feat: add support for skew protection by vicb · Pull Request #746 · opennextjs/opennextjs-cloudflare

vicb · 2025-06-20T12:59:38Z

There are 2 main files in this PR:

packages/cloudflare/src/cli/commands/skew-protection.ts (build time)

This builds a mapping from deploymentId to the worker version at build time.
Note that because the worker you are building has no version yet, "current" is used instead.

packages/cloudflare/src/cli/templates/skew-protection.ts (runtime)

At runtime, if a particular version is requested and it is present in the mapping,
we'll fetch the result from a preview URL with a hostname of <version>-<worker_name>.<domain>.workers.dev

How to use it:

set cloudflare.skewProtection.enabled to true in your OpenNext config
provide values for the new env vars added to packages/cloudflare/src/api/cloudflare-context.ts
update your next config to set the deployementId - you can use the getDeploymentId() helper
set run_worker_first to true

Docs PR opennextjs/docs#164

TODO:

add tests
handle assets (will need to run the worker before the asset worker)
follow-up: move the skew protection logic in the aws/routing layer with pluggable overrides -> see feat: add support for serving assets from the routing layer #768

changeset-bot · 2025-06-20T12:59:41Z

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Latest commit: 17064f4

The changes in this PR will be included in the next version bump.

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@opennextjs/cloudflare	Minor

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pkg-pr-new · 2025-06-20T13:00:32Z

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npm i https://pkg.pr.new/@opennextjs/cloudflare@746

commit: 17064f4

conico974

I just took a really quick look for now, will make a proper review later

james-elicx

I think this is looking pretty good on my initial read though. Going to have another look later on as well.

james-elicx

I think this looks good and the logic makes sense to me.

It might be nice for us to look at having an e2e that runs against a deployment at some point in the future, for testing features like this.

sommeeeer

LGTM

vicb · 2025-06-24T16:33:29Z

Thanks for the review @sommeeeer !

conico974

Just a few nits/question, other than that LGTM

conico974 · 2025-06-24T20:20:01Z

+ * @param options Options to pass to `getPlatformProxy`, i.e. to set the environment
+ * @returns the env vars
+ */
+export async function getEnvFromPlatformProxy(options: GetPlatformProxyOptions) {


I think we should have only one instance of this, that we spawn at the beginning and that we dispose at the end. It's a bit wasteful to launch multiple workerd process.
And once we have support for remote bindings here, we could reuse it to populate the cache directly (which should be way faster)

conico974 · 2025-06-24T20:32:58Z

+		path = path.slice(basePath.length);
+	}
+	if (path.startsWith("/_next/static/") || isFileInTree(path, __CF_ASSETS_TREE__)) {
+		return assets.fetch(request);


Does this one respect the _headers file ?

It should but I'll test that

Actually it doesn't, see https://developers.cloudflare.com/workers/static-assets/headers/#custom-headers

Follow up:

Check what Next does add by default and apply that in the asset resolver

Document how to override (using middleware or Next config)

Co-authored-by: conico974 <nicodorseuil@yahoo.fr>

vicb · 2025-07-09T09:42:05Z

I have rebase the PR on top of #768 as the asset resolver will be used to resolve the assets from previous versions (when run_worker_first=false the worker does not get a chance to override the assets as they are served even before the worker is executed).

Docs plan (today/tomorrow)

write some new doc for the asset resolver
update the existing doc for the skew protection to sync with this PR

@dario-piotrowicz @james-elicx @conico974 please take a look at the PR when you get a chance.

Thanks!

conico974

Just a few nits/question, but other than that LGTM.
BTW do we want to allow users to override the assets resolver ?

conico974 · 2025-07-09T11:55:42Z


 export async function GET() {
-	return new Response(JSON.stringify(process.env));
+	return new Response(JSON.stringify(process.env, null, 2), {


Why this change ?

I used this API for debugging (the env contains the build id, deployment id, and deployment mapping) and the response was easier to read when formatted this way.

conico974 · 2025-07-09T12:01:17Z

+
+			const now = Date.now();
+
+			client.workers.scripts.versions.list = vi.fn().mockReturnValue([


Can the client return this in the wrong order ? This is not tested here

In my experience, the client always returns an ordered lists.

BUT I agree we should not rely on the result of a few experiments.

That's why I pay special attention to not order the input (~2 is before ~1) and you can see that the output of listWorkerVersions is ordered (~2 after ~1)

Co-authored-by: conico974 <nicodorseuil@yahoo.fr>

vicb · 2025-07-09T15:20:28Z

BTW do we want to allow users to override the assets resolver ?

Yes we should but I agree that our current defineCloudflareConfig is not flexible enough:

export default {
	...defineCloudflareConfig({
		incrementalCache: r2IncrementalCache,
	}),
	cloudflare: {
		skewProtection: {
			enabled: false,
		},
	},
} satisfies OpenNextConfig;

As of today users can override the assets resolver but the syntax is not great.

I'll try to work on a better way to do that.

vicb force-pushed the vicb/skew-protection branch from 2356748 to 0a6f2dd Compare June 20, 2025 13:11

vicb requested review from conico974, dario-piotrowicz, james-elicx and sommeeeer and removed request for conico974 June 20, 2025 13:11

vicb force-pushed the vicb/skew-protection branch from 0a6f2dd to 18ba05a Compare June 20, 2025 13:14

vicb requested a review from IgorMinar June 20, 2025 13:26

conico974 reviewed Jun 20, 2025

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Comment thread packages/cloudflare/src/cli/templates/skew-protection.ts Outdated

james-elicx reviewed Jun 20, 2025

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Comment thread packages/cloudflare/src/cli/commands/skew-protection.ts Outdated

james-elicx approved these changes Jun 22, 2025

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vicb force-pushed the vicb/skew-protection branch 4 times, most recently from 4c21542 to 471111c Compare June 23, 2025 12:13

vicb mentioned this pull request Jun 24, 2025

[Blocked by release] docs(cloudflare): skew protection opennextjs/docs#164

Merged

vicb changed the title ~~[Preview] Add support for skew protection~~ Add support for skew protection Jun 24, 2025

sommeeeer reviewed Jun 24, 2025

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Comment thread packages/cloudflare/src/cli/build/open-next/compile-skew-protection.ts Outdated

sommeeeer reviewed Jun 24, 2025

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Comment thread packages/cloudflare/src/cli/build/open-next/compile-skew-protection.ts Outdated

sommeeeer approved these changes Jun 24, 2025

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Comment thread packages/cloudflare/src/cli/commands/skew-protection.ts

Comment thread packages/cloudflare/src/cli/templates/skew-protection.ts Outdated

sommeeeer approved these changes Jun 24, 2025

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conico974 approved these changes Jun 24, 2025

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vicb force-pushed the vicb/skew-protection branch from 2f1f47b to 45edc9f Compare June 30, 2025 12:50

vicb changed the title ~~Add support for skew protection~~ [WIP] Add support for skew protection Jul 4, 2025

vicb force-pushed the vicb/skew-protection branch from 43be1dd to 12c4094 Compare July 8, 2025 10:03

vicb mentioned this pull request Jul 9, 2025

feat: add config flag support for deploy, preview, and upload commands #762

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vicb force-pushed the vicb/skew-protection branch from 12c4094 to 637d8f4 Compare July 9, 2025 09:32

vicb changed the title ~~[WIP] Add support for skew protection~~ feat: add support for skew protection Jul 9, 2025

Add support for skew protection

ca41ac2

Co-authored-by: conico974 <nicodorseuil@yahoo.fr>

vicb force-pushed the vicb/skew-protection branch from 637d8f4 to ca41ac2 Compare July 9, 2025 09:39

vicb requested review from conico974 and james-elicx July 9, 2025 09:42

conico974 approved these changes Jul 9, 2025

View reviewed changes

Update packages/cloudflare/src/cli/templates/skew-protection.ts

22cdb36

Co-authored-by: conico974 <nicodorseuil@yahoo.fr>

james-elicx approved these changes Jul 9, 2025

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vicb added 2 commits July 9, 2025 17:07

fixup! serve the current version on unkown dep

6b75bcf

fixup! expand doc for CF_WORKER_NAME

17064f4

vicb merged commit 6d020fe into main Jul 10, 2025
7 of 8 checks passed

vicb deleted the vicb/skew-protection branch July 10, 2025 08:13

workers-frameworks mentioned this pull request Jul 8, 2025

Version Packages #771

Merged

dario-piotrowicz mentioned this pull request Jul 14, 2025

chore: add skew-version support in Cloudflare open-next worker nodejs/nodejs.org#7980

Merged

5 tasks


		const now = Date.now();

		client.workers.scripts.versions.list = vi.fn().mockReturnValue([

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