Bug 1372639 - Track the time spent redirecting when making requests

By default New Relic only tracks the overall time spent making an
external HTTP request, when this could in fact cover multiple
sub-requests, if the first redirected.

This adds a New Relic custom event that tracks the time spent
redirecting, to help assess the priority of bug 1348072.

treeherder/etl/common.py

@@ -3,6 +3,7 @@
 import logging
 import re
 
+import newrelic.agent
 import requests
 from dateutil import parser
 from django.conf import settings
@@ -41,6 +42,15 @@ def make_request(url, method='GET', headers=None,
                                 headers=headers,
                                 timeout=timeout,
                                 **kwargs)
+
+    if response.history:
+        params = {
+            'url': url,
+            'redirects': len(response.history),
+            'duration': sum(r.elapsed.total_seconds() for r in response.history)
+        }
+        newrelic.agent.record_custom_event('RedirectedRequest', params=params)
+
     response.raise_for_status()
     return response