Two-way Variables for Multi-Platform Support

Two-way variables are there to support mixed-platform Flamenco farms. Basically they perform path prefix replacement.

Let’s look at an example configuration:

variables:
  my_storage:
    is_twoway: true
    values:
    - platform: linux
      value: /media/shared/flamenco
    - platform: windows
      value: F:\flamenco
    - platform: darwin
      value: /Volumes/shared/flamenco

The difference with regular variables is that regular variables are one-way: {variablename} is replaced with the value, and that’s it.

Two-way variables go both ways, as follows:

When submitting a job, values in the javascript jobs’ command are replaced with the corresponding variables as it’s executed on the client.
When sending a task to a worker, variables are replaced with values again.

(Do keep in mind that if you perform changes to a job, you’ll need to re-submit it.)

This may seem like a lot of unnecessary work. After all, why go through the trouble of replacing in one direction, when later the opposite is done? The power lies in the fact that each replacement step can target a different platform. In the first step the value for Linux can be recognised, and in the second step the value for Windows can be put in its place.

Let’s look at a more concrete example, based on the configuration shown above.

Alice runs Blender on macOS. She submits a job that has its render output set to /Volumes/shared/flamenco/renders/shot_010_a_anim.
Flamenco recognises the path, and stores the job as rendering to {my_storage}/renders/shot_010_a_anim.
Bob’s computer is running the Worker on Windows, so when it receives a render task Flamenco will tell it to render to F:\flamenco\renders\shot_010_a_anim.
Carol’s computer is also running a worker, but on Linux. When it receives a render task, Flamenco will tell it to render to /media/shared/flamenco/renders/shot_010_a_anim.