Use the original URL when requests are forwarded

src/handler.ts

@@ -132,34 +132,38 @@ async function handleRequest(event: FetchEvent): Promise<Response> {
   }
 
   let response: Response
-  if (request.url.includes('forward=true') == true) {
+  let url = request.headers.get('x-original-url') || request.url
+  // If the request contains a 'x-original-url' header we understand that this request is forwarded
+  // to the worker and that therefor the upstream should not be fetched. We use a custom header to
+  // change as little as possible from the original request.
+  if (request.headers.get('x-original-url') != null) {
     response = new Response('ok', { status: 200 })
   } else {
     // fetch the original request
     console.log(`Fetching origin ${request.url}`)
     response = await fetch(request.url, request)
   }
 
-  if (EXCLUDE.js && JAVASCRIPT_REGEX.test(request.url)) {
+  if (EXCLUDE.js && JAVASCRIPT_REGEX.test(url)) {
     return response
   }
 
-  if (EXCLUDE.css && CSS_REGEX.test(request.url)) {
+  if (EXCLUDE.css && CSS_REGEX.test(url)) {
     return response
   }
 
-  if (EXCLUDE.images && IMAGE_REGEX.test(request.url)) {
+  if (EXCLUDE.images && IMAGE_REGEX.test(url)) {
     return response
   }
 
-  let parsed = new URL(request.url)
+  let parsed = new URL(url)
   let userAgent = request.headers.get('user-agent')
 
   parser.setUA(`${userAgent}`)
 
   let labels = {
     method: request.method,
-    url: request.url,
+    url: url,
     status: response.status,
     referer: request.headers.get('referer'),
     user_agent: userAgent,

test/handler.ts

@@ -8,10 +8,10 @@ describe('request handler', () => {
 
   it('sends payload to storage', async () => {
     const headers: HeadersInit = new Headers({
+      host: 'some.google.host',
       'x-forwarded-proto': 'https',
       'cf-ipcountry': 'US',
       'cf-connecting-ip': '17.110.220.180',
-      host: 'some.google.host',
       'user-agent':
         'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_2) AppleWebKit/601.3.9 (KHTML, like Gecko) Version/9.0.2 Safari/601.3.9',
     })
@@ -38,6 +38,40 @@ describe('request handler', () => {
     )
     expect(body).to.not.include('17.110.220.180')
   })
+
+  it('avoid fetching upstream when the URL is forwarded', async () => {
+    const headers: HeadersInit = new Headers({
+      host: 'dashflare.test.workers.dev',
+      'x-forwarded-proto': 'https',
+      'cf-ipcountry': 'US',
+      'cf-connecting-ip': '17.110.220.180',
+      'user-agent':
+        'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_2) AppleWebKit/601.3.9 (KHTML, like Gecko) Version/9.0.2 Safari/601.3.9',
+      'x-original-url': 'https://example.com',
+      referer: 'https://t.co/gJV9DEbJVy',
+    })
+
+    const event = new FetchEvent('fetch', {
+      request: new Request('https://dashflare.test.workers.dev', {
+        headers,
+      }),
+    })
+
+    const res = await handleRequest(event)
+    expect(await res.text()).to.equal('ok')
+
+    let body = fetchMock.calls('http://loki:3100/api/prom/push')[1][1].body
+    expect(body).to.satisfy((string) =>
+      [
+        'status=200',
+        // domain is extracted from the x-original-url header
+        'domain=example.com',
+        // the referer of the original request is detected and parsed
+        'network=twitter',
+        'type=social',
+      ].every((bit) => string.includes(bit)),
+    )
+  })
 })
 
 describe('preprocessing', () => {