res_prometheus: Add Asterisk bridge metrics

This patch adds basic Asterisk bridge statistics to the res_prometheus
module. This includes:

* asterisk_bridges_count: The current number of bridges active on the
  system.

* asterisk_bridges_channels_count: The number of channels active in a
  bridge.

In all cases, enough information is provided with each bridge metric
to determine a unique instance of Asterisk that provided the data, along
with the technology, subclass, and creator of the bridge.

ASTERISK-28403

Change-Id: Ie27417dd72c5bc7624eb2a7a6a8829d7551788dc

res/prometheus/bridges.c

@@ -0,0 +1,182 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2019 Sangoma, Inc.
+ *
+ * Matt Jordan <mjordan@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.
+ */
+
+/*!
+ * \file
+ * \brief Prometheus Bridge Metrics
+ *
+ * \author Matt Jordan <mjordan@digium.com>
+ *
+ */
+
+#include "asterisk.h"
+
+#include "asterisk/stasis_bridges.h"
+#include "asterisk/res_prometheus.h"
+#include "prometheus_internal.h"
+
+#define BRIDGES_CHANNELS_COUNT_HELP "Number of channels in the bridge."
+
+/*!
+ * \internal
+ * \brief Callback function to get the number of channels in a bridge
+ *
+ * \param metric The metric to populate
+ * \snapshot Bridge snapshot
+ */
+static void get_bridge_channel_count(struct prometheus_metric *metric, struct ast_bridge_snapshot *snapshot)
+{
+	snprintf(metric->value, sizeof(metric->value), "%d", snapshot->num_channels);
+}
+
+/*!
+ * \internal
+ * \brief Helper struct for generating individual bridge stats
+ */
+struct bridge_metric_defs {
+	/*!
+	 * \brief Help text to display
+	 */
+	const char *help;
+	/*!
+	 * \brief Name of the metric
+	 */
+	const char *name;
+	/*!
+	 * \brief Callback function to generate a metric value for a given bridge
+	 */
+	void (* const get_value)(struct prometheus_metric *metric, struct ast_bridge_snapshot *snapshot);
+} bridge_metric_defs[] = {
+	{
+		.help = BRIDGES_CHANNELS_COUNT_HELP,
+		.name = "asterisk_bridges_channels_count",
+		.get_value = get_bridge_channel_count,
+	},
+};
+
+/*!
+ * \internal
+ * \brief Callback invoked when Prometheus scrapes the server
+ *
+ * \param response The response to populate with formatted metrics
+ */
+static void bridges_scrape_cb(struct ast_str **response)
+{
+	struct ao2_container *bridges;
+	struct ao2_iterator it_bridges;
+	struct ast_bridge *bridge;
+	struct prometheus_metric *bridge_metrics;
+	char eid_str[32];
+	int i, j, num_bridges;
+	struct prometheus_metric bridge_count = PROMETHEUS_METRIC_STATIC_INITIALIZATION(
+		PROMETHEUS_METRIC_GAUGE,
+		"asterisk_bridges_count",
+		"Current bridge count.",
+		NULL
+	);
+
+	ast_eid_to_str(eid_str, sizeof(eid_str), &ast_eid_default);
+
+	bridges = ast_bridges();
+	if (!bridges) {
+		return;
+	}
+	num_bridges = ao2_container_count(bridges);
+
+	/* Current endpoint count */
+	PROMETHEUS_METRIC_SET_LABEL(&bridge_count, 0, "eid", eid_str);
+	snprintf(bridge_count.value, sizeof(bridge_count.value), "%d", num_bridges);
+	prometheus_metric_to_string(&bridge_count, response);
+
+	if (num_bridges == 0) {
+		ao2_ref(bridges, -1);
+		return;
+	}
+
+	bridge_metrics = ast_calloc(ARRAY_LEN(bridge_metric_defs) * num_bridges, sizeof(*bridge_metrics));
+	if (!bridge_metrics) {
+		ao2_ref(bridges, -1);
+		return;
+	}
+
+	/* Bridge dependent values */
+	it_bridges = ao2_iterator_init(bridges, 0);
+	for (i = 0; (bridge = ao2_iterator_next(&it_bridges)); ao2_ref(bridge, -1), i++) {
+		struct ast_bridge_snapshot *snapshot = ast_bridge_get_snapshot(bridge);
+
+		for (j = 0; j < ARRAY_LEN(bridge_metric_defs); j++) {
+			int index = i * ARRAY_LEN(bridge_metric_defs) + j;
+
+			bridge_metrics[index].type = PROMETHEUS_METRIC_GAUGE;
+			ast_copy_string(bridge_metrics[index].name, bridge_metric_defs[j].name, sizeof(bridge_metrics[index].name));
+			bridge_metrics[index].help = bridge_metric_defs[j].help;
+			PROMETHEUS_METRIC_SET_LABEL(&bridge_metrics[index], 0, "eid", eid_str);
+			PROMETHEUS_METRIC_SET_LABEL(&bridge_metrics[index], 1, "id", (snapshot->uniqueid));
+			PROMETHEUS_METRIC_SET_LABEL(&bridge_metrics[index], 2, "tech", (snapshot->technology));
+			PROMETHEUS_METRIC_SET_LABEL(&bridge_metrics[index], 3, "subclass", (snapshot->subclass));
+			PROMETHEUS_METRIC_SET_LABEL(&bridge_metrics[index], 4, "creator", (snapshot->creator));
+			PROMETHEUS_METRIC_SET_LABEL(&bridge_metrics[index], 5, "name", (snapshot->name));
+			bridge_metric_defs[j].get_value(&bridge_metrics[index], snapshot);
+
+			if (i > 0) {
+				AST_LIST_INSERT_TAIL(&bridge_metrics[j].children, &bridge_metrics[index], entry);
+			}
+		}
+		ao2_ref(snapshot, -1);
+	}
+	ao2_iterator_destroy(&it_bridges);
+
+	for (j = 0; j < ARRAY_LEN(bridge_metric_defs); j++) {
+		prometheus_metric_to_string(&bridge_metrics[j], response);
+	}
+
+
+	ast_free(bridge_metrics);
+	ao2_ref(bridges, -1);
+}
+
+struct prometheus_callback bridges_callback = {
+	.name = "bridges callback",
+	.callback_fn = bridges_scrape_cb,
+};
+
+/*!
+ * \internal
+ * \brief Callback invoked when the core module is unloaded
+ */
+static void bridge_metrics_unload_cb(void)
+{
+	prometheus_callback_unregister(&bridges_callback);
+}
+
+/*!
+ * \internal
+ * \brief Metrics provider definition
+ */
+static struct prometheus_metrics_provider provider = {
+	.name = "bridges",
+	.unload_cb = bridge_metrics_unload_cb,
+};
+
+int bridge_metrics_init(void)
+{
+	prometheus_metrics_provider_register(&provider);
+	prometheus_callback_register(&bridges_callback);
+
+	return 0;
+}

res/prometheus/endpoints.c

@@ -136,8 +136,9 @@ static void endpoints_scrape_cb(struct ast_str **response)
 	/* Endpoint dependent values */
 	it_endpoints = ao2_iterator_init(endpoints, 0);
 	for (i = 0; (message = ao2_iterator_next(&it_endpoints)); ao2_ref(message, -1), i++) {
-		for (j = 0; j < ARRAY_LEN(endpoint_metric_defs); j++) {
 		struct ast_endpoint_snapshot *snapshot = stasis_message_data(message);
+
+		for (j = 0; j < ARRAY_LEN(endpoint_metric_defs); j++) {
 			int index = i * ARRAY_LEN(endpoint_metric_defs) + j;
 
 			endpoint_metrics[index].type = PROMETHEUS_METRIC_GAUGE;
@@ -153,8 +154,9 @@ static void endpoints_scrape_cb(struct ast_str **response)
 				AST_LIST_INSERT_TAIL(&endpoint_metrics[j].children, &endpoint_metrics[index], entry);
 			}
 		}
-		ao2_iterator_destroy(&it_endpoints);
+		ao2_ref(snapshot, -1);
 	}
+	ao2_iterator_destroy(&it_endpoints);
 
 	for (j = 0; j < ARRAY_LEN(endpoint_metric_defs); j++) {
 		prometheus_metric_to_string(&endpoint_metrics[j], response);

res/prometheus/prometheus_internal.h

@@ -46,4 +46,12 @@ int channel_metrics_init(void);
  */
 int endpoint_metrics_init(void);
 
+/*!
+ * \brief Initialize bridge metrics
+ *
+ * \retval 0 success
+ * \retval -1 error
+ */
+int bridge_metrics_init(void);
+
 #endif /* #define PROMETHEUS_INTERNAL_H__ */

res/res_prometheus.c

@@ -917,7 +917,9 @@ static int load_module(void)
 		goto cleanup;
 	}
 
-	if (channel_metrics_init() || endpoint_metrics_init()) {
+	if (channel_metrics_init()
+		|| endpoint_metrics_init()
+		|| bridge_metrics_init()) {
 		goto cleanup;
 	}