Trait LoggerDefinition

Source

pub trait LoggerDefinition:
    HasLoggingMetadata
    + HasLogLevel
    + HasLogFormat
    + HasLogTransport {
    // Provided methods
    fn to_message_notification(&self) -> LoggingMessageNotification { ... }
    fn to_set_level_request(&self) -> SetLevelRequest { ... }
}

Expand description

Complete MCP Logger Creation - Build structured logging systems with level control.

This trait represents a complete, working MCP logger that can emit structured log messages with configurable levels, formats, and transport mechanisms. When you implement the required metadata traits, you automatically get LoggerDefinition for free via blanket implementation.

§What You’re Building

A logger is a sophisticated logging system that:

Emits structured log messages with configurable levels
Supports different output formats (JSON, text, etc.)
Routes messages through various transports (console, files, network)
Provides runtime level control for debugging

§How to Create a Logger

Implement these four traits on your struct:


// This struct will automatically implement LoggerDefinition!
struct ApplicationLogger {
    component: String,
}

impl HasLoggingMetadata for ApplicationLogger {
    fn method(&self) -> &str {
        "notifications/message"
    }

    fn logger_name(&self) -> Option<&str> {
        Some(&self.component)
    }
}

impl HasLogLevel for ApplicationLogger {
    fn level(&self) -> LogLevel {
        LogLevel::Info
    }
}

impl HasLogFormat for ApplicationLogger {
    fn data(&self) -> &Value {
        use serde_json::{json, Value};
        static SAMPLE_DATA: &Value = &Value::Null; // Simplified for docs
        SAMPLE_DATA
    }
}

impl HasLogTransport for ApplicationLogger {
    fn should_deliver(&self, level: LoggingLevel) -> bool {
        level.priority() >= LoggingLevel::Info.priority()
    }
}

// Now you can use it with the server:
let logger = ApplicationLogger { component: "user-service".to_string() };

// The logger automatically implements LoggerDefinition
let notification = logger.to_message_notification();
let level_request = logger.to_set_level_request();