Copyright © 2004 FhG FOKUS
Copyright © 2005 Voice-System.RO
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Table of Contents
list_file (string)
db_url (string)
table_name (string)
setid_col (string)
destination_col (string)
flags_col (string)
priority_col (string)
force_dst (int)
flags (int)
use_default (int)
dst_avp (str)
grp_avp (str)
cnt_avp (str)
hash_pvar (str)
setid_pvar (str)
ds_ping_method (string)
ds_ping_from (string)
ds_ping_interval (int)
ds_probing_threshhold (int)
ds_probing_mode (int)
ds_append_branch (int)
List of Examples
ds_select_dst usageTable of Contents
list_file (string)
db_url (string)
table_name (string)
setid_col (string)
destination_col (string)
flags_col (string)
priority_col (string)
force_dst (int)
flags (int)
use_default (int)
dst_avp (str)
grp_avp (str)
cnt_avp (str)
hash_pvar (str)
setid_pvar (str)
ds_ping_method (string)
ds_ping_from (string)
ds_ping_interval (int)
ds_probing_threshhold (int)
ds_probing_mode (int)
ds_append_branch (int)
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 following modules must be loaded before this module:
TM - only if active recovery of failed hosts is required.
Path to the file with destination sets.
Default value is “/etc/kamailio/dispatcher.list” or “/usr/local/etc/kamailio/dispatcher.list”.
Example 1.1. Set the “list_file” parameter
...
modparam("dispatcher", "list_file", "/var/run/kamailio/dispatcher.list")
...
If you want to load the sets of gateways from the database you must set this parameter.
Default value is “NULL” (disable DB support).
Example 1.2. Set “db_url” parameter
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modparam("dispatcher", "db_url", "mysql://user:passwb@localhost/database")
...
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 1.3. Set “table_name” parameter
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modparam("dispatcher", "table_name", "my_dispatcher")
...
The column's name in the database storing the gateway's group id.
Default value is “setid”.
The column's name in the database storing the destination's sip uri.
Default value is “destination”.
Example 1.5. Set “destination_col” parameter
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modparam("dispatcher", "destination_col", "uri")
...
The column's name in the database storing the flags for destination uri.
Default value is “flags”.
The column's name in the database storing the priority for destination uri.
Default value is “priority”.
Example 1.7. Set “priority_col” parameter
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modparam("dispatcher", "priority_col", "dstpriority")
...
If set to 1, force overwriting of destination address when that is already set.
Default value is “0”.
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”.
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”.
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.
You must set this parameter if you want do do load balancing fail over.
Default value is “null” - don't add AVPs.
The name of the avp storing the group id of the destination set. Good to have it for later usage or checks.
You must set this parameter if you want do do load balancing fail over.
Default value is “null” - don't add AVP.
The name of the avp storing the number of destination addresses kept in dst_avp avps.
You must set this parameter if you want do do load balancing fail over.
Default value is “null” - don't add AVP.
String with PVs used for the hashing algorithm 7.
You must set this parameter if you want do hashing over custom message parts.
Default value is “null” - disabled.
Example 1.14. Use $avp(i:273) for hashing:
...
modparam("dispatcher", "hash_pvar", "$avp(i:273)")
...
Example 1.15. Use combination of PVs for hashing:
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modparam("dispatcher", "hash_pvar", "hash the $fU@$ci")
...
The name of the PV where to store the set ID (group ID) when calling ds_is_from_list() with no parameter.
Default value is “null” - don't set PV.
Example 1.16. Set the “setid_pvar” parameter
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modparam("dispatcher", "setid_pvar", "$var(setid)")
...
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 1.17. Set the “ds_ping_method” parameter
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modparam("dispatcher", "ds_ping_method", "INFO")
...
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 1.18. Set the “ds_ping_from” parameter
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modparam("dispatcher", "ds_ping_from", "sip:proxy@sip.somehost.com")
...
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 “10”.
Example 1.19. Set the “ds_ping_interval” parameter
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modparam("dispatcher", "ds_ping_interval", 30)
...
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 1.20. Set the “ds_probing_threshhold” parameter
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modparam("dispatcher", "ds_probing_threshhold", 10)
...
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 1.21. Set the “ds_probing_mode” parameter
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modparam("dispatcher", "ds_probing_mode", 1)
...
If set to 1, functions will automaticall append a new branch if called in FAILURE_ROUTE. If set to 0, script writer has to call append_branch() in config after calling dispatcher functions.
Default value is “1”.
Example 1.22. Set the “ds_append_branch” parameter
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modparam("dispatcher", "ds_append_branch", 0)
...
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. The parameter can be an integer or a variable holding an interger.
alg - the algorithm used to select the destination address. The parameter can be an integer or a variable holding an interger.
“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” - use first destination (good for failover).
“X” - if the algorithm is not implemented, the first entry in set is chosen.
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.
This function can be used from REQUEST_ROUTE.
Example 1.23. ds_select_dst usage
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ds_select_dst("1", "0");
...
$var(a) = 4;
ds_select_dst("1", "$var(a)");
...
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.
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 FAILURE_ROUTE.
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 FAILURE_ROUTE.
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 FAILURE_ROUTE.
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 FAILURE_ROUTE.
This function returns true, if the current request comes from a host from the dispatcher-list; otherwise false.
This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE and ONREPLY_ROUTE.
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_
It lists the groups and included destinations.
Name: ds_list
Parameters: none
MI FIFO Command Format:
:ds_list:_reply_fifo_file_ _empty_line_
Each destination point must be on one line. First token is the set id, followed by destination address. Optionally, the third field can be flags value (1 - destination inactive, 2 - destination in probing mod -- you can do bitwise OR to set both flags). The set id must be an integer value. Destination address must be a valid SIP URI. Empty lines or lines starting with “#” are ignored.
Example 1.24. dispatcher list file
... # $Id$ # dispatcher destination sets # # line format # setit(integer) destination(sip uri) flags (integer, optional) # proxies 2 sip:127.0.0.1:5080 2 sip:127.0.0.1:5082 # gateways 1 sip:127.0.0.1:7070 1 sip:127.0.0.1:7072 1 sip:127.0.0.1:7074 ...
Next picture displays a sample usage of dispatcher.
Example 1.25. Kamailio config script - sample dispatcher usage
...
# $Id$
# sample config file for dispatcher module
#
debug=9 # debug level (cmd line: -dddddddddd)
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: sip_router -h
# ------------------ module loading ----------------------------------
mpath="/usr/local/lib/kamailio/modules/"
loadmodule "maxfwd.so"
loadmodule "sl.so"
loadmodule "dispatcher.so"
# loadmodule "modules/tm/tm.so"
# ----------------- setting module-specific parameters ---------------
# -- dispatcher params --
modparam("dispatcher", "list_file", "../etc/dispatcher.list")
# modparam("dispatcher", "force_dst", 1)
route{
if ( !mf_process_maxfwd_header("10") )
{
sl_send_reply("483","To Many Hops");
drop();
};
ds_select_dst("2", "0");
forward();
# t_relay();
}
...
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2.1. |
Does dispatcher provide a fair distribution? |
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There is no guarantee of that. You should do some measurements to decide what distribution algorithm fits better in your environment. |
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2.2. |
Is dispatcher dialog stateful? |
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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). |
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2.3. |
Where can I find more about Kamailio? |
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Take a look at http://www.kamailio.org/. |
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2.4. |
Where can I post a question about this module? |
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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
If you want to keep the mail private, send it to |
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2.5. |
How can I report a bug? |
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Please follow the guidelines provided at: http://sourceforge.net/tracker/?group_id=139143 |