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e1b959ccbb
In working with res_stasis, I discovered a significant limitation to
the current structure of stasis_caching_topics: you cannot subscribe
to cache updates for a single channel/bridge/endpoint/etc.
To address this, this patch splits the cache away from the
stasis_caching_topic, making it a first class object. The stasis_cache
object is shared amongst individual stasis_caching_topics that are
created per channel/endpoint/etc. These are still forwarded to global
whatever_all_cached topics, so their use from most of the code does
not change.
In making these changes, I noticed that we frequently used a similar
pattern for bridges, endpoints and channels:
single_topic ----------------> all_topic
^
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single_topic_cached ----+----> all_topic_cached
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+----> cache
This pattern was extracted as the 'Stasis Caching Pattern', defined in
stasis_caching_pattern.h. This avoids a lot of duplicate code between
the different domain objects.
Since the cache is now disassociated from its upstream caching topics,
this also necessitated a change to how the 'guaranteed' flag worked
for retrieving from a cache. The code for handling the caching
guarantee was extracted into a 'stasis_topic_wait' function, which
works for any stasis_topic.
(closes issue ASTERISK-22002)
Review: https://reviewboard.asterisk.org/r/2672/
git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@395954 65c4cc65-6c06-0410-ace0-fbb531ad65f3
154 lines
4.5 KiB
C
154 lines
4.5 KiB
C
/*
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* Asterisk -- An open source telephony toolkit.
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*
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* Copyright (C) 2013, Digium, Inc.
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*
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* David M. Lee, II <dlee@digium.com>
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*
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* See http://www.asterisk.org for more information about
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* the Asterisk project. Please do not directly contact
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* any of the maintainers of this project for assistance;
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* the project provides a web site, mailing lists and IRC
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* channels for your use.
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*
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* This program is free software, distributed under the terms of
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* the GNU General Public License Version 2. See the LICENSE file
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* at the top of the source tree.
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*/
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#ifndef _ASTERISK_STASIS_CACHE_PATTERN_H
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#define _ASTERISK_STASIS_CACHE_PATTERN_H
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/*! \file
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*
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* \brief Caching pattern for \ref stasis topics.
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*
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* A typical pattern for Stasis objects is to have individual objects, which
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* have their own topic and caching topic. These individual topics feed an
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* upstream aggregate topics, and a shared cache.
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*
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* The \ref stasis_cp_all object contains the aggregate topics and shared cache.
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* This is built with the base name for the topics, and the identity function to
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* identify messages in the cache.
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*
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* The \ref stasis_cp_single object contains the \ref stasis_topic for a single
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* instance, and the corresponding \ref stasis_caching_topic.
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*
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* Since the \ref stasis_cp_single object has subscriptions for forwarding
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* and caching, it must be disposed of using stasis_cp_single_unsubscribe()
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* instead of simply ao2_cleanup().
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*/
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#include "asterisk/stasis.h"
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/*!
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* \brief The 'all' side of the cache pattern. These are typically built as
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* global objects for specific modules.
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*/
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struct stasis_cp_all;
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/*!
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* \brief Create an all instance of the cache pattern.
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*
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* This object is AO2 managed, so dispose of it with ao2_cleanup().
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*
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* \param name Base name of the topics.
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* \param id_fn Identity function for the cache.
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* \return All side instance.
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* \return \c NULL on error.
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*/
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struct stasis_cp_all *stasis_cp_all_create(const char *name,
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snapshot_get_id id_fn);
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/*!
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* \brief Get the aggregate topic.
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*
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* This topic aggregates all messages published to corresponding
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* stasis_cp_single_topic() topics.
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*
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* \param all All side caching pattern object.
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* \return The aggregate topic.
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* \return \c NULL if \a all is \c NULL
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*/
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struct stasis_topic *stasis_cp_all_topic(struct stasis_cp_all *all);
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/*!
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* \brief Get the caching topic.
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*
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* This topic aggregates all messages from the corresponding
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* stasis_cp_single_topic_cached() topics.
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*
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* Note that one normally only subscribes to the caching topic, since data
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* is fed to it from its upstream topic.
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*
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* \param all All side caching pattern object.
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* \return The aggregate caching topic.
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* \return \c NULL if \a all is \c NULL
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*/
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struct stasis_topic *stasis_cp_all_topic_cached(
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struct stasis_cp_all *all);
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/*!
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* \brief Get the cache.
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*
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* This is the shared cache for all corresponding \ref stasis_cp_single objects.
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*
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* \param all All side caching pattern object.
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* \return The cache.
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* \return \c NULL if \a all is \c NULL
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*/
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struct stasis_cache *stasis_cp_all_cache(struct stasis_cp_all *all);
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/*!
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* \brief The 'one' side of the cache pattern. These are built per-instance for
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* some corresponding object, and must be explicitly disposed of using
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* stasis_cp_single_unsubscribe().
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*/
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struct stasis_cp_single;
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/*!
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* \brief Create the 'one' side of the cache pattern.
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*
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* Dispose of using stasis_cp_single_unsubscribe().
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*
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* \param all Corresponding all side.
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* \param name Base name for the topics.
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* \return One side instance
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*/
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struct stasis_cp_single *stasis_cp_single_create(struct stasis_cp_all *all,
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const char *name);
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/*!
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* \brief Stops caching and forwarding messages.
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*
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* \param one One side of the cache pattern.
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*/
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void stasis_cp_single_unsubscribe(struct stasis_cp_single *one);
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/*!
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* \brief Get the topic for this instance.
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*
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* This is the topic to which one would post instance-specific messages, or
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* subscribe for single-instance, uncached messages.
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*
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* \param one One side of the cache pattern.
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* \return The main topic.
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* \return \c NULL if \a one is \c NULL
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*/
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struct stasis_topic *stasis_cp_single_topic(struct stasis_cp_single *one);
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/*!
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* \brief Get the caching topic for this instance.
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*
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* Note that one normally only subscribes to the caching topic, since data
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* is fed to it from its upstream topic.
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*
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* \param one One side of the cache pattern.
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* \return The caching topic.
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* \return \c NULL if \a one is \c NULL
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*/
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struct stasis_topic *stasis_cp_single_topic_cached(
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struct stasis_cp_single *one);
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#endif /* _ASTERISK_STASIS_CACHE_PATTERN_H */
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