Cloudflare Workers (Beta Assets). Broken Caching `_headers`

[predaytor]

Astro Info

Astro                    v4.15.11
Node                     v22.8.0
System                   macOS (arm64)
Package Manager          npm
Output                   server
Adapter                  @astrojs/cloudflare
Integrations             astro-robots-txts

If this issue only occurs in one browser, which browser is a problem?

No response

Describe the Bug

Using the experimental deployment of Cloudflare Workers for Astro, caching does not seem to work for paths specified in _headers.

Response headers for static assets: cache-control: public, max-age=0, must-revalidate.

https://my-astro-app.thepredaytor.workers.dev/

public/_routes.json:

{
  "version": 1,
  "include": [
    "/*"
  ],
  "exclude": [
    "/_astro/*",
    "/.assetsignore",
    "/favicon.svg"
  ]
}

public/_headers:

/_astro/*
  Cache-Control: public, max-age=31557600, immutable

/favicon.ico
  Cache-Control: public, max-age=3600, immutable

/favicon.svg
  Cache-Control: public, max-age=3600, immutable

wrangler.toml:

#:schema node_modules/wrangler/config-schema.json
name = "my-astro-app"
compatibility_date = "2024-10-04"
compatibility_flags = ["nodejs_compat_v2"]
main = "./dist/_worker.js"
assets = { directory = "./dist", binding = "ASSETS" }

# Workers Logs
# Docs: https://developers.cloudflare.com/workers/observability/logs/workers-logs/
# Configuration: https://developers.cloudflare.com/workers/observability/logs/workers-logs/#enable-workers-logs
[observability]
enabled = true

[vars]
MY_VARIABLE = "test"

What's the expected result?

The response headers must represent those defined in the _headers file.

Link to Minimal Reproducible Example

https://stackblitz.com/github/predaytor/astro-cloudflare

Participation

• I am willing to submit a pull request for this issue.

[alexanderniebuhr]

@predaytor I need to confirm with the Cloudflare Team first, before I can give you an answer, but I'm not sure if Worker Assets support the _headers file in the same level as Pages do.

[petebacondarwin]

Yes, currently Workers + Assets does not read any of _headers, _redirects nor _routes.json.
The basic configuration of Workers + Assets appears to avoid the need for _routes.json in almost every case so far.

We are deciding what to do about the other two. Both can be handled in different ways with Workers.

For example it should be possible to setup Cloudflare Snippets in front of a Workers + Assets worker that can do things like redirects and modifying headers based on requests.

[predaytor]

Still trying to find a solution for caching on Workers (Assets Beta). Either we can use Cache Rules, or spin up an additional proxy Service Worker in front of the main worker.

I also modify the response for /_astro/* files by adding a special cache-control, assuming that it does not affect CDN caching, according to docs:

Modifying cache-control, CDN-Cache-Control, or Cloudflare-CDN-Cache-Control headers will not change the way Cloudflare caches an object. Instead, you should create a Cache Rule

Applying Cache Rules doesn't work for unknown reason, the CF-Cache-Status headers are absent. (trace log attached)

{
  "trace": [
    {
      "step_name": "http_request_cache_settings",
      "type": "phase",
      "matched": true,
      "public_name": "Cache Rules",
      "trace": [
        {
          "step_name": "a45633542c1d4a3a8e19b7df0cf8cacd",
          "type": "ruleset",
          "matched": true,
          "name": "default",
          "kind": "zone",
          "trace": [
            {
              "step_name": "df03fb9a63784d08aba0560339f9593b",
              "type": "rule",
              "matched": true,
              "action_parameter": {
                "cache": true,
                "edge_ttl": { "mode": "respect_origin" },
                "browser_ttl": { "mode": "respect_origin" },
                "respect_strong_etags": true,
                "cache_key": {
                  "ignore_query_strings_order": true,
                  "cache_deception_armor": true
                },
                "origin_error_page_passthru": true
              },
              "expression": "(http.request.uri.path wildcard \"/_astro/*\")",
              "description": "Cache Everything [Template]",
              "action": "set_cache_settings"
            }
          ]
        }
      ],
      "zoneName": "predaytor.com"
    },
  ],
}

[predaytor]

The only working solution is to deploy a proxy (via service bindings) on top of the main worker and manually modify the response of the assets that need to be cached:

export default {
	async fetch(request, env, ctx) {
		try {
			return await handleRequest(request, env, ctx);
		} catch (ex) {
			console.error(ex);
			return new Response('Internal server error', { status: 500 });
		}
	},
} satisfies ExportedHandler<Env>;

async function handleRequest(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
	let response = await env.app.fetch(request.clone());
	response = cacheStaticAssets(request, response);
	return response;
}

function cacheStaticAssets(request: Request, response: Response): Response {
	// dprint-ignore
	const cacheableExtensions = new Set([
		"7z", "avi", "avif", "apk", "bin", "bmp", "bz2", "class", "css", "csv",
		"doc", "docx", "dmg", "ejs", "eot", "eps", "exe", "flac", "gif", "gz",
		"ico", "iso", "jar", "jpg", "jpeg", "js", "mid", "midi", "mkv", "mp3",
		"mp4", "ogg", "otf", "pdf", "pict", "pls", "png", "ppt", "pptx", "ps",
		"rar", "svg", "svgz", "swf", "tar", "tif", "tiff", "ttf", "webm", "webp",
		"woff", "woff2", "xls", "xlsx", "zip", "zst"
	]);

	const url = new URL(request.url);
	const extension = url.pathname.split('.').pop();

	response = new Response(response.body, response);

	if (extension && cacheableExtensions.has(extension)) {
		response.headers.set('Cache-Control', 'public, max-age=31536000, immutable');
	}

	return response;
}

[predaytor]

The thing is that the Cache Rules do work, but only if we place an proxy service (the same one described above) on top of the main worker (astro app). Without it, the deployed astro app does not take into account any Cache Rules and serves static assets as-is.

Both services are connected to a custom domain that is required for Redirect/Cache/Transform Rules to work.

[florian-lefebvre]

Since it seems related to Cloudflare not supporting headers, I'm closing this issue. Feel free to reopen if I'm wrong