Introduction¶
Various changes have been made related to "event handling" in Asterisk. One of the most important things included in these changes is the ability to share certain events between servers. The two types of events that can currently be shared between servers are:
*MWI* - Message Waiting Indication - This gives you a high performance option for letting servers in a cluster be aware of changes in the state of a mailbox. Instead of having each server have to poll an ODBC database, this lets the server that actually made the change to the mailbox generate an event which will get distributed to the other servers that have subscribed to this information.¶
*Device State* - This lets servers in a local cluster inform each other about changes in the state of a device on that particular server. When the state of a device changes on any server, the overall state of that device across the cluster will get recalculated. So, any subscriptions to the state of a device, such as hints in the dialplan or an application like Queue() which reads device state, will then reflect the state of a device across a cluster.¶
OpenAIS Installation¶
Description¶
The current solution for providing distributed events with Asterisk is done by using the AIS (Application Interface Specification), which provides an API for a distributed event service. While this API is standardized, this code has been developed exclusively against the open source implementation of AIS called OpenAIS.
For more information about OpenAIS, visit their web site http://www.openais.org/.
Install Dependencies¶
- Ubuntu
- libnss3-dev
- Fedora
- nss-devel
Download¶
Download the latest versions of Corosync and OpenAIS from http://www.corosync.org/ and http://www.openais.org/.
Compile and Install¶
OpenAIS Configuration¶
Basic OpenAIS configuration to get this working is actually pretty easy. Start by copying in a sample configuration file for Corosync and OpenAIS.
$ sudo mkdir -p /etc/ais
$ cd openais-1.1.4
$ sudo cp conf/openais.conf.sample /etc/ais/openais.conf
$ sudo mkdir -p /etc/corosync
$ cd corosync-1.2.8
$ sudo cp conf/corosync.conf.sample /etc/corosync/corosync.conf
totem {
...
interface {
ringnumber: 0
bindnetaddr: 10.24.22.144
mcastaddr: 226.94.1.1
mcastport: 5405
}
}
The default mcastaddr and mcastport is probably fine. You need to change the bindnetaddr to match the address of the network interface that this node will use to communicate with other nodes in the cluster.
Now, edit /etc/corosync/corosync.conf, as well. The same change will need to be made to the totem-interface section in that file.
Running OpenAIS¶
While testing, I recommend starting the aisexec application in the foreground so that you can see debug messages that verify that the nodes have discovered each other and joined the cluster.
For example, here is some sample output from the first server after starting aisexec on the second server:Nov 13 06:55:30 corosync [CLM ] CLM CONFIGURATION CHANGE
Nov 13 06:55:30 corosync [CLM ] New Configuration:
Nov 13 06:55:30 corosync [CLM ] r(0) ip(10.24.22.144)
Nov 13 06:55:30 corosync [CLM ] r(0) ip(10.24.22.242)
Nov 13 06:55:30 corosync [CLM ] Members Left:
Nov 13 06:55:30 corosync [CLM ] Members Joined:
Nov 13 06:55:30 corosync [CLM ] r(0) ip(10.24.22.242)
Nov 13 06:55:30 corosync [TOTEM ] A processor joined or left the membership and a new membership was formed.
Nov 13 06:55:30 corosync [MAIN ] Completed service synchronization, ready to provide service.
Installing Asterisk¶
Install Asterisk as usual. Just make sure that you run the configure script after OpenAIS gets installed. That way, it will find the AIS header files and will let you build the res_ais module. Check menuselect to make sure that res_ais is going to get compiled and installed.
If you have existing configuration on the system being used for testing, just be sure to install the addition configuration file needed for res_ais.Configuring Asterisk¶
First, ensure that you have a unique "entity ID" set for each server.
The code will attempt to generate a unique entity ID for you by reading MAC addresses off of a network interface. However, you can also set it manually in the [options] section of asterisk.conf.Edit the Asterisk ais.conf to enable distributed events. For example, if you would like to enable distributed device state, you should add the following section to the file:
For more information on the contents and available options in this configuration file, please see the sample configuration file:
Basic Testing of Asterisk with OpenAIS¶
If you have OpenAIS successfully installed and running, as well as Asterisk with OpenAIS support successfully installed, configured, and running, then you are ready to test out some of the AIS functionality in Asterisk.
The first thing to test is to verify that all of the nodes that you think should be in your cluster are actually there. There is an Asterisk CLI command which will list the current cluster members using the AIS Cluster Membership Service (CLM).
\*CLI> ais clm show members
=============================================================
=== Cluster Members =========================================
=============================================================
===
=== ---------------------------------------------------------
=== Node Name: 10.24.22.144
=== ==> ID: 0x9016180a
=== ==> Address: 10.24.22.144
=== ==> Member: Yes
=== ---------------------------------------------------------
===
=== ---------------------------------------------------------
=== Node Name: 10.24.22.242
=== ==> ID: 0xf216180a
=== ==> Address: 10.24.22.242
=== ==> Member: Yes
=== ---------------------------------------------------------
===
=============================================================
The next thing to do is to verify that you have successfully configured some event channels in the Asterisk ais.conf file. This command is related to the event service (EVT), so like the previous command, uses the syntax: ais <service name> <command>.
\*CLI> ais evt show event channels
=============================================================
=== Event Channels ==========================================
=============================================================
===
=== ---------------------------------------------------------
=== Event Channel Name: device_state
=== ==> Publishing Event Type: device_state
=== ==> Subscribing to Event Type: device_state
=== ---------------------------------------------------------
===
=============================================================
Testing Distributed Device State¶
The easiest way to test distributed device state is to use the DEVICE_STATE() diaplan function. For example, you could have the following piece of dialplan on every server:
Now, you can test that the cluster-wide state of "Custom:mystate" is what you would expect after going to the CLI of each server and adjusting the state.
server1\*CLI> dialplan set global DEVICE_STATE(Custom:mystate) NOT_INUSE
...
server2\*CLI> dialplan set global DEVICE_STATE(Custom:mystate) INUSE
...