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Processes

A process runs alongside the tasks; this page shows how to write one, and an example in which processes and tasks interact.

How to Use It

A Process

A process runs alongside the tasks. This one sends the packers on a 5-second break every 50 seconds:

docs/snippets/yaml/tasks.yaml:process
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processes:
  # Called as breaks(context, resource="packers", every=50, duration=5)
  - function: !python shop_logic.breaks
    kwargs: {resource: packers, every: 50, duration: 5}
docs/snippets/pages/tasks.py:builder-process
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def breaks(context: SimulationContext, resource: str, every: float, duration: float):
    """Takes every packer off for a break of `duration` seconds every `every` seconds."""
    path = f"{context.sim_id}.resources.{resource}.current_cap"
    registry = context.env.registry
    while True:
        yield context.env.timeout(every)
        normal = registry.get(path).value
        registry.update(path, 0)
        yield context.env.timeout(duration)
        registry.update(path, normal)


app.add_process(breaks, resource="packers", every=50, duration=5)
docs/snippets/pages/tasks.py:low-level-process
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def breaks_process(env, resource: str, every: float, duration: float):
    """What add_process starts, by hand: a plain SimPy generator."""
    path = f"Shop.resources.{resource}.current_cap"
    while True:
        yield env.timeout(every)
        normal = env.registry.get(path).value
        env.registry.update(path, 0)
        yield env.timeout(duration)
        env.registry.update(path, normal)

Setting current_cap to 0 stops new work but not the work in progress: Resources explains what happens to busy units when a capacity drops.

Example: Process Interaction

The process-interaction example puts these together: a child flow, a failure that on_fail handles, and orders that wait for a courier's signal or a time limit. It needs no Docker service and ends on its own after 300 simulation seconds.

Quick Start

desflow examples get downloads the example at the release you install, into a folder of its own. Pick uv or pip:

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# 1. Install
uv tool install desflow

# 2. Download the example
desflow examples get process-interaction --api yaml
cd process-interaction/yaml

# 3. Run it
desflow run process_interaction.yaml

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# 1. Install
pip install desflow

# 2. Download the example
desflow examples get process-interaction --api yaml
cd process-interaction/yaml

# 3. Run it
desflow run process_interaction.yaml

The whole file is examples/yaml/process_interaction.yaml.

Quick Start

desflow examples get downloads the example at the release you install, into a folder of its own. Pick uv or pip:

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# 1. Install
uv tool install desflow

# 2. Download the example
desflow examples get process-interaction --api builder
cd process-interaction/builder

# 3. Run it
uv run --no-project --with desflow process_interaction_example.py

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# 1. Install
pip install desflow

# 2. Download the example
desflow examples get process-interaction --api builder
cd process-interaction/builder

# 3. Run it
python process_interaction_example.py

The whole file is examples/builder/process_interaction_example.py.

Quick Start

desflow examples get downloads the example at the release you install, into a folder of its own. Pick uv or pip:

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# 1. Install
uv tool install desflow

# 2. Download the example
desflow examples get process-interaction --api low-level
cd process-interaction/low-level

# 3. Run it
uv run --no-project --with desflow process_interaction_example.py

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# 1. Install
pip install desflow

# 2. Download the example
desflow examples get process-interaction --api low-level
cd process-interaction/low-level

# 3. Run it
python process_interaction_example.py

The whole file is examples/low-level/process_interaction_example.py.