Event (based) Routing Module
     __________________________________________________________

   Table of Contents

   1. Admin Guide

        1.1. Overview
        1.2. Dependencies

              1.2.1. OpenSIPS Modules
              1.2.2. External Libraries or Applications

        1.3. Exported Parameters
        1.4. Exported Functions

              1.4.1. notify_on_event(event, filter, route,
                      timeout)

        1.5. Exported Asynchronous Functions

              1.5.1. wait_for_event(event,filter,timeout)

        1.6. Usage Examples

              1.6.1. Push Notification
              1.6.2. Call pickup

   2. Developer Guide

        2.1.

   3. Frequently Asked Questions
   4. Contributors

        4.1. By Commit Statistics
        4.2. By Commit Activity

   5. Documentation

        5.1. Contributors

   List of Tables

   4.1. Top contributors by DevScore^(1), authored commits^(2) and
          lines added/removed^(3)

   4.2. Most recently active contributors^(1) to this module

   List of Examples

   1.1. notify_on_event() usage
   1.2. wait_for_event usage
   1.3. Push Notification script
   1.4. Call Pickup script

Chapter 1. Admin Guide

1.1. Overview

   The Event (based) Routing module, or shortly the EBR module,
   provides a mechanism that allows different SIP processings (of
   messages in script) to communicate and synchronize between
   through OpenSIPS Events (see
   https://opensips.org/Documentation/Interface-Events-2-3).

   This mechanism is based on the Subscribe-Notify concept. Any
   SIP processing may subscribe to various OpenSIPS Events Upon
   Event raising, the subscriber will be notified, so it will be
   able to make use of the data attached to the Event. Note that
   the Event raising may take place in a completely different SIP
   processing context, completely unrelated to the subscriber
   processing.

   Also, the Events are generated either internally by OpenSIPS
   (predefined Events), either from the script level (custom
   Events). Please refer to the Event Interface documentation for
   more on how the Events are generated
   (https://opensips.org/Documentation/Interface-Events-2-3).

   Depending on how the notification is handled by the subscribing
   processing, we distinguish two main scenarios:
     * The subscriber waits in async. mode for the receiving the
       notification; the processing of the subscriber will suspend
       and it will be fully resumed when the notification is
       received (or a timeout occurs).
     * The subscriber continues its processing after subscription,
       without any waiting. Whenever a notification is received, a
       script route (armed by the subscription) will be executed.
       Note that this notification route is executed outside any
       context of the original processing (nothing is inherited in
       this route). The Event triggering the notification is
       exposed in the notification route, via AVP variables.

   So, EBR allows your SIP processing to synchronize or the
   exchange info between, even if these processings are completely
   unrelated from SIP, time or handling perspective.

   With the help of the EBR support, more advanced routing
   scenarios are possible now, scenarios where you need to handle
   and put together different processing as type and time, like
   the handling of various calls with the handling of
   registrations or with the DTMF extraction. For more, see the
   Examples section.

1.2. Dependencies

1.2.1. OpenSIPS Modules

   The following modules are required by this module:
     * TM - Transaction module

1.2.2. External Libraries or Applications

   The following libraries or applications must be installed
   before running OpenSIPS with this module loaded:
     * None.

1.3. Exported Parameters

   This module does not provide any script parameters.

1.4. Exported Functions

1.4.1.  notify_on_event(event, filter, route, timeout)

   This function creates a subscription to a given Event. A filter
   can be used (over the attributes of the Event) in order to
   filter even more the needed notifications (only Events matching
   the filter will be notified to this subscriber).

   Upon Event notification, the given script route (usually called
   notification route) will be executed. No variables, SIP
   message, SIP transaction/dialog or any other context related to
   subscriber will be inherited from subscriber processing into
   this notification route.

   The Event attributes will be exposed in the notification route
   via AVP variables as $avp(attr_name) = attr_value.

   As an exception, in the notification route, the EBR module will
   make available the transaction ID from the subscriber context.
   Note that it's not the transaction itself, but its ID. There
   are some TM functions (like t_inject_branches) which can
   operate on transactions based on their ID. Of course, you need
   to have a transaction create in the subscriber processing
   before calling the notify_on_event() function.

   This function can be used from REQUEST_ROUTE.

   Parameters:
     * event (string) -the name of the Event to subscribe for
     * filter (var) - a AVP variable holding (as multi value
       array) all the filters to be applied on the event (before
       notification). The filter value has the format "key=value"
       where the "key" must match an attribute name of the Event.
       The "value" is the desired value for the attribute; it may
       be a shell wildcard pattern. Ex: "aor=bob@*"
     * route (string) -the name of the script route to be executed
       upon Event notification
     * timeout (int) - for how long the subscription is active
       before expiring (integer in seconds). Note: during its
       lifetime, a subscription may be notified several or zero
       times.

   Example 1.1. notify_on_event() usage
...
$avp(filter) = "aor=*@opensips.org"
notify_on_event("E_UL_AOR_INSERT",$avp(filter),"reg_done",60);
...
route[reg_done] {
        xlog("a new user $avp(aor) registered with opensips.org domain\n
");
}

1.5. Exported Asynchronous Functions

1.5.1.  wait_for_event(event,filter,timeout)

   Similar to the notify_on_event, this function creates an Event
   subscriber for the given event and filter. But this function
   will do async waiting (with suspend and resume) for receiving
   the notification on the desired Event.

   The meaning of the parameters is the same as for
   notify_on_event.

   Example 1.2. wait_for_event usage
...
# wait for callee to register
$avp(filter) = "aor="+$rU+"@"+$rd
async( wait_for_event("E_UL_AOR_INSERT",$avp(filter), 40),  resume_call)
;
# done
...
route[resume_call] {
        xlog("user $avp(aor) is now registered\n");
        lookup("location");
        t_relay();
}

1.6. Usage Examples

1.6.1.  Push Notification

   We use notify_on_event to capture the events on new contact
   registrations for callee. Once the call is sent to callee,
   based on the notification (for new contacts) we inject the
   newly registered contacts as new branches in the ongoing
   transaction.

   Schematics : when we send a call to a user, we subscribe to see
   any new contacts being registered by the user. On such a
   notification, we add the new contact as a new branch to the
   ongoing transaction (ringing) to user.

   Example 1.3. Push Notification script
...
route[route_to_user] {

    # prepare transaction for branch injection; it is mandatory
    # to create the transaction before the subscription, otherwise
    # the EBR module will not pass the transaction ID into the
    # notification route
    t_newtran();

    # keep the transaction alive (even if all branches will
    # terminate) until the FR INVITE timer hits (we want to wait
    # for new possible contacts being registered)
    t_wait_for_new_branches();

    # subscribe to new contact registration event,
    # but for our callee only
    $avp(filter) = "aor="+$rU;
    notify_on_event("E_UL_CONTACT_INSERT",$avp(filter),
        "fork_call", 20);

    # fetch already registered contacts and relay if any
    if (lookup("location"))
        route(relay);
    # if there were no contacts available (so no branches
    # created so far), the created transaction will still be
    # waiting for new branches due to the usage of the
    # t_wait_for_new_branches() function

    exit;
}

route[fork_call]
{
    xlog("user $avp(aor) registered a new "
        "contact $avp(uri), injecting\n");
    # take the contact described by the E_UL_CONTACT_INSERT
    # event and inject it as a new branch into the original
    # transaction
    t_inject_branches("event");
}
...

1.6.2.  Call pickup

   The scenario is Alice calling to bob, Bob does not pickup and
   Charlie is performing call pickup (to get the call from Alice)

   We use notify_on_event to link the two calls: the one from
   Alice to Bob and the one from Charlie to call pickup service.

   Schematics: when we send a call to a user within a pickup
   group, we subscribe to see if there is any call to the pickup
   service (from another member of the same pickup group). When we
   have a call to the pickup service, we raise from script an
   event - this event will be notified to the first call and we
   cancel the branches to Bob and inject the registered contacts
   for the user calling to pickup group (Charlie).

   Example 1.4. Call Pickup script
...
route[handle_call]
    if ($rU=="33") {
        ## this is a call to the pickup service
        ## (Charlie calling 33)

        # reject incoming call as we will generate an back call
        # from the original call (Alice to Bob)
        t_newtran();
        send_reply(480, "Gone");

        # raise the pickup custom event
        # with pickup group 1 and picker being Charlie (caller)
        $avp(attr-name) = "group";
        $avp(attr-val) = "1";
        $avp(attr-name) = "picker";
        $avp(attr-val) = $fu;
        raise_event("E_CALL_PICKUP", $avp(attr-name), $avp(attr-val));

        exit;
    } else {

        ## this is a call to a subscriber
        ## (Alice calls Bob)

        # apply user location
        if (!lookup("location", "method-filtering")) {
            send_reply(404, "Not Found");
            exit;
        }

        # prepare transaction for branch injection; it is mandatory
        # to create the transaction before the subscription, otherwise
        # the EBR module will not pass the transaction ID into the
        # notification route
        t_newtran();

        # subscribe to a call pickup event, but for our group only
        $avp(filter) = "group=1";
        notify_on_event("E_CALL_PICKUP",$avp(filter),
            "handle_pickup", 20);

        t_relay();
    }
    exit;
}

route[handle_pickup]
{
    xlog("call picked by $avp(picker), fetching its contacts\n");
    if (lookup("location","", $avp(picker))) {
        # take the contacts retured by lookup() (for Charlie)
        # and inject them into the original call, but also cancel
        # any existing ongoing branch (ringing to Bob)
        t_inject_branches("msg","cancel");
    }
}

Chapter 2. Developer Guide

   This modules does not export any internal API.

Chapter 3. Frequently Asked Questions

   3.1.

   Where can I find more about OpenSIPS?

   Take a look at https://opensips.org/.

   3.2.

   Where can I post a question about this module?

   First at all check if your question was already answered on one
   of our mailing lists:
     * User Mailing List -
       http://lists.opensips.org/cgi-bin/mailman/listinfo/users
     * Developer Mailing List -
       http://lists.opensips.org/cgi-bin/mailman/listinfo/devel

   E-mails regarding any stable OpenSIPS release should be sent to
   <users@lists.opensips.org> and e-mails regarding development
   versions should be sent to <devel@lists.opensips.org>.

   If you want to keep the mail private, send it to
   <users@lists.opensips.org>.

   3.3.

   How can I report a bug?

   Please follow the guidelines provided at:
   https://github.com/OpenSIPS/opensips/issues.

Chapter 4. Contributors

4.1. By Commit Statistics

   Table 4.1. Top contributors by DevScore^(1), authored
   commits^(2) and lines added/removed^(3)
     Name DevScore Commits Lines ++ Lines --
   1. Bogdan-Andrei Iancu (@bogdan-iancu) 27 11 1751 34
   2. Liviu Chircu (@liviuchircu) 26 18 485 196
   3. Vlad Patrascu (@rvlad-patrascu) 9 5 75 148
   4. Razvan Crainea (@razvancrainea) 6 4 9 5
   5. Fabian Gast (@fgast) 4 2 27 7
   6. Maksym Sobolyev (@sobomax) 4 2 5 6
   7. Zero King (@l2dy) 3 1 2 2
   8. Peter Lemenkov (@lemenkov) 3 1 1 1

   (1) DevScore = author_commits + author_lines_added /
   (project_lines_added / project_commits) + author_lines_deleted
   / (project_lines_deleted / project_commits)

   (2) including any documentation-related commits, excluding
   merge commits. Regarding imported patches/code, we do our best
   to count the work on behalf of the proper owner, as per the
   "fix_authors" and "mod_renames" arrays in
   opensips/doc/build-contrib.sh. If you identify any
   patches/commits which do not get properly attributed to you,
   please submit a pull request which extends "fix_authors" and/or
   "mod_renames".

   (3) ignoring whitespace edits, renamed files and auto-generated
   files

4.2. By Commit Activity

   Table 4.2. Most recently active contributors^(1) to this module
                     Name                   Commit Activity
   1. Maksym Sobolyev (@sobomax)          Feb 2023 - Feb 2023
   2. Liviu Chircu (@liviuchircu)         Sep 2017 - Dec 2021
   3. Bogdan-Andrei Iancu (@bogdan-iancu) Mar 2017 - Sep 2021
   4. Vlad Patrascu (@rvlad-patrascu)     May 2017 - Jul 2020
   5. Zero King (@l2dy)                   Mar 2020 - Mar 2020
   6. Razvan Crainea (@razvancrainea)     Apr 2017 - Sep 2019
   7. Fabian Gast (@fgast)                Nov 2018 - Dec 2018
   8. Peter Lemenkov (@lemenkov)          Jun 2018 - Jun 2018

   (1) including any documentation-related commits, excluding
   merge commits

Chapter 5. Documentation

5.1. Contributors

   Last edited by: Zero King (@l2dy), Vlad Patrascu
   (@rvlad-patrascu), Fabian Gast (@fgast), Peter Lemenkov
   (@lemenkov), Liviu Chircu (@liviuchircu), Bogdan-Andrei Iancu
   (@bogdan-iancu).

   Documentation Copyrights:

   Copyright © 2017 www.opensips-solutions.com
