Advanced Hello World Example¶
This example demonstrates advanced features of the workflow engine including: - Input validation with error handling - Conditional execution based on validation results - File operations in different formats (txt, json, yaml) - Shell command execution - Template rendering with variable substitution - Multi-step workflow with dependencies
Workflow Definition¶
name: Advanced Hello World
description: >
An advanced hello world workflow demonstrating:
- Input validation
- Conditional execution
- Error handling
- Multiple output formats
- Shell commands
- Template rendering
- Custom module tasks
params:
name:
description: Name to include in the greeting
default: World
steps:
# Step 1: Validate the input name parameter
- name: validate_input
task: shell
command: |
mkdir -p "output/"
if [ -z "{{ name|default('') }}" ]; then
echo "Error: Name parameter is required" > "output/validation_result.txt"
elif [ "{{ name|length }}" -lt 2 ]; then
echo "Error: Name must be at least 2 characters long" > "output/validation_result.txt"
elif [ "{{ name|length }}" -gt 50 ]; then
echo "Error: Name must not exceed 50 characters" > "output/validation_result.txt"
else
echo "Valid: {{ name }}" > "output/validation_result.txt"
fi
# Step 2: Read validation result
- name: check_validation
task: read_file
params:
file_path: "output/validation_result.txt"
encoding: "utf-8"
outputs: validation_content
# Step 3: Process validation result
- name: process_validation
task: shell
command: |
if grep -q "^Error:" "output/validation_result.txt"; then
echo "Validation failed:" >&2
cat "output/validation_result.txt" >&2
printf "false" > "output/validation_passed.txt"
else
echo "Validation passed"
printf "true" > "output/validation_passed.txt"
fi
# Step 4: Read validation flag
- name: read_validation
task: read_file
params:
file_path: "output/validation_passed.txt"
outputs: validation_content
# Step 5: Get current timestamp (only if validation passed)
- name: get_timestamp
task: shell
command: date -u +"%Y-%m-%dT%H:%M:%SZ"
outputs: current_timestamp
condition: "'{{ validation_content }}' == 'true'"
# Step 6: Create JSON greeting (only if validation passed)
- name: create_greeting
task: write_json
params:
file_path: "output/greeting.json"
data:
greeting: "Hello, {{ name }}!"
timestamp: "{{ current_timestamp }}"
run_number: "{{ run_number }}"
language: "en"
indent: 2
condition: "'{{ validation_content }}' == 'true'"
# Step 7: Create multi-language greetings (only if validation passed)
- name: translate_greeting
task: write_yaml
params:
file_path: "output/greetings.yaml"
data:
English: "Hello, {{ name }}!"
Spanish: "¡Hola, {{ name }}!"
French: "Bonjour, {{ name }}!"
German: "Hallo, {{ name }}!"
Italian: "Ciao, {{ name }}!"
Japanese: "こんにちは、{{ name }}さん！"
condition: "'{{ validation_content }}' == 'true'"
# Step 8: Format and display results (only if validation passed)
- name: format_output
task: shell
command: |
if [ -f "output/greeting.json" ]; then
echo "=== Workflow Results ==="
echo "Run #{{ run_number }} at {{ current_timestamp }}"
echo
echo "JSON Greeting:"
cat "output/greeting.json"
echo
echo "Multiple Languages:"
cat "output/greetings.yaml"
echo
echo "=== End of Results ==="
fi
condition: "'{{ validation_content }}' == 'true'"
# Step 9: Handle validation errors (only if validation failed)
- name: handle_error
task: write_file
params:
file_path: "output/error_report.txt"
content: |
Workflow encountered an error:
Input validation failed{% if name %} for name: {{ name }}{% else %}: name parameter not provided{% endif %}
Please check the requirements and try again.
Requirements:
- Name must be provided
- Name must be between 2 and 50 characters
- Name must not contain special characters
condition: "'{{ validation_content }}' == 'false'"
# Step 10: Final status notification
- name: notify_status
task: shell
command: |
if [ "$(cat output/validation_passed.txt)" = "true" ]; then
echo "Workflow completed successfully!"
echo "Check the output files for detailed results:"
echo "- greeting.json: JSON formatted greeting"
echo "- greetings.yaml: Multi-language greetings"
echo "- validation_result.txt: Input validation details"
else
echo "Workflow failed due to validation errors."
echo "Check error_report.txt for details."
if [ -f "output/error_report.txt" ]; then
cat "output/error_report.txt"
else
cat "output/validation_result.txt"
fi
fi
Usage Examples¶
-
Run with default name:
-
Run with a custom name:
-
Test validation error (name too short):
Key Features Demonstrated¶
- Input Validation
- Length checks (2-50 characters)
- Required parameter validation
-
Validation result storage in files
-
Conditional Execution
- Steps that run only if validation passes
- Error handling steps for validation failures
-
Condition-based file operations
-
File Operations
- Reading and writing files
- Multiple formats (TXT, JSON, YAML)
-
File-based state management
-
Variable Management
- Step output capture using
outputs - Variable interpolation in templates
-
Built-in variables (
run_number) -
Error Handling
- Validation error reporting
- Custom error messages
-
Error state management
-
Multi-language Support
- Greetings in multiple languages
- Unicode text handling
- YAML formatting
Example Outputs¶
Successful Run¶
=== Workflow Results ===
Run #1 at 2024-01-23T10:30:00Z
JSON Greeting:
{
"greeting": "Hello, Alice!",
"timestamp": "2024-01-23T10:30:00Z",
"run_number": "1",
"language": "en"
}
Multiple Languages:
English: Hello, Alice!
Spanish: ¡Hola, Alice!
French: Bonjour, Alice!
German: Hallo, Alice!
Italian: Ciao, Alice!
Japanese: こんにちは、Aliceさん！
=== End of Results ===
Workflow completed successfully!
Check the output files for detailed results:
- greeting.json: JSON formatted greeting
- greetings.yaml: Multi-language greetings
- validation_result.txt: Input validation details
Failed Validation¶
Validation failed:
Error: Name must be at least 2 characters long
Workflow failed due to validation errors.
Check error_report.txt for details.
Workflow encountered an error:
Input validation failed for name: A
Please check the requirements and try again.
Requirements:
- Name must be provided
- Name must be between 2 and 50 characters
- Name must not contain special characters