DISPATCHER Module

Daniel-Constantin Mierla

Edited by

Ovidiu Sas

Edited by

Daniel-Constantin Mierla

Edited by

Carsten Bock

BASIS AudioNet GmbH
Revision History
Revision $Revision: 6771 $$Date$

Table of Contents

1. Admin Guide
1.1. Overview
1.2. Dependencies
1.2.1. OpenSIPS modules
1.2.2. External libraries or applications
1.3. Exported Parameters
1.3.1. db_url (string)
1.3.2. flags (int)
1.3.3. force_dst (int)
1.3.4. use_default (int)
1.3.5. attrs_avp (str)
1.3.6. hash_pvar (str)
1.3.7. setid_pvar (str)
1.3.8. ds_ping_method (string)
1.3.9. ds_ping_from (string)
1.3.10. ds_ping_interval (int)
1.3.11. ds_probing_sock (str)
1.3.12. ds_probing_threshhold (int)
1.3.13. ds_probing_mode (int)
1.3.14. ds_define_blacklist (str)
1.3.15. options_reply_codes (str)
1.3.16. dst_avp (str)
1.3.17. grp_avp (str)
1.3.18. cnt_avp (str)
1.3.19. sock_avp (str)
1.3.20. pvar_algo_pattern (str)
1.3.21. table_name (string)
1.3.22. setid_col (string)
1.3.23. destination_col (string)
1.3.24. flags_col (string)
1.3.25. weight_col (string)
1.3.26. attrs_col (string)
1.3.27. socket_col (string)
1.4. Exported Functions
1.4.1. ds_select_dst(set, alg [, max_results])
1.4.2. ds_select_domain(set, alg [, max_results])
1.4.3. ds_next_dst()
1.4.4. ds_next_domain()
1.4.5. ds_mark_dst()
1.4.6. ds_mark_dst("s")
1.4.7. ds_count(set, filter, result)
1.4.8. ds_is_in_list(ip, port [,set [,active_only]])
1.5. Exported MI Functions
1.5.1. ds_set_state
1.5.2. ds_list
1.5.3. ds_reload
1.6. Exported Events
1.6.1. E_DISPATCHER_STATUS
1.7. Installation and Running
1.7.1. OpenSIPS config file
2. Frequently Asked Questions

List of Examples

1.1. Set “db_url” parameter
1.2. Set the “flags” parameter
1.3. Set the “force_dst” parameter
1.4. Set the “use_default” parameter
1.5. Set the “attrs_avp” parameter
1.6. Use $avp(273) for hashing:
1.7. Use combination of PVs for hashing:
1.8. Set the “setid_pvar” parameter
1.9. Set the “ds_ping_method” parameter
1.10. Set the “ds_ping_from” parameter
1.11. Set the “ds_ping_interval” parameter
1.12. Set the “ds_probing_sock” parameter
1.13. Set the “ds_probing_threshhold” parameter
1.14. Set the “ds_probing_mode” parameter
1.15. Set the “ds_define_blacklist” parameter
1.16. Set the “options_reply_codes” parameter
1.17. Set the “dst_avp” parameter
1.18. Set the “grp_avp” parameter
1.19. Set the “cnt_avp” parameter
1.20. Set the “sock_avp” parameter
1.21. Set the “pvar_algo_pattern” parameter
1.22. Set “table_name” parameter
1.23. Set “setid_col” parameter
1.24. Set “destination_col” parameter
1.25. Set “flags_col” parameter
1.26. Set “weight_col” parameter
1.27. Set “attrs_col” parameter
1.28. Set “socket_col” parameter
1.29. ds_select_dst usage
1.30. ds_count usage
1.31. ds_is_in_list usage
1.32. OpenSIPS config script - sample dispatcher usage

Chapter 1. Admin Guide

1.1. Overview

This modules implements a dispatcher for destination addresses. It computes hashes over various parts of the request and selects an address from a destination set. The selected address is then used as outbound proxy.

The module can be used as a stateless load balancer, having no guarantee of fair distribution.

For the distribution algotrithm, the module allows the definition of weights for the destination. This is useful in order to get a different ratio of traffic between destinations.

1.2. Dependencies

1.2.1. OpenSIPS modules

The following modules must be loaded before this module:

  • TM - only if active recovery of failed hosts is required.

1.2.2. External libraries or applications

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

  • none.

1.3. Exported Parameters

1.3.1. db_url (string)

Database where to load the destinations from.

Default value is “NULL” (use default DB URL from core).

Example 1.1. Set “db_url” parameter

...
modparam("dispatcher", "db_url", "mysql://user:passwb@localhost/database")
...

1.3.2. flags (int)

Various flags that affect dispatcher's behaviour. The flags are defined as a bitmask on an integer value. If flag 1 is set only the username part of the uri will be used when computing an uri based hash. If no flags are set the username, hostname and port will be used The port is used only if different from 5060 (normal sip uri) or 5061 (in the sips case).

If flag 2 is set, then the failover support is enabled. The functions exported by the module will store the rest of addresses from the destination set in AVP, and use these AVPs to contact next address when the current-tried fails.

Default value is “0”.

Example 1.2. Set the “flags” parameter

...
modparam("dispatcher", "flags", 3)
...

1.3.3. force_dst (int)

If set to 1, force overwriting of destination address when that is already set.

Default value is “0”.

Example 1.3. Set the “force_dst” parameter

...
modparam("dispatcher", "force_dst", 1)
...

1.3.4. use_default (int)

If the parameter is set to 1, the last address in destination set is used as last option to send the message. For example, it is good when wanting to send the call to an anouncement server saying: "the gateways are full, try later".

Default value is “0”.

Example 1.4. Set the “use_default” parameter

...
modparam("dispatcher", "use_default", 1)
...

1.3.5. attrs_avp (str)

The name of the avp to contain the attributes string of the current destination. When a destination is selected, automatically, this AVP will provide the attributes string - this is an opaque string (from OpenSIPS point of view) : it is loaded from destination definition ( via DB) and blindly provided in the script.

Note

Default value is “null” - don't provide ATTRIBUTEs.

Example 1.5. Set the “attrs_avp” parameter

...
modparam("dispatcher", "attrs_avp", "$avp(272)")
...

1.3.6. hash_pvar (str)

String with PVs used for the hashing algorithm 7.

Note

You must set this parameter if you want do hashing over custom message parts.

Default value is “null” - disabled.

Example 1.6. Use $avp(273) for hashing:

...
modparam("dispatcher", "hash_pvar", "$avp(273)")
...

Example 1.7. Use combination of PVs for hashing:

...
modparam("dispatcher", "hash_pvar", "hash the $fU@$ci")
...

1.3.7. setid_pvar (str)

The name of the PV where to store the set ID (group ID) when calling ds_is_in_list() without group parameter (third parameter).

Default value is “null” - don't set PV.

Example 1.8. Set the “setid_pvar” parameter

...
modparam("dispatcher", "setid_pvar", "$var(setid)")
...

1.3.8. ds_ping_method (string)

With this Method you can define, with which method you want to probe the failed gateways. This method is only available, if compiled with the probing of failed gateways enabled.

Default value is “OPTIONS”.

Example 1.9. Set the “ds_ping_method” parameter

...
modparam("dispatcher", "ds_ping_method", "INFO")
...

1.3.9. ds_ping_from (string)

With this Method you can define the "From:"-Line for the request, sent to the failed gateways. This method is only available, if compiled with the probing of failed gateways enabled.

Default value is “sip:dispatcher@localhost”.

Example 1.10. Set the “ds_ping_from” parameter

...
modparam("dispatcher", "ds_ping_from", "sip:proxy@sip.somehost.com")
...

1.3.10. ds_ping_interval (int)

With this Method you can define the interval for sending a request to a failed gateway. This parameter is only used, when the TM-Module is loaded. If set to “0”, the pinging of failed requests is disabled.

Default value is “0” (disabled).

Example 1.11. Set the “ds_ping_interval” parameter

...
modparam("dispatcher", "ds_ping_interval", 30)
...

1.3.11. ds_probing_sock (str)

A socket description [proto:]host[:port] of the local socket (which is used by OpenSIPS for SIP traffic) to be used (if multiple) for sending the probing messages from.

Default value is “NULL(none)”.

Example 1.12. Set the “ds_probing_sock” parameter

...
modparam("dispatcher", "ds_probing_sock", "udp:192.168.1.100:5077")
...

1.3.12. ds_probing_threshhold (int)

If you want to set a gateway into probing mode, you will need a specific number of requests until it will change from "active" to probing. The number of attempts can be set with this parameter.

Default value is “3”.

Example 1.13. Set the “ds_probing_threshhold” parameter

...
modparam("dispatcher", "ds_probing_threshhold", 10)
...

1.3.13. ds_probing_mode (int)

Controls what gateways are tested to see if they are reachable. If set to 0, only the gateways with state PROBING are tested, if set to 1, all gateways are tested. If set to 1 and the response is 408 (timeout), an active gateway is set to PROBING state.

Default value is “0”.

Example 1.14. Set the “ds_probing_mode” parameter

...
modparam("dispatcher", "ds_probing_mode", 1)
...

1.3.14. ds_define_blacklist (str)

Defines a blacklist based on a dispatching setid. This list will contain the IPs (no port, all protocols) of the destinations matching the given setid.

Multiple instances of this param are allowed.

Default value is “NULL”.

Example 1.15. Set the “ds_define_blacklist” parameter

...
modparam("dispatcher", "ds_define_blacklist", "list= 1,4,3")
modparam("dispatcher", "ds_define_blacklist", "blist2= 2,10,6")
...

1.3.15. options_reply_codes (str)

This parameter must contain a list of SIP reply codes separated by comma. The codes defined here will be considered as valid reply codes for OPTIONS messages used for pinging, apart for 200.

Default value is “NULL”.

Example 1.16. Set the “options_reply_codes” parameter

...
modparam("dispatcher", "options_reply_codes", "501, 403")
...

1.3.16. dst_avp (str)

This is mainly for internal usage and represents the name of the avp which will hold the list with addresses, in the order they have been selected by the chosen algorithm. If use_default is 1, the value of last dst_avp_id is the last address in destination set. The first dst_avp_id is the selected destinations. All the other addresses from the destination set will be added in the avp list to be able to implement serial forking.

Default value is “$avp(ds_dst_failover)

Example 1.17. Set the “dst_avp” parameter

...
modparam("dispatcher", "dst_avp", "$avp(271)")
...

1.3.17. grp_avp (str)

This is mainly for internal usage and represents the name of the avp storing the group id of the destination set. Good to have it for later usage or checks.

Default value is “$avp(ds_grp_failover)”.

Example 1.18. Set the “grp_avp” parameter

...
modparam("dispatcher", "grp_avp", "$avp(273)")
...

1.3.18. cnt_avp (str)

This is mainly for internal usage and represents the name of the avp storing the number of destination addresses kept in dst_avp avps.

Default value is “$avp(ds_cnt_failover)”.

Example 1.19. Set the “cnt_avp” parameter

...
modparam("dispatcher", "cnt_avp", "$avp(274)")
...

1.3.19. sock_avp (str)

This is mainly for internal usage and represents the name of the avp storing the sockets to be used for the destination addresses kept in dst_avp avps.

Default value is “$avp(ds_sock_failover)”.

Example 1.20. Set the “sock_avp” parameter

...
modparam("dispatcher", "sock_avp", "$avp(275)")
...

1.3.20. pvar_algo_pattern (str)

This parameter is used by the PVAR(9) algorithm to specify the pseudovariable pattern used to detect the load of each destination. The name of the pseudovariable should contain the string “%u”, which will be internally replaced by the module with the uri of the destination.

Default value is “none”.

Example 1.21. Set the “pvar_algo_pattern” parameter

...
modparam("dispatcher", "sock_avp", "$stat(load_%u)")
...

1.3.21. table_name (string)

If you want to load the sets of gateways from the database you must set this parameter as the database name.

Default value is “dispatcher”.

Example 1.22. Set “table_name” parameter

...
modparam("dispatcher", "table_name", "my_dispatcher")
...

1.3.22. setid_col (string)

The column's name in the database storing the gateway's group id.

Default value is “setid”.

Example 1.23. Set “setid_col” parameter

...
modparam("dispatcher", "setid_col", "groupid")
...

1.3.23. destination_col (string)

The column's name in the database storing the destination's sip uri.

Default value is “destination”.

Example 1.24. Set “destination_col” parameter

...
modparam("dispatcher", "destination_col", "uri")
...

1.3.24. flags_col (string)

The column's name in the database storing the flags for destination uri.

Default value is “flags”.

Example 1.25. Set “flags_col” parameter

...
modparam("dispatcher", "flags_col", "dstflags")
...

1.3.25. weight_col (string)

The column's name in the database storing the weight for destination uri.

Default value is “weight”.

Example 1.26. Set “weight_col” parameter

...
modparam("dispatcher", "weight_col", "dstweight")
...

1.3.26. attrs_col (string)

The column's name in the database storing the attributes (opaque string) for destination uri.

Default value is “attrs”.

Example 1.27. Set “attrs_col” parameter

...
modparam("dispatcher", "attrs_col", "dstattrs")
...

1.3.27. socket_col (string)

The column's name in the database storing the socket (as string) for destination uri.

Default value is “socket”.

Example 1.28. Set “socket_col” parameter

...
modparam("dispatcher", "socket_col", "my_sock")
...

1.4. Exported Functions

1.4.1.  ds_select_dst(set, alg [, max_results])

The method selects a destination from the given set of addresses. It will overwrite the "destination URI" of a SIP request ($du).

Meaning of the parameters is as follows:

  • set - the id of the set or a list of sets from where to pick up destination address (variables are accepted).

  • alg - the algorithm(s) used to select the destination address (variables are accepted).

    • 0” - hash over callid

    • 1” - hash over from uri.

    • 2” - hash over to uri.

    • 3” - hash over request-uri.

    • 4” - round-robin (next destination).

    • 5” - hash over authorization-username (Proxy-Authorization or "normal" authorization). If no username is found, round robin is used.

    • 6” - random (using rand()).

    • 7” - hash over the content of PVs string. Note: This works only when the parameter hash_pvar is set.

    • 8” - the first entry in set is chosen.

    • 9” - The pvar_algo_pattern parameter is used to determine the load on each server. If the parameter is not specified, then the first entry in the set is chosen.

    • X” - if the algorithm is not implemented, the first entry in set is chosen.

  • max_results - If specified, only that many results will be put into the specified avp for failover. This allows having many destinations but limit the useless traffic in case of a number that is bound to fail everywhere. It can accept variables.

If the bit 2 in 'flags' is set, the rest of the addresses from the destination set is stored in AVP list. You can use 'ds_next_dst()' to use next address to achieve serial forking to all possible destinations. If multiple dispatching groups are used, the AVP list is constructed based on the position of each dispatching id in the list: first one has the higher priority, followed by the second one and so on.

This function can be used from REQUEST_ROUTE and FAILURE_ROUTE.

Example 1.29. ds_select_dst usage

...
ds_select_dst("1", "0");
...
ds_select_dst("1", "0", "5");
...
# dispatch over multiple dispatching groups
$var(setid) = "1, 2";
$var(alg) = "4, 2";
$var(max) = "2,3";
ds_select_dst("$var(setid)", "$var(alg)", "$var(max)");
...

1.4.2.  ds_select_domain(set, alg [, max_results])

The method selects a destination from addresses set and rewrites the host and port from R-URI. The parameters have same meaning as for ds_select_dst().

If the bit 2 in 'flags' is set, the rest of the addresses from the destination set is stored in AVP list. You can use 'ds_next_domain()' to use next address to achieve serial forking to all possible destinations.

This function can be used from REQUEST_ROUTE and FAILURE_ROUTE.

1.4.3.  ds_next_dst()

Takes the next destination address from the AVPs with id 'dst_avp_id' and sets the dst_uri (outbound proxy address).

This function can be used from REQUEST_ROUTE and FAILURE_ROUTE.

1.4.4.  ds_next_domain()

Takes the next destination address from the AVPs with id 'dst_avp_id' and sets the domain part of the request uri.

This function can be used from REQUEST_ROUTE and FAILURE_ROUTE.

1.4.5.  ds_mark_dst()

Mark the last used address from destination set as inactive, in order to be ingnored in the future. In this way it can be implemented an automatic detection of failed gateways. When an address is marked as inactive, it will be ignored by 'ds_select_dst' and 'ds_select_domain'.

This function can be used from REQUEST_ROUTE and FAILURE_ROUTE.

1.4.6.  ds_mark_dst("s")

Mark the last used address from destination set as inactive ("i"/"I"/"0"), active ("a"/"A"/"1") or probing ("p"/"P"/"2"). With this function, an automatic detection of failed gateways can be implemented. When an address is marked as inactive or probing, it will be ignored by 'ds_select_dst' and 'ds_select_domain'.

possible parameters:

  • "i", "I" or "0" - the last destination should be set to inactive and will be ignored in future requests.

  • "a", "A" or "1" - the last destination should be set to active.

  • "p", "P" or "2" - the last destination will be set to probing. Note: You will need to call this function "threshhold"-times, before it will be actually set to probing.

This function can be used from REQUEST_ROUTE and FAILURE_ROUTE.

1.4.7.  ds_count(set, filter, result)

Returns the number of active, inactive or probing destinations in a set, or combinations between these properties.

Meaning of the parameters:

  • set - a set of dispatching destinations. The set parameter can have the following types:

    • integer - the dispatching set is passed in a static manner

    • pvar - the dispatching set is the value of an existing pseudo-variable (as integer value)

  • filter - which destinations should be counted. Either active destinations("a", "A" or "1"), inactive destinations("i", "I" or "0") or probing ones("p", "P" or "2") or different combinations between these flags, such as "pI", "1i", "ipA"... The filter parameter can have the following types:

    • string - the filtering flags are statically assigned

  • result - A pseudovariable for storing the result.

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE, LOCAL_ROUTE, TIMER_ROUTE, EVENT_ROUTE

Example 1.30. ds_count usage

...
if (ds_count("1", "a", "$avp(result)")) {
	...
}
...
if (ds_count("$avp(set)", "ip", "$avp(result)")) {
	...
}
...

1.4.8.  ds_is_in_list(ip, port [,set [,active_only]])

This function returns true, if the parameters ip and port point to a host from the dispatcher-list; otherwise false.

Meaning of the parameters:

  • ip - a PV (pseudo-variable) containing (as string) the IP to test against the dispatcher list. This cannot be empty.

  • port - a PV (pseudo-variable) containing (as integer) the PORT to test against the dispatcher list. This can be empty - in this case the port will excluded from the matching of IP against the dispatcher list.

  • set (optional) - the set ID of a dispatcher list to test agaist - if missing, all the dispatching sets will the checked.

  • active_only (optional) - search only through the active destinations (ignore the ones in probing and inactive mode).

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE and ONREPLY_ROUTE.

Example 1.31. ds_is_in_list usage

...
if (ds_is_in_list("$si", "$sp")) {
	# source IP:PORT is in a dispatcher list
}
...
if (ds_is_in_list("$rd", "$rp", "2")) {
	# source RURI (ip and port) is in the dispatcher list id "2"
}
...

1.5. Exported MI Functions

1.5.1.  ds_set_state

Sets the status for a destination address (can be use to mark the destination as active or inactive).

Name: ds_set_state

Parameters:

  • _state_ : state of the destination address

    • a”: active

    • i”: inactive

    • p”: probing

  • _group_: destination group id

  • _address_: address of the destination in the _group_

MI FIFO Command Format:

:ds_set_state:_reply_fifo_file_
_state_
_group_
_address_
_empty_line_

1.5.2.  ds_list

It lists the groups and included destinations.

Name: ds_list

Parameters: none

MI FIFO Command Format:

:ds_list:_reply_fifo_file_
_empty_line_

1.5.3.  ds_reload

It reloads the groups and included destinations.

Name: ds_reload

Parameters: none

MI DATAGRAM Command Format:

":ds_reload:\n."

1.6. Exported Events

1.6.1.  E_DISPATCHER_STATUS

This event is raised when the dispatcher module marks a destination as activated or deactivated.

Parameters:

  • group - the group of the destination.

  • address - the address of the destination.

  • status - active if the destination gets activated or inactive if the destination is detected unresponsive.

1.7. Installation and Running

1.7.1. OpenSIPS config file

Next picture displays a sample usage of dispatcher.

Example 1.32. OpenSIPS config script - sample dispatcher usage

...
#
# $Id$
# sample config file for dispatcher module
#

debug=9          # debug level (cmd line: -ddddddd)
fork=no
log_stderror=yes  # (cmd line: -E)

children=2
check_via=no      # (cmd. line: -v)
dns=off           # (cmd. line: -r)
rev_dns=off       # (cmd. line: -R)
port=5060

# for more info: opensips -h

# ------------------ module loading ----------------------------------
mpath="/usr/local/lib/opensips/modules/"
loadmodule "maxfwd.so"
loadmodule "signaling.so"
loadmodule "sl.so"
loadmodule "tm.so"
loadmodule "db_mysql.so"
loadmodule "dispatcher.so"


# ----------------- setting module-specific parameters ---------------
# -- dispatcher params --

modparam("dispatcher", "db_url", "mysql://opensips:opensipsrw@localhost/opensips")

route{
	if ( !mf_process_maxfwd_header("10") )
	{
		send_reply("483","To Many Hops");
		exit;
	};

	if ( !ds_select_dst("2", "0") ) {
		send_reply("500","Unable to route");
		exit;
	}

	t_relay();
}

...

Chapter 2. Frequently Asked Questions

2.1.

Does dispatcher provide a fair distribution?

There is no guarantee of that. You should do some measurements to decide what distribution algorithm fits better in your environment.

2.2.

Is dispatcher dialog stateful?

No. Dispatcher is stateless, although some distribution algorithms are designed to select same destination for subsequent requests of the same dialog (e.g., hashing the call-id).

2.3.

What happend with the ds_is_from_list() function?

The function was replaced by the more generic ds_is_in_list() function that takes as parameters the IP and PORT to test against the dispatcher list.

ds_is_from_list() == ds_is_in_list("$si","$sp")

2.4.

What happend with the list_file module parameter ?

The support for text file (for provisioning destinations) was dropped. Only the DB support (provisioning via a DB table) is now available - if you still want to use a text file for provisioning, use db_text DB driver (DB emulated via text files)

2.5.

Where can I find more about OpenSIPS?

Take a look at http://www.opensips.org/.

2.6.

Where can I post a question about this module?

First at all check if your question was already answered on one of our mailing lists:

E-mails regarding any stable version should be sent to and e-mail regarding development versions or SVN snapshots should be send to .

If you want to keep the mail private, send it to .

2.7.

How can I report a bug?

Please follow the guidelines provided at: https://github.com/OpenSIPS/opensips/issues