CHanges based on comment

src/python/grpcio_tests/tests_py3_only/interop/xds_interop_client.py

@@ -18,7 +18,6 @@
 import datetime
 import logging
 import signal
-import sys
 import threading
 import time
 from typing import (
@@ -31,6 +30,7 @@
     Sequence,
     Set,
     Tuple,
+    Union,
 )
 
 import grpc
@@ -67,6 +67,7 @@
 _METHOD_ENUM_TO_STR = {v: k for k, v in _METHOD_STR_TO_ENUM.items()}
 
 PerMethodMetadataType = Mapping[str, Sequence[Tuple[str, str]]]
+MetadataType = Sequence[Tuple[str, Union[str, bytes]]]
 # FutureFromCall is both a grpc.Call and grpc.Future
 FutureFromCallType = Any
 
@@ -82,7 +83,7 @@ class _StatsWatcher:
     _no_remote_peer: int
     _lock: threading.Lock
     _condition: threading.Condition
-    _metadata_keys: List[str]
+    _metadata_keys: Set[str]
     _include_all_metadata: bool
     _metadata_by_peer: DefaultDict[
         str, messages_pb2.LoadBalancerStatsResponse.MetadataByPeer
@@ -98,7 +99,7 @@ def __init__(self, start: int, end: int, metadata_keys: Iterable[str]):
         )
         self._condition = threading.Condition()
         self._no_remote_peer = 0
-        self._metadata_keys = [key.lower() for key in metadata_keys]
+        self._metadata_keys = set(key.lower() for key in metadata_keys)
         self._include_all_metadata = "*" in [
             key.strip() for key in metadata_keys
         ]
@@ -109,25 +110,20 @@ def __init__(self, start: int, end: int, metadata_keys: Iterable[str]):
     def _add_metadata(
         self,
         rpc_metadata: messages_pb2.LoadBalancerStatsResponse.RpcMetadata,
-        metadata: MetadataType,
-        type: messages_pb2.LoadBalancerStatsResponse.MetadataType,
+        metadata_to_add: MetadataType,
+        metadata_type: messages_pb2.LoadBalancerStatsResponse.MetadataType,
     ) -> None:
-        for key, value in metadata:
+        for key, value in metadata_to_add:
             if self._include_all_metadata or key.lower() in self._metadata_keys:
-                metadata_entry = (
-                    messages_pb2.LoadBalancerStatsResponse.MetadataEntry()
-                )
-                metadata_entry.key = key
-                metadata_entry.value = value
-                metadata_entry.type = type
-
-                rpc_metadata.metadata.append(metadata_entry)
+                rpc_metadata.metadata.append(
+                    messages_pb2.LoadBalancerStatsResponse.MetadataEntry(key=key, value=value, type=metadata_type))
 
     def on_rpc_complete(
         self,
         request_id: int,
         peer: str,
         method: str,
+        *,
         initial_metadata: MetadataType,
         trailing_metadata: MetadataType,
     ) -> None:
@@ -315,22 +311,22 @@ def _on_rpc_done(
                 rpc_id,
                 hostname,
                 method,
-                future.initial_metadata(),
-                future.trailing_metadata(),
+                initial_metadata = future.initial_metadata(),
+                trailing_metadata = future.trailing_metadata(),
             )
 
 
 def _remove_completed_rpcs(
-    futures: Mapping[int, FutureFromCallType], print_response: bool
+    rpc_futures: Mapping[int, FutureFromCallType], print_response: bool
 ) -> None:
     logger.debug("Removing completed RPCs")
     done = []
-    for future_id, (future, method) in futures.items():
+    for future_id, (future, method) in rpc_futures.items():
         if future.done():
             _on_rpc_done(future_id, future, method, args.print_response)
             done.append(future_id)
     for rpc_id in done:
-        del futures[rpc_id]
+        del rpc_futures[rpc_id]
 
 
 def _cancel_all_rpcs(futures: Mapping[int, Tuple[grpc.Future, str]]) -> None: