feature: Add flow control settings for StreamingPullRequest to pubsub…

….proto

PiperOrigin-RevId: 317914250

google/pubsub/v1/pubsub.proto

@@ -1109,6 +1109,28 @@ message StreamingPullRequest {
   // transferred to the new stream. The same client_id should not be used for
   // different client instances.
   string client_id = 6;
+
+  // Flow control settings for the maximum number of outstanding messages. When
+  // there are `max_outstanding_messages` or more currently sent to the
+  // streaming pull client that have not yet been acked or nacked, the server
+  // stops sending more messages. The sending of messages resumes once the
+  // number of outstanding messages is less than this value. If the value is
+  // <= 0, there is no limit to the number of outstanding messages. This
+  // property can only be set on the initial StreamingPullRequest. If it is set
+  // on a subsequent request, the stream will be aborted with status
+  // `INVALID_ARGUMENT`.
+  int64 max_outstanding_messages = 7;
+
+  // Flow control settings for the maximum number of outstanding bytes. When
+  // there are `max_outstanding_bytes` or more worth of messages currently sent
+  // to the streaming pull client that have not yet been acked or nacked, the
+  // server will stop sending more messages. The sending of messages resumes
+  // once the number of outstanding bytes is less than this value. If the value
+  // is <= 0, there is no limit to the number of outstanding bytes. This
+  // property can only be set on the initial StreamingPullRequest. If it is set
+  // on a subsequent request, the stream will be aborted with status
+  // `INVALID_ARGUMENT`.
+  int64 max_outstanding_bytes = 8;
 }
 
 // Response for the `StreamingPull` method. This response is used to stream