KeepAlive Module

Guillaume Bour

Edited by

Guillaume Bour

Table of Contents

1. Admin Guide
1. Overview
2. Dependencies
2.1. Kamailio Modules
2.2. External Libraries or Applications
2.3. Parameters
2.3.1. ping_interval (integer)
2.3.2. destination (string)
2.4. Functions
2.4.1. is_alive(destination)
2. Developer Guide
1. Available Functions
1.1. add_destination(uri, owner, flags, [callback, [user_attr]])
1.2. Examples

List of Examples

1.1. Set ping_interval parameter
1.2. Set destination parameter
1.3. is_alive() usage
2.1. Loading KeepAlive module's API from another module, adding a destination to monitor & registering a callback

Chapter 1. Admin Guide

1. Overview

This module performs destinations monitoring either for itself, or on the behalf of other modules. The monitoring is done by sending SIP OPTIONS requests, more or less in the same fashion as the dispatcher module (which was the initial source for this module).

As an example of usage by other modules, see drouting, which was enhanced to use this module to monitor its gateways.

2. Dependencies

2.1. Kamailio Modules

The following modules must be loaded before this module:

  • tm - Transaction module

2.2. External Libraries or Applications

The following libraries or applications must be installed before running Kamailio with this module loaded:

  • none

2.3. Parameters

2.3.1. ping_interval (integer)

Define the interval (in seconds) ping requests are sent to destinations

Default value is 30 seconds.

Example 1.1. Set ping_interval parameter

modparam("keepalive", "ping_interval", 10)

2.3.2. destination (string)

Allows to statically define destinations you want to monitor

Example 1.2. Set destination parameter

modparam("keepalive", "destination", "")
modparam("keepalive", "destination", "")

2.4. Functions

2.4.1.  is_alive(destination)

Get destination status.

The Parameter destination is destination you want to check status

Returned value:

  • 1 if destination is up
  • 2 if destination is down
  • -1 on error

This function can be used from ANY_ROUTE.

Example 1.3. is_alive() usage

if(is_alive("") == 1) {
  // do stuff

Chapter 2. Developer Guide

The KeepAlive module provides an internal API to be used by other Kamailio modules. This API offers support for destinations monitoring.

For internal (non-script) usage, the KeepAlive module offers to other module the possibility to register callback functions to be executed for each destination's status change.

1. Available Functions

1.1.  add_destination(uri, owner, flags, [callback, [user_attr]])

This function registers a new destination to monitor. Monitoring of the destination starts as soon as it returns with success (0 value).

Meaning of the parameters is as follows:

  • uri (string) - address of destination to monitor. Valid format is [proto:]ip[:port], with:

    • proto being one of sip or sips (SIP over TLS). If omitted, sip is used by default
    • port being optional (using default standard port, 5060 for sip and 5061 for sips)
  • owner (string) - module name owning the destination (for information purpose)

  • flags (integer) - destination flags (unused for now, use 0 value)

  • callback (ka_statechanged_f, optional) - callback function, executed on destination's state change.

    The callback function is of type void (*ka_statechanged_f)(str *uri, int state, void *user_attr);. Use NULL to set no callback.

    destination's state value is one of:

    • 0 - unknown state (this is the destination state at first, waiting first ping replies or timeout)
    • 1 - destination is UP
    • 2 - destination is DOWN
  • user_attr (void * pointer, optional) - If callback function is setup, this parameter will be forwarded to it, as last parameter. Use NULL to set no user_attr parameter.

Returned values:

  • 0 if ok
  • -1 if an error occurred

1.2. Examples

Example 2.1. Loading KeepAlive module's API from another module, adding a destination to monitor & registering a callback

#include "../keepalive/api.h"
keepalive_api_t ka_api;
/* loading keepalive API */
if (bind_keepalive( &ka_api ) != 0) {
    LM_ERR("can't load KeepAlive API\n");
    goto error;
/* callback function */
void my_callback(str uri, int state, void *user_attr) {

	printf("%.*s new state is: %d\n", uri.len, uri.str, state)

/* register a new destination */
str dest  = str_init("sip:");
str owner = str_init("mymodule");

if (ka_api.add_destination(dest, owner, 0, my_callback, NULL) != 0) {
    LM_ERR("can't add destination\n");
    goto error;