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Custom cache

Control cache programmatically. Use this template to optimize performance and implement custom caching strategies.

// Define configurable cache duration in seconds (default: 30 days)
const CACHE_DURATION_SECONDS = 30 * 24 * 60 * 60;


// Define which parts of the request to include in the cache key
const USE_PATH = true; // Include path in the cache key
const USE_QUERY_STRING = true; // Include query string in the cache key
const INCLUDE_HEADERS = ["User-Agent"]; // Headers to include in the cache key


export default {
    async fetch(request, env, ctx) {
        // Generate a custom cache key based on user preferences
        const cacheKey = createCacheKey(request);
        console.log(`Retrieving cache for: ${cacheKey.url}.`)


        // Access the default Cache API
        const cache = caches.default;


        // Attempt to retrieve the cached response
        let response = await cache.match(cacheKey);


        if (!response) {
            // Cache miss: Fetch the asset from the origin
            console.log(`Cache miss for: ${cacheKey.url}. Fetching from origin...`);
            response = await fetch(request);


            // Wrap the origin response for caching
            response = new Response(response.body, response);


            // Set Cache-Control headers to define the TTL
            response.headers.set("Cache-Control", `s-maxage=${CACHE_DURATION_SECONDS}`);
            response.headers.set("x-snippets-cache", "stored");


            // Store the response in the cache
            await cache.put(cacheKey, response.clone());
        } else {
            // Cache hit: Return the cached response
            console.log(`Cache hit for: ${cacheKey.url}.`);
            response = new Response(response.body, response);
            response.headers.set("x-snippets-cache", "hit");


            // Optionally check if the cache should expire based on age
            const ageHeader = response.headers.get("Age");
            if (ageHeader && parseInt(ageHeader, 10) > CACHE_DURATION_SECONDS) {
                console.log(`Cache expired for: ${cacheKey.url}. Deleting cached response...`);
                await cache.delete(cacheKey);
                response.headers.set("x-snippets-cache", "deleted");
            }
        }


        // Return the response to the client
        return response;
    },
};


/**
 * Function to create a custom cache key based on request properties
 * @param {Request} request - The incoming request object
 * @returns {Request} - A valid cache key based on the URL
 */
function createCacheKey(request) {
    const url = new URL(request.url); // Use the request's base URL
    const cacheKey = new URL(url.origin); // Start with the origin (scheme + hostname)


    // Optionally include the path
    if (USE_PATH) {
        cacheKey.pathname = url.pathname;
    }


    // Optionally include the query string
    if (USE_QUERY_STRING) {
        cacheKey.search = url.search;
    }


    // Optionally include specific headers
    if (INCLUDE_HEADERS.length > 0) {
        const headerParts = INCLUDE_HEADERS.map(header => `${header}=${request.headers.get(header) || ""}`).join("&");
        cacheKey.searchParams.append("headers", headerParts);
    }


    // Return the constructed URL as the cache key
    return new Request(cacheKey.toString(), {
        method: "GET"
    });
}
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