Make apply_http2_patches_for_grpc_support safe for potential re-use

Author: purcell

typedb/localstack_typedb/utils/h2_proxy.py

@@ -55,6 +55,8 @@ def close(self):
             pass
 
 
+patch_counter = 1
+
 def apply_http2_patches_for_grpc_support(
     target_host: str, target_port: int, request_matcher: ProxyRequestMatcher
 ):
@@ -102,17 +104,28 @@ def received_from_http2_client(self, data, default_handler):
         def close(self):
             self.backend.close()
 
+    # In case multiple such patches are attached (which is likely inadvisable anyway),
+    # we need the instance vars to not clash. A simple counter at least shows us
+    # when we've done that.
+    global patch_counter
+    bufvar = f"_ls_buffer_{patch_counter}"
+    patch_counter += 1
+    def bufget(o) -> ForwardingBuffer:
+        return getattr(o, bufvar)
+    def bufset(o, v: ForwardingBuffer):
+        return setattr(o, bufvar, v)
+
     @patch(H2Connection.connectionMade)
     def _connectionMade(fn, self, *args, **kwargs):
-        self._ls_forwarding_buffer = ForwardingBuffer(self.transport)
+        bufset(self, ForwardingBuffer(self.transport))
 
     @patch(H2Connection.dataReceived)
     def _dataReceived(fn, self, data, *args, **kwargs):
-        self._ls_forwarding_buffer.received_from_http2_client(data, lambda d: fn(d, *args, **kwargs))
+        bufget(self).received_from_http2_client(data, lambda d: fn(d, *args, **kwargs))
 
     @patch(H2Connection.connectionLost)
     def connectionLost(fn, self, *args, **kwargs):
-        self._ls_forwarding_buffer.close()
+        bufget(self).close()
 
 
 def get_headers_from_data_stream(data_list: Iterable[bytes]) -> Headers: