How can I share the /data/Data directory between two running Foundry containers?

[Nicoolai]

Hi,
So, I love this container image already but I have a bit of an edge-case (probably) that I'm trying to make work.
I am running two instances on the same host. I want them to share the same data/Data folder.
I've tried to symlink my way out of it, so instance 2 points to the same place on my host.

However, with symlink, I get an issue when it tries to chown the folders on startup.
So, following some other discussions in here, I have set FOUNDRY_GID, FOUNDRY_UID and CONTAINER_PRESERVE_OWNER.
This seems to be in the right direction, I no longer get fatal chown issues, but unfortunately it means that it doesn't see my symlink as a folder (I think) so it tries to mkdir the Data folder, causing another exception as the symlink is there, with the same name.

Any ideas on how I could get this setup working?

[felddy]

I'm glad the container is working well for you. I have an idea that I think will work.

So, I'm pretty sure Docker will be unhappy trying to resolve a symlink across volumes.

In the second container try mounting the Data directory (from the first) on top of the data mount of second. I just tried this and it seems to work well. (see below).

It's a little confusing with all the things named "data".

Host:

└── parent
    ├── data
    |  └── Data
    └── data1

Container 1:

└── /data (host data)
    └── Data

Container 2:

└── /data (host data1)
    └── Data (host data/Data)

---
version: "3.8"

secrets:
  credentials:
    file: credentials-mine.json

services:
  foundry0:
    image: felddy/foundryvtt:release
    hostname: felddy_foundryvtt
    init: true
    restart: "no"
    volumes:
      - type: bind
        source: ./data
        target: /data
    environment:
      - CONTAINER_CACHE=/data/container_cache
      - CONTAINER_VERBOSE=true
      - TIMEZONE=US/Eastern
      - FOUNDRY_UID=501
      - FOUNDRY_GID=20
      - FOUNDRY_MINIFY_STATIC_FILES=true
      - FOUNDRY_UPNP=false
    secrets:
      - source: credentials
        target: config.json
    ports:
      - target: "30000"
        published: "30000"
        protocol: tcp
  foundry1:
    image: felddy/foundryvtt:release
    hostname: felddy_foundryvtt_1
    init: true
    restart: "no"
    volumes:
      - type: bind
        source: ./data1
        target: /data
      - type: bind
        source: ./data/Data
        target: /data/Data
      - type: bind
        source: ./data/container_cache
        target: /data/container_cache
    environment:
      - CONTAINER_CACHE=/data/container_cache
      - CONTAINER_VERBOSE=true
      - TIMEZONE=US/Eastern
      - FOUNDRY_UID=501
      - FOUNDRY_GID=20
      - FOUNDRY_MINIFY_STATIC_FILES=true
      - FOUNDRY_UPNP=false
    secrets:
      - source: credentials
        target: config.json
    ports:
      - target: "30000"
        published: "30001"
        protocol: tcp

Couple of things to be careful with:

• This black magic is probably breaking some of the assumptions that Foundry is making in order to protect the integrity of the Data files. I'd be careful accessing the same world on both instances.
• The FoundryVTT License has terms regarding player access to duplicate instances sharing a key.

Let me know if this works for you.

[Nicoolai]

You're a genius! That worked perfectly. (Atleast for starting up).
Cross your fingers that it doesn't crash and burn when we start using it :)

I feel [foolish] now, I tried something along those lines but just tried to map the WHOLE data to instance1.

Of course that didn't work. This, on the other hand, is brilliant!

Regarding assumptions; The setup is so our GM can prep one world (on an instance only he can access) while we have another world active on the instance players can access.

That way, he can prep a one-shot in another system while players can still do their thing, on the campaign we play.

SO, my hope is that both instances will always be working in different /worlds folders but we can prep without having to export/import.