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Echo Module

The Echo module is a simple and fundamental module that returns exactly what it receives as input. It's useful for debugging, testing, data passing, and as a basic example of Phlow module implementation.

🚀 Features​

Key Features​

  • ✅ Simplicity: Returns exactly what it receives
  • ✅ Any type: Accepts any type of input
  • ✅ Data preservation: Maintains original structure and type
  • ✅ Performance: Direct passthrough operation, no processing
  • ✅ Debug: Useful for checking data in pipelines
  • ✅ Observability: Fully integrated with OpenTelemetry

📝 Configuration​

Basic Configuration​

steps:
  - name: "echo_step"
    use: "echo_module"
    input: "Hello, World!"

Configuration with Structured Data​

steps:
  - name: "echo_object"
    use: "echo_module"
    input:
      message: "Hello"
      timestamp: "2024-01-01T00:00:00Z"
      data:
        items: [1, 2, 3]
        active: true

🔧 Parameters​

Input​

  • Type: any (any type)
  • Required: true
  • Description: The message or data to be echoed
  • Default: null

Output​

  • Type: any (same type as input)
  • Required: true
  • Description: The echoed data (identical to input)
  • Default: null

💻 Usage Examples​

Simple String Echo​

steps:
  - name: "simple_echo"
    use: "echo_module"
    input: "Esta mensagem será ecoada"
    
  # Output: "This message will be echoed"

Number Echo​

steps:
  - name: "number_echo"
    use: "echo_module"
    input: 42
    
  # Output: 42

Boolean Echo​

steps:
  - name: "boolean_echo"
    use: "echo_module"
    input: true
    
  # Output: true

Array Echo​

steps:
  - name: "array_echo"
    use: "echo_module"
    input: [1, 2, 3, "test", true]
    
  # Output: [1, 2, 3, "test", true]

Complex Object Echo​

steps:
  - name: "object_echo"
    use: "echo_module"
    input:
      user:
        id: 123
        name: "João Silva"
        email: "joao@example.com"
        active: true
        preferences:
          theme: "dark"
          notifications: true
        tags: ["admin", "premium"]
      metadata:
        created_at: "2024-01-01T00:00:00Z"
        updated_at: "2024-01-15T14:30:00Z"
        version: "1.2.3"
    
  # Output: (identical object to input)

Echo with Dynamic Data​

steps:
  - name: "process_user"
    # Some processing that returns user data
    
  - name: "echo_user_data"
    use: "echo_module"
    input: "{{ $process_user }}"
    
  # Output: (user data from previous step)

🔍 Use Cases​

1. Pipeline Debug​

steps:
  - name: "fetch_data"
    use: "http_request"
    input:
      url: "https://api.example.com/users"
      
  - name: "debug_response"
    use: "echo_module"
    input: "{{ $fetch_data }}"
    # Useful to see exactly what the API returned
    
  - name: "process_data"
    # Continue processing...

2. Data Passing​

steps:
  - name: "calculate_result"
    script: |
      let result = input.a + input.b;
      result * 2;
    
  - name: "pass_result"
    use: "echo_module"
    input: "{{ $calculate_result }}"
    
  - name: "format_output"
    input: "Result: {{ $pass_result }}"

3. Structure Validation​

steps:
  - name: "create_user_object"
    script: |
      {
        id: 123,
        name: "Test User",
        email: "test@example.com",
        created_at: new Date().toISOString()
      }
    
  - name: "validate_structure"
    use: "echo_module"
    input: "{{ $create_user_object }}"
    # Checks if object was created correctly
    
  - name: "save_user"
    use: "database_save"
    input: "{{ $validate_structure }}"

4. Testing and Development​

steps:
  - name: "mock_api_response"
    use: "echo_module"
    input:
      status: "success"
      data:
        users: [
          { id: 1, name: "Alice" },
          { id: 2, name: "Bob" }
        ]
      timestamp: "2024-01-01T00:00:00Z"
    
  - name: "process_users"
    # Process as if it came from a real API
    input: "{{ $mock_api_response.data.users }}"

🌐 Complete Example​

name: "echo-demo"
version: "1.0.0"
description: "Echo module demonstration"

modules:
  - name: "echo_module"
    module: "echo"
    version: "0.0.1"

steps:
  - name: "echo_string"
    use: "echo_module"
    input: "Hello from Echo!"
    
  - name: "echo_number"
    use: "echo_module"
    input: 3.14159
    
  - name: "echo_complex_object"
    use: "echo_module"
    input:
      application:
        name: "MyApp"
        version: "2.1.0"
        config:
          debug: true
          max_connections: 100
          features: ["auth", "cache", "logging"]
      environment:
        stage: "production"
        region: "us-east-1"
        
  - name: "echo_with_interpolation"
    use: "echo_module"
    input: "App: {{ $echo_complex_object.application.name }} v{{ $echo_complex_object.application.version }}"
    
  - name: "final_output"
    script: |
      {
        string_echo: $echo_string,
        number_echo: $echo_number,
        object_echo: $echo_complex_object,
        interpolated_echo: $echo_with_interpolation
      }

📊 Observability​

The Echo module inherits the standard Phlow SDK observability:

  • Tracing: Each execution generates OpenTelemetry spans
  • Logging: Structured logs for debugging
  • Metrics: Performance and usage metrics
  • Context: Context propagation between steps

🔒 Security​

  • Data preservation: Does not modify or expose sensitive data
  • No side effects: Purely functional operation
  • Memory: Passes references when possible for efficiency

📈 Performance​

  • Minimal latency: Direct passthrough operation
  • Efficient memory: No unnecessary copies
  • Threading: Full support for asynchronous execution
  • Scalability: No throughput limitations

🛠️ Implementation​

The Echo module is implemented in a minimalist way:

pub async fn echo(rx: ModuleReceiver) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
    listen!(rx, move |package: ModulePackage| async {
        let input = package.input().unwrap_or(Value::Null);
        sender_safe!(package.sender, input.into());
    });
    
    Ok(())
}

🏷️ Tags​

  • echo
  • debug
  • passthrough
  • testing
  • utility

Version: 0.0.1
Author: Philippe Assis <codephilippe@gmail.com> License: MIT
Repository: https://github.com/phlowdotdev/phlow