fix: Capture WSGI variables early (#223)

* fix: Capture WSGI variables early

* doc: Explain reasoning behind change

Author: untitaker

sentry_sdk/integrations/wsgi.py

@@ -163,6 +163,25 @@ def close(self):
 
 
 def _make_wsgi_event_processor(environ):
+    # It's a bit unfortunate that we have to extract and parse the request data
+    # from the environ so eagerly, but there are a few good reasons for this.
+    #
+    # We might be in a situation where the scope/hub never gets torn down
+    # properly. In that case we will have an unnecessary strong reference to
+    # all objects in the environ (some of which may take a lot of memory) when
+    # we're really just interested in a few of them.
+    #
+    # Keeping the environment around for longer than the request lifecycle is
+    # also not necessarily something uWSGI can deal with:
+    # https://github.com/unbit/uwsgi/issues/1950
+
+    client_ip = get_client_ip(environ)
+    request_url = get_request_url(environ)
+    query_string = environ.get("QUERY_STRING")
+    method = environ.get("REQUEST_METHOD")
+    env = dict(_get_environ(environ))
+    headers = _filter_headers(dict(_get_headers(environ)))
+
     def event_processor(event, hint):
         with capture_internal_exceptions():
             # if the code below fails halfway through we at least have some data
@@ -171,22 +190,13 @@ def event_processor(event, hint):
             if _should_send_default_pii():
                 user_info = event.setdefault("user", {})
                 if "ip_address" not in user_info:
-                    user_info["ip_address"] = get_client_ip(environ)
-
-            if "url" not in request_info:
-                request_info["url"] = get_request_url(environ)
-
-            if "query_string" not in request_info:
-                request_info["query_string"] = environ.get("QUERY_STRING")
-
-            if "method" not in request_info:
-                request_info["method"] = environ.get("REQUEST_METHOD")
-
-            if "env" not in request_info:
-                request_info["env"] = dict(_get_environ(environ))
+                    user_info.setdefault("ip_address", client_ip)
 
-            if "headers" not in request_info:
-                request_info["headers"] = _filter_headers(dict(_get_headers(environ)))
+            request_info.setdefault("url", request_url)
+            request_info.setdefault("query_string", query_string)
+            request_info.setdefault("method", method)
+            request_info.setdefault("env", env)
+            request_info.setdefault("headers", headers)
 
         return event