Module middleware 

Middleware system for MCP servers

This module provides a trait-based middleware architecture that allows intercepting and modifying MCP requests and responses. Middleware can be used for authentication, logging, rate limiting, and custom business logic.

Overview

The middleware system consists of:

• McpMiddleware - Core trait for implementing middleware
• RequestContext - Normalized request context across transports
• SessionInjection - Write-only mechanism for populating session state
• MiddlewareStack - Ordered execution of multiple middleware layers

Examples

use turul_http_mcp_server::middleware::{McpMiddleware, RequestContext, SessionInjection, MiddlewareError};
use turul_mcp_session_storage::SessionView;
use async_trait::async_trait;

// Define custom middleware
struct LoggingMiddleware;

#[async_trait]
impl McpMiddleware for LoggingMiddleware {
    async fn before_dispatch(
        &self,
        ctx: &mut RequestContext<'_>,
        _session: Option<&dyn SessionView>,
        _injection: &mut SessionInjection,
    ) -> Result<(), MiddlewareError> {
        println!("Request: {}", ctx.method());
        Ok(())
    }
}

Re-exports

pub use traits::McpMiddleware;

pub use context::RequestContext;

pub use context::SessionInjection;

pub use context::DispatcherResult;

pub use error::MiddlewareError;

pub use error::error_codes;

pub use stack::MiddlewareStack;

pub use session_view_adapter::StorageBackedSessionView;

Modules

builtins

Built-in middleware implementations

context

Request context and session injection types

error

Middleware error types

session_view_adapter

SessionView adapter for BoxedSessionStorage

stack

Middleware stack execution

traits

Core middleware trait definitions