Doover Device Apps

Doover App Development

This skill provides comprehensive guidance for creating, developing, and deploying Doover device applications.

This skill focuses on device apps. For cloud apps (processors and integrations), see the doover-cloud-apps skill.

This skill focuses on development of existing device applications. for guidance specifically on creating / setting up devops of a new application - please see the 'doover-app-workflow' skill.

What is a Device App?

A device app is a containerized (docker) Python application (primarily, but not exclusively python) that runs on Doover devices. Device apps:

• Run in Docker containers on linux devices
• Communicate via channels (data streaming) and tags (state persistence)
• Provide UI components for user interaction
• Can control hardware via the platform interface
• Support state machines for complex workflows

Typical Project Structure

my-app/
├── src/my_app/
│   ├── __init__.py         # Entry point with main() function
│   ├── application.py      # Core Application class
│   ├── app_config.py       # Configuration schema definitions
│   ├── app_ui.py           # UI component definitions
│   └── app_state.py        # State machine (optional)
├── simulators/
│   ├── sample/
│   │   ├── main.py         # Simulator application
│   │   ├── Dockerfile
│   │   └── pyproject.toml
│   ├── docker-compose.yml  # Local testing orchestration
│   └── app_config.json     # Sample configuration
├── tests/
│   ├── __init__.py
│   └── test_imports.py     # Basic validation tests
├── doover_config.json      # Application metadata and schema
├── pyproject.toml          # Python project configuration
├── Dockerfile              # Application container
└── README.md

Application Class

The core of every Doover app is a class inheriting from pydoover.docker.Application.

Basic Structure

from pydoover.docker import Application, run_app
from pydoover import ui

class MyApplication(Application):
    config: MyConfig  # Type hint for IDE autocomplete

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.ui = None
        self.state = None

    async def setup(self):
        """Initialize UI, state machine, and resources."""
        self.ui = MyUI()
        self.ui_manager.add_children(*self.ui.fetch())
        self.ui_manager.set_display_name(self.config.display_name.value)

    async def main_loop(self):
        """Called repeatedly - implement your main logic here."""
        # Read inputs
        value = self.get_tag("sensor_value")

        # Process data
        result = self.process(value)

        # Update outputs
        self.ui.update(result)
        await self.set_tag("processed_value", result)

Lifecycle Methods

UI Callbacks

Handle user interactions with the @ui.callback() decorator:

class MyApplication(Application):
    async def setup(self):
        self.ui = MyUI()
        self.ui_manager.add_children(*self.ui.fetch())

    @ui.callback("start_button")
    async def on_start(self, new_value):
        """Called when user clicks start button."""
        await self.set_tag("running", True)
        self.ui.start_button.coerce(None)  # Clear button state

    @ui.callback("threshold_param")
    async def on_threshold_change(self, new_value):
        """Called when user changes threshold parameter."""
        self.threshold = new_value

Accessing Configuration

Access configuration values via the config attribute:

async def main_loop(self):
    # Access config values
    pin = self.config.output_pin.value
    enabled = self.config.feature_enabled.value
    items = [item.value for item in self.config.items.elements]

Loop Control

Control the main loop timing:

class MyApplication(Application):
    loop_target_period = 2  # Target 2 seconds between loop iterations

Configuration Schema

Define user-configurable parameters in app_config.py.

Basic Types

from pydoover import config
from pathlib import Path

class MyConfig(config.Schema):
    def __init__(self):
        # Boolean with default
        self.enabled = config.Boolean(
            "Feature Enabled",
            description="Enable this feature",
            default=True
        )

        # Required string (no default)
        self.api_key = config.String(
            "API Key",
            description="Your API key"
        )

        # Integer with constraints
        self.retry_count = config.Integer(
            "Retry Count",
            description="Number of retries",
            default=3
        )

        # Number (float)
        self.threshold = config.Number(
            "Threshold",
            description="Detection threshold",
            default=0.5
        )

def export():
    """Export configuration schema to doover_config.json."""
    MyConfig().export(
        Path(__file__).parents[2] / "doover_config.json",
        "my_app"
    )

Application References

Reference other Doover apps:

self.simulator_key = config.Application(
    "Simulator App Key",
    description="Key of the simulator app to read from"
)

This generates a special format field that validates app keys.

Arrays

Define lists of values:

# Simple array
self.pins = config.Array(
    "Output Pins",
    element=config.Integer("Pin Number")
)

# Access elements
for pin in self.config.pins.elements:
    value = pin.value

Nested Objects

Create complex nested structures:

self.modbus_device = config.Object("Modbus Device")
self.modbus_device.add_elements(
    config.String("Host", default="localhost"),
    config.Integer("Port", default=502),
    config.Integer("Unit ID", default=1)
)

Enums

Define enumerated choices:

self.mode = config.Enum(
    "Operating Mode",
    choices=["auto", "manual", "standby"],
    default="auto"
)

Computed Properties

Add convenience properties:

class MyConfig(config.Schema):
    def __init__(self):
        self.timeout_minutes = config.Integer("Timeout (minutes)", default=5)

    @property
    def timeout_seconds(self):
        return self.timeout_minutes.value * 60

UI Components

Define user interface elements in app_ui.py.

Variables (Display)

Show values to users:

from pydoover import ui

class MyUI:
    def __init__(self):
        # Boolean status
        self.is_running = ui.BooleanVariable("running", "Running")

        # Text display
        self.status_text = ui.TextVariable("status", "Status")

        # Numeric with precision
        self.temperature = ui.NumericVariable(
            "temp",
            "Temperature",
            precision=1,
            unit="°C"
        )

        # DateTime
        self.last_update = ui.DateTimeVariable("updated", "Last Update")

    def fetch(self):
        return (self.is_running, self.status_text,
                self.temperature, self.last_update)

    def update(self, running, status, temp):
        self.is_running.update(running)
        self.status_text.update(status)
        self.temperature.update(temp)
        self.last_update.update(datetime.now())

Parameters (User Input)

Accept input from users:

# Text input
self.message = ui.TextParameter("message", "Message to Send")

# Numeric input
self.setpoint = ui.NumericParameter(
    "setpoint",
    "Temperature Setpoint",
    precision=1
)

Actions (Buttons)

Create clickable actions:

# Simple button
self.start = ui.Action("start", "Start")

# Styled button with confirmation
self.emergency_stop = ui.Action(
    "estop",
    "Emergency Stop",
    colour=ui.Colour.red,
    requires_confirm=True
)

# Hidden button (show/hide dynamically)
self.reset = ui.Action("reset", "Reset", hidden=True)

# Position for ordering
self.action1 = ui.Action("a1", "First", position=1)
self.action2 = ui.Action("a2", "Second", position=2)

State Commands (Multi-Option)

Create option selectors:

self.mode = ui.StateCommand(
    "mode",
    "Operating Mode",
    user_options=[
        ui.Option("auto", "Automatic"),
        ui.Option("manual", "Manual"),
        ui.Option("standby", "Standby")
    ]
)

Warnings and Alerts

Display warnings and send notifications:

# Warning indicator (show/hide based on condition)
self.low_battery = ui.WarningIndicator(
    "low_battery",
    "Low Battery Warning",
    hidden=True
)

# Alert stream for notifications
self.notifications = ui.AlertStream()

# In application code:
await self.ui.notifications.send_alert("Battery critically low!")

Range Coloring

Color numeric values based on ranges:

self.voltage = ui.NumericVariable(
    "voltage",
    "Battery Voltage",
    precision=2,
    ranges=[
        ui.Range("Low", 0, 11.5, ui.Colour.red),
        ui.Range("Normal", 11.5, 13.5, ui.Colour.green),
        ui.Range("High", 13.5, 15, ui.Colour.yellow)
    ]
)

Submodules (Grouping)

Group related UI elements:

class MyUI:
    def __init__(self):
        # Create submodule
        self.battery = ui.Submodule("battery", "Battery Status")

        # Create child elements
        self.voltage = ui.NumericVariable("voltage", "Voltage")
        self.current = ui.NumericVariable("current", "Current")
        self.charge_btn = ui.Action("charge", "Start Charging")

        # Add children to submodule
        self.battery.add_children(
            self.voltage,
            self.current,
            self.charge_btn
        )

    def fetch(self):
        return (self.battery,)  # Return parent, children included

doover_config.json

The doover_config.json file contains application metadata and is auto-generated from your config schema.

Structure

{
  "my_app": {
    "key": "uuid-goes-here",
    "name": "my_app",
    "display_name": "My Application",
    "type": "DEV",
    "visibility": "PUB",
    "allow_many": true,
    "description": "Short description",
    "long_description": "README.md",
    "depends_on": ["platform_interface"],
    "owner_org_key": "",
    "image_name": "ghcr.io/getdoover/my_app",
    "container_registry_profile_key": "",
    "build_args": "--platform linux/amd64,linux/arm64",
    "config_schema": {
      "$schema": "https://json-schema.org/draft/2020-12/schema",
      "type": "object",
      "properties": {
        "enabled": {
          "title": "Feature Enabled",
          "type": "boolean",
          "default": true
        }
      },
      "required": ["api_key"]
    }
  }
}

Key Fields

Regenerating

Regenerate after config changes:

uv run export-config

Or via Python:

from my_app.app_config import export
export()

Simulators

Simulators enable local testing without real hardware.

Simulator Application

Create simulators/sample/main.py:

import random
from pydoover.docker import Application, run_app
from pydoover import config

class SampleSimulator(Application):
    async def setup(self):
        pass

    async def main_loop(self):
        # Simulate sensor data
        await self.set_tag("temperature", random.uniform(20, 30))
        await self.set_tag("humidity", random.uniform(40, 60))

def main():
    run_app(SampleSimulator(config=config.Schema()))

if __name__ == "__main__":
    main()

Docker Compose

Create simulators/docker-compose.yml:

services:
  device_agent:
    image: spaneng/doover_device_agent:apps
    network_mode: host

  sample_simulator:
    build: ./sample
    network_mode: host
    environment:
      - APP_KEY=sim_app_key

  my_app:
    build: ../
    network_mode: host
    environment:
      - APP_KEY=test_app_key
      - CONFIG_FP=/app/simulators/app_config.json

Sample Configuration

Create simulators/app_config.json:

{
  "enabled": true,
  "simulator_app_key": "sim_app_key",
  "threshold": 25.0
}

Running Locally

doover app run

This runs docker compose up in the simulators directory.

Platform Interface

Access hardware I/O via the platform interface.

Digital I/O

class MyApplication(Application):
    async def main_loop(self):
        # Read digital input
        value = await self.platform_iface.get_di_async([1, 2, 3])
        # value = {1: True, 2: False, 3: True}

        # Write digital output
        await self.platform_iface.set_do_async(pin=4, value=True)

Reading Multiple Pins

# Get pin numbers from config
pins = [p.value for p in self.config.input_pins.elements]

# Read all pins
values = await self.platform_iface.get_di_async(pins)

# Check specific pin
if values.get(pins[0]):
    # Pin is HIGH
    pass

Tags (State Persistence)

Tags store state that persists between loop iterations and can be shared between apps.

Setting Tags

# Set a simple value
await self.set_tag("temperature", 25.5)

# Set structured data
await self.set_tag("status", {
    "state": "running",
    "uptime": 3600,
    "errors": []
})

Getting Tags

# Get with default
temp = self.get_tag("temperature", default=0.0)

# Get from another app
sim_value = self.get_tag("sensor_reading", app_key="sim_app_key")

Channels (Data Streaming)

Publish data to channels for logging and external consumption.

Publishing Data

import json

async def main_loop(self):
    data = {
        "timestamp": datetime.now().isoformat(),
        "temperature": 25.5,
        "humidity": 60.0
    }

    await self.device_agent.publish_to_channel_async(
        "sensor_data",
        json.dumps(data)
    )

Debugging Channels

Open the channel viewer:

doover app channels

Entry Point

The __init__.py file bootstraps your application.

Standard Pattern

from pydoover.docker import run_app
from .application import MyApplication
from .app_config import MyConfig

def main():
    run_app(MyApplication(config=MyConfig()))

pyproject.toml Script

[project.scripts]
doover-app-run = "my_app:main"
export-config = "my_app.app_config:export"

Dockerfile

Use the multi-stage build pattern for efficient images.

Standard Dockerfile

FROM spaneng/doover_device_base AS base_image
LABEL com.doover.app="true"
LABEL com.doover.managed="true"
HEALTHCHECK --interval=30s --timeout=2s --start-period=5s \
    CMD curl -f "127.0.0.1:$HEALTHCHECK_PORT" || exit 1

## BUILDER STAGE ##
FROM base_image AS builder
COPY --from=ghcr.io/astral-sh/uv:0.7.3 /uv /uvx /bin/
ENV UV_COMPILE_BYTECODE=1 UV_LINK_MODE=copy
ENV UV_PYTHON_DOWNLOADS=0
WORKDIR /app
RUN uv venv --system-site-packages
RUN --mount=type=cache,target=/root/.cache/uv \
    --mount=type=bind,source=uv.lock,target=uv.lock \
    --mount=type=bind,source=pyproject.toml,target=pyproject.toml \
    uv sync --locked --no-install-project --no-dev
COPY . /app
RUN --mount=type=cache,target=/root/.cache/uv \
    uv sync --locked --no-dev

## FINAL STAGE ##
FROM base_image AS final_image
COPY --from=builder --chown=app:app /app /app
ENV PATH="/app/.venv/bin:$PATH"
CMD ["doover-app-run"]

Key Labels

Advanced Patterns

Patterns extracted from production device apps: state machines, workers, and hardware I/O.

State Machines

State machines manage complex device lifecycles with multiple modes, timeouts, and transitions. Use pydoover.state.StateMachine with queued=True so transitions are serialized during processing.

Basic state machine: define states (with optional timeout and on_timeout) and transitions (trigger, source, dest; use "*" for any source). Implement on_enter_<state> and on_exit_<state> async callbacks for side effects.

from pydoover.state import StateMachine
import logging
log = logging.getLogger(__name__)

class MyAppState:
    states = [
        {"name": "off"},
        {"name": "starting", "timeout": 10, "on_timeout": "timeout_error"},
        {"name": "running"},
        {"name": "stopping", "timeout": 5, "on_timeout": "force_stop"},
        {"name": "error", "timeout": 60, "on_timeout": "reset"},
    ]
    transitions = [
        {"trigger": "start", "source": "off", "dest": "starting"},
        {"trigger": "started", "source": "starting", "dest": "running"},
        {"trigger": "stop", "source": "running", "dest": "stopping"},
        {"trigger": "stopped", "source": "stopping", "dest": "off"},
        {"trigger": "timeout_error", "source": "starting", "dest": "error"},
        {"trigger": "force_stop", "source": "stopping", "dest": "off"},
        {"trigger": "reset", "source": "error", "dest": "off"},
        {"trigger": "error", "source": "*", "dest": "error"},
    ]

    def __init__(self):
        self.state_machine = StateMachine(
            states=self.states,
            transitions=self.transitions,
            model=self,
            initial="off",
            queued=True,
        )

    async def on_enter_starting(self):
        log.info("Starting device...")
    async def on_enter_running(self):
        log.info("Device is running")
    async def on_enter_error(self):
        log.error("Device entered error state")

State machine with conditions: add an evaluate_state() that reads inputs/tags and triggers transitions (e.g. when run_requested and state is off, call await self.start_auto()). Use spin_state(max_iterations=15) to re-evaluate until the state stabilizes.

async def evaluate_state(self):
    is_running = self.app.get_is_running()
    run_requested = self.app.get_tag("run_requested")
    if self.state == "off" and run_requested:
        await self.start_auto()
    elif self.state == "starting_auto" and is_running:
        await self.started()
    elif self.state == "running_auto" and not run_requested:
        await self.stop_auto()
    # ... etc

async def spin_state(self, max_iterations=15):
    for _ in range(max_iterations):
        old = self.state
        await self.evaluate_state()
        if self.state == old:
            break
    return self.state

Using in the application: in setup(), create self.state = MyAppState() (or MyAppState(self) if it needs app reference). In main_loop(), call current_state = await self.state.spin_state(), then drive outputs and UI from current_state and await self.set_tag("state", current_state).

Workers and Scheduled Tasks

• Async worker: use an asyncio.Event to gate work, an asyncio.Queue for results, and asyncio.create_task(worker.run()) in setup(). For CPU-bound work use loop.run_in_executor(None, fn).
• Thread worker: for I/O (e.g. video capture) use a threading.Thread with a queue.Queue; from the main loop call queue.get(timeout=1.0) to receive the latest frame.
• Scheduled task: store shutdown_at and run asyncio.create_task(_worker(shutdown_at)) that sleeps in a loop (e.g. min(remaining, 60) seconds) until the time, then perform the action. Cancel the task to cancel the schedule.

Hardware I/O Patterns

• Debounced input: keep last_value, last_change_time, and confirmed_value; only set confirmed_value when time.time() - last_change_time >= stable_time. Use for noisy digital inputs.
• Output with safety: rate-limit changes (min interval between toggles), skip if state unchanged, and check a config flag (e.g. outputs_enabled) before calling set_do_async.
• Multiple pins: read all at once with get_di_async(pin_list) and map results by pin number; use helpers like any(inputs.values()) or all(inputs.values()) for combined conditions.

Error Recovery and Performance

• State-based recovery: add an error state with timeout and on_timeout: "attempt_recovery", and a recovering state that calls app recovery logic and triggers recovery_success or recovery_failed; track retry count and cap it.
• Graceful degradation: try primary source, then secondary, then cached data; update cache when any source succeeds and set a status tag when none are available.
• Throttling: only publish or call external APIs when time.time() - last_time >= interval.
• Batching: accumulate updates in a dict and flush when size reaches a limit or on a timer.

Best Practices

Loop Period

Set an appropriate loop period to balance responsiveness and resource usage:

class MyApplication(Application):
    loop_target_period = 2  # 2 seconds for most apps
    # Use 0.1-0.5 for responsive hardware control
    # Use 5-60 for slow-changing data

Error Handling

Handle errors gracefully to prevent app crashes:

async def main_loop(self):
    try:
        data = await self.fetch_data()
        await self.process(data)
    except ConnectionError as e:
        log.error(f"Connection failed: {e}")
        await self.set_tag("status", "error")
        # Don't re-raise - let loop continue
    except Exception as e:
        log.exception(f"Unexpected error: {e}")
        raise  # Re-raise critical errors

Debouncing Hardware Inputs

Prevent spurious state changes from noisy inputs:

class MyApplication(Application):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.last_value = None
        self.last_change_time = 0

    def get_debounced_value(self, current_value, stable_time=0.5):
        """Return stable value after debounce period."""
        if current_value != self.last_value:
            self.last_value = current_value
            self.last_change_time = time.time()

        if time.time() - self.last_change_time < stable_time:
            return None  # Still settling

        return current_value

Clearing Action States

Always clear action buttons after handling:

@ui.callback("start_button")
async def on_start(self, new_value):
    await self.start_process()
    self.ui.start_button.coerce(None)  # Clear button

Logging

Use Python's logging module:

import logging

log = logging.getLogger(__name__)

class MyApplication(Application):
    async def main_loop(self):
        log.info(f"Processing started")
        log.debug(f"Current state: {self.state}")
        log.warning(f"Low battery: {voltage}V")
        log.error(f"Failed to connect: {error}")

Testing

Write basic import and config tests:

# tests/test_imports.py
def test_import_app():
    from my_app.application import MyApplication
    assert MyApplication

def test_config():
    from my_app.app_config import MyConfig
    config = MyConfig()
    assert isinstance(config.to_dict(), dict)

def test_ui():
    from my_app.app_ui import MyUI
    ui = MyUI()
    assert ui.fetch()

Run tests:

doover app test

Code Quality

Lint and format your code:

doover app lint --fix
doover app format --fix

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