1. Dispatcher Module

Daniel-Constantin Mierla


1.1. Overview
1.2. Parameters
1.2.1. list_file (string)
1.2.2. force_dst (int)
1.2.3. flags (int)
1.3. Functions
1.3.1. ds_select_dst(set, alg)
1.4. FIFO Interface
1.4.1. Dumping the current configuration
1.4.2. Reloading the dispatcher list
1.5. Installation And Running

1.1. Overview

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

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

The dispatcher module offers reloads on the fly using sercmd.

1.2. Parameters

1.2.1. list_file (string)

Path to the file with destination sets.

Default value is "/etc/ser/dispatcher.list" or "/usr/local/etc/ser/dispatcher.list".

Example 1. Set the "list_file" parameter

modparam("dispatcher", "list_file", "/var/run/ser/dispatcher.list")

1.2.2. force_dst (int)

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

Default value is "0".

Example 2. Set the "force_dst" parameter

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

1.2.3. flags (int)

Various flags that affect the hashing behaviour. For now only the flag 1 and 2 are defined. If flag 1 is set only the username part of the uri will be used when computing an uri based hash. If flag 2 is set the username part of the uri will be used and if no username part is present the hostname part will be used. 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).

Default value is "0".

Example 3. Set the "flags" parameter

modparam("dispatcher", "flags", 1)

1.3. Functions

1.3.1.  ds_select_dst(set, alg)

The method selects a destination from addresses set.

Meaning of the parameters is as follows:

  • set - the id of the set from where to pick up destination address. It is the first column in destination list file.

  • alg - the algorithm used to select the destination address.

    • "0" - hash over callid

    • "1" - hash over from URI.

    • "2" - hash over to URI.

    • "3" - hash over the Request-URI.

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

Example 4. ds_select_dst usage

ds_select_dst("1", "0");

1.4. FIFO Interface

The module allows dumping the current configuration as well as dispatcher list reloading via the FIFO interface.

There are two FIFO commands to use with dispatcher.

  • dispatcher.dump - dump the current dispatcher sets

  • dispatcher.reload - reload the dispatcher list text file

1.4.1. Dumping the current configuration

The command dispatcher.dump can be used to dump the currently deployed dispatcher list in the SER internal notation.

Example 5. dumping the active dispatcher list

# sercmd dispatcher.dump
Active dispatcher list: 0
Set '0'
  node  0 sip:
  node  1 sip:
  node  2 sip:
  node  3 sip:
Set '1' is empty
Set '2' is empty
Set '3' is empty
Set '4' is empty
Set '5' is empty
Set '6' is empty
Set '7' is empty
Set '8' is empty
Set '9' is empty
Set '10' is empty
Set '11' is empty
Set '12' is empty
Set '13' is empty
Set '14' is empty
Set '15' is empty

End of dispatcher list

1.4.2. Reloading the dispatcher list

The command dispatcher.reload can be used to update the dispatcher list while running SER.

Example 6. Reloading the dispatcher list

# sercmd fifo dispatcher.reload
dispatcher list 1 activated

1.5. Installation And Running

Example 7. Destination List File

Each destination point must be on one line. First token is the set id and next is destination address. The set id must be an integer value. Destination address must be a valid SIP URI. Empty lines or lines starting with "#" are ignored.

# $Id$
# dispatcher destination sets

# proxies
2 sip:
2 sip:

# gateways
1 sip:
1 sip:
1 sip:

Example 8. SER Configuration File

# $Id$
# sample config file for dispatcher module

debug=9          # debug level (cmd line: -dddddddddd)
log_stderror=yes  # (cmd line: -E)

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

# for more info: sip_router -h

# ------------------ module loading ----------------------------------

loadmodule "../sip_router/modules/maxfwd/maxfwd.so"
loadmodule "../sip_router/modules/sl/sl.so"
# loadmodule "../sip_router/modules/tm/tm.so"
loadmodule "../sip_router/modules/dispatcher/dispatcher.so"

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

modparam("dispatcher", "list_file", "../etc/dispatcher.list")
# modparam("dispatcher", "force_dst", 1)

	if ( !mf_process_maxfwd_header("10") )
	 	sl_send_reply("483","To Many Hops");
	ds_select_dst("2", "0");
	forward(uri:host, uri:port);
	# t_relay();