res_chan_stats.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2013, Digium, Inc.
 *
 * David M. Lee, II <[email protected]>
 *
 * 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.
 */

/*!
 * \brief Statsd channel stats. Exmaple of how to subscribe to Stasis events.
 *
 * This module subscribes to the channel caching topic and issues statsd stats
 * based on the received messages.
 *
 * \author David M. Lee, II <[email protected]>
 * \since 12
 */

/*** MODULEINFO
   <depend>res_statsd</depend>
   <defaultenabled>no</defaultenabled>
   <support_level>extended</support_level>
 ***/

#include "asterisk.h"

#include "asterisk/module.h"
#include "asterisk/stasis_channels.h"
#include "asterisk/stasis_message_router.h"
#include "asterisk/statsd.h"
#include "asterisk/time.h"

/*! Regular Stasis subscription */
static struct stasis_subscription *sub;
/*! Stasis message router */
static struct stasis_message_router *router;

/*!
 * \brief Subscription callback for all channel messages.
 * \param data Data pointer given when creating the subscription.
 * \param sub This subscription.
 * \param topic The topic the message was posted to. This is not necessarily the
 *              topic you subscribed to, since messages may be forwarded between
 *              topics.
 * \param message The message itself.
 */
static void statsmaker(void *data, struct stasis_subscription *sub,
   struct stasis_message *message)
{
   RAII_VAR(struct ast_str *, metric, NULL, ast_free);

   if (stasis_subscription_final_message(sub, message)) {
      /* Normally, data points to an object that must be cleaned up.
       * The final message is an unsubscribe notification that's
       * guaranteed to be the last message this subscription receives.
       * This would be a safe place to kick off any needed cleanup.
       */
      return;
   }

   /* For no good reason, count message types */
   metric = ast_str_create(80);
   if (metric) {
      ast_str_set(&metric, 0, "stasis.message.%s",
         stasis_message_type_name(stasis_message_type(message)));
      ast_statsd_log(ast_str_buffer(metric), AST_STATSD_METER, 1);
   }
}

/*!
 * \brief Router callback for \ref ast_channel_snapshot_update messages.
 * \param data Data pointer given when added to router.
 * \param sub This subscription.
 * \param topic The topic the message was posted to. This is not necessarily the
 *              topic you subscribed to, since messages may be forwarded between
 *              topics.
 * \param message The message itself.
 */
static void updates(void *data, struct stasis_subscription *sub,
   struct stasis_message *message)
{
   /* Since this came from a message router, we know the type of the
    * message. We can cast the data without checking its type.
    */
   struct ast_channel_snapshot_update *update = stasis_message_data(message);

   /* There are three types of channel snapshot updates.
    * !old && new -> Initial channel creation
    * old && new -> Updated channel snapshot
    * old && dead -> Final channel snapshot
    */

   if (!update->old_snapshot && update->new_snapshot) {
      /* Initial channel snapshot; count a channel creation */
      ast_statsd_log_string("channels.count", AST_STATSD_GAUGE, "+1", 1.0);
   } else if (update->old_snapshot && ast_test_flag(&update->new_snapshot->flags, AST_FLAG_DEAD)) {
      /* Channel is gone. Compute the age of the channel and post
       * that, as well as decrementing the channel count.
       */
      int64_t age;

      age = ast_tvdiff_ms(*stasis_message_timestamp(message),
         update->new_snapshot->base->creationtime);
      ast_statsd_log("channels.calltime", AST_STATSD_TIMER, age);

      /* And decrement the channel count */
      ast_statsd_log_string("channels.count", AST_STATSD_GAUGE, "-1", 1.0);
   }
}

/*!
 * \brief Router callback for any message that doesn't otherwise have a route.
 * \param data Data pointer given when added to router.
 * \param sub This subscription.
 * \param topic The topic the message was posted to. This is not necessarily the
 *              topic you subscribed to, since messages may be forwarded between
 *              topics.
 * \param message The message itself.
 */
static void default_route(void *data, struct stasis_subscription *sub,
   struct stasis_message *message)
{
   if (stasis_subscription_final_message(sub, message)) {
      /* Much like with the regular subscription, you may need to
       * perform some cleanup when done with a message router. You
       * can look for the final message in the default route.
       */
      return;
   }
}

static int unload_module(void)
{
   stasis_unsubscribe_and_join(sub);
   sub = NULL;
   stasis_message_router_unsubscribe_and_join(router);
   router = NULL;
   return 0;
}

static int load_module(void)
{
   /* You can create a message router to route messages by type */
   router = stasis_message_router_create(
      ast_channel_topic_all());
   if (!router) {
      return AST_MODULE_LOAD_DECLINE;
   }
   stasis_message_router_add(router, ast_channel_snapshot_type(),
      updates, NULL);
   stasis_message_router_set_default(router, default_route, NULL);

   /* Or a subscription to receive all of the messages from a topic */
   sub = stasis_subscribe(ast_channel_topic_all(), statsmaker, NULL);
   if (!sub) {
      unload_module();
      return AST_MODULE_LOAD_DECLINE;
   }
   return AST_MODULE_LOAD_SUCCESS;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_DEFAULT, "Example of how to use Stasis",
   .support_level = AST_MODULE_SUPPORT_EXTENDED,
   .load = load_module,
   .unload = unload_module,
   .requires = "res_statsd"
);