HTable Module

Elena-Ramona Modroiu

asipto.com

Edited by

Elena-Ramona Modroiu

Edited by

Alex Balashov

Edited by

Ovidiu Sas


Table of Contents

1. Admin Guide
1. Overview
2. Dependencies
2.1. Kamailio Modules
2.2. External Libraries or Applications
2.3. Loading from database
3. Parameters
3.1. htable (str)
3.2. db_url (str)
3.3. key_name_column (str)
3.4. key_type_column (str)
3.5. value_type_column (str)
3.6. key_value_column (str)
3.7. expires_column (str)
3.8. array_size_suffix (str)
3.9. fetch_rows (integer)
3.10. timer_interval (integer)
3.11. db_expires (integer)
3.12. enable_dmq (integer)
3.13. timer_procs (integer)
3.14. event_callback (str)
3.15. event_callback_mode (int)
4. Functions
4.1. sht_print()
4.2. sht_rm_name_re(htable=>regexp)
4.3. sht_rm_value_re(htable=>regexp)
4.4. sht_rm_name(htable, op, val)
4.5. sht_rm_value(htable, op, val)
4.6. sht_reset(htable)
4.7. sht_lock(htable=>key)
4.8. sht_unlock(htable=>key)
4.9. sht_iterator_start(iname, hname)
4.10. sht_iterator_end(iname)
4.11. sht_iterator_next(iname)
5. Exported pseudo-variables
6. RPC Commands
6.1. htable.get htable key
6.2. htable.delete htable key
6.3. htable.sets htable key value
6.4. htable.seti htable key value
6.5. htable.dump htable
6.6. htable.reload htable
6.7. htable.listTables
6.8. htable.stats
7. Event routes
7.1. htable:mod-init
7.2. htable:expired:<table>

List of Examples

1.1. Accessing $sht(htname=>key)
1.2. Dictionary attack limitation
1.3. Storing array values
1.4. Set hash_size parameter
1.5. Set db_url parameter
1.6. Set key_name_column parameter
1.7. Set key_type_column parameter
1.8. Set value_type_column parameter
1.9. Set key_value_column parameter
1.10. Set expires_column parameter
1.11. Set array_size_suffix parameter
1.12. Set fetch_rows parameter
1.13. Set timer_interval parameter
1.14. Set db_expires parameter
1.15. Set enable_dmq parameter
1.16. Set timer_procs parameter
1.17. Set event_callback parameter
1.18. Set event_callback_mode parameter
1.19. sht_print usage
1.20. sht_rm_name_re usage
1.21. sht_rm_value_re usage
1.22. sht_rm_name usage
1.23. sht_rm_value usage
1.24. sht_reset usage
1.25. sht_lock usage
1.26. sht_unlock usage
1.27. sht_iterator_start usage
1.28. sht_iterator_end usage
1.29. sht_iterator_next usage

Chapter 1. Admin Guide

1. Overview

The module adds a hash table container to the configuration language. The hash table is stored in shared memory and the access to it can be done via pseudo-variables: $sht(htname=>name). The module supports definition of many hash tables and can load values at startup from a database table.

A typical use case for the SIP server is to implement a cache system in configuration file - if a value is not found in hash table, load it from database and store it in hash table so next time the access to it is very fast. In the definition of the table you can define the default expiration time of cached items. The expiration time can be adjusted per item via assignment operation at runtime.

Replication between multiple servers is performed automatically (if enabled) via the DMQ module.

You can read more about hash tables at: http://en.wikipedia.org/wiki/Hash_table.

The name can be a static string or can include pseudo- variables that will be replaced at runtime.

Example 1.1. Accessing $sht(htname=>key)

...
modparam("htable", "htable", "a=>size=8;")
...
$sht(a=>test) = 1;
$sht(a=>$ci::srcip) = $si;
...

The next example shows a way to protect against dictionary attacks. If someone fails to authenticate 3 times, it is forbidden for 15 minutes. Authentication against database is expensive as it does a select on the subscriber table. By disabling the DB auth for 15 minutes, resources on the server are saved and time to discover the password is increased substantially. Additional alerting can be done by writing a message to syslog or sending email, etc.

To implement the logic, two hash table variables are used: one counting the failed authentications per user and one for storing the time of the last authentication attempt. To ensure a unique name per user, the hash table uses a combination of authentication username and text ::auth_count and ::last_auth.

Example 1.2. Dictionary attack limitation

...
modparam("htable", "htable", "a=>size=8;")
...
if(is_present_hf("Authorization"))
{
    if($sht(a=>$au::auth_count)==3)
    {
		$var(exp) = $Ts - 900;
        if($sht(a=>$au::last_auth) > $var(exp))
        {
            sl_send_reply("403", "Try later");
            exit;
        } else {
            $sht(a=>$au::auth_count) = 0;
        }
    }
    if(!www_authenticate("$td", "subscriber"))
    {
        switch ($retcode) {
            case -1:
                sl_send_reply("403", "Forbidden");
            exit;
            case -2:
                if($sht(a=>$au::auth_count) == $null)
                    $sht(a=>$au::auth_count) = 0;
                $sht(a=>$au::auth_count) = $sht(a=>$au::auth_count) + 1;
                if($sht(a=>$au::auth_count) == 3)
                    xlog("auth failed 3rd time - src ip: $si\n");
                $sht(a=>$au::last_auth) = $Ts;
            break;
        }
        www_challenge("$td"/*realm*/,"0"/*qop*/);
        exit;
    }
    $sht(a=>$au::auth_count) = 0;
} else {
    www_challenge("$td","0");
    exit;
}
...

The module also provides a way to store multiple values for a single key. This is emulated by storing individual keys as 'key_name[n]', where n is incremented for each key. The total number of keys is stored in a dedicated key, by default: 'key_name::size'.

The array is built when the table is loaded in memory and afterwards all the keys are treated as individual keys. If a particular entry in the array is deleted, it is the administrator's responsibility to update the size of the array and any other elements (if required).

Example 1.3. Storing array values

# Example of dbtext with multiple keys
$ cat /usr/local/etc/kamailio/dbtext/htable
1:key:1:0:value3:0
2:key:1:0:value2:0
3:key:1:0:value1:0

# The array key will be loaded in memory in the following format:
$ kamcmd htable.dump htable
{
        entry: 35
        size: 1
        slot: {
                item: {
                        name: key[0]
                        value: value1
                }
        }
}
{
        entry: 50
        size: 1
        slot: {
                item: {
                        name: key::size
                        value: 3
                }
        }
}
{
        entry: 67
        size: 1
        slot: {
                item: {
                        name: key[1]
                        value: value2
                }
        }
}
{
        entry: 227
        size: 1
        slot: {
                item: {
                        name: key[2]
                        value: value3
                }
        }
}

# Now let's delete a particular entry in the array: key[0].
$ kamcmd htable.delete htable key[0]

# The array key will look like this after a key was deleted:
$ kamcmd htable.dump htable
{
        entry: 50
        size: 1
        slot: {
                item: {
                        name: key::size
                        value: 3
                }
        }
}
{
        entry: 67
        size: 1
        slot: {
                item: {
                        name: key[1]
                        value: value2
                }
        }
}
{
        entry: 227
        size: 1
        slot: {
                item: {
                        name: key[2]
                        value: value3
                }
        }
}

2. Dependencies

2.1. Kamailio Modules

The following modules must be loaded before this module:

  • If DMQ replication is enabled, the DMQ module must be loaded first..

2.2. External Libraries or Applications

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

  • None.

2.3. Loading from database

The module is able to load values in a hash table at startup upon providing a DB URL and table name.

The structure of the table must contain:

  • key name - string containing the name of the key.

  • key type - the type of the key

    • 0 - simple key - the key is added as 'key_name'.

    • 1 - array key - the key is added as 'key_name[n]' - n is incremented for each key with this name to build an array in hash table. In addition, an additional key is built to hold the total number of key in the array, by default key_name::size (see array_size_suffix parameter).

  • value type - the type of the key value

    • 0 - value is string.

    • 1 - value is integer.

  • key value - string containing the value of the key.

3. Parameters

3.1. htable (str)

The definition of a hash table. The value of the parameter may have the following format:

  • "htname=>size=_number_;autoexpire=_number_;dbtable=_string_"

The parameter can be set multiple times to get more hash tables in same configuration file.

  • htname - string specifying the name of the hash table. This string is used by $sht(...) to refer to the hash table.

  • size - number specifying the size of hash table. Larger value means less collisions. The number of entries (aka slots or buckets) in the table is 2^size. The possible range for this value is from 2 to 31, smaller or larger values will be increased to 3 (8 slots) or decreased to 14 (16384 slots).

  • autoexpire -time in seconds to delete an item from a hash table if no update was done to it. If is missing or set to 0, the items won't expire.

  • dbtable - name of database to be loaded at startup in hash table. If empty or missing, no data will be loaded.

  • cols - the column names of the database table. They must be enclosed in quotes in order to form a valid SIP parameter value and be separated by comma. The first column corresponds to key_name. When specified, there must be at least two columns. If this attribute is not specified, then the global module parameters for column names are used. If more than one value columns are specified, the hash table will pack the column values in a comma separated string, which will be associated with the key (string transformation {s.select,...} can be used in configuration file to extract a specific column value). When cols attribute is present, writing back to database table is disabled.

  • dbmode - if set to 1, the content of hash table is written to database table when the SIP server is stopped (i.e., ensure persistency over restarts). Default value is 0 (no write back to db table).

  • initval - the integer value to be returned instead of $null when a requested key is not set.

  • updateexpire - if set to 1 (default), the time until expiration of an item is reset when that item is updated. Certain uses of htable may dictate that updates should not reset the expiration timeout, however, in which case this attribute can be set to 0.

  • dmqreplicate - if set to 1, any actions (set, update, delete etc.) performed upon entries in this table will be replicated to other nodes (htable peers). Please note, module parameter enable_dmq must also be set in order for this to apply (see below). Default is 0 (no replication).

Default value is NULL.

Example 1.4. Set hash_size parameter

...
modparam("htable", "htable", "a=>size=4;autoexpire=7200;dbtable=htable_a;")
modparam("htable", "htable", "b=>size=5;")
modparam("htable", "htable", "c=>size=4;autoexpire=7200;initval=1;dmqreplicate=1;")
...

3.2. db_url (str)

The URL to connect to database for loading values in hash table at start up.

Default value is NULL (do not connect).

Example 1.5. Set db_url parameter

...
modparam("htable", "db_url", "mysql://kamailio:kamailiorw@localhost/kamailio")
...

3.3. key_name_column (str)

The name of the column containing the hash table key name.

Default value is 'key_name'.

Example 1.6. Set key_name_column parameter

...
modparam("htable", "key_name_column", "kname")
...

3.4. key_type_column (str)

The name of the column containing the hash table key type.

Default value is 'key_type'.

Example 1.7. Set key_type_column parameter

...
modparam("htable", "key_type_column", "ktype")
...

3.5. value_type_column (str)

The name of the column containing the hash table value type.

Default value is 'value_type'.

Example 1.8. Set value_type_column parameter

...
modparam("htable", "value_type_column", "vtype")
...

3.6. key_value_column (str)

The name of the column containing hash table key value.

Default value is 'key_value'.

Example 1.9. Set key_value_column parameter

...
modparam("htable", "key_value_column", "kvalue")
...

3.7. expires_column (str)

The name of the column containing the expires value.

Default value is 'expires'.

Example 1.10. Set expires_column parameter

...
modparam("htable", "expires_column", "expiry")
...

3.8. array_size_suffix (str)

The suffix to be added to store the number of items in an array (see key type).

Default value is '::size'.

Example 1.11. Set array_size_suffix parameter

...
modparam("htable", "array_size_suffix", "-count")
...

3.9. fetch_rows (integer)

How many rows to fetch at once from database.

Default value is 100.

Example 1.12. Set fetch_rows parameter

...
modparam("htable", "fetch_rows", 1000)
...

3.10. timer_interval (integer)

Interval in seconds to check for expired htable values.

Default value is 20.

Example 1.13. Set timer_interval parameter

...
modparam("htable", "timer_interval", 10)
...

3.11. db_expires (integer)

If set to 1, the module will load/save the expires values of the items in hash table from/to database. It applies only to hash tables that have the auto-expires attribute defined.

Default value is 0.

Example 1.14. Set db_expires parameter

...
modparam("htable", "db_expires", 1)
...

3.12. enable_dmq (integer)

If set to 1, will enable DMQ replication of actions performed upon entries in all tables having "dmqreplicate" parameter set. Any update action performed via pseudo-variables and RPC commands will be repeated on all other nodes. Therefore, it is important to ensure the table definition (size, autoexpire etc.) is identical across all instances.

Important: If this parameter is enabled, the DMQ module must be loaded first - otherwise, startup will fail.

Currently, values are not replicated on load from DB as it is expected that in these cases, all servers will load their values from the same DB.

Default value is 0.

Example 1.15. Set enable_dmq parameter

...
modparam("htable", "enable_dmq", 1)
...

3.13. timer_procs (integer)

If set to 1 or greater, the module will create its own timer processes to scan for expired items in hash tables. If set to zero, it will use the core timer for this task. Set it to 1 if you store a lot of items with autoexpire property.

Default value is 0.

Example 1.16. Set timer_procs parameter

...
modparam("htable", "timer_procs", 4)
...

3.14. event_callback (str)

The name of the function in the kemi configuration file (embedded scripting language such as Lua, Python, ...) to be executed instead of event_route[...] blocks.

The function receives a string parameter with the name of the event, the values can be: 'htable:mod-init', 'htable:expired:htname' ('htname' being the name of hash table).

Default value is 'empty' (no function is executed for events).

Example 1.17. Set event_callback parameter

...
modparam("htable", "event_callback", "ksr_htable_event")
...
-- event callback function implemented in Lua
function ksr_htable_event(evname)
	KSR.info("===== htable module triggered event: " .. evname .. "\n");
	return 1;
end
...

3.15. event_callback_mode (int)

Control when event_route[htable:init] is executed: 0 - after all modules were initialized; 1 - in first worker process.

Set it to 1 if used in a KEMI script or when needing to use database (e.g., via sqlops) inside event_route[htable:init].

Default value is 0.

Example 1.18. Set event_callback_mode parameter

...
modparam("htable", "event_callback_mode", 1)
...

4. Functions

4.1.  sht_print()

Dump content of hash table to L_ERR log level. Intended for debug purposes.

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

Example 1.19. sht_print usage

...
sht_print();
...

4.2.  sht_rm_name_re(htable=>regexp)

Delete all entries in the htable that match the name against regular expression.

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

Example 1.20. sht_rm_name_re usage

...
sht_rm_name_re("ha=>.*");
...

4.3.  sht_rm_value_re(htable=>regexp)

Delete all entries in the htable that match the value against regular expression.

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

Example 1.21. sht_rm_value_re usage

...
sht_rm_value_re("ha=>.*");
...

4.4.  sht_rm_name(htable, op, val)

Delete all entries in the htable that match the name against the val parameter.

The op parameter can be:

  • re - match the val parameter as regular expression.

  • sw - match the val parameter as 'starts with'.

All parameters can be static strings or contain variables.

This function can be used from ANY_ROUTE.

Example 1.22. sht_rm_name usage

...
sht_rm_name("ha", "re", ".*");
...

4.5.  sht_rm_value(htable, op, val)

Delete all entries in the htable that match the value against the val parameter.

The op parameter can be:

  • re - match the val parameter as regular expression.

  • sw - match the val parameter as 'starts with'.

All parameters can be static strings or contain variables.

This function can be used from ANY_ROUTE.

Example 1.23. sht_rm_value usage

...
sht_rm_value("ha", "re", ".*");
...

4.6.  sht_reset(htable)

Delete all entries in the htable. The name of the hash table can be a dynamic string with variables.

This function can be used from ANY_ROUTE.

Example 1.24. sht_reset usage

...
sht_reset("ha$var(x)");
...

4.7.  sht_lock(htable=>key)

Lock the slot in htable corresponding to the key item. Note that the locking is re-entrant for the process, therefore the lock and unlock should be done by the same process.

This function can be used from ANY_ROUTE.

Example 1.25. sht_lock usage

...
sht_lock("ha=>test");
...

4.8.  sht_unlock(htable=>key)

Unlock the slot in htable corresponding to the key item. Note that the locking is re-entrant for the process, therefore the lock and unlock should be done by the same process.

This function can be used from ANY_ROUTE.

Example 1.26. sht_unlock usage

...
sht_lock("ha=>test");
$sht(ha=>test) = $sht(ha=>test) + 10;
sht_unlock("ha=>test");
...

4.9.  sht_iterator_start(iname, hname)

Start an iterator for hash table named by the value of parameter hname. The parameter iname is used to identify the iterator. There can be up to 4 iterators at the same time, with different name.

Both parameters can be dynamic strings with variables.

IMPORTANT: the slot of the hash table is left locked when retrieving in item. Therefore be sure you do not update the content of the hash table in between sht_iterator_start() and sht_iterator_end(), because it may end up in dead lock.

This function can be used from ANY_ROUTE.

Example 1.27. sht_iterator_start usage

...
sht_iterator_start("i1", "h1");
...

4.10.  sht_iterator_end(iname)

Close the iterator identified by iname parameter and release the hash table slot acquired by the iterator. The iname value must be the same used for sht_iterator_start().

The parameter can be dynamic string with variables.

This function can be used from ANY_ROUTE.

Example 1.28. sht_iterator_end usage

...
sht_iterator_end("i1");
...

4.11.  sht_iterator_next(iname)

Move the iterator to the next item in hash table. It must be called also after sht_iterator_start() to get the first item in the hash table. Items are returned as they are found in the hash table slot, starting with the first slot.

The return code is false when there is no (more) item in the hash table.

The item name and value are accessible via variables: $shtitkey(iname) and $shtitval(iname).

The parameter can be dynamic string with variables.

This function can be used from ANY_ROUTE.

Example 1.29. sht_iterator_next usage

...
    sht_iterator_start("i1", "h1");
    while(sht_iterator_next("i1")) {
        xlog("h1[$shtitkey(i1)] is: $shtitval(i1)\n");
    }
    sht_iterator_end("i1");
...

5. Exported pseudo-variables

  • $sht(htable=>key)

  • $shtex(htable=>key)

  • $shtcn(htable=>key)

  • $shtcv(htable=>key)

  • $shtinc(htable=>key)

  • $shtitkey(iname)

  • $shtitval(iname)

  • $shtrecord(attribute)

Exported pseudo-variables are documented at https://www.kamailio.org/wiki/.

6. RPC Commands

6.1.  htable.get htable key

Lists one value in a hash table

Name: htable.get

Parameters:

  • htable : Name of the hash table to dump

  • key : Key name of the hash table value to dump

Example:

...
# Dump $sht(students=>alice)
kamcmd htable.get students alice

# Dump first entry in array key course $sht(students=>course[0])
kamcmd htable.get students course[0]
...

6.2.  htable.delete htable key

Delete one value in a hash table

Name: htable.delete

Parameters:

  • htable : Name of the hash table to delete

  • key : Key name of the hash table value to delete

Example:

...
# Delete $sht(students=>alice)
kamcmd htable.delete students alice

# Delete first entry in array key course $sht(students=>course[0])
kamcmd htable.delete students course[0]
...

6.3.  htable.sets htable key value

Set an item in hash table to string value.

Name: htable.sets

Parameters:

  • htable : Name of the hash table

  • key : Key name in the hash table

  • Value : String value for the item

Example:

...
# Set $sht(test=>x) as string
kamcmd htable.sets test x abc

# Set firsti entry in array key x $sht(test=>x[0]) as string
kamcmd htable.sets test x[0] abc
...

6.4.  htable.seti htable key value

Set an item in hash table to integer value.

Name: htable.seti

Parameters:

  • htable : Name of the hash table

  • key : Key name in the hash table

  • Value : Integer value for the item

Example:

...
# Set $sht(test=>x) as integer
kamcmd htable.seti test x 123

# Set first entry in array key x $sht(test=>x[0]) as integer
kamcmd htable.sets test x[0] 123
...

6.5.  htable.dump htable

Lists all the values in a hash table

Name: dhtable.dump

Parameters:

  • htable : Name of the hash table to dump

Example:

...
kamcmd htable.dump ipban
...

6.6.  htable.reload htable

Reload hash table from database.

Name: dhtable.reload

Parameters:

  • htable : Name of the hash table to reload

Example:

...
kamcmd htable.reload ipban
...

6.7.  htable.listTables

Lists all defined tables

Name: htable.listTables

Parameters:

  • None

Example:

...
kamcmd htable.listTables
...

6.8.  htable.stats

Get statistics for hash tables - name, number of slots, number of items, max number of items per slot, min number of items per slot.

Name: htable.stats

Parameters:

  • None

Example:

...
kamcmd htable.stats
...

7. Event routes

7.1.  htable:mod-init

When defined, the module calls event_route[htable:mod-init] after all modules have been initialized. A typical use case is to initialise items in hash tables. The event route is executed only once, after core and module initialization, but before Kamailio forks any child processes.

...
event_route[htable:mod-init] {
    $sht(a=>x) = 1;
}
...

7.2.  htable:expired:<table>

When defined, the module calls event_route[htable:expired:<table>] when an entry in the given table expires. In this event route, the key and value of the expired record are available with the $shtrecord(key) and $shtrecord(value) pseudo-variables.

...

event_route[htable:expired:mytable] {
    xlog("mytable record expired $shtrecord(key) => $shtrecord(value)\n");
}
...