Draft 2.6 whats new

docs/whatsnew-2.6.rst

@@ -36,6 +36,203 @@ as well as PyPy and Jython.
 Important Notes
 ===============
 
+* Task registry is no longer a global.
+
+* celery.task.Task is no longer bound to an app by default,
+  so configuration of the task is lazy.
+
+* The @task decorator is now lazy when used with custom apps
+
+    If ``accept_magic_kwargs`` is enabled (herby called "compat mode"), the task
+    decorator executes inline like before, however for custom apps the @task
+    decorator now returns a special PromiseProxy object that is only evaluated
+    on access.
+
+    All promises will be evaluated when `app.finalize` is called, or implicitly
+    when the task registry is first used.
+
+* chain: Chain tasks together using callbacks under the hood.
+
+    .. code-block:: python
+
+        from celery import chain
+
+        # (2 + 2) * 8 / 2
+        res = chain(add.subtask((4, 4)),
+                    mul.subtask((8, )),
+                    div.subtask((2,))).apply_async()
+        res.get() == 16
+
+        res.parent.get() == 32
+
+        res.parent.parent.get() == 4
+
+
+* The Celery instance can now be created with a broker URL
+
+    .. code-block:: python
+
+        celery = Celery(broker="redis://")
+
+* Result backends can now be set using an URL
+
+    Currently only supported by redis.  Example use::
+
+        CELERY_RESULT_BACKEND = "redis://localhost/1"
+
+* Heartbeat frequency now every 5s, and frequency sent with event
+
+    The heartbeat frequency is now available in the worker event messages,
+    so that clients can decide when to consider workers offline based on
+    this value.
+
+* Module celery.actors has been removed, and will be part of cl instead.
+
+* Introduces new ``celery`` command, which is an entrypoint for all other
+  commands.
+
+    The main for this command can be run by calling ``celery.start()``.
+
+* Tasks can now have callbacks and errbacks, and dependencies are recorded
+
+    - The task message format have been updated with two new extension keys
+
+        Both keys can be empty/undefined or a list of subtasks.
+
+        - ``callbacks``
+
+            Applied if the task exits successfully, with the result
+            of the task as an argument.
+
+        - ``errbacks``
+
+            Applied if an error occurred while executing the task,
+            with the uuid of the task as an argument.  Since it may not be possible
+            to serialize the exception instance, it passes the uuid of the task
+            instead.  The uuid can then be used to retrieve the exception and
+            traceback of the task from the result backend.
+
+   - ``link`` and ``link_error`` keyword arguments has been added
+      to ``apply_async``.
+
+        The value passed can be either a subtask or a list of
+        subtasks:
+
+        .. code-block:: python
+
+            add.apply_async((2, 2), link=mul.subtask())
+            add.apply_async((2, 2), link=[mul.subtask(), echo.subtask()])
+
+        Example error callback:
+
+        .. code-block:: python
+
+            @task
+            def error_handler(uuid):
+                result = AsyncResult(uuid)
+                exc = result.get(propagate=False)
+                print("Task %r raised exception: %r\n%r" % (
+                    exc, result.traceback))
+
+            >>> add.apply_async((2, 2), link_error=error_handler)
+
+    - We now track what subtasks a task sends, and some result backends
+      supports retrieving this information.
+
+        - task.request.children
+
+            Contains the result instances of the subtasks
+            the currently executing task has applied.
+
+        - AsyncResult.children
+
+            Returns the tasks dependencies, as a list of
+            ``AsyncResult``/``ResultSet`` instances.
+
+        - AsyncResult.iterdeps
+
+            Recursively iterates over the tasks dependencies,
+            yielding `(parent, node)` tuples.
+
+            Raises IncompleteStream if any of the dependencies
+            has not returned yet.
+
+       - AsyncResult.graph
+
+            A ``DependencyGraph`` of the tasks dependencies.
+            This can also be used to convert to dot format:
+
+            .. code-block:: python
+
+                with open("graph.dot") as fh:
+                    result.graph.to_dot(fh)
+
+            which can than be used to produce an image::
+
+                $ dot -Tpng graph.dot -o graph.png
+
+* Bugreport now available as a command and broadcast command
+
+    - Get it from a Python repl::
+
+        >>> import celery
+        >>> print(celery.bugreport())
+
+    - Use celeryctl::
+
+        $ celeryctl report
+
+    - Get it from remote workers::
+
+        $ celeryctl inspect report
+
+* Module ``celery.log`` moved to :mod:`celery.app.log`.
+* Module ``celery.task.control`` moved to :mod:`celery.app.control`.
+
+* Adds :meth:`AsyncResult.get_leaf`
+
+    Waits and returns the result of the leaf subtask.
+    That is the last node found when traversing the graph,
+    but this means that the graph can be 1-dimensional only (in effect
+    a list).
+
+* Adds ``subtask.link(subtask)`` + ``subtask.link_error(subtask)``
+
+    Shortcut to ``s.options.setdefault("link", []).append(subtask)``
+
+* Adds ``subtask.flatten_links()``
+
+    Returns a flattened list of all dependencies (recursively)
+
+* ``AsyncResult.task_id`` renamed to ``AsyncResult.id``
+
+* ``TasksetResult.taskset_id`` renamed to ``.id``
+
+
+
+
+Internals
+---------
+
+* Compat modules are now generated dynamically upon use.
+
+    These modules are ``celery.messaging``, ``celery.log``,
+    ``celery.decorators`` and ``celery.registry``.
+
+* :mod:`celery.utils` refactored into multiple modules:
+
+    :mod:`celery.utils.text`
+    :mod:`celery.utils.imports`
+    :mod:`celery.utils.functional`
+
+* Now using :mod:`kombu.utils.encoding` instead of
+  `:mod:`celery.utils.encoding`.
+
+* Renamed module ``celery.routes`` -> :mod:`celery.app.routes`.
+
+* Renamed package ``celery.db`` -> :mod:`celery.backends.database`.
+
+* Renamed module ``celery.abstract`` -> :mod:`celery.worker.abstract`.
 
 .. _v260-deprecations: