High Availability (HA)

The HA solution in Wazo makes it possible to maintain basic telephony function whether your main Wazo server is running or not. When running a Wazo HA cluster, users are guaranteed to never experience a downtime of more than 5 minutes of their basic telephony service.

The HA solution in Wazo is based on a 2-nodes “master and slave” architecture. In the normal situation, both the master and slave nodes are running in parallel, the slave acting as a “hot standby”, and all the telephony services are provided by the master node. If the master fails or must be shutdown for maintenance, then the telephony devices automatically communicate with the slave node instead of the master one. Once the master is up again, the telephony devices failback to the master node. Both the failover and the failback operation are done automatically, i.e. without any user intervention, although an administrator might want to run some manual operations after failback as to, for example, make sure any voicemail messages that were left on the slave are copied back to the master.

Prerequisites

The HA in Wazo only works with telephony devices (i.e. phones) that support the notion of a primary and backup telephony server.

  • Phones must be able to reach the master and the slave (take special care if master and slave are not in the same subnet)
  • If firewalling, the master must be allowed to join the slave on ports 22 and 5432
  • If firewalling, the slave must be allowed to join the master with an ICMP ping
  • Trunk registration timeout (expiry) should be less than 300 seconds (5 minutes)
  • The slave must have no provisioning plugins installed.

The HA solution is guaranteed to work correctly with the following devices.

Quick Summary

  • You need two configured Wazo (wizard passed)
  • Configure one Wazo as a master -> setup the slave address (VoIP interface)
  • Restart services (wazo-service restart) on master
  • Configure the other Wazo as a slave -> setup the master address (VoIP interface)
  • Configure file synchronization by running the script xivo-sync -i on the master
  • Start configuration synchronization by running the script xivo-master-slave-db-replication <slave_ip> on the master
  • Resynchronize all your devices

That’s it, you now have a HA configuration, and every hour all the configuration done on the master will be reported to the slave.

Configuration Details

First thing to do is to install 2 Wazo.

Important

When you upgrade a node of your cluster, you must also upgrade the other so that they both are running the same version of Wazo. Otherwise, the replication might not work properly.

You must configure the HA with PUT /ha

You can configure the master and slave in whatever order you want.

You must also run xivo-sync -i on the master to setup file synchronization. Running xivo-sync -i will create a passwordless SSH key on the master, stored under the /root/.ssh directory, and will add it to the /root/.ssh/authorized_keys file on the slave. The following directories will then be rsync’ed every hour:

  • /etc/asterisk/extensions_extra.d
  • /etc/xivo/asterisk
  • /var/lib/asterisk/agi-bin
  • /var/lib/asterisk/moh
  • /var/lib/xivo/certificates
  • /var/lib/wazo/sounds/tenants

Warning

When the HA is configured, some changes will be automatically made to the configuration of Wazo.

SIP expiry value on master and slave will be automatically updated:

  • GET /asterisk/sip/general
    • minexpiry: 3 minutes
    • maxexpiry: 5 minutes
    • defaultexpiry: 4 minutes

The provisioning server configuration will be automatically updated in order to allow phones to switch from Wazo power failure.

  • GET /provd/cfg_mgr/configs?q={"X_type": "registrar"}

    registrar_backup: <slave ip> proxy_backup: <slave ip>

Warning

Do not change these values when the HA is configured, as this may cause problems. These values will be reset to blank when the HA is disabled.

Important

For the telephony devices to take the new proxy/registrar settings into account, you must resynchronize the devices or restart them manually.

Master node

In choosing the node_type: master you must enter the remote_address of the VoIP interface of the slave node.

Important

You have to restart all services (wazo-service restart) once the master node is configured.

Slave node

In choosing the node_type: slave you must enter the remote_address of the VoIP interface of the master node.

Replication Configuration

Once master slave configuration is completed, Wazo configuration is replicated from the master node to the slave every hour (:00).

Replication can be started manually by running the replication scripts on the master:

xivo-master-slave-db-replication <slave_ip>
xivo-sync

The replication does not copy the full Wazo configuration of the master. Notably, these are excluded:

  • All the network configuration
  • All the support configuration
  • Call logs
  • Call center statistics
  • Certificates
  • HA settings
  • Provisioning configuration
  • Voicemail messages

Less importantly, these are also excluded:

  • Queue logs
  • CELs

Internals

4 scripts are used to manage services and data replication.

  • xivo-master-slave-db-replication <slave_ip> is used on the master to replicate the master’s data on the slave server. It runs on the master.
  • xivo-manage-slave-services {start,stop} is used on the slave to start, stop monit and asterisk. The services won’t be restarted after an upgrade or restart.
  • xivo-check-master-status <master_ip> is used to check the status of the master and enable or disable services accordingly.
  • xivo-sync is used to sync directories from master to slave.

Limitations

When the master node is down, some features are not available and some behave a bit differently. This includes:

  • Call history / call records are not recorded.
  • Voicemail messages saved on the master node are not available.
  • Custom voicemail greetings recorded on the master node are not available.
  • Phone provisioning is disabled, i.e. a phone will always keep the same configuration, even after restarting it.
  • Phone remote directory is not accessible, because provisioned IP address points to the master.

Note that, on failover and on failback:

  • DND, call forwards, call filtering, …, statuses may be lost if changed recently.
  • If you are connected as an agent, then you might need to reconnect as an agent when the master goes down.

Additionally, only on failback:

  • Voicemail messages are not copied from the slave to the master, i.e. if someone left a message on your voicemail when the master was down, you won’t be able to consult it once the master is up again.
  • More generally, custom sounds are not copied back. This includes recordings.

Here’s the list of limitations that are more relevant on an administrator standpoint:

  • The master status is up or down, there’s no middle status. This mean that if Asterisk is crashed the Wazo is still up and the failover will NOT happen.

Troubleshooting

When replicating the database between master and slave, if you encounter problems related to the system locale, see PostgreSQL localization errors.