[Azure Monitor] [OTEL Exporter] Fix azure monitor redirect error logging (Azure#27321)

Author: TimoWilhelm

sdk/monitor/azure-monitor-opentelemetry-exporter/azure/monitor/opentelemetry/exporter/export/_base.py

@@ -206,18 +206,22 @@ def _transmit(self, envelopes: List[TelemetryItem]) -> ExportResult:
                     self._consecutive_redirects = self._consecutive_redirects + 1
                     if self._consecutive_redirects < self.client._config.redirect_policy.max_redirects:  # pylint: disable=W0212
                         if response_error.response and response_error.response.headers:
+                            redirect_has_headers = True
                             location = response_error.response.headers.get("location")
-                            if location:
-                                url = urlparse(location)
-                                if url.scheme and url.netloc:
-                                    # Change the host to the new redirected host
-                                    self.client._config.host = "{}://{}".format(url.scheme, url.netloc)  # pylint: disable=W0212
-                                    # Attempt to export again
-                                    result =  self._transmit(envelopes)
-                        if not self._is_stats_exporter():
-                            logger.error(
-                                "Error parsing redirect information."
-                            )
+                            url = urlparse(location)
+                        else:
+                            redirect_has_headers = False
+                        if redirect_has_headers and url.scheme and url.netloc:
+                            # Change the host to the new redirected host
+                            self.client._config.host = "{}://{}".format(url.scheme, url.netloc)  # pylint: disable=W0212
+                            # Attempt to export again
+                            result = self._transmit(envelopes)
+                        else:
+                            if not self._is_stats_exporter():
+                                logger.error(
+                                    "Error parsing redirect information.",
+                                )
+                            result = ExportResult.FAILED_NOT_RETRYABLE
                     else:
                         if not self._is_stats_exporter():
                             logger.error(

sdk/monitor/azure-monitor-opentelemetry-exporter/tests/test_base_exporter.py

@@ -192,6 +192,32 @@ def test_transmit_http_error_redirect(self):
         self._base.client._config.redirect_policy.max_redirects = prev_redirects
         self._base.client._config.host = prev_host
 
+    def test_transmit_http_error_redirect_missing_headers(self):
+        response = HttpResponse(None, None)
+        response.status_code = 307
+        response.headers = None
+        error = HttpResponseError(response=response)
+        prev_host = self._base.client._config.host
+        with mock.patch.object(AzureMonitorClient, 'track') as post:
+            post.side_effect = error
+            result = self._base._transmit(self._envelopes_to_export)
+            self.assertEqual(result, ExportResult.FAILED_NOT_RETRYABLE)
+            self.assertEqual(post.call_count, 1)
+            self.assertEqual(self._base.client._config.host, prev_host)
+
+    def test_transmit_http_error_redirect_invalid_location_header(self):
+        response = HttpResponse(None, None)
+        response.status_code = 307
+        response.headers = {"location":"123"}
+        error = HttpResponseError(response=response)
+        prev_host = self._base.client._config.host
+        with mock.patch.object(AzureMonitorClient, 'track') as post:
+            post.side_effect = error
+            result = self._base._transmit(self._envelopes_to_export)
+            self.assertEqual(result, ExportResult.FAILED_NOT_RETRYABLE)
+            self.assertEqual(post.call_count, 1)
+            self.assertEqual(self._base.client._config.host, prev_host)
+
     def test_transmit_request_error(self):
         with mock.patch.object(AzureMonitorClient, 'track', throw(ServiceRequestError, message="error")):
             result = self._base._transmit(self._envelopes_to_export)