Feat: Add Streaming functionalities to file uploads (#174)

docs/usage/file_upload.rst

@@ -19,7 +19,7 @@ In order to upload a single file, you need to:
 
     transport = AIOHTTPTransport(url='YOUR_URL')
 
-    client = Client(transport=sample_transport)
+    client = Client(transport=transport)
 
     query = gql('''
       mutation($file: Upload!) {
@@ -46,7 +46,7 @@ It is also possible to upload multiple files using a list.
 
     transport = AIOHTTPTransport(url='YOUR_URL')
 
-    client = Client(transport=sample_transport)
+    client = Client(transport=transport)
 
     query = gql('''
       mutation($files: [Upload!]!) {
@@ -67,3 +67,111 @@ It is also possible to upload multiple files using a list.
 
     f1.close()
     f2.close()
+
+
+Streaming
+---------
+
+If you use the above methods to send files, then the entire contents of the files
+must be loaded in memory before the files are sent.
+If the files are not too big and you have enough RAM, it is not a problem.
+On another hand if you want to avoid using too much memory, then it is better
+to read the files and send them in small chunks so that the entire file contents
+don't have to be in memory at once.
+
+We provide methods to do that for two different uses cases:
+
+* Sending local files
+* Streaming downloaded files from an external URL to the GraphQL API
+
+Streaming local files
+^^^^^^^^^^^^^^^^^^^^^
+
+aiohttp allows to upload files using an asynchronous generator.
+See `Streaming uploads on aiohttp docs`_.
+
+
+In order to stream local files, instead of providing opened files to the
+`variables_values` argument of `execute`, you need to provide an async generator
+which will provide parts of the files.
+
+You can use `aiofiles`_
+to read the files in chunks and create this asynchronous generator.
+
+.. _Streaming uploads on aiohttp docs: https://docs.aiohttp.org/en/stable/client_quickstart.html#streaming-uploads
+.. _aiofiles: https://github.com/Tinche/aiofiles
+
+Example:
+
+.. code-block:: python
+
+    transport = AIOHTTPTransport(url='YOUR_URL')
+
+    client = Client(transport=transport)
+
+    query = gql('''
+      mutation($file: Upload!) {
+        singleUpload(file: $file) {
+          id
+        }
+      }
+    ''')
+
+    async def file_sender(file_name):
+        async with aiofiles.open(file_name, 'rb') as f:
+            chunk = await f.read(64*1024)
+                while chunk:
+                    yield chunk
+                    chunk = await f.read(64*1024)
+
+    params = {"file": file_sender(file_name='YOUR_FILE_PATH')}
+
+    result = client.execute(
+		query, variable_values=params, upload_files=True
+	)
+
+Streaming downloaded files
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+If the file you want to upload to the GraphQL API is not present locally
+and needs to be downloaded from elsewhere, then it is possible to chain the download
+and the upload in order to limit the amout of memory used.
+
+Because the `content` attribute of an aiohttp response is a `StreamReader`
+(it provides an async iterator protocol), you can chain the download and the upload
+together.
+
+In order to do that, you need to:
+
+* get the response from an aiohttp request and then get the StreamReader instance
+  from `resp.content`
+* provide the StreamReader instance to the `variable_values` argument of `execute`
+
+Example:
+
+.. code-block:: python
+
+    # First request to download your file with aiohttp
+    async with aiohttp.ClientSession() as http_client:
+        async with http_client.get('YOUR_DOWNLOAD_URL') as resp:
+
+            # We now have a StreamReader instance in resp.content
+            # and we provide it to the variable_values argument of execute
+
+            transport = AIOHTTPTransport(url='YOUR_GRAPHQL_URL')
+
+            client = Client(transport=transport)
+
+            query = gql('''
+              mutation($file: Upload!) {
+                singleUpload(file: $file) {
+                  id
+                }
+              }
+            ''')
+
+            params = {"file": resp.content}
+
+            result = client.execute(
+                query, variable_values=params, upload_files=True
+            )

gql/transport/aiohttp.py

@@ -1,7 +1,8 @@
+import io
 import json
 import logging
 from ssl import SSLContext
-from typing import Any, AsyncGenerator, Dict, Optional, Union
+from typing import Any, AsyncGenerator, Dict, Optional, Tuple, Type, Union
 
 import aiohttp
 from aiohttp.client_exceptions import ClientResponseError
@@ -29,6 +30,12 @@ class AIOHTTPTransport(AsyncTransport):
     This transport use the aiohttp library with asyncio.
     """
 
+    file_classes: Tuple[Type[Any], ...] = (
+        io.IOBase,
+        aiohttp.StreamReader,
+        AsyncGenerator,
+    )
+
     def __init__(
         self,
         url: str,
@@ -144,7 +151,9 @@ async def execute(
 
             # If we upload files, we will extract the files present in the
             # variable_values dict and replace them by null values
-            nulled_variable_values, files = extract_files(variable_values)
+            nulled_variable_values, files = extract_files(
+                variables=variable_values, file_classes=self.file_classes,
+            )
 
             # Save the nulled variable values in the payload
             payload["variables"] = nulled_variable_values
@@ -175,7 +184,8 @@ async def execute(
             data.add_field("map", file_map_str, content_type="application/json")
 
             # Add the extracted files as remaining fields
-            data.add_fields(*file_streams.items())
+            for k, v in file_streams.items():
+                data.add_field(k, v, filename=k)
 
             post_args: Dict[str, Any] = {"data": data}
 

gql/utils.py

@@ -1,7 +1,6 @@
 """Utilities to manipulate several python objects."""
 
-import io
-from typing import Any, Dict, Tuple
+from typing import Any, Dict, Tuple, Type
 
 
 # From this response in Stackoverflow
@@ -13,12 +12,9 @@ def to_camel_case(snake_str):
     return components[0] + "".join(x.title() if x else "_" for x in components[1:])
 
 
-def is_file_like(value: Any) -> bool:
-    """Check if a value represents a file like object"""
-    return isinstance(value, io.IOBase)
-
-
-def extract_files(variables: Dict) -> Tuple[Dict, Dict]:
+def extract_files(
+    variables: Dict, file_classes: Tuple[Type[Any], ...]
+) -> Tuple[Dict, Dict]:
     files = {}
 
     def recurse_extract(path, obj):
@@ -40,7 +36,7 @@ def recurse_extract(path, obj):
                 value = recurse_extract(f"{path}.{key}", value)
                 nulled_obj[key] = value
             return nulled_obj
-        elif is_file_like(obj):
+        elif isinstance(obj, file_classes):
             # extract obj from its parent and put it into files instead.
             files[path] = obj
             return None

setup.py

@@ -18,6 +18,7 @@
     "pytest-cov==2.8.1",
     "mock==4.0.2",
     "vcrpy==4.0.2",
+    "aiofiles",
 ]
 
 dev_requires = [

tests/test_aiohttp.py

@@ -582,6 +582,84 @@ async def test_aiohttp_binary_file_upload(event_loop, aiohttp_server):
             assert success
 
 
+@pytest.mark.asyncio
+async def test_aiohttp_stream_reader_upload(event_loop, aiohttp_server):
+    from aiohttp import web, ClientSession
+    from gql.transport.aiohttp import AIOHTTPTransport
+
+    async def binary_data_handler(request):
+        return web.Response(
+            body=binary_file_content, content_type="binary/octet-stream"
+        )
+
+    app = web.Application()
+    app.router.add_route("POST", "/", binary_upload_handler)
+    app.router.add_route("GET", "/binary_data", binary_data_handler)
+
+    server = await aiohttp_server(app)
+
+    url = server.make_url("/")
+    binary_data_url = server.make_url("/binary_data")
+
+    sample_transport = AIOHTTPTransport(url=url, timeout=10)
+
+    async with Client(transport=sample_transport) as session:
+        query = gql(file_upload_mutation_1)
+        async with ClientSession() as client:
+            async with client.get(binary_data_url) as resp:
+                params = {"file": resp.content, "other_var": 42}
+
+                # Execute query asynchronously
+                result = await session.execute(
+                    query, variable_values=params, upload_files=True
+                )
+
+    success = result["success"]
+
+    assert success
+
+
+@pytest.mark.asyncio
+async def test_aiohttp_async_generator_upload(event_loop, aiohttp_server):
+    import aiofiles
+    from aiohttp import web
+    from gql.transport.aiohttp import AIOHTTPTransport
+
+    app = web.Application()
+    app.router.add_route("POST", "/", binary_upload_handler)
+    server = await aiohttp_server(app)
+
+    url = server.make_url("/")
+
+    sample_transport = AIOHTTPTransport(url=url, timeout=10)
+
+    with TemporaryFile(binary_file_content) as test_file:
+
+        async with Client(transport=sample_transport,) as session:
+
+            query = gql(file_upload_mutation_1)
+
+            file_path = test_file.filename
+
+            async def file_sender(file_name):
+                async with aiofiles.open(file_name, "rb") as f:
+                    chunk = await f.read(64 * 1024)
+                    while chunk:
+                        yield chunk
+                        chunk = await f.read(64 * 1024)
+
+            params = {"file": file_sender(file_path), "other_var": 42}
+
+            # Execute query asynchronously
+            result = await session.execute(
+                query, variable_values=params, upload_files=True
+            )
+
+            success = result["success"]
+
+            assert success
+
+
 file_upload_mutation_2 = """
     mutation($file1: Upload!, $file2: Upload!) {
       uploadFile(input:{file1:$file, file2:$file}) {