Wait until all data in buffer is flushed to client when upstream server finishes.

proxy/http/handler.py

@@ -37,6 +37,8 @@ class HttpProtocolHandler(BaseTcpServerHandler[HttpClientConnection]):
     Accepts `Client` connection and delegates to HttpProtocolHandlerPlugin.
     """
 
+    server_teared = False
+
     def __init__(self, *args: Any, **kwargs: Any):
         super().__init__(*args, **kwargs)
         self.start_time: float = time.time()
@@ -145,15 +147,19 @@ class HttpProtocolHandler(BaseTcpServerHandler[HttpClientConnection]):
             teardown = await self.plugin.write_to_descriptors(writables)
             if teardown:
                 return True
-        # Read from ready to read sockets
-        teardown = await self.handle_readables(readables)
-        if teardown:
-            return True
-        # Invoke plugin.read_from_descriptors
-        if self.plugin:
-            teardown = await self.plugin.read_from_descriptors(readables)
+        if not self.server_teared:
+            # Read from ready to read sockets
+            teardown = await self.handle_readables(readables)
             if teardown:
-                return True
+                self.server_teared = True
+            # Invoke plugin.read_from_descriptors
+            if self.plugin:
+                teardown = await self.plugin.read_from_descriptors(readables)
+                if teardown:
+                    self.server_teared = True
+        if self.server_teared and not self.work.has_buffer():
+            # Wait until client buffer flushed when server teared down.
+            return True
         return False
 
     def handle_data(self, data: memoryview) -> Optional[bool]: