Crate http_cache

Expand description

A caching middleware that follows HTTP caching rules, thanks to http-cache-semantics. By default, it uses cacache as the backend cache manager.

This crate provides the core HTTP caching functionality that can be used to build caching middleware for various HTTP clients and server frameworks. It implements RFC 7234 HTTP caching semantics, supporting features like:

Automatic cache invalidation for unsafe HTTP methods (PUT, POST, DELETE, PATCH)
Respect for HTTP cache-control headers
Conditional requests (ETag, Last-Modified)
Multiple cache storage backends
Streaming response support

§Basic Usage

The core types for building HTTP caches:

use http_cache::{CACacheManager, HttpCache, CacheMode, HttpCacheOptions};

// Create a cache manager with disk storage
let manager = CACacheManager::new("./cache".into(), true);

// Create an HTTP cache with default behavior
let cache = HttpCache {
    mode: CacheMode::Default,
    manager,
    options: HttpCacheOptions::default(),
};

§Cache Modes

Different cache modes provide different behaviors:

use http_cache::{CacheMode, HttpCache, CACacheManager, HttpCacheOptions};

let manager = CACacheManager::new("./cache".into(), true);

// Default mode: follows HTTP caching rules
let default_cache = HttpCache {
    mode: CacheMode::Default,
    manager: manager.clone(),
    options: HttpCacheOptions::default(),
};

// NoStore mode: never caches responses
let no_store_cache = HttpCache {
    mode: CacheMode::NoStore,
    manager: manager.clone(),
    options: HttpCacheOptions::default(),
};

// ForceCache mode: caches responses even if headers suggest otherwise
let force_cache = HttpCache {
    mode: CacheMode::ForceCache,
    manager,
    options: HttpCacheOptions::default(),
};

§Custom Cache Keys

You can customize how cache keys are generated:

use http_cache::{HttpCacheOptions, CACacheManager, HttpCache, CacheMode};
use std::sync::Arc;
use http::request::Parts;

let manager = CACacheManager::new("./cache".into(), true);

let options = HttpCacheOptions {
    cache_key: Some(Arc::new(|req: &Parts| {
        // Custom cache key that includes query parameters
        format!("{}:{}", req.method, req.uri)
    })),
    ..Default::default()
};

let cache = HttpCache {
    mode: CacheMode::Default,
    manager,
    options,
};

§Response-Based Cache Mode Override

Override cache behavior based on the response you receive. This is useful for scenarios like forcing cache for successful responses even when headers say not to cache, or never caching error responses like rate limits:

use http_cache::{HttpCacheOptions, CACacheManager, HttpCache, CacheMode};
use std::sync::Arc;

let manager = CACacheManager::new("./cache".into(), true);

let options = HttpCacheOptions {
    response_cache_mode_fn: Some(Arc::new(|_request_parts, response| {
        match response.status {
            // Force cache successful responses even if headers say not to cache
            200..=299 => Some(CacheMode::ForceCache),
            // Never cache rate-limited responses  
            429 => Some(CacheMode::NoStore),
            // Use default behavior for everything else
            _ => None,
        }
    })),
    ..Default::default()
};

let cache = HttpCache {
    mode: CacheMode::Default,
    manager,
    options,
};

§Streaming Support

For handling large responses without full buffering, use the StreamingManager:

use http_cache::{StreamingBody, HttpStreamingCache, StreamingManager};
use bytes::Bytes;
use std::path::PathBuf;
use http_body::Body;
use http_body_util::Full;

// Create a file-based streaming cache manager
let manager = StreamingManager::new(PathBuf::from("./streaming-cache"));

// StreamingBody can handle both buffered and streaming scenarios
let body: StreamingBody<Full<Bytes>> = StreamingBody::buffered(Bytes::from("cached content"));
println!("Body size: {:?}", body.size_hint());

Note: Streaming support requires the StreamingManager with the streaming feature. Other cache managers (CACacheManager, MokaManager, QuickManager) do not support streaming and will buffer response bodies in memory.

§Features

The following features are available. By default manager-cacache and cacache-smol are enabled.

manager-cacache (default): enable cacache, a disk cache, backend manager.
cacache-smol (default): enable smol runtime support for cacache.
cacache-tokio (disabled): enable tokio runtime support for cacache.
manager-moka (disabled): enable moka, an in-memory cache, backend manager.
streaming (disabled): enable the StreamingManager for streaming cache support.
streaming-tokio (disabled): enable streaming with tokio runtime support.
streaming-smol (disabled): enable streaming with smol runtime support.
with-http-types (disabled): enable http-types type conversion support

Note: Only StreamingManager (via the streaming feature) provides streaming support. Other managers will buffer response bodies in memory even when used with StreamingManager.

§Integration

This crate is designed to be used as a foundation for HTTP client and server middleware. See the companion crates for specific integrations:

http-cache-reqwest for reqwest client middleware
http-cache-surf for surf client middleware
http-cache-tower for tower service middleware

Structs§

BadHeader: Error type for bad header values
BadVersion: Error type for unknown http versions
CACacheManager: Implements CacheManager with cacache as the backend.
CacheAnalysis: Analysis result for a request, containing cache key and caching decisions
CacheOptions: Options struct provided by http-cache-semantics. Configuration options which control behavior of the cache. Use with CachePolicy::new_options().
HttpCache: Caches requests according to http spec.
HttpCacheOptions: Configuration options for customizing HTTP cache behavior on a per-request basis.
HttpResponse: A basic generic type that represents an HTTP response
HttpStreamingCache: Streaming version of HTTP cache that supports streaming request/response bodies without buffering them in memory.
StreamingError: Error type for streaming operations

Enums§

CacheMode: Cache mode determines how the HTTP cache behaves for requests.
HitOrMiss: Represents a basic cache status Used in the custom headers x-cache and x-cache-lookup
HttpVersion: Represents an HTTP version
StreamingBody: A body type that can represent either buffered data from cache or streaming body from upstream.

Constants§

XCACHE: x-cache header: Value will be HIT if the response was served from cache, MISS if not
XCACHELOOKUP: x-cache-lookup header: Value will be HIT if a response existed in cache, MISS if not

Traits§

CacheManager: A trait providing methods for storing, reading, and removing cache records.
HttpCacheInterface: An interface for HTTP caching that works with composable middleware patterns like Tower. This trait separates the concerns of request analysis, cache lookup, and response processing into discrete steps.
HttpCacheStreamInterface: Streaming version of the HTTP cache interface that supports streaming request/response bodies without buffering them in memory. This is ideal for large responses or when memory usage is a concern.
Middleware: Describes the functionality required for interfacing with HTTP client middleware
StreamingCacheManager: A streaming cache manager that supports streaming request/response bodies without buffering them in memory. This is ideal for large responses.

Type Aliases§

BoxError: Generic error type for the HttpCache middleware.
CacheBust: A closure that takes http::request::Parts, Option<CacheKey>, the default cache key (&str) and returns Vec<String> of keys to bust the cache for. An empty vector means that no cache busting will be performed.
CacheKey: A closure that takes http::request::Parts and returns a String. By default, the cache key is a combination of the request method and uri with a colon in between.
CacheModeFn: A closure that takes http::request::Parts and returns a CacheMode
ResponseCacheModeFn: A closure that takes http::request::Parts, HttpResponse and returns a CacheMode to override caching behavior based on the response
Result: A Result typedef to use with the BoxError type

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