The DMQ module implements a distributed message queue on top of Kamailio in order to enable the passing/replication of data between multiple instances. The DMQ "nodes" within the system are grouped in a logical entity called the DMQ "bus" and are able to communicate with each other by sending/receiving messages (either by broadcast or directly to a specific node). The system transparently deals with node discovery, consistency, retransmissions, etc.

Other entities ("peers") are then able to utlize the DMQ bus to pass messages between themselves. Peers are grouped by name in order to ensure the correct messages are passed to the relevant peers. This grouping of peers can be compared to a topic in a typical pub/sub system.

2. Dependencies

2.1. Kamailio Modules

The following modules must be loaded before this module:

2.2. External Libraries or Applications

The DMQ module itself has no external dependencies. However, each peer will need to use its own (de)serialization mechanism. Some examples are libtpl, protobuf. .

3. Parameters

3.1. `server_address`(str)

The local server address. This is the interface over which the DMQ engine will send/receive messages.

Default value is “NULL”.

Example 1.1. Set server_address parameter

...
modparam("dmq", "server_address", "sip:10.0.0.20:5060")
...

3.2. `notification_address`(str)

The address of another DMQ node from which the local node should retrieve initial information about all other nodes.

Default value is “NULL”.

Example 1.2. Set notification_address parameter

...
modparam("dmq", "notification_address", "sip:10.0.0.21:5060")
...

3.3. `num_workers`(int)

The number of worker threads for sending/receiving messages.

Default value is “2”.

Example 1.3. Set num_workers parameter

...
modparam("dmq", "num_threads", 4)
...

3.4. `ping_interval`(int)

The number of seconds between node pings (for checking status of other nodes).

Minimum value is “60” (default).

Example 1.4. Set ping_interval parameter

...
modparam("dmq", "ping_interval", 90)
...

4. Functions

4.1. `dmq_handle_message()`

Handles a DMQ message by passing it to the appropriate local peer (module). The peer is identified by the user part of the To header.

This function can be used from REQUEST_ROUTE.

Example 1.5. dmq_handle_message usage

...
        if(is_method("KDMQ"))
        {
                dmq_handle_message();
        }
...

4.2. `dmq_send_message(peer, node, body, content_type)`

Sends a DMQ message directly from config file.

Meaning of parameters:

peer - name of peer that should handle the message.
node - the node to which the message should be sent.
body - the message body.
content_type - the MIME type of the message body.

This function can be used from any route.

Example 1.6. dmq_send_message usage

...
	dmq_send_message("peer_name", "sip:10.0.0.21:5060", "Message body...", "text/plain");
...

Chapter 2. Developer Guide

Table of Contents

1. dmq_load_api(dmq_api_t* api)
2. register_dmq_peer(dmq_peer_t* peer)
3. bcast_message(dmq_peer_t* peer, str* body, dmq_node_t* except, dmq_resp_cback_t* resp_cback, int max_forwards, str* content_type)
4. send_message(dmq_peer_t* peer, str* body, dmq_node_t* node, dmq_resp_cback_t* resp_cback, int max_forwards, str* content_type)

The module provides the following functions that can be used in other Kamailio modules.

1. `dmq_load_api(dmq_api_t* api)`

This function binds the DMQ module and fills the structure with the exported functions below.

Example 2.1. dmq_api_t structure

...
typedef struct dmq_api {
	register_dmq_peer_t register_dmq_peer;
	bcast_message_t bcast_message;
	send_message_t send_message;
} dmq_api_t;
...

2. `register_dmq_peer(dmq_peer_t* peer)`

Registers an entity as a DMQ peer which permits receiving/sending messages between nodes which support the same peer.

Example 2.2. register_dmq_peer usage

...
	Example to follow.
...

3. `bcast_message(dmq_peer_t* peer, str* body, dmq_node_t* except, dmq_resp_cback_t* resp_cback, int max_forwards, str* content_type)`

Broadcast a DMQ message to all nodes in the DMQ bus excluding self, inactive nodes and "except" if specified.

Example 2.3. bcast_message usage

...
        Example to follow.
...

4. `send_message(dmq_peer_t* peer, str* body, dmq_node_t* node, dmq_resp_cback_t* resp_cback, int max_forwards, str* content_type)`

Send a DMQ message to a single node.

Example 2.4. send_message usage

...
        Example to follow.
...

Distributed Message Queue Module

Marius Ovidiu Bucur

Charles Chance

Edited by

Marius Ovidiu Bucur

Edited by

Charles Chance

Chapter 1. Admin Guide

1. Overview

2. Dependencies

2.1. Kamailio Modules

2.2. External Libraries or Applications

3. Parameters

3.1. server_address(str)

3.2. notification_address(str)

3.3. num_workers(int)

3.4. ping_interval(int)

4. Functions

4.1. dmq_handle_message()

4.2. dmq_send_message(peer, node, body, content_type)