Base64-encode "." and ".." in Pushgateway URL path segments (#1251)

A job or grouping key value of "." or ".." was put into the URL path
as is. These are dot segments: the Pushgateway router cleans the path
and answers with a 307 redirect to a different group (".." points at
the parent), so push_to_gateway, pushadd_to_gateway and
delete_from_gateway fail with "HTTP Error 307". Encode such values
with base64, as client_golang does.

Signed-off-by: sarankumar1325 <120080287+sarankumar1325@users.noreply.github.com>

Author: sarankumar1325

prometheus_client/exposition.py

@@ -822,9 +822,11 @@ def _escape_grouping_key(k, v):
     if v == "":
         # Per https://github.com/prometheus/pushgateway/pull/346.
         return k + "@base64", "="
-    elif '/' in v or ' ' in v:
+    elif '/' in v or ' ' in v or v in ('.', '..'):
         # Added in Pushgateway 0.9.0.
-        # Use base64 encoding for values containing slashes or spaces
+        # Use base64 encoding for values containing slashes or spaces, and
+        # for "." and "..", which would otherwise be removed from the URL
+        # path as dot segments (the Pushgateway answers with a redirect).
         return k + "@base64", base64.urlsafe_b64encode(v.encode("utf-8")).decode("utf-8")
     else:
         return k, quote_plus(v)

tests/test_exposition.py

@@ -317,6 +317,17 @@ def test_push_with_complex_groupingkey(self):
         self.assertEqual(self.requests[0][0].headers.get('content-type'), CONTENT_TYPE_PLAIN_0_0_4)
         self.assertEqual(self.requests[0][1], b'# HELP g help\n# TYPE g gauge\ng 0.0\n')
 
+    def test_push_with_groupingkey_dot_segments(self):
+        push_to_gateway(self.address, "my_job", self.registry, {'a': '.', 'b': '..'})
+        self.assertEqual(self.requests[0][0].command, 'PUT')
+        self.assertEqual(self.requests[0][0].path, '/metrics/job/my_job/a@base64/Lg==/b@base64/Li4=')
+        self.assertEqual(self.requests[0][1], b'# HELP g help\n# TYPE g gauge\ng 0.0\n')
+
+    def test_push_with_dot_segment_job(self):
+        push_to_gateway(self.address, "..", self.registry)
+        self.assertEqual(self.requests[0][0].command, 'PUT')
+        self.assertEqual(self.requests[0][0].path, '/metrics/job@base64/Li4=')
+
     def test_push_with_complex_job(self):
         push_to_gateway(self.address, "my/job", self.registry)
         self.assertEqual(self.requests[0][0].command, 'PUT')