TaskStar — Atomic Execution Unit

Overview

TaskStar represents the atomic unit of computation in UFO Galaxy—the smallest indivisible task scheduled on a device agent. Each TaskStar encapsulates complete context necessary for autonomous execution, including semantic description, assigned device, execution state, and dependency relationships.

Formal Definition: A TaskStar $t_i$ is formally defined as:

$$ t_i = (\text{name}_i, \text{description}_i, \text{device}_i, \text{tips}_i, \text{status}_i, \text{dependencies}_i) $$

Architecture

Core Properties

Property	Type	Description
task_id	`str`	Unique identifier (auto-generated UUID if not provided)
name	`str`	Short, human-readable task name
description	`str`	Natural-language specification of what the task should do
tips	`List[str]`	Guidance list to help device agent complete the task
target_device_id	`str`	ID of the device agent responsible for execution
device_type	`DeviceType`	Type of target device (Windows, Linux, Android, etc.)
status	`TaskStatus`	Current execution state
priority	`TaskPriority`	Priority level for scheduling (LOW, MEDIUM, HIGH, CRITICAL)
timeout	`float`	Maximum execution time in seconds
retry_count	`int`	Number of allowed retries on failure
task_data	`Dict[str, Any]`	Additional data needed for task execution
expected_output_type	`str`	Expected type/format of the output

Note: The property task_description is available as a backward compatibility alias for description.

Execution Tracking

Property	Type	Description
result	`Any`	Task execution result (if completed successfully)
error	`Exception`	Error information (if failed)
execution_start_time	`datetime`	Timestamp when execution started
execution_end_time	`datetime`	Timestamp when execution ended
execution_duration	`float`	Duration in seconds (calculated)
created_at	`datetime`	Task creation timestamp
updated_at	`datetime`	Last modification timestamp

Note: All execution tracking properties are read-only and automatically managed by the TaskStar lifecycle methods.

Computed Properties

Property	Type	Description
is_terminal	`bool`	True if task is in a terminal state (COMPLETED, FAILED, or CANCELLED)
is_ready_to_execute	`bool`	True if task is PENDING and has no pending dependencies

Task Status Lifecycle

stateDiagram-v2
    [*] --> PENDING: Create
    PENDING --> WAITING_DEPENDENCY: Has dependencies
    WAITING_DEPENDENCY --> PENDING: Dependencies satisfied
    PENDING --> RUNNING: Start execution
    RUNNING --> COMPLETED: Success
    RUNNING --> FAILED: Error
    RUNNING --> CANCELLED: User cancels
    FAILED --> PENDING: Retry
    COMPLETED --> [*]
    FAILED --> [*]
    CANCELLED --> [*]

Status Definitions

Status	Description	Terminal
PENDING	Task is ready to execute (no pending dependencies)	❌
WAITING_DEPENDENCY	Task is waiting for prerequisite tasks	❌
RUNNING	Task is currently executing on device	❌
COMPLETED	Task finished successfully	✅
FAILED	Task encountered an error	✅
CANCELLED	Task was cancelled by user	✅

Note: Terminal states (COMPLETED, FAILED, CANCELLED) are final—tasks in these states cannot transition to other states without explicit retry.

Priority Levels

Tasks are scheduled based on priority when multiple tasks are ready to execute:

Priority	Value	Use Case
LOW	1	Background tasks, cleanup operations
MEDIUM	2	Standard tasks (default)
HIGH	3	Important tasks requiring quick execution
CRITICAL	4	Time-sensitive tasks, system health checks

Usage Examples

Creating a TaskStar

from galaxy.constellation import TaskStar
from galaxy.constellation.enums import DeviceType, TaskPriority

# Basic task creation
task = TaskStar(
    task_id="build_docker_image",
    name="Docker Build",
    description="Build the Docker image from Dockerfile in the current directory",
    tips=[
        "Use docker build command",
        "Tag the image as 'myapp:latest'",
        "Check for build errors in output"
    ],
    target_device_id="linux_gpu_server",
    device_type=DeviceType.LINUX,
    priority=TaskPriority.HIGH,
    timeout=300.0,  # 5 minutes
    retry_count=2
)

Task with Additional Data

# Task with custom data payload
task = TaskStar(
    task_id="process_dataset",
    description="Preprocess the dataset and save to output directory",
    task_data={
        "input_path": "/data/raw/dataset.csv",
        "output_path": "/data/processed/dataset_clean.csv",
        "columns_to_drop": ["temp_col1", "temp_col2"],
        "normalization": "min-max"
    },
    target_device_id="linux_cpu_1",
    device_type=DeviceType.LINUX
)

Auto-Generated Task

# Minimal creation with auto-generated ID and defaults
task = TaskStar(
    description="Run unit tests",
    target_device_id="windows_desktop"
)

print(task.task_id)  # Auto-generated UUID
print(task.name)     # Auto-generated: "task_{first 8 chars of UUID}"
print(task.priority) # Default: TaskPriority.MEDIUM

Core Operations

Execution Management

# Start execution
task.start_execution()
print(f"Started at: {task.execution_start_time}")

# Mark as completed (success)
result = {"status": "success", "output": "Tests passed: 45/45"}
task.complete_with_success(result)
print(f"Duration: {task.execution_duration} seconds")

# Mark as failed
try:
    # ... execution code ...
    raise Exception("Docker build failed")
except Exception as e:
    task.complete_with_failure(e)
    print(f"Error: {task.error}")

Retry Logic

# Check if task should retry
if task.should_retry():
    task.retry()
    print(f"Retry attempt {task._current_retry}/{task._retry_count}")
    # Task status is now PENDING again

Validation

# Validate task configuration
if task.validate():
    print("Task configuration is valid")
else:
    errors = task.get_validation_errors()
    print(f"Validation errors: {errors}")

State Queries

Checking Task State

# Check if task is ready to execute
if task.is_ready_to_execute:
    print("Task can be started")

# Check if task is in terminal state
if task.is_terminal:
    print("Task has finished executing")

# Query specific status
if task.status == TaskStatus.RUNNING:
    elapsed = datetime.now(timezone.utc) - task.execution_start_time
    print(f"Running for {elapsed.total_seconds()} seconds")

Accessing Results

# Access execution results
if task.status == TaskStatus.COMPLETED:
    print(f"Result: {task.result}")
    print(f"Duration: {task.execution_duration}s")
    
elif task.status == TaskStatus.FAILED:
    print(f"Error: {task.error}")
    print(f"Failed at: {task.execution_end_time}")

Serialization

JSON Export/Import

# Export to JSON
json_string = task.to_json()
print(json_string)

# Save to file
task.to_json(save_path="task_backup.json")

# Load from JSON string
restored_task = TaskStar.from_json(json_data=json_string)

# Load from file
loaded_task = TaskStar.from_json(file_path="task_backup.json")

Dictionary Conversion

# Convert to dictionary
task_dict = task.to_dict()

# Create from dictionary
new_task = TaskStar.from_dict(task_dict)

Pydantic Schema Conversion

# Convert to Pydantic BaseModel
schema = task.to_basemodel()

# Create from Pydantic schema
task_from_schema = TaskStar.from_basemodel(schema)

Advanced Features

Request String Formatting

The to_request_string() method formats the task for device agent consumption:

request = task.to_request_string()

# Output:
# Task Description: Build the Docker image from Dockerfile
# Tips for Completion:
#  - Use docker build command
#  - Tag the image as 'myapp:latest'
#  - Check for build errors in output

This formatted string is sent to device agents for execution.

Dynamic Data Updates

# Update task data
task.update_task_data({
    "additional_flags": ["--no-cache", "--pull"],
    "build_args": {"VERSION": "1.2.3"}
})

# Access task data
data = task.task_data
print(data["additional_flags"])

!!! warning "Modification Restrictions" Task properties cannot be modified while the task is in RUNNING status. This prevents race conditions and ensures execution consistency.

Dependency Management

Internal Dependency Tracking

TaskStar maintains internal sets of dependencies and dependents:

# Add dependency (internal use by TaskConstellation)
task.add_dependency("prerequisite_task_id")

# Remove dependency
task.remove_dependency("prerequisite_task_id")

# Add dependent task
task.add_dependent("dependent_task_id")

# Check dependencies
print(f"Dependencies: {task._dependencies}")
print(f"Dependents: {task._dependents}")

!!! note "Managed by TaskConstellation" Dependency management methods are primarily used internally by TaskConstellation. Direct manipulation is not recommended—use ConstellationEditor for safe editing with undo/redo support.

Integration with Constellation

Adding to Constellation

from galaxy.constellation import TaskConstellation

constellation = TaskConstellation(name="my_workflow")

# Add task to constellation
constellation.add_task(task)

# Task is now managed by constellation
ready_tasks = constellation.get_ready_tasks()

Execution via Device Manager

from galaxy.client.device_manager import ConstellationDeviceManager

# Execute task using device manager
device_manager = ConstellationDeviceManager()

# Execute returns an ExecutionResult object
execution_result = await task.execute(device_manager)

print(f"Status: {execution_result.status}")
print(f"Result: {execution_result.result}")
print(f"Execution Time: {execution_result.execution_time}s")

Error Handling

Validation Errors

task = TaskStar(
    task_id="",  # Invalid: empty ID
    name="",  # Invalid: empty name
    description="",  # Invalid: empty description
    timeout=-1.0  # Invalid: negative timeout
)

if not task.validate():
    for error in task.get_validation_errors():
        print(f"❌ {error}")

# Output:
# ❌ Task ID must be a non-empty string
# ❌ Task name must be a non-empty string
# ❌ Task description must be a non-empty string
# ❌ Timeout must be a positive number

Execution Errors

try:
    task.start_execution()
except ValueError as e:
    print(f"Cannot start: {e}")
    # Example: "Cannot start task in status RUNNING"

try:
    task.complete_with_success(result)
except ValueError as e:
    print(f"Cannot complete: {e}")
    # Example: "Cannot complete task in status PENDING"

Example Workflows

Simple Task Execution

# Create task
task = TaskStar(
    description="Run Python script",
    target_device_id="linux_server_1",
    timeout=60.0
)

# Execute
task.start_execution()
try:
    # ... actual execution ...
    result = {"output": "Script completed", "exit_code": 0}
    task.complete_with_success(result)
except Exception as e:
    task.complete_with_failure(e)

# Check result
if task.status == TaskStatus.COMPLETED:
    print(f"✅ Success: {task.result}")
else:
    print(f"❌ Failed: {task.error}")

Retry on Failure

max_attempts = 3
attempt = 0

while attempt < max_attempts:
    attempt += 1
    task.start_execution()
    
    try:
        # ... execution code ...
        task.complete_with_success(result)
        break
    except Exception as e:
        task.complete_with_failure(e)
        
        if task.should_retry():
            task.retry()
            print(f"Retry {attempt}/{max_attempts}")
        else:
            print("Max retries exceeded")
            break

Best Practices

Task Design Guidelines

Keep tasks atomic: Each task should represent a single, well-defined operation
Provide clear descriptions: Use natural language that device agents can understand
Include helpful tips: Guide the agent with specific instructions or common pitfalls
Set appropriate timeouts: Prevent hanging tasks with realistic timeout values
Use retry wisely: Enable retries for transient failures, not logic errors

Good vs. Bad Task Descriptions

✅ Good: "Build the Docker image from the Dockerfile in /app directory and tag it as 'myapp:v1.2.3'"

❌ Bad: "Build stuff"

✅ Good: "Run pytest on the test/ directory and generate a coverage report in HTML format"

❌ Bad: "Test the code"

!!! warning "Common Pitfalls" - Don't modify running tasks: Attempting to change properties during execution raises ValueError - Don't forget validation: Always validate tasks before adding to constellation - Don't ignore timeouts: Set realistic timeouts to prevent resource exhaustion

Related Components

TaskStarLine — Dependency relationships between tasks
TaskConstellation — DAG orchestration and execution
ConstellationEditor — Safe task editing with undo/redo
ConstellationDeviceManager — Device management and task assignment
Overview — Task Constellation framework overview

API Reference

Constructor

TaskStar(
    task_id: Optional[str] = None,
    name: str = "",
    description: str = "",
    tips: List[str] = None,
    target_device_id: Optional[str] = None,
    device_type: Optional[DeviceType] = None,
    priority: TaskPriority = TaskPriority.MEDIUM,
    timeout: Optional[float] = None,
    retry_count: int = 0,
    task_data: Optional[Dict[str, Any]] = None,
    expected_output_type: Optional[str] = None,
    config: Optional[TaskConfiguration] = None
)

Key Methods

Method	Description
`execute(device_manager)`	Execute task using device manager (async, returns `ExecutionResult`)
`validate()`	Validate task configuration (returns `bool`)
`get_validation_errors()`	Get list of validation errors (returns `List[str]`)
`start_execution()`	Mark task as started
`complete_with_success(result)`	Mark task as completed successfully
`complete_with_failure(error)`	Mark task as failed
`retry()`	Reset task for retry attempt
`cancel()`	Cancel the task
`should_retry()`	Check if task should be retried (returns `bool`)
`to_dict()`	Convert to dictionary
`to_json(save_path)`	Export to JSON string or file
`from_dict(data)`	Create from dictionary (classmethod)
`from_json(json_data, file_path)`	Create from JSON (classmethod)
`to_basemodel()`	Convert to Pydantic BaseModel schema
`from_basemodel(schema)`	Create from Pydantic schema (classmethod)

TaskStar — The atomic building block of distributed workflows

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