only apply the backpressure to get object

Author: TingDaoK

include/aws/s3/s3_client.h

@@ -1220,7 +1220,7 @@ struct aws_future_void *aws_s3_meta_request_write(
  * no backpressure is being applied and data is being downloaded as fast as possible.
  *
  * WARNING: This feature is experimental.
- * Currently, backpressure is only applied to GetObject requests which are split into multiple parts,
+ * Currently, backpressure is applied to GetObject requests,
  * - If you set body_callback, no more data will be delivered once the window reaches 0.
  * - If you set body_callback_ex, you may still receive some data after the window reaches 0. TODO: fix it.
  */

source/s3_meta_request.c

@@ -1985,6 +1985,23 @@ static struct aws_s3_request_metrics *s_s3_request_finish_up_and_release_metrics
     return NULL;
 }
 
+static bool s_apply_backpressure(struct aws_s3_request *request) {
+    struct aws_s3_meta_request *meta_request = request->meta_request;
+    if (!meta_request->body_callback) {
+        return false;
+    }
+    if (!meta_request->client->enable_read_backpressure) {
+        return false;
+    }
+    if (meta_request->type == AWS_S3_META_REQUEST_TYPE_GET_OBJECT) {
+        return true;
+    }
+    if (aws_string_eq_c_str(request->operation_name, "GetObject")) {
+        return true;
+    }
+    return false;
+}
+
 /* Deliver events in event_delivery_array.
  * This task runs on the meta-request's io_event_loop thread. */
 static void s_s3_meta_request_event_delivery_task(struct aws_task *task, void *arg, enum aws_task_status task_status) {
@@ -2059,9 +2076,8 @@ static void s_s3_meta_request_event_delivery_task(struct aws_task *task, void *a
                     break;
                 }
 
-                if (meta_request->body_callback && meta_request->client->enable_read_backpressure) {
-                    /* If customer set the body callback, make sure we are not delivery them more than asked via the
-                     * callback. */
+                if (s_apply_backpressure(request)) {
+                    /* Apply backpressure for the request, only deliver the bytes that allowed to deliver. */
                     aws_byte_cursor_advance(&response_body, bytes_delivered_for_request);
                     if (response_body.len > (size_t)bytes_allowed_to_deliver) {
                         response_body.len = (size_t)bytes_allowed_to_deliver;