Copyright © 2011 Marius Bucur
Copyright © 2013 Charles Chance, Sipcentric Ltd.
Copyright © 2015 Olle E. Johansson, Edvina AB
Table of Contents
dmq_load_api(dmq_api_t* api)
register_dmq_peer(dmq_peer_t* peer)
bcast_message(dmq_peer_t* peer, str* body, dmq_node_t* except,
dmq_resp_cback_t* resp_cback, int max_forwards, str* content_type)
send_message(dmq_peer_t* peer, str* body, dmq_node_t* node,
dmq_resp_cback_t* resp_cback, int max_forwards, str* content_type)
List of Examples
server_address parameterserver_socket parameternotification_address parameternotification_channel parametermulti_notify parameternum_workers parameterworker_usleep parameterping_interval parameterdmq_handle_message usagedmq_process_message usagedmq_send_message usagedmq_bcast_message usagedmq_t_replicate usagedmq_is_from_node usagedmq_api_t structureregister_dmq_peer usagebcast_message usagesend_message usageTable of Contents
The DMQ module implements a distributed message queue on top of Kamailio in order to facilitate data propagation and replication between multiple instances, referred as "nodes" (or "peers").
The DMQ data flow between nodes is grouped in a logical entity referred as "channel" (or "bus"), many flows (channels) can be active at the same time.
The communication between the nodes is done using SIP messages, after all Kamailio's best ability is routing SIP traffic, therefore reusing the same protocol empowers DMQ cluster with flexible routing policies, advanced authorization and security policies, a.s.o. DMQ sends SIP requests using the KDMQ request method (a custom method type specific to Kamailio, compliant with SIP specifications RFC3261). Data can be sent to all the other active nodes (aka "broadcast") or to a specific single node (aka "unicast").
The nodes can utilize the DMQ channels to pass messages between them to distribute data for various services (e.g., cached items, location records, active calls, ...). This grouping of messages on channels (per service) is similar to the topic concept in a typical pub/sub system. The channel name appears in the R-URI username part of KDMQ requests.
The DMQ cluster transparently deals with node discovery, availability, consistency, retransmissions, etc. A new node can join the DMQ cluster by sending an availability notification to an existing node in the clusters. Nodes that are not responding to KDMQ reguests are removed the from local list of active nodes, no longer being considered to be part of the KDMQ cluster.
IMPORTANT: DMQ must be used only between Kamailio instances having same major version. Internal structures can be incompatible between different major versions and can lead to crashes or unexpected behaviour.
KDMQ messages can have different format and content for R-URI username, headers and body, being specific to each component that leverages DMQ to replicate data, such as htable, dialog or usrloc modules.
Next request is generated by DMQ module for peers availability notifications.
Example 1.1. KDMQ Request Example
... KDMQ sip:notification_peer@192.168.40.15:5090 SIP/2.0 Via: SIP/2.0/UDP 192.168.40.15;branch=z9hG4bK55e5.423d95110000 To: <sip:notification_peer@192.168.40.15:5090> From: <sip:notification_peer@192.168.40.15:5060>;tag=2cdb7a33a7f21abb98fd3a44968e3ffd-5b01 CSeq: 10 KDMQ Call-ID: 1fe138e07b5d0a7a-50419@192.168.40.15 Content-Length: 116 User-Agent: kamailio (4.3.0 (x86_64/linneaus)) Max-Forwards: 1 Content-Type: text/plain sip:192.168.40.16:5060;status=active sip:192.168.40.15:5060;status=disabled sip:192.168.40.17:5060;status=active ...
The local server address. This is the address with which the local DMQ node joins the servers group to send/receive messages.
Note: if server_socket is not set, then this address has to match a local socket, which will be used to send/receive messages.
Default value is “NULL”.
Example 1.2. Set server_address parameter
...
modparam("dmq", "server_address", "sip:10.0.0.20:5060")
...
modparam("dmq", "server_address", "sip:10.0.0.20:5061;transport=tls")
...
The local listen address. This is the interface over which the DMQ engine will send/receive messages.
Note: if this parameter is not set, the socket to send/receive messages is built from server_address parameter.
Default value is “NULL”.
Example 1.3. Set server_socket parameter
...
modparam("dmq", "server_socket", "udp:10.0.0.20:5060")
...
The address of another DMQ node from which the local node should retrieve initial information about all other nodes. This parameter can be specified multiple times in the configuration, to configure multiple notification servers. If you configure multiple notification servers, the multi_notify parameter needs to be disabled.
Default value is “NULL”.
Example 1.4. Set notification_address parameter
...
modparam("dmq", "notification_address", "sip:10.0.0.21:5060")
...
modparam("dmq", "notification_address", "sip:10.0.0.21:5061;transport=tls")
...
The name of the channel for notifications about peers availability.
Default value is “notification_peer”.
Example 1.5. Set notification_channel parameter
...
modparam("dmq", "notification_channel", "peers")
...
Enables the ability to resolve multiple IPv4/IPv6 addresses for a single notification address. Please note that this mode is not supported if you specify multiple notification address parameter.
A value of zero resolves to the first IP address found. A non-zero value resolves to all IP addresses associated with the host. This includes addresses from DNS SRV records, A and AAAA records.
Default value is “0”.
The number of worker threads for sending/receiving messages.
Default value is “2”.
The default locking/synchronisation mechanism between producer/consumer threads is the optimum for most environments. On some systems (e.g. FreeBSD) it can cause high CPU load and in such cases, it can be useful to disable locking and switch to polling for tasks at set intervals instead - putting the thread to sleep in-between and taking it out of process during that time.
A value >0 will disable the default locking and set the polling interval (in microseconds), which can be tuned to suit the specific environment.
Default value is 0 (recommended for most systems).
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.
Meaning of parameters:
continue - by default, dmq_handle_message() will end execution of routing script. If this optional parameter is set to "1", dmq_handle_message() will continue executing the routing script after it's been called.
This function can be used from REQUEST_ROUTE.
Similar to dmq_handle_message, but the processing is happening immediately, no longer cloning the request in shared memory to be passed to a DMQ worker process.
Meaning of parameters:
continue - by default, dmq_process_message() will end execution of routing script by returning 0. If this optional parameter is set to "1", dmq_process_message() will continue executing the routing script after it is been executed, returning 1.
This function can be used from REQUEST_ROUTE.
Sends a DMQ message directly from config file to a single node.
Meaning of parameters:
channel - name of the channel that should handle the message.
node - the SIP address of 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 1.12. dmq_send_message usage
...
dmq_send_message("channel1", "sip:10.0.0.21:5060", "Message body...", "text/plain");
...
Broadcasts a DMQ message from config file to all active nodes (except self) on the specific channel.
Meaning of parameters:
channel - name of the channel that should handle the message.
body - the message body.
content_type - the MIME type of the message body.
This function can be used from any route.
Example 1.13. dmq_bcast_message usage
...
dmq_bcast_message("channel1", "Message body...", "text/plain");
...
Replicates the current SIP message to all active nodes (except self). Useful for replicating REGISTER, PUBLISH etc. in a clustered environment.
Meaning of parameters:
skip_loop_test - by default, DMQ checks the source IP of the message prior to replication, to ensure it has not been sent by another DMQ node (to avoid infinite loops). If this optional parameter is set to "1", the loop test is not performed. This makes sense, from a performance perspective, if you have already performed the necessary checks in the config script (see dmq_is_from_node()).
This function can be used from REQUEST_ROUTE only.
Checks whether the current message has been sent by another active DMQ node in the cluster.
This function can be used from REQUEST_ROUTE only.
Example 1.15. dmq_is_from_node usage
...
# basic example for REGISTER replication
if(is_method("REGISTER")) {
if (dmq_is_from_node()) {
# coming from a DMQ node - already authenticated there
# now just save contact, etc...
} else {
# coming from end point - authenticate, save contact, etc...
dmq_t_replicate("1"); # source address checked, skip the loop test
}
}
...
List the DMQ nodes. It has no parameters.
Table of Contents
dmq_load_api(dmq_api_t* api)
register_dmq_peer(dmq_peer_t* peer)
bcast_message(dmq_peer_t* peer, str* body, dmq_node_t* except,
dmq_resp_cback_t* resp_cback, int max_forwards, str* content_type)
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.
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;
...
Registers an entity as a DMQ peer which permits receiving/sending messages between nodes which support the same peer.
Broadcast a DMQ message to all nodes in the DMQ bus excluding self, inactive nodes and "except" if specified.