Support file-like objects in CRT transfer manager

.changes/next-release/enhancement-crt-51520.json

@@ -0,0 +1,5 @@
+{
+  "type": "enhancement",
+  "category": "``crt``",
+  "description": "Add support for uploading and downloading file-like objects using CRT transfer manager. It supports both seekable and non-seekable file-like objects."
+}

s3transfer/crt.py

@@ -428,19 +428,12 @@ def _crt_request_from_aws_request(self, aws_request):
                 headers_list.append((name, str(value, 'utf-8')))
 
         crt_headers = awscrt.http.HttpHeaders(headers_list)
-        # CRT requires body (if it exists) to be an I/O stream.
-        crt_body_stream = None
-        if aws_request.body:
-            if hasattr(aws_request.body, 'seek'):
-                crt_body_stream = aws_request.body
-            else:
-                crt_body_stream = BytesIO(aws_request.body)
 
         crt_request = awscrt.http.HttpRequest(
             method=aws_request.method,
             path=crt_path,
             headers=crt_headers,
-            body_stream=crt_body_stream,
+            body_stream=aws_request.body,
         )
         return crt_request
 
@@ -453,6 +446,25 @@ def _convert_to_crt_http_request(self, botocore_http_request):
             crt_request.headers.set("host", url_parts.netloc)
         if crt_request.headers.get('Content-MD5') is not None:
             crt_request.headers.remove("Content-MD5")
+
+        # In general, the CRT S3 client expects a content length header. It
+        # only expects a missing content length header if the body is not
+        # seekable. However, botocore does not set the content length header
+        # for GetObject API requests and so we set the content length to zero
+        # to meet the CRT S3 client's expectation that the content length
+        # header is set even if there is no body.
+        if crt_request.headers.get('Content-Length') is None:
+            if botocore_http_request.body is None:
+                crt_request.headers.add('Content-Length', "0")
+
+        # Botocore sets the Transfer-Encoding header when it cannot determine
+        # the content length of the request body (e.g. it's not seekable).
+        # However, CRT does not support this header, but it supports
+        # non-seekable bodies. So we remove this header to not cause issues
+        # in the downstream CRT S3 request.
+        if crt_request.headers.get('Transfer-Encoding') is not None:
+            crt_request.headers.remove('Transfer-Encoding')
+
         return crt_request
 
     def _capture_http_request(self, request, **kwargs):
@@ -555,39 +567,20 @@ def __init__(self, crt_request_serializer, os_utils):
     def get_make_request_args(
         self, request_type, call_args, coordinator, future, on_done_after_calls
     ):
-        recv_filepath = None
-        send_filepath = None
-        s3_meta_request_type = getattr(
-            S3RequestType, request_type.upper(), S3RequestType.DEFAULT
+        request_args_handler = getattr(
+            self,
+            f'_get_make_request_args_{request_type}',
+            self._default_get_make_request_args,
         )
-        on_done_before_calls = []
-        if s3_meta_request_type == S3RequestType.GET_OBJECT:
-            final_filepath = call_args.fileobj
-            recv_filepath = self._os_utils.get_temp_filename(final_filepath)
-            file_ondone_call = RenameTempFileHandler(
-                coordinator, final_filepath, recv_filepath, self._os_utils
-            )
-            on_done_before_calls.append(file_ondone_call)
-        elif s3_meta_request_type == S3RequestType.PUT_OBJECT:
-            send_filepath = call_args.fileobj
-            data_len = self._os_utils.get_file_size(send_filepath)
-            call_args.extra_args["ContentLength"] = data_len
-
-        crt_request = self._request_serializer.serialize_http_request(
-            request_type, future
+        return request_args_handler(
+            request_type=request_type,
+            call_args=call_args,
+            coordinator=coordinator,
+            future=future,
+            on_done_before_calls=[],
+            on_done_after_calls=on_done_after_calls,
         )
 
-        return {
-            'request': crt_request,
-            'type': s3_meta_request_type,
-            'recv_filepath': recv_filepath,
-            'send_filepath': send_filepath,
-            'on_done': self.get_crt_callback(
-                future, 'done', on_done_before_calls, on_done_after_calls
-            ),
-            'on_progress': self.get_crt_callback(future, 'progress'),
-        }
-
     def get_crt_callback(
         self,
         future,
@@ -613,6 +606,97 @@ def invoke_all_callbacks(*args, **kwargs):
 
         return invoke_all_callbacks
 
+    def _get_make_request_args_put_object(
+        self,
+        request_type,
+        call_args,
+        coordinator,
+        future,
+        on_done_before_calls,
+        on_done_after_calls,
+    ):
+        send_filepath = None
+        if isinstance(call_args.fileobj, str):
+            send_filepath = call_args.fileobj
+            data_len = self._os_utils.get_file_size(send_filepath)
+            call_args.extra_args["ContentLength"] = data_len
+        else:
+            call_args.extra_args["Body"] = call_args.fileobj
+
+        # Suppress botocore's automatic MD5 calculation by setting an override
+        # value that will get deleted in the BotocoreCRTRequestSerializer.
+        # The CRT S3 client is able automatically compute checksums as part of
+        # requests it makes, and the intention is to configure automatic
+        # checksums in a future update.
+        call_args.extra_args["ContentMD5"] = "override-to-be-removed"
+
+        make_request_args = self._default_get_make_request_args(
+            request_type=request_type,
+            call_args=call_args,
+            coordinator=coordinator,
+            future=future,
+            on_done_before_calls=on_done_before_calls,
+            on_done_after_calls=on_done_after_calls,
+        )
+        make_request_args['send_filepath'] = send_filepath
+        return make_request_args
+
+    def _get_make_request_args_get_object(
+        self,
+        request_type,
+        call_args,
+        coordinator,
+        future,
+        on_done_before_calls,
+        on_done_after_calls,
+    ):
+        recv_filepath = None
+        on_body = None
+        if isinstance(call_args.fileobj, str):
+            final_filepath = call_args.fileobj
+            recv_filepath = self._os_utils.get_temp_filename(final_filepath)
+            on_done_before_calls.append(
+                RenameTempFileHandler(
+                    coordinator, final_filepath, recv_filepath, self._os_utils
+                )
+            )
+        else:
+            on_body = OnBodyFileObjWriter(call_args.fileobj)
+
+        make_request_args = self._default_get_make_request_args(
+            request_type=request_type,
+            call_args=call_args,
+            coordinator=coordinator,
+            future=future,
+            on_done_before_calls=on_done_before_calls,
+            on_done_after_calls=on_done_after_calls,
+        )
+        make_request_args['recv_filepath'] = recv_filepath
+        make_request_args['on_body'] = on_body
+        return make_request_args
+
+    def _default_get_make_request_args(
+        self,
+        request_type,
+        call_args,
+        coordinator,
+        future,
+        on_done_before_calls,
+        on_done_after_calls,
+    ):
+        return {
+            'request': self._request_serializer.serialize_http_request(
+                request_type, future
+            ),
+            'type': getattr(
+                S3RequestType, request_type.upper(), S3RequestType.DEFAULT
+            ),
+            'on_done': self.get_crt_callback(
+                future, 'done', on_done_before_calls, on_done_after_calls
+            ),
+            'on_progress': self.get_crt_callback(future, 'progress'),
+        }
+
 
 class RenameTempFileHandler:
     def __init__(self, coordinator, final_filename, temp_filename, osutil):
@@ -642,3 +726,11 @@ def __init__(self, coordinator):
 
     def __call__(self, **kwargs):
         self._coordinator.set_done_callbacks_complete()
+
+
+class OnBodyFileObjWriter:
+    def __init__(self, fileobj):
+        self._fileobj = fileobj
+
+    def __call__(self, chunk, **kwargs):
+        self._fileobj.write(chunk)

tests/__init__.py

@@ -509,6 +509,9 @@ def write(self, b):
     def read(self, n=-1):
         return self._data.read(n)
 
+    def readinto(self, b):
+        return self._data.readinto(b)
+
 
 class NonSeekableWriter(io.RawIOBase):
     def __init__(self, fileobj):