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LogicApp

Logic Application Configuration

The N2SVCD Logic Application is an extensible, general-purpose application which runs Lua scripts to perform control logic. The scripts can be initiated by various inbound agents, via Lua Services.

Lua scripts running within LogicApp may perform additional actions by calling upon Lua Agents.

This page describes general information about configuring LogicApp. Please refer to the relevant Service or Agent documentation for examples and API specifications for each of the different use-cases.

A sample LogicApp configuration entry is as follows:

<?xml version="1.0" encoding="utf-8"?>
<n2svcd>
  ...
  <applications>
    ...
    <application name="Logic" module="LogicApp">
      <include>
        <lib>../apps/logic/lib</lib>
      </include>
      <parameters>
        <parameter name="trace_level" value="0"/>
        <parameter name="edr_enabled" value="1"/>
        <parameter name="edr_directory" value="/tmp/edr"/>
        <parameter name="default_lua_lib_path" value="../lua/lib/?.lua;../../n2sip/lua/lib/?.lua"/>
        <parameter name="default_smpp_app_name" value="SMPP-Client-Tester"/>
        <parameter name="default_rest_app_name" value="REST-CLIENT"/>
        <parameter name="default_outcall_app_name" value="IVR"/>
      </parameters>
      <config>
        <services>
          <service module="IvrApp::IvrIncallLuaService" libs="../../n2sip/apps/ivr/lib" script_dir="../../n2sip/demo/logic/incall">
            <triggers>
              <trigger called_prefix="800" script_name="800_digit_menu"/>
              <trigger called_prefix="811" script_name="811_rest"/>
              <trigger called_prefix="822" script_name="822_smpp"/>
              <trigger called_prefix="900" script_name="900_mca"/>
            </triggers>
          </service>
          <service module="RestServerApp::RestLuaService" libs="../apps/rest_s/lib" script_dir="../../n2sip/demo/logic/rest"/>
        </services>
        <agents>
          <agent module="RestClientApp::RestLuaAgent" libs="../apps/rest_c/lib"/>
          <agent module="SMPPApp::SMPPLuaAgent" libs="../apps/smpp/lib"/>
          <agent module="IvrApp::IvrOutcallLuaAgent" libs="../../n2sip/apps/ivr/lib"/>
        </agents>
      </config>
    </application>
    ...
  </application>
  ...
</n2svcd>

Configuration Details

The application element attributes for a Logic Application instance may include the below.

For details of the various parameter types used, refer to Common Configuration.

Parameter Name Type XML Type Description
See: Common Application configuration
module String Attribute [Required] LogicApp
include.lib String Element [Required] ../apps/logic/lib
parameters Array Element [Required] As per Common Configuration Application parameters.
"edr_prefix" String Parameter As per common Application configuration for edr_prefix.
(Default = n2logic)
"default_nil_marker" String Parameter This defines an optional default special string which is used to represent nil within Logic processing. Under normal processing, a table member with a nil value returned from Lua logic will be ignored.
If a nil_marker is configured then any undef value present in n2svcd will have this string value when converted into Lua. Conversely any time this string value is returned from Lua, it will be converted into undef within n2svcd internal processing.
This value may be overridden by individual service libraries.
(Default = none)
"default_lua_lib_path" String Parameter Additional paths to search when loading Lua libraries with the require statement.
This has the same rules as the LUA_PATH environment variable, i.e. must use ?.lua.
Multiple paths may be separated with a ; semicolon.
This value may be overridden (not extended) by individual service libraries.
(Default = empty)
"default_lua_clib_path" String Parameter Additional paths to search when loading Lua C-libraries with the require statement.
This has the same rules as the LUA_CPATH environment variable, i.e. must use ?.so.
Multiple paths may be separated with a ; semicolon.
This value may be overridden (not extended) by individual service libraries.
(Default = empty)
"default_<action>_app_name" String Attribute Agents will use a parameter of this form to configure the name of the Agent Application which will perform its activity, e.g. default_rest_app_name is used by the RestClientLuaAgent to specify which RestClientApp will handle outbound REST Client actions. Refer to the documentation for the specific Lua Agent to determine which values it uses.
(Default = Agent Actions cannot talk to Agent Applications)
"<action>_app_name_<route>" String Attribute Agents use the concept of "routes" to handle case such as the need to communicate with more than one end-point. Refer to the documentation for the specific Lua Agent for more information.
(Default = Agent Actions use only the default route)
config Object Element This is a container for extended configuration for the LogicApp.
.services Array of service Objects Element Defines the configured Services for this LogicApp. At least one service must be defined in order to use the LogicApp. One LogicApp may handle more than one service.
.agents Array of agent Objects Element Defines the configured Agents for this LogicApp. Agents are not required in order to execute a LogicApp Lua Script, but they can extend the functionality available.

Service Configuration

A Lua Service Library handles an inbound message from a Service Application and uses the contents of that message to:

  1. Determine which Lua script to execute, and
  2. Determine what arguments to supply to that executing Lua script.

When the Lua script completes, the Lua Service Library may send back a final response the originating application.

This section describes the common configuration for adding a Lua Service Library to the Logic Application. For more information on per-Service configuration, please refer to the individual documentation for each Service Library.

A service entry within the services element of the LogicApp configuration has the following attributes:

Parameter Name Type XML Type Description
module String Attribute [Required] The module name containing the Lua Service Library code.
libs String Attribute Optional library path to include when searching for the module for this Service Library.
lua_lib_path String Parameter Additional paths to search when loading Lua libraries with the require statement.
This has the same rules as the LUA_PATH environment variable, i.e. must use ?.lua.
Multiple paths may be separated with a ; semicolon.
If specified at the service level, this will replace the Application-level configured path.
(Default = the default_lua_lib_path value from the Application)
lua_clib_path String Parameter Additional paths to search when loading Lua C-libraries with the require statement.
This has the same rules as the LUA_CPATH environment variable, i.e. must use ?.so.
Multiple paths may be separated with a ; semicolon.
If specified at the library level, this will replace the Application-level configured path.
(Default = the default_lua_clib_path value from the Application)
use_stale_lua 0 / 1 Attribute When reading LUA scripts from file or from database, if the reload or the version freshness check fails, we may still have a stale LUA chunk (and associated cached contexts) in memory. This flag determines if we should continue to process the stale script, or if we should fail and teardown the instance.
(Default = 0, do not use stale LUA chunks/contexts)
chunk_reload_secs 0 - 3600 Attribute When reading LUA scripts from file or from database, the LUA script loader will periodically perform a full reload of the chunk. This attribute specifies how many seconds must pass before the script loader will force-reload the LUA script chunk.
Setting this value to 0 will force full-reload check for every LUA execution.
(Default = 300)
version_check_secs 0 - 600 Attribute When reading LUA scripts from file or from database, the LUA script loader will periodically check the disk or database to determine if the script version has changed. This attribute specifies how many seconds must pass before the script loader will re-examine the on-disk or database row to check for a change in the modified time (or version number) for the LUA script body.
Setting this value to 0 will force mtime/version check for every LUA execution.
(Default = 5)
failure_retry_secs 0 - 600 Attribute When a LUA script read from file or database fails, then the LUA script loader will reject LUA script execution for that same Script Name for this number of seconds, before checking again to see if the on-disk or in-database lookup succeeds.
Setting this value to 0 will force disk/database lookup for every LUA execution after failure.
(Default = 5)
cc_free_per_script 0 - 100 Attribute When LUA processing finishes, the LUA context may be retained to use for subsequent logic performed using the exact same Script Name, for the purpose of reducing script start-up overhead and improving performance.
However, a burst of simultaneous calls for the same script may generate an excess of LUA contexts which subsequently are not needed.
This attribute defines the maximum number of LUA contexts which will ever be cached as free/spares for any single Script Name.
Setting this value to 0 will disable caching/re-use of LUA contexts.
(Default = 10)
cc_unused_secs 0 - 3600 Attribute When LUA processing finishes, the LUA context may be retained to use for subsequent logic performed using the exact same Script Name, for the purpose of reducing script start-up overhead and improving performance.
However, a burst of simultaneous calls for the same script may generate an excess of LUA contexts which subsequently remain idle.
Free LUA context which are not used for this number of seconds will be discarded.
Setting this value to 0 will disable caching/re-use of LUA contexts.
(Default = 300)
load_timeout_ms 100 - 10000 Attribute Applies for asynchronous loaders only (e.g. loaders fetching LUA script from Database).
This is the allowed time in milliseconds for the LUA script load to complete.
(Default = 1000)

Many Lua Service Libraries also define additional configuration elements within the service element.
For example, Service Libraries which read their LUA scripts from disk will typically define a script_dir attribute. Refer to the per-Service Library documentation for details.

Agent Configuration

A Lua Agent is used to send messages to an AgentApp, typically for the purpose of communicating with external agents. The Lua script execution will suspend while the agent waits for its response.

This section describes the common configuration for adding a Lua Agent to the Logic Application. For more information on per-Agent configuration, please refer to the individual documentation for each Agent Library.

An agent entry within the agents element of the LogicApp configuration has the following attributes:

Parameter Name Type XML Type Description
module String Attribute [Required] The module name containing the Lua Agent code.
libs String Attribute Optional library path to include when searching for the module for this Agent.

A Lua Agent typically also requires the configuration of a default_<action>_app_name entry specifying the name of the AgentApp which will receive the messages sent by the Lua Agent. Refer to the per-Agent documentation for details.

Message Handling

In addition to the common Application management messages, the LogicApp uses the following messages:

Agent libraries are provided in this package which implement the following messgaes:

Service libraries are provided in this package which support the following messages:

Also, the ProcessUSSDLuaService library uses these messages for MAP USSD processing: