concern the RPC cache dir @kahuang ?

[kahuang]

Anywhere that disk space can grow unbounded!

[kahuang]

Actually after reading the code, it seems like this always mounts at /tmp then generate a random filename.Although it may be nice to be able to specify a dir specifically for this data: https://docs.rs/tempdir/latest/tempdir/struct.TempDir.html

Not high pri IMO

[emilianobonassi]

I need it too to be able to restart a session from a specific state.