@@ -346,7 +346,8 @@ def create_subscription(
 
                 If a dict is provided, it must be of the same form as the protobuf
                 message :class:`~google.cloud.pubsub_v1.types.ExpirationPolicy`
-            filter_ (str): An expression written in the Cloud Pub/Sub filter language. If
+            filter_ (str): An expression written in the Pub/Sub `filter
+                language <https://cloud.google.com/pubsub/docs/filtering>`__. If
                 non-empty, then only ``PubsubMessage``\ s whose ``attributes`` field
                 matches the filter are delivered on this subscription. If empty, then no
                 messages are filtered out.
 
@@ -191,7 +191,8 @@ message PubsubMessage {
   bytes data = 1;
 
   // Attributes for this message. If this field is empty, the message must
-  // contain non-empty data.
+  // contain non-empty data. This can be used to filter messages on the
+  // subscription.
   map<string, string> attributes = 2;
 
   // ID of this message, assigned by the server when the message is published.
@@ -700,7 +701,8 @@ message Subscription {
   // value for `expiration_policy.ttl` is 1 day.
   ExpirationPolicy expiration_policy = 11;
 
-  // An expression written in the Cloud Pub/Sub filter language. If non-empty,
+  // An expression written in the Pub/Sub [filter
+  // language](https://cloud.google.com/pubsub/docs/filtering). If non-empty,
   // then only `PubsubMessage`s whose `attributes` field matches the filter are
   // delivered on this subscription. If empty, then no messages are filtered
   // out.
@@ -1107,6 +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