Document `@tractor.stream`

README.rst

@@ -362,10 +362,10 @@ actors can compose nicely in a data streaming pipeline.
 
 Streaming
 *********
-By now you've figured out that ``tractor`` lets you spawn
-process based actors that can invoke cross-process async functions
-between each other and all with structured concurrency built in, but,
-the **real power** is the ability to accomplish cross-process *streaming*.
+By now you've figured out that ``tractor`` lets you spawn process based
+*actors* that can invoke cross-process (async) functions and all with
+structured concurrency built in. But the **real cool stuff** is the
+native support for cross-process *streaming*.
 
 
 Asynchronous generators
@@ -423,21 +423,22 @@ is necessary.
 Channels and Contexts
 +++++++++++++++++++++
 If you aren't fond of having to write an async generator to stream data
-between actors (or need something more flexible) you can instead use a
-``Context``. A context wraps an actor-local spawned task and a ``Channel``
-so that tasks executing across multiple processes can stream data
-to one another using a low level, request oriented API.
+between actors (or need something more flexible) you can instead use
+a ``Context``. A context wraps an actor-local spawned task and
+a ``Channel`` so that tasks executing across multiple processes can
+stream data to one another using a low level, request oriented API.
 
-``Channel`` is the API which wraps an underlying *transport* and *interchange*
-format to enable *inter-actor-communication*. In its present state ``tractor``
+A ``Channel`` wraps an underlying *transport* and *interchange* format
+to enable *inter-actor-communication*. In its present state ``tractor``
 uses TCP and msgpack_.
 
 As an example if you wanted to create a streaming server without writing
-an async generator that *yields* values you instead define an async
-function:
+an async generator that *yields* values you instead define a decorated
+async function:
 
 .. code:: python
 
+   @tractor.stream
    async def streamer(ctx: tractor.Context, rate: int = 2) -> None:
       """A simple web response streaming server.
       """
@@ -450,15 +451,20 @@ function:
          await trio.sleep(1 / rate)
 
 
-All that's required is declaring a ``ctx`` argument name somewhere in
-your function signature and ``tractor`` will treat the async function
-like an async generator - as a streaming function from the client side.
-This turns out to be handy particularly if you have
-multiple tasks streaming responses concurrently:
+You must decorate the function with ``@tractor.stream`` and declare
+a ``ctx`` argument as the first in your function signature and then
+``tractor`` will treat the async function like an async generator - as
+a stream from the calling/client side.
+
+This turns out to be handy particularly if you have multiple tasks
+pushing responses concurrently:
 
 .. code:: python
 
-   async def streamer(ctx: tractor.Context, rate: int = 2) -> None:
+   async def streamer(
+      ctx: tractor.Context,
+      rate: int = 2
+   ) -> None:
       """A simple web response streaming server.
       """
       while True:
@@ -470,8 +476,10 @@ multiple tasks streaming responses concurrently:
          await trio.sleep(1 / rate)
 
 
+   @tractor.stream
    async def stream_multiple_sources(
-      ctx: tractor.Context, sources: List[str]
+      ctx: tractor.Context,
+      sources: List[str]
    ) -> None:
       async with trio.open_nursery() as n:
          for url in sources: