Struct SlidingWindowRateLimitingMiddleware 

pub struct SlidingWindowRateLimitingMiddleware { /* private fields */ }

Rate limiting middleware using sliding window algorithm.

Uses a sliding window approach which provides more precise rate limiting but uses more memory to track individual request timestamps.

Example

use fastmcp_server::rate_limiting::SlidingWindowRateLimitingMiddleware;

// Allow 100 requests per minute
let rate_limiter = SlidingWindowRateLimitingMiddleware::new(100, 60);

Implementations

impl SlidingWindowRateLimitingMiddleware

pub fn new(max_requests: usize, window_seconds: u64) -> Self

Creates a new sliding window rate limiting middleware.

Arguments

• max_requests - Maximum requests allowed in the time window
• window_seconds - Time window duration in seconds

pub fn per_minute(max_requests: usize, window_minutes: u64) -> Self

Creates a sliding window rate limiter with minutes-based window.

Arguments

• max_requests - Maximum requests allowed in the time window
• window_minutes - Time window duration in minutes

pub fn client_id_extractor<F>(self, extractor: F) -> Self

where F: Fn(&McpContext, &JsonRpcRequest) -> Option<String> + Send + Sync + 'static,

Sets a custom function to extract client ID from the request context.

Identifiers longer than 4096 bytes are rejected. Accepted identifiers are immediately reduced to fixed-width SHA-256 partition keys; their raw values are neither retained nor included in rate-limit errors or debug output. At most 4095 distinct keys receive dedicated partitions. At the cap, a least-recently-used partition idle for at least 60 seconds is reclaimed only after its limiter has naturally reset; otherwise new keys share one overflow partition.

Trait Implementations

impl Debug for SlidingWindowRateLimitingMiddleware

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Middleware for SlidingWindowRateLimitingMiddleware

fn on_request( &self, ctx: &McpContext, request: &JsonRpcRequest, ) -> McpResult<MiddlewareDecision>

Invoked before routing the request.

fn on_response( &self, _ctx: &McpContext, _request: &JsonRpcRequest, response: Value, ) -> McpResult<Value>

Invoked after a successful handler result is produced.

fn on_error( &self, _ctx: &McpContext, _request: &JsonRpcRequest, error: McpError, ) -> McpError

Invoked when a handler or middleware returns an error.