flamenco/web/project-website/content/usage/job-compiler-scripts/_index.md

title	weight
Job Compiler Scripts	10

Flamenco uses job compiler scripts to convert a job definition (like "render this Blend file") into concrete tasks that can be executed by workers.

Example

These scripts are written in JavaScript. Before describing how they work, here is a simple example that just logs a message (one task) and sleeps for a bit (another task):

const JOB_TYPE = {
    label: "Log and Sleep",
    settings: [
        { key: "message", type: "string", required: true },
        { key: "sleep_duration_seconds", type: "int32", default: 1 },
    ]
};

function compileJob(job) {
    const settings = job.settings;

    const echoTask = author.Task("echo", "misc");
    echoTask.addCommand(author.Command("echo", {
        message: settings.message,
    }));
    job.addTask(echoTask);

    const sleepTask = author.Task("sleep", "misc")
    sleepTask.addCommand(author.Command("sleep", {
        duration_in_seconds: settings.sleep_duration_seconds,
    }))
    job.addTask(sleepTask);
}

Each job compiler has two parts to it:

• the JOB_TYPE that defines the settings and how it's shown in the Blender add-on, and
• the compileJob() function that takes those settings and creates the tasks.

TODO: write more documentation. For now, you can refer to the built-in job compiler scripts as examples.

Task Types

In the above example code, you can see calls like author.Task("echo", "misc"). The first parameter is the task name, which will be shown in the web interface and can help to identify each task. The second parameter is the task type.

The following task types are defined by the standard job compiler scripts:

• blender: any task that runs Blender.
• ffmpeg: any task that runs FFmpeg.
• file-management: moving or copying files, creating directories, moving old renders out of the way to make place for new ones, etc.
• misc: tasks mostly used for testing things, such as "log a debug message" or "do nothing for 5 seconds".

These can be used to determine which worker executes which task. For example, let a puny machine do the file management and maybe video compression with FFmpeg, while the Blender tasks are left for the big ones. By default the workers can run all the above task types. See [worker configuration][worker-config] for more info.

In the end, these are just strings. When you create your own job compiler scripts, you can follow these types or make them up yourself. Don't forget to configure your workers to run them!

[worker-config]: {{< ref "usage/worker-configuration" >}}

Job Settings

The JOB_TYPE object contains the job settings. These can be shown in Blender's user interface for submitting files, but can also be automatically calculated based on the current file, the context, etc.

The exact specifications of these settings can be found via the "API" link in the top-right corner of the Flamenco Manager web interface. Search for the AvailableJobSetting schema. This will always be accurate for your particular version of Flamenco.

TODO: write about these in more detail.

Available Python names for Evaluation

Job settings can have an eval key, which is a Python expression that determines the value of the setting. That Python expression has access to the following names:

• jobname: The name of the current Flamenco job.
• settings: The settings of the current Flamenco job.
• bpy: Blender's Python interface (docs)
• C: The current context, short-hand for bpy.context.
• Path: The Path class from Python's pathlib library for file & directory path manipulation. Note that this does not understand Blender's // prefix for blendfile-relative paths. Use bpy.path.abspath() to turn those into an absolute path if necessary.
• last_n_dir_parts(n, Optional[file_path]): a function that returns the last n directory parts of some file's path. For example, last_n_dir_parts(2, '/complex/path/to/a/file.blend') will return to/a, as those are the last 2 components of the directory. If file_path is ommitted, it uses the current blend file, i.e. bpy.data.filepath.