voip Archives - IT AND DEVELOPMENT

asterisk_logo Did you ever wanted an automatic failover solution for Asterisk? With just a few seconds downtime? Here’s how you do it.

This setup consists of the following steps:

Download and instal AsteriskNow image (a bundle with Asterisk and FreePBX ready to deploy)
Download and install keepalived daemon to get IP switchover
Set up MySQL Master – Master replication
Enjoy peace of mind 🙂

I assume your setup will be AsteriskNow based (which is Red Hat / CentOS based) but it should be painlessly applied to other Linux distributions. Also, reserve 3 or more IP addresses, one for each Asterisk instance and the third one for the cluster. Finally, the commands / edits will be done as root. This is NOT a best practice, but I want to show an easy setup and I won’t assume your user is configured as sudoer.

DOWNLOAD AND INSTALL ASTERISKNOW

We’ll go with AsteriskNow as it’s a “ready to go” Asterisk + FreePBX bundle which can be downloaded at the Asterisk’s official site: Download AsteriskNow

Burn and install / Boot from the iso and follow the installation procedure. In the installation, you’ll have to specify a fixed IP address (we’ll use it later for mysql replication), but remember not to use the one the one for the cluster. The third (cluster) IP must be unused.

Now, go on and install the two AsteriskNow instances.

SETTING UP FAILOVER WITH KEEPALIVED

For this step, we’ll use keepalived. It’s available in the repos, but in case you are on another setup or you want some more information, you can read more about keepalived here.

Now, login into your primary Asterisk instance and install and configure keepalived:

 # yum install keepalived
# cd /etc/keepalived/
# vi keepalived.conf

Change the bold marked parameters (higher priority means it’ll be the primary server):

vrrp_instance VI_1 {
       interface eth0
       state MASTER
       virtual_router_id 51
       priority 100
       authentication {
           auth_type PASS
           auth_pass Add-Your-Password-Here
       }
       virtual_ipaddress {
               192.168.15.23
               172.12.1.45
       }
}

Hints:

Priority: Higher priority means the server will be used if alive. It must be different in the primary and the secondary server
auth_pass: It only takes into account 8 characters
virtual_ipaddress: Those will be the cluster addresses and must be the same for primary and secondary server. It can be one or more addresses which can be on different IP ranges or even on another network interface. There’s quite some info for more advanced setups (also, there’s always #man keepalived.conf). We are going for a simple working setup

A SIMPLE WORKING KEEPALIVED CONFIGURATION FOR PRIMARY SERVER

Remember to configure you SMTP server and change bold parameters to adapt to your particular setup.

! Configuration File for keepalived
global_defs {
  notification_email {
    voip@example.com
    failover@example.com
    sysadmin@example.com
  }
  notification_email_from server.asterisk@example.com
  smtp_server xxx.yyy.zzz.aaa
  smtp_connect_timeout 30
  router_id LVS_DEVEL
}
vrrp_instance VI_1 {
   state MASTER
   interface eth0
   virtual_router_id 51
   priority 101
   advert_int 1
   authentication {
       auth_type PASS
       auth_pass hunter2
   }
   virtual_ipaddress {
       192.168.143.200

   }
}

auth_pass must be the same in both servers, but please, change it. You don’t want to be THAT guy with hunter2 as a password.

A SIMPLE WORKING KEEPALIVED CONFIGURATION FOR SECONDARY SERVER

Remember to configure you SMTP server and change bold parameters to adapt to your particular setup.

! Configuration File for keepalived
global_defs {
  notification_email {
    voip@example.com
    failover@example.com
    sysadmin@example.com
  }
  notification_email_from server.asterisk@example.com
  smtp_server xxx.yyy.zzz.aaa
  smtp_connect_timeout 30
  router_id LVS_DEVEL
}
vrrp_instance VI_1 {
   state MASTER
   interface eth0
   virtual_router_id 51
   priority 100
   advert_int 1
   authentication {
       auth_type PASS
       auth_pass hunter2
   }
   virtual_ipaddress {
       192.168.143.200
   }
}

TESTING FAILOVER WITH KEEPALIVED

Starting with the secondary server, you’ll have to start the service manually and once it’s tested, configure it to start on boot.

Let’s start the service to check for startup errors

# service keepalived start

Optionally, to check virtual IP and switchover info:

# tail -f /var/log/messages

From a third PC, launch a ping to your virtual IP to see if it’s alive (it should be) and leave it running.

Now start the service on the primary server and optionally take a look at switchover information:

# service keepalived start
# tail -f /var/log/messages

The running ping might have lost a couple of packets during the switchover, but by now, the primary server should have the cluster IP assigned.

Finally, configure keepalive to automatically run on boot on both servers

# chkconfig keepalived on

CONFIGURING MYSQL MASTER MASTER REPLICATION

Now that we have an automatic failover mechanism in place, it’s time to set up MySQL redundancy.

MODIFY MYSQL CONFIGURATION (MY.CNF)

The first step will be to modify MySQL configuration following those steps:

Enable remote conections
Identify the server. As a default when it’s not otherwise said, it takes a value of 1 so it’s better to take another id
Location of binary log
Explicitly add which databases we want to replicate
Explicitly add which databases we don’t want to replicate. This step shouldn’t be necessary but I’ve had some passwords related problems because mysql system database got replicated.

The configuration file is llocated at /etc/my.cnf and you should have something similar to the following:

Initial configuration:

[mysqld]
bind-address = 127.0.0.1
general_log = 0
general_log_file = /var/log/mysql/mysql.log
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid

Final working setup for primary server:

[mysqld]
#bind-address = 127.0.0.1
server-id = 2
log_bin = /var/log/mysql/mysql-bin.log
binlog_do_db = asterisk
binlog_do_db = asteriskcdrdb
binlog_ignore_db = mysql
general_log = 0
general_log_file = /var/log/mysql/mysql.log
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid

Restart mysql service:

# service mysqld restart

And we’re done with the primary server. For the secondary server, repeat the steps remembering to change server-id to 3 or any other value.

Final working setup for secondary server:

[mysqld]
#bind-address = 127.0.0.1
server-id = 3
log_bin = /var/log/mysql/mysql-bin.log
binlog_do_db = asterisk
binlog_do_db = asteriskcdrdb
binlog_ignore_db = mysql
general_log = 0
general_log_file = /var/log/mysql/mysql.log
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid

Restart mysql service:

# service mysqld restart

ADDING AND CONFIGURING REPLICATION USER

Log into primary server and add the user which will do the replication:

# mysql -u root -p
mysql> create user 'replicator'@'%' identified by 'ChangeMePlease!!!!!';
Query OK, 0 rows affected (0.00 sec)

Add permission for replication to the user:

mysql> grant replication slave on *.* to 'replicator'@'%';
Query OK, 0 rows affected (0.00 sec)

As far as I can tell, it’s not possible to grant permissions to specific databases for this to work. Now, let’s get information from which point on the primary server we want to replicate on the secondary server:


mysql> show master status;
File Position Binlog_Do_DB Binlog_Ignore_DB
mysql-bin.000001 254163 asterisk,asteriskcdrdb mysql
 1 row in set (0.00 sec)

The important parts are File and Position. Take note of them as we’ll need them later.

Log into secondary server and add the user which will do the replication:

# mysql -u root -p
mysql> create user 'replicator'@'%' identified by 'ChangeMePlease!!!!!';
Query OK, 0 rows affected (0.00 sec)

Add permission for replication to the user:


mysql> grant replication slave on *.* to 'replicator'@'%';
Query OK, 0 rows affected (0.00 sec)

SETTING UP MYSQL MASTER MASTER REPLICATION

Now, on the secondary server, we’ll configure replication from primary to secondary server (remember to use server’s fixed IP address and not the virtual one):

mysql> slave stop;
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> CHANGE MASTER TO MASTER_HOST = '192.168.143.201', MASTER_USER = 'replicator', MASTER_PASSWORD = 'ChangeMePlease!!!!!', MASTER_LOG_FILE = 'mysql-bin.000001', MASTER_LOG_POS = 254163;
Query OK, 0 rows affected (0.03 sec)
mysql> slave start;
Query OK, 0 rows affected (0.00 sec)

Still on the secondary server, we’ll get information for setting up secondary to primary replication:

mysql> show master status;
File Position Binlog_Do_DB Binlog_Ignore_DB
mysql-bin.000001 383123 asterisk,asteriskcdrdb mysql
  1 row in set (0.00 sec)
Finally, set up replication on the primary server from secondary to primary (remember to use server's fixed IP address and not the virtual one):

mysql> slave stop;
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> CHANGE MASTER TO MASTER_HOST = '192.168.143.202', MASTER_USER = 'replicator', MASTER_PASSWORD = 'ChangeMePlease!!!!!', MASTER_LOG_FILE = 'mysql-bin.000001', MASTER_LOG_POS = 383123;
Query OK, 0 rows affected (0.02 sec)
mysql> slave start;
Query OK, 0 rows affected (0.00 sec)

That’s it. Easy, isn’t it? Now you can go on and configure your installation.

FINAL THOUGHTS, NEXT STEPS AND HELPFUL LINKS

Depending on the client used, I’ve got under 5 seconds downtime.
Passwords, too open configuration …. Please change the passwords stated here. Also, the configuration can (and should) be thightened.
You can configure the whole installation in one server and the configuration will be synchronized at FreePBX level. You must apply changes on the secondary server for Asterisk to notice them (there are workarounds but see next point)
If you can afford it (if you need HA, it’s probable you can afford this), please consider purchasing FreePBX HA module. This way, they get paid so they can go on developing and everyone benefits on the long run (Disclaimer: I have no relation with FreePBX. I just think they’re developing an amazing piece of software)
Recordings, if you use them, they are (still) not synchronized on the filesystem. They get stored on the server which is running in the moment the call is made. You’ll have to set up a synchronization mechanism

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LINKS I USED FOR SETTING EVERYTHING UP

Nov 1, 2016

IT AND DEVELOPMENT

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Tag: voip

Simple Automatic Failover for Asterisk and FreePBX