Using Next.js rewrites as a reverse proxy

Thank you for the docs! As you see in the title we have a conflict about the trailing slash between SEO crawlers and the posthog settings:

PostHog requires

skipTrailingSlashRedirect: true

API requests like /ph_proxy_path/ with or without a trailing slash must not be redirected.

But SEO crawler penalize duplicate content, meaning my website is accessible at both /page and /page/, creating duplicate pages from Google's perspective...

What is the recommended solution? Just manually adjust all urls in the nextjs middleware?

seeing this after deploying my app to Cloudflare Workers

name: "TypeError", trigger: "POST /ingest/i/v0/e/", message: "Response with null body status (101, 204, 205, or 304) cannot have a body.",

video doesn't use the ui_host setting on init, but current docs mention it alongside api_host.

should we add it? what should it's value be?

What kind of potential security issues might be out there while not using managed reverse proxy and configured them in nextjs project?

Seeing this below after doing the setting as mentioned in the article

Uncaught SyntaxError: Unexpected token '<' (at config.js:1:1)

This is where config is getting created:

Failed to proxy https://us-assets.i.posthog.com/static/recorder.js?v=1.140.1 Error: socket hang up at connResetException (node:internal/errors:720:14) at TLSSocket.socketCloseListener (node:_http_client:474:25) at TLSSocket.emit (node:events:529:35) at node:net:350:12 at TCP.done (node:_tls_wrap:657:7) at TCP.callbackTrampoline (node:internal/async_hooks:128:17) { code: 'ECONNRESET' }

Failed to proxy https://us-assets.i.posthog.com/static/recorder.js?v=1.140.1 Error: socket hang up at connResetException (node:internal/errors:720:14) at TLSSocket.socketCloseListener (node:_http_client:474:25) at TLSSocket.emit (node:events:529:35) at node:net:350:12 at TCP.done (node:_tls_wrap:657:7) at TCP.callbackTrampoline (node:internal/async_hooks:128:17) { code: 'ECONNRESET' }

The config above includes this:

// This is required to support PostHog trailing slash API requests
  skipTrailingSlashRedirect: true, 

Is this required for the proxy to work? Or only for specific cases?

The docs on next.config.js show a trailingSlash key as well.

I have reverse proxy like this:

next.config.mjs

async rewrites() {
    return [
      {
        source: "/ingest/static/:path*",
        destination: "https://us-assets.i.posthog.com/static/:path*",
      },
      {
        source: "/ingest/:path*",
        destination: "https://us.i.posthog.com/:path*",
      },
    ];
  }

and this:

if (typeof window !== 'undefined') {
  posthog.init(env.NEXT_PUBLIC_POSTHOG_KEY, {
    api_host: `${env.NEXT_PUBLIC_APP_BASE_URL}/ingest`,
    ui_host: env.NEXT_PUBLIC_POSTHOG_HOST,
    capture_pageview: true,
  });
}

and some logs are being recoreded and some not, i see in vercel people are hitting on pages but some of the logs are not being added

Since requests are now being passed to other subdomains as well I imagine we need an update on these?

When trying to do this, I'm seeing a few different errors.

For the request to the posthog /decide/ endpoint I get a 401 response back with this body:

{
    "type": "authentication_error",
    "code": "no_api_key",
    "detail": "No project API key provided. You can find your project API key in PostHog project settings.",
    "attr": null
}

then the following request to the /e/ endpoint I get a 400 response back with this body:

{
    "type": "validation_error",
    "code": "no_data",
    "detail": "No data found. Make sure to use a POST request when sending the payload in the body of the request.",
    "attr": null
}

But without rewrites both these request work without issue. I can see the cookie passed along with the request. Only thing I notice as a difference is the one with rewrites doesn't seem to have a request body.