Merge "stasis_state: Add new stasis_state module"

include/asterisk/stasis_state.h

+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2019, Sangoma Technologies Corporation
+ *
+ * Kevin Harwell <kharwell@digium.com>
+ *
+ * See http://www.asterisk.org for more information about
+ * the Asterisk project. Please do not directly contact
+ * any of the maintainers of this project for assistance;
+ * the project provides a web site, mailing lists and IRC
+ * channels for your use.
+ *
+ * This program is free software, distributed under the terms of
+ * the GNU General Public License Version 2. See the LICENSE file
+ * at the top of the source tree.
+ */
+
+#ifndef _STASIS_STATE_H
+#define _STASIS_STATE_H
+
+/*! \file
+ *
+ * \brief Stasis State API.
+ *
+ * \par Intro
+ *
+ * This module defines the data structures, and handling of "state" for topics within
+ * stasis. State is defined as the last stasis message, and its contained message data,
+ * published on a given topic.
+ *
+ * Concepts to know:
+ *  - \ref stasis_state_manager
+ *  - \ref stasis_state_subscriber
+ *  - \ref stasis_state_publisher
+ *  - \ref stasis_state_observer
+ *
+ * \par stasis_state_manager
+ *
+ * The manager stores and well, manages state data. Each state is an association of
+ * a unique stasis topic, and the last known published stasis message on that topic.
+ * There is only ever one managed state object per topic. For each topic all messages
+ * are forwarded to an "all" topic also maintained by the manager. This allows
+ * subscriptions to all managed topics, and their state. Managed state is created in
+ * one of several ways:
+ *
+ *   Adding an explicit subscriber
+ *   Adding an explicit publisher
+ *   Adding an implicit publisher
+ *   Retrieving a stasis state topic from the manager via the \ref stasis_state_topic
+ *     function prior to doing one of the above (DO NOT DO THIS).
+ *
+ * More on the first three options later (see relevant section descriptions below). The
+ * last option, creation through retrieving a topic is not only NOT recommended, but
+ * should NOT even BE DONE. Doing so will inevitably result in a memory leak. Why then
+ * is this even allowed? The short answer is backwards compatibility. The slightly longer
+ * answer is at the time of this module's creation that's how things were historically
+ * done using a combination of stasis topic management spread throughout various other
+ * modules, and stasis caching. And yes it did cause a memory leak.
+ *
+ * Preferably, any new code wishing to track topics and states should do so by adding
+ * either an explicit subscriber and/or publisher.
+ *
+ * \par stasis_state_subscriber
+ *
+ * As mentioned, topic and state can be created, or referenced within the manager by adding
+ * a \ref stasis_state_subscriber. When adding a subscriber if no state currently exists
+ * new managed state is immediately created. If managed state already exists then a new
+ * subscriber is created referencing that state. The managed state is guaranteed to live
+ * throughout the subscriber's lifetime. State is only removed from the manager when no
+ * other entities require it (no more subscribers, or publishers).
+ *
+ * Subscribers are ao2 objects. Therefore there is no explicit cleanup required aside from
+ * dereferencing the subscriber object using normal ao2 dereferencing methods.
+ *
+ * \par stasis_state_publisher
+ *
+ * There are two ways of tracking publishers: explicitly and implicitly.
+ *
+ * Topic and state can be created, or referenced within the manager by also explicitly adding
+ * a \ref stasis_state_publisher. When adding a publisher if no state currently exists new
+ * managed state is created. If managed state already exists then a new publisher is created
+ * referencing that state. The managed state is guaranteed to live throughout the publisher's
+ * lifetime. State is only removed from the manager when no other entities require it (no more
+ * publishers, or subscribers).
+ *
+ * Explicit publishers are ao2 objects. Therefore there is no cleanup required aside from
+ * dereferencing the publisher object using normal ao2 dereferencing methods.
+ *
+ * When adding an explicit publisher, messages should be published using the \ref
+ * stasis_state_publish function. This not only skips a lookup, but doesn't add an implicit
+ * publisher. They are not necessarily mutually exclusive it's just that the two ways exist
+ * to solve two different problems.
+ *
+ * For example (using an explicit publisher):
+ *
+ * // Add an explicit publisher to topic/state "8675309" within
+ * // a given manager context
+ * pub = stasis_state_add_publisher(manager, "8675309");
+ *
+ * // Publish a stasis message to the topic/state
+ * stasis_state_publish(pub, msg);
+ *
+ * // Publish another a stasis message to the topic/state
+ * stasis_state_publish(pub, msg);
+ *
+ * // Done with the publisher release the reference
+ * ao2_ref(pub, -1);
+ *
+ * An implicit publisher can also be created by calling \ref stasis_state_publish_by_id. Calling
+ * this function not only publishes the message within stasis (creating managed state if needed)
+ * it also sets up internal tracking of the publishing module using an \ref ast_eid. However, a
+ * final call to \ref stasis_state_remove_publish_by_id must be done in order to remove the eid
+ * reference, which will subsequently allow the underlying managed state to be eventually deleted.
+ *
+ * For example (using an implicit publisher):
+ *
+ *  // Publish a stasis message to topic/state 8675309 within a
+ *  // given manager context and use the system's default eid
+ *  stasis_state_publish_by_id(manager, "8675309", NULL, msg);
+ *
+ *  // Do some stuff and then publish again
+ *  stasis_state_publish_by_id(manager, "8675309", NULL, msg);
+ *
+ *  // Done with all our publishing, so post a final clearing
+ *  // message and remove the implicit publisher
+ *  stasis_state_remove_publish_by_id(manager, "8675309", NULL, msg);
+ *
+ * Explicit publisher/publishing is preferred. However, implicit publishing is allowed for those
+ * situations where it makes more sense to do so, but has been implemented mostly for backwards
+ * compatibility with some modules (using implicit publishing required less initial code changes
+ * to some legacy subsystems).
+ *
+ * \par stasis_state_observer
+ *
+ * Some modules may wish to watch for, and react to managed state events. By registering a state
+ * observer, and implementing handlers for the desired callbacks those modules can do so.
+ */
+
+#include "asterisk/stasis.h"
+
+struct ast_eid;
+
+/*!
+ * \brief Manages a collection of stasis states.
+ *
+ * Maintains data related to stasis state. Managed state is an association of a unique stasis
+ * topic (named by a given unique id), and the last known published message.
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+struct stasis_state_manager;
+
+/*!
+ * \brief Create a stasis state manager.
+ *
+ * \note The state manager is an ao2_object. When done simply decrement its reference
+ * for object cleanup.
+ *
+ * \param topic_name The name of the topic to create that all state topics
+ *        get forwarded to
+ *
+ * \retval A stasis state manager
+ * \retval NULL if an error occurred
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+struct stasis_state_manager *stasis_state_manager_create(const char *topic_name);
+
+/*!
+ * \brief Retrieve the manager's topic (the topic that all state topics get forwarded to)
+ *
+ * \param manager The manager object
+ *
+ * \retval The manager's topic.
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+struct stasis_topic *stasis_state_all_topic(struct stasis_state_manager *manager);
+
+/*!
+ * \brief Retrieve a managed topic creating one if not currently managed.
+ *
+ * WARNING This function should not be called before adding a publisher or subscriber or
+ * it will cause a memory leak within the stasis state manager. This function is here in
+ * order to allow for compatibility with how things used to work.
+ *
+ * Also much like the similar functionality from before it returns the stasis topic, but
+ * does not bump its reference.
+ *
+ * \param manager The manager object
+ * \param id The unique id of/for the topic
+ *
+ * \retval A managed stasis topic.
+ * \retval NULL if an error occurred
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+struct stasis_topic *stasis_state_topic(struct stasis_state_manager *manager, const char *id);
+
+/*!
+ * \brief A stasis state subscriber
+ *
+ * A subscriber to a particular stasis state. As such it holds a reference to the
+ * underlying stasis state, so that managed state is guaranteed to exist for the
+ * lifetime of the subscriber.
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+struct stasis_state_subscriber;
+
+/*!
+ * \brief Add a subscriber to the managed stasis state for the given id
+ *
+ * Adds a subscriber to a managed state based on id. If managed state does not already
+ * exists for the given id then new managed state is created. Otherwise the existing
+ * state is subscribed to.
+ *
+ * \param manager The manager object
+ * \param id The unique id of a managed state
+ *
+ * \retval A stasis state subscriber
+ * \retval NULL if an error occurred
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+struct stasis_state_subscriber *stasis_state_add_subscriber(
+	struct stasis_state_manager *manager, const char *id);
+
+/*!
+ * \brief Add a subscriber, and subscribe to its underlying stasis topic.
+ *
+ * Adds a subscriber to a managed state based on id. If managed state does not already
+ * exists for the given id then new managed state is created. Otherwise the existing
+ * state is subscribed to. If the state is successfully subscribed to then a stasis
+ * subscription is subsequently created as well.
+ *
+ * \param manager The manager object
+ * \param id The unique id of a managed state
+ * \param callback The stasis subscription callback
+ * \param data A user data object passed to the stasis subscription
+ *
+ * \retval A stasis state subscriber
+ * \retval NULL if an error occurred
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+struct stasis_state_subscriber *stasis_state_subscribe_pool(struct stasis_state_manager *manager,
+	const char *id, stasis_subscription_cb callback, void *data);
+
+/*!
+ * \brief Unsubscribe from the stasis topic and stasis state.
+ *
+ * \param sub A stasis state subscriber
+ *
+ * \retval NULL
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+void *stasis_state_unsubscribe(struct stasis_state_subscriber *sub);
+
+/*!
+ * \brief Unsubscribe from the stasis topic, block until the final message
+ * is received, and then unsubscribe from stasis state.
+ *
+ * \param sub A stasis state subscriber
+ *
+ * \retval NULL
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+void *stasis_state_unsubscribe_and_join(struct stasis_state_subscriber *sub);
+
+/*!
+ * \brief Retrieve the underlying subscribed to state's unique id
+ *
+ * \param sub A stasis state subscriber
+ *
+ * \retval The managed state's id
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+const char *stasis_state_subscriber_id(const struct stasis_state_subscriber *sub);
+
+/*!
+ * \brief Retrieve the subscriber's topic
+ *
+ * \note Returned topic's reference count is NOT incremented. However, the topic is
+ * guaranteed to live for the lifetime of the subscriber.
+ *
+ * \param sub A stasis state subscriber
+ *
+ * \retval The subscriber's topic
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+struct stasis_topic *stasis_state_subscriber_topic(struct stasis_state_subscriber *sub);
+
+/*!
+ * \brief Retrieve the last known state stasis message payload for the subscriber
+ *
+ * If a stasis message has been published to this state, this function returns
+ * that message's payload object. If no stasis message has been published on the
+ * state, or the message's payload does not exist then NULL is returned.
+ *
+ * \note Returned data's reference count is incremented
+ *
+ * \param sub A stasis state subscriber
+ *
+ * \retval The subscriber's state message data
+ * \retval NULL if no data has been published yet
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+void *stasis_state_subscriber_data(struct stasis_state_subscriber *sub);
+
+/*!
+ * \brief Retrieve the stasis topic subscription if available.
+ *
+ * \param sub A stasis state subscriber
+ *
+ * \retval The subscriber's stasis subscription
+ * \retval NULL if no subscription available
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+struct stasis_subscription *stasis_state_subscriber_subscription(
+	struct stasis_state_subscriber *sub);
+
+/*!
+ * \brief A stasis state publisher
+ *
+ * A publisher to a particular stasis state and topic. As such it holds a reference to
+ * the underlying stasis state, so that managed state is guaranteed to exist for the
+ * lifetime of the publisher.
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+struct stasis_state_publisher;
+
+/*!
+ * \brief Add a publisher to the managed state for the given id
+ *
+ * Adds a publisher to a managed state based on id. If managed state does not already
+ * exists for the given id then new managed state is created. Otherwise the existing
+ * state is used.
+ *
+ * \param manager The manager object
+ * \param id The unique id of a managed state
+ *
+ * \retval A stasis state publisher
+ * \retval NULL if an error occurred
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+struct stasis_state_publisher *stasis_state_add_publisher(
+	struct stasis_state_manager *manager, const char *id);
+
+/*!
+ * \brief Retrieve the publisher's underlying state's unique id
+ *
+ * \param pub A stasis state publisher
+ *
+ * \retval The managed state's id
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+const char *stasis_state_publisher_id(const struct stasis_state_publisher *pub);
+
+/*!
+ * \brief Retrieve the publisher's topic
+ *
+ * \note Returned topic's reference count is NOT incremented. However, the topic is
+ * guaranteed to live for the lifetime of the publisher.
+ *
+ * \param pub A stasis state publisher
+ *
+ * \retval The publisher's topic
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+struct stasis_topic *stasis_state_publisher_topic(struct stasis_state_publisher *pub);
+
+/*!
+ * \brief Publish to a managed state (topic) using a publisher.
+ *
+ * \param pub The publisher to use to publish the message
+ * \param msg The message to publish
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+void stasis_state_publish(struct stasis_state_publisher *pub, struct stasis_message *msg);
+
+/*!
+ * \brief Publish to a managed named by id topic, and add an implicit subscriber.
+ *
+ * \note It is recommended when adding new publisher functionality within a module
+ * to create and use an explicit publisher instead of using this method.
+ *
+ * This creates an implicit publisher keyed off the eid. This ability was mainly
+ * implemented in order to maintain compatibility with already established code.
+ * Allowing the creation of an implicit publisher made is so less changes were
+ * required when stasis state module was initially added.
+ *
+ * There should only ever be one publisher for a specifically named managed topic
+ * within the system. This being the case we can use the eid to implicitly track
+ * the publisher. However once publishing is no longer needed for a topic a call
+ * to stasis_state_remove_publish_by_id is required in order to remove the implicit
+ * publisher. Thus allowing for its eventual destruction. Without the call to remove
+ * a memory leak will occur.
+ *
+ * \param manager The state manager
+ * \param id A state's unique id
+ * \param eid The unique system id
+ * \param msg The message to publish
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+void stasis_state_publish_by_id(struct stasis_state_manager *manager, const char *id,
+	const struct ast_eid *eid, struct stasis_message *msg);
+
+/*!
+ * \brief Publish to a managed named by id topic, and remove an implicit publisher.
+ *
+ * This function should be called after calling stasis_state_publish_by_id at least once
+ * for the same manager, id, and eid. If the given stasis message is NULL then the implicit
+ * publisher is removed, but no last message is published.
+ *
+ * See note and description on stasis_state_publish_by_id for more details about if, and
+ * when this function should be used.
+ *
+ * \param manager The state manager
+ * \param id A state's unique id
+ * \param eid The unique system id
+ * \param msg The message to publish (can be NULL)
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+void stasis_state_remove_publish_by_id(struct stasis_state_manager *manager,
+	const char *id, const struct ast_eid *eid, struct stasis_message *msg);
+
+/*! \brief Managed stasis state event interface */
+struct stasis_state_observer {
+	/*!
+	 * \brief Raised when any managed state is being subscribed.
+	 *
+	 * \param id The unique id of the managed state
+	 * \param sub The subscriber subscribed
+	 */
+	void (*on_subscribe)(const char *id, struct stasis_state_subscriber *sub);
+
+	/*!
+	 * \brief Raised when any managed state is being unsubscribed.
+	 *
+	 * \param id The unique id of the managed state
+	 * \param sub The subscriber to unsubscribe
+	 */
+	void (*on_unsubscribe)(const char *id, struct stasis_state_subscriber *sub);
+};
+
+/*!
+ * \brief Add an observer to receive managed state related events.
+ *
+ * \param manager The state manager
+ * \param observer The observer handling events
+ *
+ * \retval 0 if successfully registered
+ * \retval -1 on failure
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+int stasis_state_add_observer(struct stasis_state_manager *manager,
+	struct stasis_state_observer *observer);
+
+/*!
+ * \brief Remove an observer (will no longer receive managed state related events).
+ *
+ * \param manager The state manager
+ * \param observer The observer being removed
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+void stasis_state_remove_observer(struct stasis_state_manager *manager,
+	struct stasis_state_observer *observer);
+
+/*!
+ * \brief The delegate called for each managed state.
+ *
+ * \param id The unique id of a managed state object
+ * \param msg The last published message on the state, or NULL
+ * \param user_data Data object the user passed into the manager callback
+ *
+ * \retval 0 to continue traversing
+ * \retval CMP_STOP (2) to stop traversing
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+typedef int (*on_stasis_state)(const char *id, struct stasis_message *msg, void *user_data);
+
+/*!
+ * \brief For each managed state call the given handler.
+ *
+ * \param manager The state manager
+ * \param handler The handler to call for each managed state
+ * \param data User to data to pass on to the handler
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+void stasis_state_callback_all(struct stasis_state_manager *manager, on_stasis_state handler,
+	void *data);
+
+/*!
+ * \brief For each managed, and explicitly subscribed state call the given handler.
+ *
+ * \param manager The state manager
+ * \param handler The handler to call for each managed state
+ * \param data User to data to pass on to the handler
+ *
+ * \since 13.28.0
+ * \since 16.5.0
+ */
+void stasis_state_callback_subscribed(struct stasis_state_manager *manager, on_stasis_state handler,
+	void *data);
+
+#endif /* _STASIS_STATE_H */

tests/test_stasis_state.c

+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2019, Sangoma Technologies Corporation
+ *
+ * Kevin Harwell <kharwell@digium.com>
+ *
+ * See http://www.asterisk.org for more information about
+ * the Asterisk project. Please do not directly contact
+ * any of the maintainers of this project for assistance;
+ * the project provides a web site, mailing lists and IRC
+ * channels for your use.
+ *
+ * This program is free software, distributed under the terms of
+ * the GNU General Public License Version 2. See the LICENSE file
+ * at the top of the source tree.
+ */
+
+/*** MODULEINFO
+	<depend>TEST_FRAMEWORK</depend>
+	<support_level>core</support_level>
+ ***/
+
+#include "asterisk.h"
+
+#include "asterisk/astobj2.h"
+#include "asterisk/conversions.h"
+#include "asterisk/module.h"
+#include "asterisk/stasis_state.h"
+#include "asterisk/test.h"
+
+#define test_category "/stasis/core/state/"
+
+#define TOPIC_COUNT 500
+
+#define MANAGER_TOPIC "foo"
+
+struct stasis_message_type *foo_type(void);
+
+/*! foo stasis message type */
+STASIS_MESSAGE_TYPE_DEFN(foo_type);
+
+/*! foo_type data */
+struct foo_data {
+	size_t bar;
+};
+
+AST_VECTOR(subscriptions, struct stasis_state_subscriber *);
+AST_VECTOR(publishers, struct stasis_state_publisher *);
+
+/*!
+ * For testing purposes each subscribed state's id is a number. This value is
+ * the summation of all id's.
+ */
+static size_t sum_total;
+
+/*! Test variable that tracks the running total of state ids */
+static size_t running_total;
+
+/*! This value is set to check if state data is NULL before publishing */
+static int expect_null;
+
+static int validate_data(const char *id, struct foo_data *foo)
+{
+	size_t num;
+
+	if (ast_str_to_umax(id, &num)) {
+		ast_log(LOG_ERROR, "Unable to convert the state's id '%s' to numeric\n", id);
+		return -1;
+	}
+
+	running_total += num;
+
+	if (!foo) {
+		if (expect_null) {
+			return 0;
+		}
+
+		ast_log(LOG_ERROR, "Expected state data for '%s'\n", id);
+		return -1;
+	}
+
+	if (expect_null) {
+		ast_log(LOG_ERROR, "Expected NULL state data for '%s'\n", id);
+		return -1;
+	}
+
+	if (foo->bar != num) {
+		ast_log(LOG_ERROR, "Unexpected state data for '%s'\n", id);
+		return -1;
+	}
+
+	return 0;
+}
+
+static void handle_validate(const char *id, struct stasis_state_subscriber *sub)
+{
+	struct foo_data *foo = stasis_state_subscriber_data(sub);
+	validate_data(id, foo);
+	ao2_cleanup(foo);
+}
+
+struct stasis_state_observer foo_observer = {
+	.on_subscribe = handle_validate,
+	.on_unsubscribe = handle_validate
+};
+
+static void foo_type_cb(void *data, struct stasis_subscription *sub, struct stasis_message *message)
+{
+	/* No op since we are not really testing stasis topic handling here */
+}
+
+static int subscriptions_destroy(struct stasis_state_manager *manager, struct subscriptions *subs)
+{
+	running_total = expect_null = 0;
+
+	AST_VECTOR_CALLBACK_VOID(subs, stasis_state_unsubscribe_and_join);
+	AST_VECTOR_FREE(subs);
+
+	stasis_state_remove_observer(manager, &foo_observer);
+
+	if (running_total != sum_total) {
+		ast_log(LOG_ERROR, "Failed to destroy all subscriptions: running=%zu, sum=%zu\n",
+				running_total, sum_total);
+		return -1;
+	}
+
+	return 0;
+}
+
+static int subscriptions_create(struct stasis_state_manager *manager,
+	struct subscriptions *subs)
+{
+	size_t i;
+
+	if (stasis_state_add_observer(manager, &foo_observer) ||
+		AST_VECTOR_INIT(subs, TOPIC_COUNT)) {
+		return -1;
+	}
+
+	sum_total = running_total = 0;
+	expect_null = 1;
+
+	for (i = 0; i < TOPIC_COUNT; ++i) {
+		struct stasis_state_subscriber *sub;
+		char id[32];
+
+		if (snprintf(id, 10, "%zu", i) == -1) {
+			ast_log(LOG_ERROR, "Unable to convert subscriber id to string\n");
+			break;
+		}
+
+		sub = stasis_state_subscribe_pool(manager, id, foo_type_cb, NULL);
+		if (!sub) {
+			ast_log(LOG_ERROR, "Failed to create a state subscriber for id '%s'\n", id);
+			ao2_ref(sub, -1);
+			break;
+		}
+
+		if (AST_VECTOR_APPEND(subs, sub)) {
+			ast_log(LOG_ERROR, "Failed to add to foo_sub to vector for id '%s'\n", id);
+			ao2_ref(sub, -1);
+			break;
+		}
+
+		sum_total += i;
+	}
+
+	if (i != TOPIC_COUNT || running_total != sum_total) {
+		ast_log(LOG_ERROR, "Failed to create all subscriptions: running=%zu, sum=%zu\n",
+				running_total, sum_total);
+		subscriptions_destroy(manager, subs);
+		return -1;
+	}
+
+	return 0;
+}
+
+static int publishers_destroy(struct stasis_state_manager *manager, struct publishers *pubs)
+{
+	size_t i;
+
+	if (pubs) {
+		/* Remove explicit publishers */
+		AST_VECTOR_CALLBACK_VOID(pubs, ao2_cleanup);
+		AST_VECTOR_FREE(pubs);
+		return 0;
+	}
+
+	for (i = 0; i < TOPIC_COUNT; ++i) {
+		char id[32];
+
+		/* Remove implicit publishers */
+		if (snprintf(id, 10, "%zu", i) == -1) {
+			ast_log(LOG_ERROR, "Unable to convert publisher id to string\n");
+			return -1;
+		}
+
+		stasis_state_remove_publish_by_id(manager, id, NULL, NULL);
+	}
+
+	return 0;
+}
+
+static int publishers_create(struct stasis_state_manager *manager,
+	struct publishers *pubs)
+{
+	size_t i;
+
+	if (AST_VECTOR_INIT(pubs, TOPIC_COUNT)) {
+		return -1;
+	}
+
+	for (i = 0; i < TOPIC_COUNT; ++i) {
+		struct stasis_state_publisher *pub;
+		char id[32];
+
+		if (snprintf(id, 10, "%zu", i) == -1) {
+			ast_log(LOG_ERROR, "Unable to convert publisher id to string\n");
+			break;
+		}
+
+		/* Create the state publisher */
+		pub = stasis_state_add_publisher(manager, id);
+		if (!pub) {
+			ast_log(LOG_ERROR, "Failed to create a state publisher for id '%s'\n", id);
+			break;
+		}
+
+		if (AST_VECTOR_APPEND(pubs, pub)) {
+			ast_log(LOG_ERROR, "Failed to add to publisher to vector for id '%s'\n", id);
+			ao2_ref(pub, -1);
+			break;
+		}
+	}
+
+	if (i != TOPIC_COUNT) {
+		ast_log(LOG_ERROR, "Failed to create all publishers: count=%zu\n", i);
+		publishers_destroy(manager, pubs);
+		return -1;
+	}
+
+	return 0;
+}
+
+static struct stasis_message *create_foo_type_message(const char *id)
+{
+	struct stasis_message *msg;
+	struct foo_data *foo;
+
+	foo = ao2_alloc(sizeof(*foo), NULL);
+	if (!foo) {
+		ast_log(LOG_ERROR, "Failed to allocate foo data for '%s'\n", id);
+		return NULL;
+	}
+
+	if (ast_str_to_umax(id, &foo->bar)) {
+		ast_log(LOG_ERROR, "Unable to convert the state's id '%s' to numeric\n", id);
+		ao2_ref(foo, -1);
+		return NULL;
+	}
+
+	msg = stasis_message_create_full(foo_type(), foo, NULL);
+	if (!msg) {
+		ast_log(LOG_ERROR, "Failed to create stasis message for '%s'\n", id);
+	}
+
+	ao2_ref(foo, -1);
+	return msg;
+}
+
+static int implicit_publish_cb(const char *id, struct stasis_message *msg, void *user_data)
+{
+	/* For each state object create and publish new state data */
+	struct foo_data *foo = stasis_message_data(msg);
+
+	if (validate_data(id, foo)) {
+		return CMP_STOP;
+	}
+
+	msg = create_foo_type_message(id);
+	if (!msg) {
+		return CMP_STOP;
+	}
+
+	/* Now publish it on the managed state object */
+	stasis_state_publish_by_id(user_data, id, NULL, msg);
+	ao2_ref(msg, -1);
+
+	return 0;
+}
+
+static int explicit_publish_cb(const char *id, struct stasis_message *msg, void *user_data)
+{
+	/* For each state object create and publish new state data */
+	struct publishers *pubs = user_data;
+	struct stasis_state_publisher *pub = NULL;
+	struct foo_data *foo = stasis_message_data(msg);
+	size_t i;
+
+	if (validate_data(id, foo)) {
+		return CMP_STOP;
+	}
+
+	msg = create_foo_type_message(id);
+	if (!msg) {
+		return CMP_STOP;
+	}
+
+	for (i = 0; i < AST_VECTOR_SIZE(pubs); ++i) {
+		if (!strcmp(stasis_state_publisher_id(AST_VECTOR_GET(pubs, i)), id)) {
+			pub = AST_VECTOR_GET(pubs, i);
+			break;
+		}
+	}
+
+	if (!pub) {
+		ast_log(LOG_ERROR, "Unable to locate publisher for id '%s'\n", id);
+		return CMP_STOP;
+	}
+
+	stasis_state_publish(pub, msg);
+	ao2_ref(msg, -1);
+
+	return 0;
+}
+
+static int publish(struct stasis_state_manager *manager, on_stasis_state cb,
+	void *user_data)
+{
+	/* First time there is no state data */
+	expect_null = 1;
+
+	running_total = 0;
+	stasis_state_callback_all(manager, cb, user_data);
+
+	if (running_total != sum_total) {
+		ast_log(LOG_ERROR, "Failed manager_callback (1): running=%zu, sum=%zu\n",
+				running_total, sum_total);
+		return -1;
+	}
+
+	/* Second time check valid state data exists */
+	running_total = expect_null = 0;
+	stasis_state_callback_all(manager, cb, user_data);
+
+	if (running_total != sum_total) {
+		ast_log(LOG_ERROR, "Failed manager_callback (2): running=%zu, sum=%zu\n",
+				running_total, sum_total);
+		return -1;
+	}
+
+	return 0;
+}
+
+AST_TEST_DEFINE(implicit_publish)
+{
+	RAII_VAR(struct stasis_state_manager *, manager, NULL, ao2_cleanup);
+	struct subscriptions subs;
+	int rc = AST_TEST_PASS;
+
+	switch (cmd) {
+	case TEST_INIT:
+		info->name = __func__;
+		info->category = test_category;
+		info->summary = "Test implicit publishing of stasis state";
+		info->description = info->summary;
+		return AST_TEST_NOT_RUN;
+	case TEST_EXECUTE:
+		break;
+	}
+
+	manager = stasis_state_manager_create(MANAGER_TOPIC);
+	ast_test_validate(test, manager != NULL);
+
+	ast_test_validate(test, !subscriptions_create(manager, &subs));
+
+	ast_test_validate_cleanup(test, !publish(manager, implicit_publish_cb, manager),
+		rc, cleanup);
+
+cleanup:
+	if (subscriptions_destroy(manager, &subs) || publishers_destroy(manager, NULL)) {
+		return AST_TEST_FAIL;
+	}
+
+	/*
+	 * State subscriptions add a ref a state. The state in turn adds a ref
+	 * to the manager. So if more than one ref is held on the manager before
+	 * exiting, there is a ref leak some place.
+	 */
+	if (ao2_ref(manager, 0) != 1) {
+		ast_log(LOG_ERROR, "Memory leak - Too many references held on manager\n");
+		return AST_TEST_FAIL;
+	}
+
+	return rc;
+}
+
+AST_TEST_DEFINE(explicit_publish)
+{
+	RAII_VAR(struct stasis_state_manager *, manager, NULL, ao2_cleanup);
+	struct subscriptions subs;
+	struct publishers pubs;
+	int rc = AST_TEST_PASS;
+
+	switch (cmd) {
+	case TEST_INIT:
+		info->name = __func__;
+		info->category = test_category;
+		info->summary = "Test explicit publishing of stasis state";
+		info->description = info->summary;
+		return AST_TEST_NOT_RUN;
+	case TEST_EXECUTE:
+		break;
+	}
+
+	manager = stasis_state_manager_create(MANAGER_TOPIC);
+	ast_test_validate(test, manager != NULL);
+
+	ast_test_validate(test, !subscriptions_create(manager, &subs));
+	ast_test_validate_cleanup(test, !publishers_create(manager, &pubs), rc, cleanup);
+
+	ast_test_validate_cleanup(test, !publish(manager, explicit_publish_cb, &pubs),
+		rc, cleanup);
+
+cleanup:
+	if (subscriptions_destroy(manager, &subs) || publishers_destroy(manager, &pubs)) {
+		return AST_TEST_FAIL;
+	}
+
+	/*
+	 * State subscriptions add a ref a state. The state in turn adds a ref
+	 * to the manager. So if more than one ref is held on the manager before
+	 * exiting, there is a ref leak some place.
+	 */
+	if (ao2_ref(manager, 0) != 1) {
+		ast_log(LOG_ERROR, "Memory leak - Too many references held on manager\n");
+		return AST_TEST_FAIL;
+	}
+
+	return rc;
+}
+
+static int unload_module(void)
+{
+	AST_TEST_UNREGISTER(implicit_publish);
+	AST_TEST_UNREGISTER(explicit_publish);
+
+	STASIS_MESSAGE_TYPE_CLEANUP(foo_type);
+
+	return 0;
+}
+
+static int load_module(void)
+{
+	if (STASIS_MESSAGE_TYPE_INIT(foo_type) != 0) {
+		return -1;
+	}
+
+	AST_TEST_REGISTER(implicit_publish);
+	AST_TEST_REGISTER(explicit_publish);
+
+	return AST_MODULE_LOAD_SUCCESS;
+}
+
+AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Stasis state testing");