Copyright © 2007, 2008 1und1 Internet AG, BASIS AudioNet GmbH, Elena-Ramona Modroiu
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| Revision $Revision: 3898 $ | $Date: 2008-03-08 00:03:56 +0100 (Sat, 08 Mar 2008) $ |
Table of Contents
List of Examples
initial_probability parameter usagehash_file parameter usageshvset parameter usagevarset parameter usagerand_event() usagerand_set_prob() usagerand_reset_prob() usagerand_get_prob() usagesleep usageusleep usageabort usagepkg_status usageshm_status usagerand_set_prob usagerand_reset_prob usagerand_get_prob usagecheck_config_hash usageget_config_hash usageshv_set usageshv_get usageRANDOM pseudo-variable usagetime(name) pseudo-variable usageshv(name) pseudo-variable usageUseful extensions for the server configuration.
The cfgutils module can be used to introduce randomness to the behaviour of the server. It provides setup functions and the “rand_event” function. This function return either true or false, depending on a random value and a specified probability. E.g. if you set via fifo or script a probability value of 5%, then 5% of all calls to rand_event will return true. The pseudovariable “$RANDOM” could be used to introduce random values e.g. into a SIP reply.
The benefit of this module is the probability of the decision can be manipulated by external applications such as web interface or command line tools. The probability must be specified as percent value, ranging from 0 to 100.
The module exports commands to FIFO server that can be used to change the global settings via FIFO interface. The FIFO commands are: “set_prob”, “reset_prob” and “get_prob”.
This module can be used for simple load-shedding, e.g. reply 5% of the Invites with a 503 error and a adequate random Retry-After value.
The module provides as well functions to delay the execution of the server. The functions “sleep” and “usleep” could be used to let the server wait a specific time interval.
It can also hash the config file used from the server with a (weak) cryptographic hash function on startup. This value is saved and can be later compared to the actual hash, to detect modifications of this file after the server start. This functions are available as the FIFO commands “check_config_hash” and “get_config_hash”.
The module depends on the following modules (in the other words the listed modules must be loaded before this module):
none
The initial value of the probability.
Default value is “10”.
The config file name for that a hash value should be calculated on startup.
There is no default value, is no parameter is given the hash functionality is disabled.
Example 1.2. hash_file parameter usage
modparam("cfgutils", "hash_file", "/etc/kamailio/kamailio.cfg")
Set the value of a shared variable ($shv(name)). The parameter can be set many times.
The value of the parameter has the format: _name_ '=' _type_ ':' _value_
_name_: shared variable name
_type_: type of the value
“i”: integer value
“s”: string value
_value_: value to be set
Default value is “NULL”.
Example 1.3. shvset parameter usage
...
modparam("cfgutils", "shvset", "debug=i:1")
modparam("cfgutils", "shvset", "pstngw=s:sip:10.10.10.10")
...
Set the value of a script variable ($var(name)). The parameter can be set many times.
The value of the parameter has the format: _name_ '=' _type_ ':' _value_
_name_: shared variable name
_type_: type of the value
“i”: integer value
“s”: string value
_value_: value to be set
Default value is “NULL”.
Example 1.4. varset parameter usage
...
modparam("cfgutils", "varset", "init=i:1")
modparam("cfgutils", "varset", "gw=s:sip:11.11.11.11;transport=tcp")
...
Return true or false, depending on a random value and a probability value.
Example 1.5. rand_event() usage
...
if (rand_event()) {
append_to_reply("Retry-After: 120\n");
sl_send_reply("503", "Try later");
exit;
};
# normal message processing follows
...
Set the “probability” of the decision.
“probability” can have a value from the range 0..100.
Reset the probability back to the inital value.
Return the current probability setting, e.g. for logging purposes.
Waits "time" seconds.
Meaning of the parameters is as follows:
time - Time to wait in seconds.
This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE.
Waits "time" milli-seconds.
Meaning of the parameters is as follows:
time - Time to wait in milli-seconds.
This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE.
Debugging function that aborts the server. Depending on the configuration of the server a core dump will be created.
This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE.
Debugging function that dumps the status for the private (PKG) memory. This information is logged to the default log facility, depending on the general log level and the memlog setting. You need to compile the server with activated memory debugging to get detailed informations.
This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE.
Debugging function that dumps the status for the shared (SHM) memory. This information is logged to the default log facility, depending on the general log level and the memlog setting. You need to compile the server with activated memory debugging to get detailed informations.
This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE.
Set the probability value to the given parameter. The parameter should be a percent value.
The parameter value must be a number from 0 to 100.
Reset the probability value to the inital start value.
This command don't need a parameter.
Return the actual probability setting.
The function return the actual probability value.
Example 1.16. rand_get_prob usage
... $ kamctl fifo get_prob The actual probability is 50 percent. ...
Check if the actual config file hash is identical to the stored one.
The function returns 200 OK if the hash values are identical, 400 if there are not identical, 404 if no file for hashing has been configured and 500 on errors. Additional a short text message is printed.
Example 1.17. check_config_hash usage
... $ kamctl fifo check_config_hash The actual config file hash is identical to the stored one. ...
Return the stored config file hash.
The function returns 200 OK and the hash value on success or 404 if no file for hashing has been configured.
Example 1.18. get_config_hash usage
... $ kamctl fifo get_config_hash 1580a37104eb4de69ab9f31ce8d6e3e0 ...
Set the value of a shared variable ($shv(name)).
Parameters:
_name_: shared variable name
_type_: type of the value
“int”: integer value
“str”: string value
_value_: value to be set
MI FIFO Command Format:
:shv_set:_reply_fifo_file_ _name_ _type_ _value_ _empty_line_
Get the value of a shared variable ($shv(name)).
Parameters:
_name_: shared variable name. If this parameter is missing, all shared variables are returned.
MI FIFO Command Format:
:shv_get:_reply_fifo_file_ _name_ _empty_line_
Returns a random value from the [0 - 2^31) range.
Example 1.21. RANDOM pseudo-variable usage
...
if (get_random()) {
$avp(i:10) = ($RANDOM / 16777216); # 2^24
if ($avp(i:10) < 10) {
$avp(i:10) = 10;
}
append_to_reply("Retry-After: $avp(i:10)\n");
sl_send_reply("503", "Try later");
exit;
};
# normal message processing follows
The PV provides access to broken-down time attributes.
The “name” can be:
sec - return seconds (int 0-59)
min - return minutes (int 0-59)
hour - return hours (int 0-23)
mday - return the day of month (int 0-59)
mon - return the month (int 1-12)
year - return the year (int, e.g., 2008)
wday - return the day of week (int, 1=Sunday - 7=Saturday)
yday - return the day of year (int, 1-366)
isdst - return daylight saving time status (int, 0 - DST off, >0 DST on)
Example 1.22. time(name) pseudo-variable usage
...
if ($time(year) == 2008) {
xlog("request: $rm from $fu to $ru in year 2008\n");
}
...
It is a class of pseudo-variables stored in shared memory. The value of $shv(name) is visible across all openser processes. Each “shv” has single value and it is initialized to integer 0. You can use “shvset” parameter to initialize the shared variable. The module exports a set of MI functions to get/set the value of shared variables.
Example 1.23. shv(name) pseudo-variable usage
...
modparam("cfgutils", "shvset", "debug=i:1")
...
if ($shv(debug) == 1) {
xlog("request: $rm from $fu to $ru\n");
}
...