fast-twitch.middlewares.cache-policy

Usage and execution boundary

Adds cache header policies without replacing existing headers. Its LRU/TTL backend memoizes policy maps, not response bodies. A native stream cannot be reused merely because its policy was cached.

(ns application.middleware
  (:require [fast-twitch.middlewares.cache-policy :as middleware]))

(defn handler [_]
  {:status 200 :headers {"content-type" "text/plain"} :body "Hello"})

(def app (middleware/wrap-cache-policy handler {:max-age 3600 :immutable? false}))

This defines the Ring handler portion. Adapt app through routing/ft-handler or pass it to server/listen!; startup instructions and a complete walkthrough show the surrounding project.

Settings and defaults

Setting	Meaning
:static-prefixes	Default /static/, /assets/, /favicon
:max-age	Default 31536000 for static policy
:immutable?	Enabled unless false
:dynamic-policy	Default no-cache/no-store map; may be supplied as policy function
:static-policy	Custom map/function
:cacheable?	Predicate [request options]
:etag-fn	Function [request]
:key-fn	Function [request options]
:backend / :max-entries	Policy memoization backend / default LRU capacity 256

Wrapper order and all middleware families. The function reference below preserves the upstream signatures and source links; helper functions do not all share the wrapper's arity.

Upstream function reference

Applies configurable HTTP cache policy headers with @std/cache-backed memoization.

LruCache

The @std/cache LruCache constructor used by the default policy backend. Source

TtlCache

The @std/cache TtlCache constructor available for custom policy backends. Source

cache-policy

(cache-policy request options)

Function.

Returns cache policy headers for the request, using the configured backend. Source

cache-policy-key

(cache-policy-key request options)

Function.

Builds the backend key used for memoizing cache policy headers. Source

cache-policy-response

(cache-policy-response response request options)

Function.

Adds cache policy headers to a response without replacing existing headers. Source

cacheable-request?

(cacheable-request? request)
(cacheable-request? request options)

Function.

Returns true when the request should receive a static cache policy. Source

default-dynamic-policy

The default cache policy for non-static responses. Source

default-static-prefixes

The default URI prefixes treated as static cacheable assets. Source

dynamic-cache-policy

(dynamic-cache-policy _request options)

Function.

Builds the cache policy used for non-static responses. Source

lru-cache-backend

(lru-cache-backend)
(lru-cache-backend max-size)

Function.

Creates an @std/cache LRU backend for memoized cache policy headers. Source

static-cache-policy

(static-cache-policy request options)

Function.

Builds the cache policy used for static cacheable assets. Source

ttl-cache-backend

(ttl-cache-backend ttl-ms)

Function.

Creates an @std/cache TTL backend for memoized cache policy headers. Source

wrap-cache-policy

(wrap-cache-policy handler)
(wrap-cache-policy handler options)

Function.

Wraps a handler so responses receive configurable cache policy headers. Source

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