Datacenter failover

While you can use geolocation-based load balancing to route traffic to the datacenter nearest to the client, you can also use HAProxy ALOHA for basic failover and failback between datacenters without the geolocation component. If a critical resource fails and service is disrupted, traffic is automatically redirected to healthy datacenters. This minimizes impact and avoids intervention.

1. In the Services tab, click gslb setup.

   

2. Add a listen directive for each IP address/network port pair at which the GSLB should listen for DNS queries. By default, it listens on all IP addresses (0.0.0.0) at port 53.

3. To enable the service to start automatically when the appliance boots, delete the no autostart line, click OK and then Close.

4. In the Services tab, click [advanced mode]. Then edit the gslb configuration.

   

   The current configuration displays.

   zone mydomain.com
     ttl 10
   
     # ORIGIN records
     record @ SOA ns1.mydomain.com hostmaster.mydomain.com 1 86400 3600 3600 3600 60
     record @ NS  ns1.mydomain.com
     record @ ttl 3600 MX 100  mail1.mydomain.com
   
     # static records
     record ns1   ttl 10 A 10.0.0.1
     record mail1 ttl 10 A 10.0.0.2

5. Add a new list record directive to the zone section. This type of record specifies a list of space-separated answer-list names. Essentially, you are specifying datacenters in order of preference, with fallback datacenters following primary datacenters.

   The list record www enumerates two answer-list sections, DC1 and DC2, where DC1 is the primary datacenter and DC2 is the fallback. You could list additional fallback datacenters too.

   zone mydomain.com
     ttl 10
   
     # ORIGIN records
     record @ SOA ns1.mydomain.com hostmaster.mydomain.com 1 86400 3600 3600 3600 60
     record @ NS  ns1.mydomain.com
     record @ ttl 3600 MX 100  mail1.mydomain.com
   
     # static records
     record ns1   ttl 10 A 10.0.0.1
     record mail1 ttl 10 A 10.0.0.2
   
     # dynamic records - DC1 is primary, DC2 is a fallback
     record www ttl 30 list DC1 DC2

6. Create answer-list sections that match the names you listed on the list record in the zone section.

   We define two answer-list sections named DC1 and DC2. These return DNS records to the client for different datacenters.

   zone mydomain.com
     ttl 10
   
     # ORIGIN records
     record @ SOA ns1.mydomain.com hostmaster.mydomain.com 1 86400 3600 3600 3600 60
     record @ NS  ns1.mydomain.com
     record @ ttl 3600 MX 100  mail1.mydomain.com
   
     # static records
     record ns1   ttl 10 A 10.0.0.1
     record mail1 ttl 10 A 10.0.0.2
   
     # dynamic records
     record www ttl 30 list DC1 DC2
   
   answer-list DC1
     up_threshold 1
     method multi-up
     option httpchk
     http-check connect
     http-check send uri /health.html hdr host www.mydomain.com
     http-check expect status 200,301,302
     answer-record srv1 20.0.0.1
   
   answer-list DC2
     up_threshold 1
     method multi-up
     option httpchk
     http-check connect
     http-check send uri /health.html hdr host www.mydomain.com
     answer-record srv1 30.0.0.1

   The answer-list section directives syntax is as follows.

   Directive	Description
   up_threshold	Determines the percentage of servers that must be up. Otherwise, traffic is routed to a different datacenter altogether. A threshold of 1 means that all servers in an answer-list must be healthy for the corresponding datacenter to be regarded as active. If you specify 0.1, then 10% of the total weighted number of servers must be up.
   method	Determines which IP addresses to return. As with geolocation-based load balancing, you can: return a single IP in a round-robin rotation (single-rr) return multiple addresses in a round-robin rotation (method multi-rr) return all servers that are up (method multi-up) return all servers, even if they are down (method multi-all)
   option	Specify httpchk to monitor the health of servers.
   http-check	Set any relevant health check parameters.
   answer-record	Enter any number of answer-record directives, which denote IP addresses assigned to the datacenter.

7. Save your configuration, close the configuration editor, then apply your changes on the gslb line in the Services tab.

   

8. In the Setup tab, click Save under Local Configuration to persist your changes after a reboot.

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