Include pushgateway response body in HTTP error messages

prometheus_client/exposition.py

@@ -515,9 +515,18 @@ def handle() -> None:
         request.get_method = lambda: method  # type: ignore
         for k, v in headers:
             request.add_header(k, v)
-        resp = build_opener(base_handler).open(request, timeout=timeout)
+        try:
+            resp = build_opener(base_handler).open(request, timeout=timeout)
+        except HTTPError as e:
+            # The pushgateway reports what was wrong with the request in the
+            # response body, so include it in the error message.
+            body = e.read().decode('utf-8', 'replace').strip()
+            if not body:
+                raise
+            raise HTTPError(e.url, e.code, f'{e.reason} ({body})', e.headers, None) from e
         if resp.code >= 400:
-            raise OSError(f"error talking to pushgateway: {resp.code} {resp.msg}")
+            body = resp.read().decode('utf-8', 'replace').strip()
+            raise OSError(f"error talking to pushgateway: {resp.code} {resp.msg} ({body})")
 
     return handle
 

tests/test_exposition.py

@@ -231,7 +231,12 @@ def setUp(self):
 
         class TestHandler(BaseHTTPRequestHandler):
             def do_PUT(self):
-                if 'with_basic_auth' in self.requestline and self.headers['authorization'] != 'Basic Zm9vOmJhcg==':
+                error_body = None
+                if 'error' in self.requestline:
+                    error_body = b'text format parsing error in line 1'
+                    self.send_response(500)
+                    self.send_header('Content-Length', str(len(error_body)))
+                elif 'with_basic_auth' in self.requestline and self.headers['authorization'] != 'Basic Zm9vOmJhcg==':
                     self.send_response(401)
                 elif 'redirect' in self.requestline and redirect_flag not in self.requestline:
                     # checks for an initial test request with 'redirect' but without the redirect_flag,
@@ -243,6 +248,8 @@ def do_PUT(self):
                 length = int(self.headers['content-length'])
                 requests.append((self, self.rfile.read(length)))
                 self.end_headers()
+                if error_body:
+                    self.wfile.write(error_body)
 
             do_POST = do_PUT
             do_DELETE = do_PUT
@@ -324,6 +331,12 @@ def test_push_with_complex_job(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_error_includes_response_body(self):
+        with self.assertRaises(urllib.error.HTTPError) as cm:
+            push_to_gateway(self.address, "error_job", self.registry)
+        self.assertEqual(cm.exception.code, 500)
+        self.assertIn('text format parsing error in line 1', str(cm.exception))
+
     def test_pushadd(self):
         pushadd_to_gateway(self.address, "my_job", self.registry)
         self.assertEqual(self.requests[0][0].command, 'POST')