A Cloudflare Worker to handle requests to static.pantsbuild.org.

build-support/cloudflare/BUILD

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+# Copyright 2023 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+javascript_sources()

build-support/cloudflare/redirect2githubpages.js

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+// Copyright 2023 Pants project contributors (see CONTRIBUTORS.md).
+// Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+// This is the source code for a Cloudflare Worker that redirects requests
+// (currently against static.pantsbuild.org) to https://pantsbuild.github.io
+// and logs them with Google Analytics.
+//
+// (For context, a Cloudflare Worker (https://developers.cloudflare.com/workers/)
+// is a cloud function that runs on the Cloudflare edge network.)
+//
+// To deploy this code, log in to our Cloudflare account, and go to
+// Workers Routes > Manage Workers > redirect2githubpages > Quick edit. Then paste the
+// code in the text area. You can use the UI to send a test request to test out
+// your changes before clicking "Save and Deploy".
+
+// Note that we have a proxied DNS A record pointing static.pantsbuild.org to a dummy IP.
+// That is necessary for this worker to work.
+
+// GA4_API_SECRET must be set under Settings > Variables > Environment Variables for the worker.
+// The secret is obtained under "Measurement Protocol API secrets" on the stream details page
+// in Google Analytics.
+const apiSecret = GA4_API_SECRET;
+
+// The measurement id is obtained from the stream details page in Google Analytics.
+const measurementId = "G-Z7HQ5KDHDP";
+
+const ga4URL = `https://www.google-analytics.com/mp/collect?measurement_id=${measurementId}&api_secret=${apiSecret}`;
+
+function sendToGA4(headers, host, path) {
+  const clientId = Math.random().toString(16).substring(2);
+  const clientIP = headers.get("CF-Connecting-IP") || "";
+
+  // GA drops hits with non-browser user agents on the floor,
+  // including curl, which is what we expect people to mostly use.
+  // So we detect if the userAgent isn't a browser,and adjust if so.
+  let userAgent = headers.get("User-Agent") || "";
+  if (
+    !userAgent.toLowerCase().startsWith("mozilla") &&
+    !userAgent.toLowerCase().startsWith("opera")
+  ) {
+    userAgent = ""; // GA accepts an empty user agent, go figure.
+  }
+
+  const events = [
+    {
+      name: "page_view",
+      params: {
+        page_host: host,
+        page_path: path,
+        ip: clientIP,
+        user_agent: userAgent,
+      },
+    },
+  ];
+
+  const data = {
+    client_id: clientId,
+    events: events,
+  };
+
+  const payload = JSON.stringify(data);
+  const gaHeaders = new Headers();
+  gaHeaders.append("Content-Type", "application/json");
+  return fetch(ga4URL, { method: "POST", headers: gaHeaders, body: payload });
+}
+
+// UA is being phased out in mid-2023, so we'll delete this once we have GA4 set up properly.
+function sendToUA(headers, host, path) {
+  const url = "https://www.google-analytics.com/collect";
+  const uuid = Math.random().toString(16).substring(2);
+  const clientIP = headers.get("CF-Connecting-IP") || "";
+
+  // GA drops hits with non-browser user agents on the floor,
+  // including curl, which is what we expect people to mostly use.
+  // So we detect if the userAgent isn't a browser,and adjust if so.
+  userAgent = headers.get("User-Agent") || "";
+  if (
+    !userAgent.toLowerCase().startsWith("mozilla") &&
+    !userAgent.toLowerCase().startsWith("opera")
+  ) {
+    userAgent = ""; // GA accepts an empty user agent, go figure.
+  }
+
+  data = {
+    v: "1",
+    tid: "UA-78111411-2",
+    cid: uuid,
+    t: "pageview",
+    dh: host,
+    dp: path,
+    uip: clientIP,
+    ua: userAgent,
+  };
+
+  const payload = new URLSearchParams(data).toString();
+  return fetch(url, { method: "POST", body: payload });
+}
+
+async function handleRequest(event) {
+  const url = new URL(event.request.url);
+  const { pathname, search } = url;
+  const destinationURL = "https://pantsbuild.github.io" + pathname + search;
+  event.waitUntil(
+    Promise.all([
+      sendToGA4(event.request.headers, url.host, pathname),
+      sendToUA(event.request.headers, url.host, pathname),
+    ])
+  );
+  return Response.redirect(destinationURL, 302);
+}
+
+addEventListener("fetch", async (event) => {
+  event.respondWith(handleRequest(event));
+});