====================== Asynchronous Interface ====================== .. module:: couchbase_core.asynchronous .. _async_intro: The asynchronous interface to the SDK is a work in progress, and is currently intended to be used by integrators into higher level async wrappers. See the ``txcouchbase`` package for an example. This document largely explains the current internals of how the Couchbase async module works in a lower level. For a higher level overview, see: http://blog.couchbase.com/python-sdk-and-twisted Key-Value Interface =================== The Key-Value interface of the async subsystem functions as closely as possible like its synchronous counterpart. The primary difference is that where the synchronous interface would return an instance of a :class:`~couchbase_core.result.Result` or a :class:`~couchbase_core.result.MultiResult`, the asynchronous interface returns an :class:`~couchbase_core.result.AsyncResult` object. The :class:`~couchbase_core.result.AsyncResult` object contains fields for two callbacks which are invoked when the result is ready. One is the :attr:`~couchbase_core.result.AsyncResult.callback` field which is called with a ``Result`` or ``MultiResult`` upon success, and the other is the :attr:`~couchbase_core.result.AsyncResult.errback` field which is invoked with an exception object upon error. The semantics of when an exception is passed follows the rules of the ``quiet`` parameter just like the synchronous API. .. currentmodule:: couchbase_core.asynchronous.bucket .. class:: couchbase_core.result.AsyncResult .. autoattribute:: callback .. autoattribute:: errback .. autoclass:: AsyncBucket :members: :show-inheritance: Views Interface =============== Different from the key-value interface, the synchronous view API returns a :class:`~couchbase_core.views.iterator.View` object which is itself an iterator which yields results. Because this is a synchronous API, the iterator interface must be replaced with a class interface which must be subclassed by a user. .. currentmodule:: couchbase_core.asynchronous.view .. class:: AsyncViewBase .. automethod:: __init__ .. automethod:: on_rows .. automethod:: on_error .. automethod:: on_done .. automethod:: start I/O Interface ============= The async API is divided into several sections. In order to have an async client which interacts with other async libraries and frameworks, it is necessary to make the Couchbase extension aware of that environment. To this end, the ``IOPS`` interface is provided. The ``IOPS`` API is entirely separate from the key-value API and should be treated as belonging to a different library. It is simply the extension's I/O abstraction. .. currentmodule:: couchbase_core.iops.base .. class:: Event This class represents an `Event`. This concept should be familiar to the intended audience, who should be familiar with event loops and their terminology. It represents a certain event in the future, which shall be triggered either by something happening or by the passage of time. When said event takes place, the object should be signalled via the :meth:`ready` method. .. automethod:: ready .. class:: IOEvent A subclass of :class:`Event`, this represents a socket. Events applied to this socket are triggered when the socket becomes available for reading or writing. .. automethod:: ready_r .. automethod:: ready_w .. automethod:: ready_rw .. automethod:: fileno .. class:: TimerEvent Subclass of :class:`Event` which represents a passage of time. .. class:: IOPS .. automethod:: __init__ .. automethod:: update_event .. automethod:: update_timer .. automethod:: start_watching .. automethod:: stop_watching .. automethod:: io_event_factory .. automethod:: timer_event_factory Action Constants ---------------- .. data:: PYCBC_EVACTION_WATCH Action indicating the specific event should be added to the event loop's "watcher" list, and should be have its :meth:`~Event.ready` method called when the IO implementation has detected the specific event is ready .. data:: PYCBC_EVACTION_UNWATCH Action indicating that the specific object should not be notified when the IO state changes. This is typically done by removing it from the watcher list .. data:: PYCBC_EVACTION_CLEANUP Action to permanently erase any references to this event IO Event Constants ------------------ .. data:: LCB_READ_EVENT IO Flag indicating that this event should be notified on file readbility .. data:: LCB_WRITE_EVENT IO flag indicating that this event should be notified on file writeability .. data:: LCB_RW_EVENT Equivalent to ``LCB_READ_EVENT|LCB_WRITE_EVENT``