mqueue Module

Elena-Ramona Modroiu

Edited by

Elena-Ramona Modroiu

Edited by

Alex Balashov

Evariste Systems

Table of Contents

1. Admin Guide
1. Overview
2. Dependencies
2.1. Kamailio Modules
2.2. External Libraries or Applications
3. Parameters
3.1. mqueue (string)
4. Functions
4.1. mq_add(queue, key, value)
4.2. mq_fetch(queue)
4.3. mq_pv_free(queue)
4.4. mq_size(queue)
5. Exported Pseudo-variables

List of Examples

1.1. Set mqueue parameter
1.2. mq_add usage
1.3. mq_fetch usage
1.4. mq_pv_free usage
1.5. mq_size usage

Chapter 1. Admin Guide

1. Overview

The mqueue module offers a generic message queue system in shared memory for inter-process communication using the config file. One example of usage is to send time consuming operations to one or several timer processes that consumes items in the queue, without affecting SIP message handling in the socket-listening process.

There can be many defined queues. Access to queued values is done via pseudo variables.

2. Dependencies

2.1. Kamailio Modules

The following modules must be loaded before this module:

  • None.

2.2. External Libraries or Applications

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

  • None.

3. Parameters

3.1. mqueue (string)

Definition of a memory queue

Default value is none.

Value must be a list of parameters: attr=value;... The attribute 'name' is mandatory, defining the name of the queue. Optional attribute 'size' specifies the maximum number of items in queue, if it is execeeded the oldest one is removed.

The parameter can be set many times, each holding the definition of one queue.

Example 1.1. Set mqueue parameter

modparam("mqueue", "mqueue", "name=myq;size=20;")
modparam("mqueue", "mqueue", "name=qaz")

4. Functions

4.1.  mq_add(queue, key, value)

Add a new item (key, value) in the queue. If max size of queue is exceeded, the oldest one is removed.

Example 1.2. mq_add usage

mq_add("myq", "$rU", "call from $fU");

4.2.  mq_fetch(queue)

Take oldest item from queue and fill $mqk(queue) and $mqv(queue) pseudo variables.

Return: true on success (1); false on failure (-1) or no item fetched (-2).

Example 1.3. mq_fetch usage

   xlog("$mqk(myq) - $mqv(myq)\n");

4.3.  mq_pv_free(queue)

Free the item fetched in pseudo-variables. It is optional, a new fetch frees the previous values.

Example 1.4. mq_pv_free usage


4.4.  mq_size(queue)

Returns the current number of elements in the mqueue.

If the mqueue is empty, the function returns -1. If the mqueue is not found, the function returns -2.

Example 1.5. mq_size usage

$var(q_size) = mq_size("queue");
xlog("L_INFO", "Size of queue is: $var(q_size)\n");

5. Exported Pseudo-variables

  • $mqv(mqueue) - the most recent item key fetched from the specified mqueue
  • $mqv(mqueue) - the most recent item value fetched from the specified mqueue
  • $mq_size(mqueue) - the size of the specified mqueue

Exported pseudo-variables are documented at