[asterisk-app-dev] Moving the Asterisk Bridge from one Asterisk to another

[Matthew Jordan]

On Fri, May 13, 2016 at 2:20 PM, Ben Merrills <b.merrills at mersontech.co.uk>
wrote:

> Let me answer your last question first.
>
>
>
> Asterisk doesn’t handle multiple Stasis applications connecting with the
> same name. The relationship between Asterisk and Stasis application is one
> to one (one web socket per application name). However, you can get round
> this using an ARI proxy (see below). Using an ARI proxy allows you to
>
> 1.      Have multiple instances of your application run on multiple
> servers
>
> 2.      Provide load balancing between application servers
>
> 3.      Failover support for your application
>
>
>
> There are two implementations of an ARI proxy. The first written by me, in
> .NET (supports mono)can be found here
> https://github.com/skrusty/AsterNET-ARI-Proxy
>
> The second is written in GoLang and can be found here:
> https://github.com/nvisibleinc/go-ari-proxy
>
>
>
> You can read about the concepts behind ARI proxy on my blog.
> http://www.xdev.net/2015/09/18/distributed-applications-with-ari/
>
>
>
> With regards to stopping new calls in Asterisk, you can use the stop
> graceful cli command to prevent new calls from being processed on that
> asterisk box.
>
>
>
> Hope that helps a little,
>
>
>
> Ben
>
>
>
> *From:* asterisk-app-dev-bounces at lists.digium.com [mailto:
> asterisk-app-dev-bounces at lists.digium.com] *On Behalf Of *Nitesh Bansal
> *Sent:* 13 May 2016 14:56
> *To:* Asterisk Application Development discussion <
> asterisk-app-dev at lists.digium.com>
> *Subject:* [asterisk-app-dev] Moving the Asterisk Bridge from one
> Asterisk to another
>
>
>
> Hello,
>
> I'm working on an ARI based bridging application.
>
> My concern is how to gracefully handle the failovers, upgrades.
>
> In case of planned upgrade, 0
> I can see following possibilities but I have no clue about how they
> will work out?
> 1. Move the Bridge to the new Asterisk?
>
> 2. Bridge the old asterisk to the new asterisk, but don't forward any new
>
>     calls to the Asterisk under upgrade. Wait for call count to drop to
> zero
>
>     for Asterisk under upgrade.
>
>
>
> 3. Let first Asterisk run until the call count drops to zero, keep
> accepting calls
>
> for the existing bridge, but forward any new Bridge request to the new
> Asterisk.
>
> How does Asterisk behaving if multiple ARI clients connect with Asterisk
> for the same
>
> Stasis application?
>
>
>
> Any ideas/recommendations?
>
>
>

To follow on a bit with what Ben said:

If you're building a multi-Asterisk system, you'll need some middleware -
like the aforementioned ARI proxies - to manage the information coming from
multiple Asterisk systems. That's certainly the first step.

Once you have some middle layer managing the events coming from multiple
Asterisk systems, as well as which objects (such as a Bridge or a Channel)
live on which Asterisk system, the process of handling a graceful migration
would look something like the following:

Given a conference on Asterisk A, consisting of Bridge 1A and multiple
Channels, and given an Asterisk B instance:
* Create a new Bridge 1B on the Asterisk B instance
* Issue a redirect [1] to each channel in Bridge 1A to the Asterisk B
instance. Note that the redirect command uses the same syntax as the
Transfer dialplan application [2] (where the endpoint being redirected to
replaces the dial string in the Transfer app). I've found it useful in the
past to have a special extension 'entrance' on Asterisk instances the
understand that channels entering there came from another Asterisk
instance, so that they can convey that information appropriately to the
listening external applications, who will have to update their channel
state information.
* As each channel arrives on the Asterisk B instance, place them into the
new Bridge 1B

That handles the scenario for graceful failover.

For non-graceful, Asterisk does not today have the ability to re-INVITE
channels to a new Asterisk instance within the same dialog. The best your
application can do is to detect the death of an Asterisk instance, build a
new Bridge on a new Asterisk instance, and create new channels to the
participants.

[1]
https://wiki.asterisk.org/wiki/display/AST/Asterisk+13+Channels+REST+API#Asterisk13ChannelsRESTAPI-redirect
[2]
https://wiki.asterisk.org/wiki/display/AST/Asterisk+13+Application_Transfer

-- 
Matthew Jordan
Digium, Inc. | Director of Technology
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
Check us out at: http://digium.com & http://asterisk.org
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