# Asterisk Project : Corosync

Added by dsessions , edited by russell on Sep 18, 2012

##### Corosync

Corosync is an open source group messaging system typically used in clusters, cloud computing, and other high availability environments.

The project, at it's core, provides four C api features:

- A closed process group communication model with virtual synchrony guarantees for creating replicated state machines.
- A simple availability manager that restarts the application process when it has failed.
- A configuration and statistics in-memory database that provide the ability to set, retrieve, and receive change notifications of information.
- A quorum system that notifies applications when quorum is achieved or lost.

##### Corosync and Asterisk

Using Corosync together with res_corosync allows events to be shared amongst a local cluster of Asterisk servers. Specifically, the types of events that may be shared include:

- Device state
- Message Waiting Indication, or MWI (to allow voicemail to live on a server that is different from where the phones are registered)

##### Setup and Configuration

###### Corosync

- ###### Installation

  Debian / Ubuntu

      apt-get install corosync corosync-dev

  Red Hat / Fedora

      yum install corosync corosynclib corosynclib-devel

- ###### Authkey

  To create an authentication key for secure communications between your nodes you need to do this on, what will be, the active node.

      corosync-keygen

  This creates a key in /etc/corosync/authkey.

      asterisk_active:~# scp /etc/corosync/authkey asterisk_standby:

  Now, on the standby node, you'll need to stick the authkey in it's new home and fix it's permissions / ownership.

      asterisk_standby:~# mv ~/authkey /etc/corosync/authkey
      asterisk_standby:~# chown root:root /etc/corosync/authkey
      asterisk_standby:~# chmod 400 /etc/corosync/authkey

- ###### /etc/corosync/corosync.conf

  The interface section under the totem block defines the communication path(s) to the other Corosync processes running on nodes within the cluster. These can be either IPv4 or IPv6 ip addresses but can not be mixed and matched within an interface. Adjustments can be made to the cluster settings based on your needs and installation environment.

  - ###### IPv4

    ###### Active Node Example

        totem {
                version: 2
                token: 160
                token_retransmits_before_loss_const: 3
                join: 30
                consensus: 300
                vsftype: none
                max_messages: 20
                threads: 0
                nodeid: 1
                rrp_mode: none
                interface {
                        ringnumber: 0
                        bindnetaddr: 192.168.1.0
                        mcastaddr: 226.94.1.1
                        mcastport: 5405
                }
        }

    ###### Standby Node Example

        totem {
                version: 2
                token: 160
                token_retransmits_before_loss_const: 3
                join: 30
                consensus: 300
                vsftype: none
                max_messages: 20
                threads: 0
                nodeid: 2
                rrp_mode: none
                interface {
                        ringnumber: 0
                        bindnetaddr: 192.168.1.0
                        mcastaddr: 226.94.1.1
                        mcastport: 5405
                }
        }

- ###### Start Corosync

      service corosync start

###### Asterisk

- ###### Installation

  In your Asterisk source directory:

      ./configure
      make
      make install

- ###### /etc/asterisk/res_corosync.conf

      ;
      ; Sample configuration file for res_corosync.
      ;
      ; This module allows events to be shared amongst a local cluster of
      ; Asterisk servers.  Specifically, the types of events that may be
      ; shared include:
      ;
      ;   - Device State (for shared presence information)
      ;
      ;   - Message Waiting Indication, or MWI (to allow Voicemail to live on
      ;     a server that is different from where the phones are registered)
      ;
      ; For more information about Corosync, see: http://www.corosync.org/
      ;

      [general]

      ;
      ;  Publish Message Waiting Indication (MWI) events from this server to the
      ;  cluster.
      publish_event = mwi
      ;
      ;  Subscribe to MWI events from the cluster.
      subscribe_event = mwi
      ;
      ;  Publish Device State (presence) events from this server to the cluster.
      publish_event = device_state
      ;
      ;  Subscribe to Device State (presence) events from the cluster.
      subscribe_event = device_state
      ;

  In the general section of the res_corosync.conf file we are specifying which events we'd like to publish and subscribe to (at the moment this is either device_state or mwi).

- ###### Verifying Installation

  If everything is setup correctly, you should see this output after executing a 'corosync show members' on the Asterisk CLI.

      *CLI> corosync show members

      =============================================================
      === Cluster members =========================================
      =============================================================
      ===
      === Node 1
      === --> Group: asterisk
      === --> Address 1: <host #1 ip goes here>
      ===
      =============================================================

After starting Corosync and Asterisk on your second node, the 'corosync show members' output should look something like this:

    *CLI> corosync show members

    =============================================================
    === Cluster members =========================================
    =============================================================
    ===
    === Node 1
    === --> Group: asterisk
    === --> Address 1: <host #1 ip goes here>
    === Node 2
    === --> Group: asterisk
    === --> Address 1: <host #2 ip goes here>
    ===
    =============================================================