refactor(telemetry): send the agentless backend URL as a URL object

The agent-telemetry fallback passed the agentless intake endpoint to `request`
as a string while the primary agentless path already constructed a `URL`. Build
it with `new URL` up front and guard it the same way, so an invalid endpoint is
logged and the request skipped rather than throwing from inside the request
helper.

Author: BridgeAR

packages/dd-trace/src/telemetry/send-data.js

@@ -182,23 +182,25 @@ function sendData (config, application, host, reqType, payload = {}, cb = () =>
         agentTelemetry = false
       }
       // figure out which data center to send to
-      const backendUrl = getAgentlessTelemetryEndpoint(config.site)
+      let backendUrl
+      try {
+        backendUrl = new URL(getAgentlessTelemetryEndpoint(config.site))
+      } catch {
+        log.error('Invalid Telemetry URL')
+        return
+      }
       const backendHeader = { ...options.headers, 'DD-API-KEY': config.apiKey }
       const backendOptions = {
         ...options,
         url: backendUrl,
         headers: backendHeader,
         path: '/api/v2/apmtelemetry',
       }
-      if (backendUrl) {
-        request(data, backendOptions, (error) => {
-          if (error) {
-            log.error('Error sending telemetry data', error)
-          }
-        })
-      } else {
-        log.error('Invalid Telemetry URL')
-      }
+      request(data, backendOptions, (error) => {
+        if (error) {
+          log.error('Error sending telemetry data', error)
+        }
+      })
     }
 
     if (!error && !agentTelemetry) {

packages/dd-trace/test/telemetry/send-data.spec.js

@@ -199,4 +199,41 @@ describe('sendData', () => {
     const { url } = options
     assert.deepStrictEqual(url, new URL('https://my-intake.example/'))
   })
+
+  it('sends the agentless backend telemetry with a URL object when the agent request fails', () => {
+    request.yields(new Error('agent unreachable'))
+
+    sendDataModule.sendData(
+      {
+        apiKey: 'secret-key',
+        site: 'datadoghq.eu',
+        tags: { 'runtime-id': '123' },
+      },
+      application,
+      host,
+      'req-type'
+    )
+
+    assert.strictEqual(request.callCount, 2)
+    const backendOptions = request.getCall(1).args[1]
+    assert.deepStrictEqual(backendOptions.url, new URL('https://instrumentation-telemetry-intake.datadoghq.eu'))
+    assert.strictEqual(backendOptions.headers['DD-API-KEY'], 'secret-key')
+  })
+
+  it('skips the agentless backend request when the endpoint URL is invalid', () => {
+    request.yields(new Error('agent unreachable'))
+
+    sendDataModule.sendData(
+      {
+        apiKey: 'secret-key',
+        site: 'x:notaport',
+        tags: { 'runtime-id': '123' },
+      },
+      application,
+      host,
+      'req-type'
+    )
+
+    assert.strictEqual(request.callCount, 1)
+  })
 })