res_pjsip/pjsip_options: Add StatsD statistics for PJSIP contacts

This patch adds the ability to send StatsD statistics related to the
state of PJSIP contacts. This includes:
 * A GUAGE statistic measuring the count of contacts in a particular state.
   This measures how many contacts are reachable, unreachable, etc.
 * The RTT time for each contact, if those contacts are qualified. This
   provides StatsD engines useful time-based data about each contact.

ASTERISK-25571

Change-Id: Ib8378d73afedfc622be0643b87c542557e0b332c

res/res_pjsip/location.c

@@ -26,6 +26,7 @@
 #include "asterisk/sorcery.h"
 #include "include/res_pjsip_private.h"
 #include "asterisk/res_pjsip_cli.h"
+#include "asterisk/statsd.h"
 
 /*! \brief Destructor for AOR */
 static void aor_destroy(void *obj)
@@ -940,6 +941,8 @@ static int contact_apply_handler(const struct ast_sorcery *sorcery, void *object
 int ast_sip_initialize_sorcery_location(void)
 {
 	struct ast_sorcery *sorcery = ast_sip_get_sorcery();
+	int i;
+
 	ast_sorcery_apply_default(sorcery, "contact", "astdb", "registrar");
 	ast_sorcery_apply_default(sorcery, "aor", "config", "pjsip.conf,criteria=type=aor");
 
@@ -1006,6 +1009,15 @@ int ast_sip_initialize_sorcery_location(void)
 	ast_sip_register_cli_formatter(aor_formatter);
 	ast_cli_register_multiple(cli_commands, ARRAY_LEN(cli_commands));
 
+	/*
+	 * Reset StatsD gauges in case we didn't shut down cleanly.
+	 * Note that this must done here, as contacts will create the contact_status
+	 * object before PJSIP options handling is initialized.
+	 */
+	for (i = 0; i < REMOVED; i++) {
+		ast_statsd_log_full_va("PJSIP.contacts.states.%s", AST_STATSD_GUAGE, 0, 1.0, ast_sip_get_contact_status_label(i));
+	}
+
 	return 0;
 }