This patch fixes an issue of message ordering that occurs when multiple topics are forwarded to an aggregator topic (such as ast_channel_topic_all()). It is (very reasonably) expected that the rules governing message dispatch order still apply, so long as the messages start from the same thread, and are received by the same subscription. Because the existing code had an additional layer of dispatching via the Stasis thread pool for forwards, those promises couldn't be kept. Forwarding subscriptions no longer have their own mailbox, and now dispatch directly from the forwarding topic's stasis_publish() call. This means that the topic's lock is held for the duration of not only a message's dispatch, but the dispatch of all the forwards. This shouldn't be a problem right now, but if an aggregator topic had many subscribers, it could become a problem. But I figure we can write more clever code when the time comes, if necessary. Review: https://reviewboard.asterisk.org/r/2419/ git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@384413 65c4cc65-6c06-0410-ace0-fbb531ad65f3
603 lines
15 KiB
C
603 lines
15 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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/*! \file
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*
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* \brief Stasis Message Bus API.
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*
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* \author David M. Lee, II <dlee@digium.com>
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*/
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/*** MODULEINFO
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<support_level>core</support_level>
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***/
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#include "asterisk.h"
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ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
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#include "asterisk/astobj2.h"
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#include "asterisk/stasis.h"
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#include "asterisk/threadpool.h"
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#include "asterisk/taskprocessor.h"
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#include "asterisk/utils.h"
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#include "asterisk/uuid.h"
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/*! Initial size of the subscribers list. */
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#define INITIAL_SUBSCRIBERS_MAX 4
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/*! The number of buckets to use for topic pools */
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#define TOPIC_POOL_BUCKETS 57
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/*! Threadpool for dispatching notifications to subscribers */
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static struct ast_threadpool *pool;
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static struct stasis_message_type *__subscription_change_message_type;
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/*! \internal */
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struct stasis_topic {
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char *name;
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/*! Variable length array of the subscribers (raw pointer to avoid cyclic references) */
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struct stasis_subscription **subscribers;
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/*! Allocated length of the subscribers array */
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size_t num_subscribers_max;
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/*! Current size of the subscribers array */
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size_t num_subscribers_current;
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};
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/* Forward declarations for the tightly-coupled subscription object */
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static int topic_add_subscription(struct stasis_topic *topic, struct stasis_subscription *sub);
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static void topic_dtor(void *obj)
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{
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struct stasis_topic *topic = obj;
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ast_free(topic->name);
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topic->name = NULL;
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ast_free(topic->subscribers);
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topic->subscribers = NULL;
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}
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struct stasis_topic *stasis_topic_create(const char *name)
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{
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RAII_VAR(struct stasis_topic *, topic, NULL, ao2_cleanup);
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topic = ao2_alloc(sizeof(*topic), topic_dtor);
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if (!topic) {
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return NULL;
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}
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topic->name = ast_strdup(name);
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if (!topic->name) {
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return NULL;
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}
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topic->num_subscribers_max = INITIAL_SUBSCRIBERS_MAX;
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topic->subscribers = ast_calloc(topic->num_subscribers_max, sizeof(*topic->subscribers));
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if (!topic->subscribers) {
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return NULL;
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}
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ao2_ref(topic, +1);
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return topic;
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}
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const char *stasis_topic_name(const struct stasis_topic *topic)
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{
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return topic->name;
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}
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/*! \internal */
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struct stasis_subscription {
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/*! Unique ID for this subscription */
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char uniqueid[AST_UUID_STR_LEN];
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/*! Topic subscribed to. */
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struct stasis_topic *topic;
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/*! Mailbox for processing incoming messages. */
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struct ast_taskprocessor *mailbox;
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/*! Callback function for incoming message processing. */
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stasis_subscription_cb callback;
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/*! Data pointer to be handed to the callback. */
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void *data;
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};
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static void subscription_dtor(void *obj)
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{
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struct stasis_subscription *sub = obj;
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ast_assert(!stasis_subscription_is_subscribed(sub));
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ao2_cleanup(sub->topic);
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sub->topic = NULL;
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ast_taskprocessor_unreference(sub->mailbox);
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sub->mailbox = NULL;
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}
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/*!
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* \brief Invoke the subscription's callback.
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* \param sub Subscription to invoke.
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* \param topic Topic message was published to.
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* \param message Message to send.
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*/
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static void subscription_invoke(struct stasis_subscription *sub,
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struct stasis_topic *topic,
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struct stasis_message *message)
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{
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/* Since sub->topic doesn't change, no need to lock sub */
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sub->callback(sub->data,
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sub,
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topic,
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message);
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}
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static void send_subscription_change_message(struct stasis_topic *topic, char *uniqueid, char *description);
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static struct stasis_subscription *__stasis_subscribe(
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struct stasis_topic *topic,
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stasis_subscription_cb callback,
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void *data,
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int needs_mailbox)
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{
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RAII_VAR(struct stasis_subscription *, sub, NULL, ao2_cleanup);
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sub = ao2_alloc(sizeof(*sub), subscription_dtor);
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if (!sub) {
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return NULL;
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}
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ast_uuid_generate_str(sub->uniqueid, sizeof(sub->uniqueid));
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if (needs_mailbox) {
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sub->mailbox = ast_threadpool_serializer(sub->uniqueid, pool);
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if (!sub->mailbox) {
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return NULL;
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}
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}
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ao2_ref(topic, +1);
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sub->topic = topic;
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sub->callback = callback;
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sub->data = data;
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if (topic_add_subscription(topic, sub) != 0) {
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return NULL;
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}
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send_subscription_change_message(topic, sub->uniqueid, "Subscribe");
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ao2_ref(sub, +1);
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return sub;
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}
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struct stasis_subscription *stasis_subscribe(
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struct stasis_topic *topic,
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stasis_subscription_cb callback,
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void *data)
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{
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return __stasis_subscribe(topic, callback, data, 1);
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}
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struct stasis_subscription *stasis_unsubscribe(struct stasis_subscription *sub)
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{
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if (sub) {
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size_t i;
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struct stasis_topic *topic = sub->topic;
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SCOPED_AO2LOCK(lock_topic, topic);
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for (i = 0; i < topic->num_subscribers_current; ++i) {
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if (topic->subscribers[i] == sub) {
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send_subscription_change_message(topic, sub->uniqueid, "Unsubscribe");
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/* swap [i] with last entry; remove last entry */
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topic->subscribers[i] = topic->subscribers[--topic->num_subscribers_current];
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/* Unsubscribing unrefs the subscription */
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ao2_cleanup(sub);
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return NULL;
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}
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}
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ast_log(LOG_ERROR, "Internal error: subscription has invalid topic\n");
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}
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return NULL;
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}
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int stasis_subscription_is_subscribed(const struct stasis_subscription *sub)
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{
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if (sub) {
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size_t i;
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struct stasis_topic *topic = sub->topic;
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SCOPED_AO2LOCK(lock_topic, topic);
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for (i = 0; i < topic->num_subscribers_current; ++i) {
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if (topic->subscribers[i] == sub) {
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return 1;
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}
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}
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}
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return 0;
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}
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const char *stasis_subscription_uniqueid(const struct stasis_subscription *sub)
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{
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return sub->uniqueid;
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}
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int stasis_subscription_final_message(struct stasis_subscription *sub, struct stasis_message *msg)
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{
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struct stasis_subscription_change *change;
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if (stasis_message_type(msg) != stasis_subscription_change_type()) {
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return 0;
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}
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change = stasis_message_data(msg);
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if (strcmp("Unsubscribe", change->description)) {
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return 0;
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}
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if (strcmp(stasis_subscription_uniqueid(sub), change->uniqueid)) {
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return 0;
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}
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return 1;
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}
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/*!
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* \brief Add a subscriber to a topic.
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* \param topic Topic
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* \param sub Subscriber
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* \return 0 on success
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* \return Non-zero on error
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*/
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static int topic_add_subscription(struct stasis_topic *topic, struct stasis_subscription *sub)
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{
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struct stasis_subscription **subscribers;
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SCOPED_AO2LOCK(lock, topic);
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/* Increase list size, if needed */
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if (topic->num_subscribers_current + 1 > topic->num_subscribers_max) {
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subscribers = realloc(topic->subscribers, 2 * topic->num_subscribers_max * sizeof(*subscribers));
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if (!subscribers) {
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return -1;
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}
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topic->subscribers = subscribers;
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topic->num_subscribers_max *= 2;
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}
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/* Don't ref sub here or we'll cause a reference cycle. */
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topic->subscribers[topic->num_subscribers_current++] = sub;
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return 0;
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}
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/*!
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* \internal
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* \brief Information needed to dispatch a message to a subscription
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*/
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struct dispatch {
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/*! Topic message was published to */
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struct stasis_topic *topic;
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/*! The message itself */
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struct stasis_message *message;
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/*! Subscription receiving the message */
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struct stasis_subscription *sub;
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};
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static void dispatch_dtor(void *data)
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{
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struct dispatch *dispatch = data;
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ao2_cleanup(dispatch->topic);
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ao2_cleanup(dispatch->message);
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ao2_cleanup(dispatch->sub);
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}
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static struct dispatch *dispatch_create(struct stasis_topic *topic, struct stasis_message *message, struct stasis_subscription *sub)
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{
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RAII_VAR(struct dispatch *, dispatch, NULL, ao2_cleanup);
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ast_assert(topic != NULL);
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ast_assert(message != NULL);
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ast_assert(sub != NULL);
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dispatch = ao2_alloc(sizeof(*dispatch), dispatch_dtor);
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if (!dispatch) {
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return NULL;
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}
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dispatch->topic = topic;
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ao2_ref(topic, +1);
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dispatch->message = message;
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ao2_ref(message, +1);
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dispatch->sub = sub;
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ao2_ref(sub, +1);
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ao2_ref(dispatch, +1);
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return dispatch;
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}
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/*!
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* \brief Dispatch a message to a subscriber
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* \param data \ref dispatch object
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* \return 0
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*/
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static int dispatch_exec(void *data)
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{
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RAII_VAR(struct dispatch *, dispatch, data, ao2_cleanup);
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subscription_invoke(dispatch->sub, dispatch->topic, dispatch->message);
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return 0;
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}
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void stasis_forward_message(struct stasis_topic *topic, struct stasis_topic *publisher_topic, struct stasis_message *message)
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{
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size_t i;
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SCOPED_AO2LOCK(lock, topic);
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ast_assert(topic != NULL);
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ast_assert(publisher_topic != NULL);
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ast_assert(message != NULL);
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for (i = 0; i < topic->num_subscribers_current; ++i) {
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struct stasis_subscription *sub = topic->subscribers[i];
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ast_assert(sub != NULL);
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if (sub->mailbox) {
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RAII_VAR(struct dispatch *, dispatch, NULL, ao2_cleanup);
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dispatch = dispatch_create(publisher_topic, message, sub);
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if (!dispatch) {
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ast_log(LOG_DEBUG, "Dropping dispatch\n");
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break;
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}
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if (ast_taskprocessor_push(sub->mailbox, dispatch_exec, dispatch) == 0) {
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/* Ownership transferred to mailbox.
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* Don't increment ref, b/c the task processor
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* may have already gotten rid of the object.
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*/
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dispatch = NULL;
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}
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} else {
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/* Dispatch directly */
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subscription_invoke(sub, publisher_topic, message);
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}
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}
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}
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void stasis_publish(struct stasis_topic *topic, struct stasis_message *message)
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{
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stasis_forward_message(topic, topic, message);
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}
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/*! \brief Forwarding subscriber */
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static void stasis_forward_cb(void *data, struct stasis_subscription *sub, struct stasis_topic *topic, struct stasis_message *message)
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{
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struct stasis_topic *to_topic = data;
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stasis_forward_message(to_topic, topic, message);
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if (stasis_subscription_final_message(sub, message)) {
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ao2_cleanup(to_topic);
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}
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}
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struct stasis_subscription *stasis_forward_all(struct stasis_topic *from_topic, struct stasis_topic *to_topic)
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{
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struct stasis_subscription *sub;
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if (!from_topic || !to_topic) {
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return NULL;
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}
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/* Forwarding subscriptions should dispatch directly instead of having a
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* mailbox. Otherwise, messages forwarded to the same topic from
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* different topics may get reordered. Which is bad.
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*/
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sub = __stasis_subscribe(from_topic, stasis_forward_cb, to_topic, 0);
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if (sub) {
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/* hold a ref to to_topic for this forwarding subscription */
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ao2_ref(to_topic, +1);
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}
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return sub;
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}
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static void subscription_change_dtor(void *obj)
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{
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struct stasis_subscription_change *change = obj;
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ast_string_field_free_memory(change);
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ao2_cleanup(change->topic);
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}
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static struct stasis_subscription_change *subscription_change_alloc(struct stasis_topic *topic, char *uniqueid, char *description)
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{
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RAII_VAR(struct stasis_subscription_change *, change, NULL, ao2_cleanup);
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change = ao2_alloc(sizeof(struct stasis_subscription_change), subscription_change_dtor);
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if (ast_string_field_init(change, 128)) {
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return NULL;
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}
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ast_string_field_set(change, uniqueid, uniqueid);
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ast_string_field_set(change, description, description);
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ao2_ref(topic, +1);
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change->topic = topic;
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ao2_ref(change, +1);
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return change;
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}
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struct stasis_message_type *stasis_subscription_change_type(void)
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{
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return __subscription_change_message_type;
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}
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static void send_subscription_change_message(struct stasis_topic *topic, char *uniqueid, char *description)
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{
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RAII_VAR(struct stasis_subscription_change *, change, NULL, ao2_cleanup);
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RAII_VAR(struct stasis_message *, msg, NULL, ao2_cleanup);
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change = subscription_change_alloc(topic, uniqueid, description);
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if (!change) {
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return;
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}
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msg = stasis_message_create(stasis_subscription_change_type(), change);
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if (!msg) {
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return;
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}
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stasis_publish(topic, msg);
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}
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struct topic_pool_entry {
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struct stasis_subscription *forward;
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struct stasis_topic *topic;
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};
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static void topic_pool_entry_dtor(void *obj)
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{
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struct topic_pool_entry *entry = obj;
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entry->forward = stasis_unsubscribe(entry->forward);
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ao2_cleanup(entry->topic);
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entry->topic = NULL;
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}
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static struct topic_pool_entry *topic_pool_entry_alloc(void)
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{
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return ao2_alloc(sizeof(struct topic_pool_entry), topic_pool_entry_dtor);
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}
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struct stasis_topic_pool {
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struct ao2_container *pool_container;
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struct stasis_topic *pool_topic;
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};
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static void topic_pool_dtor(void *obj)
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{
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struct stasis_topic_pool *pool = obj;
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ao2_cleanup(pool->pool_container);
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pool->pool_container = NULL;
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ao2_cleanup(pool->pool_topic);
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pool->pool_topic = NULL;
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}
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static int topic_pool_entry_hash(const void *obj, const int flags)
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{
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const char *topic_name = (flags & OBJ_KEY) ? obj : stasis_topic_name(((struct topic_pool_entry*) obj)->topic);
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return ast_str_case_hash(topic_name);
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}
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static int topic_pool_entry_cmp(void *obj, void *arg, int flags)
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{
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struct topic_pool_entry *opt1 = obj, *opt2 = arg;
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const char *topic_name = (flags & OBJ_KEY) ? arg : stasis_topic_name(opt2->topic);
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return strcasecmp(stasis_topic_name(opt1->topic), topic_name) ? 0 : CMP_MATCH | CMP_STOP;
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}
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struct stasis_topic_pool *stasis_topic_pool_create(struct stasis_topic *pooled_topic)
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{
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RAII_VAR(struct stasis_topic_pool *, pool, ao2_alloc(sizeof(*pool), topic_pool_dtor), ao2_cleanup);
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if (!pool) {
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return NULL;
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}
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pool->pool_container = ao2_container_alloc(TOPIC_POOL_BUCKETS, topic_pool_entry_hash, topic_pool_entry_cmp);
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ao2_ref(pooled_topic, +1);
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pool->pool_topic = pooled_topic;
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ao2_ref(pool, +1);
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return pool;
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}
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struct stasis_topic *stasis_topic_pool_get_topic(struct stasis_topic_pool *pool, const char *topic_name)
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{
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RAII_VAR(struct topic_pool_entry *, topic_pool_entry, NULL, ao2_cleanup);
|
|
SCOPED_AO2LOCK(topic_container_lock, pool->pool_container);
|
|
topic_pool_entry = ao2_find(pool->pool_container, topic_name, OBJ_KEY | OBJ_NOLOCK);
|
|
|
|
if (topic_pool_entry) {
|
|
return topic_pool_entry->topic;
|
|
}
|
|
|
|
topic_pool_entry = topic_pool_entry_alloc();
|
|
|
|
if (!topic_pool_entry) {
|
|
return NULL;
|
|
}
|
|
|
|
topic_pool_entry->topic = stasis_topic_create(topic_name);
|
|
if (!topic_pool_entry->topic) {
|
|
return NULL;
|
|
}
|
|
|
|
topic_pool_entry->forward = stasis_forward_all(topic_pool_entry->topic, pool->pool_topic);
|
|
if (!topic_pool_entry->forward) {
|
|
return NULL;
|
|
}
|
|
|
|
ao2_link_flags(pool->pool_container, topic_pool_entry, OBJ_NOLOCK);
|
|
|
|
return topic_pool_entry->topic;
|
|
}
|
|
|
|
/*! \brief Cleanup function */
|
|
static void stasis_exit(void)
|
|
{
|
|
ao2_cleanup(__subscription_change_message_type);
|
|
__subscription_change_message_type = NULL;
|
|
ast_threadpool_shutdown(pool);
|
|
pool = NULL;
|
|
}
|
|
|
|
int stasis_init(void)
|
|
{
|
|
int cache_init;
|
|
|
|
/* XXX Should this be configurable? */
|
|
struct ast_threadpool_options opts = {
|
|
.version = AST_THREADPOOL_OPTIONS_VERSION,
|
|
.idle_timeout = 20,
|
|
.auto_increment = 1,
|
|
.initial_size = 0,
|
|
.max_size = 200
|
|
};
|
|
|
|
ast_register_atexit(stasis_exit);
|
|
|
|
if (pool) {
|
|
ast_log(LOG_ERROR, "Stasis double-initialized\n");
|
|
return -1;
|
|
}
|
|
|
|
pool = ast_threadpool_create("stasis-core", NULL, &opts);
|
|
if (!pool) {
|
|
ast_log(LOG_ERROR, "Stasis threadpool allocation failed\n");
|
|
return -1;
|
|
}
|
|
|
|
cache_init = stasis_cache_init();
|
|
if (cache_init != 0) {
|
|
return -1;
|
|
}
|
|
|
|
__subscription_change_message_type = stasis_message_type_create("stasis_subscription_change");
|
|
if (!__subscription_change_message_type) {
|
|
return -1;
|
|
}
|
|
|
|
return 0;
|
|
}
|