Register Arbitrators

Eucalyptus uses a periodic ICMP echo test to an Arbitrator. This test approximates an end user's ability to access the system. If Eucalyptus determines that it cannot reach the host associated with a registered Arbitrator, all Eucalyptus services operating on that host attempt to failover to the alternate hosts running those services.

High Availability

In HA, you can register each Arbitrator service on the primary and secondary CLC and Walrus. If you are using either Managed or Managed (No VLAN) mode, you can also register Arbitrator services on both the primary CC and the secondary CC.

We recommend that you register more than one Arbitrator for each Eucalyptus component. This will allow for normal outages and maintenance. There is no limit on the number of Arbitrators on a CLC and a Walrus. You can only register up to three on a CC.

Register an Arbitrator service on each host that has a cloud component (CLC or Walrus) installed. An Arbitrator is a host-wide component: when an Arbitrator is registered on a host, it is registered with all cloud components enabled on that host. A separate arbitrator has to be registered per each network entity that needs to be monitored from the host.

To register an Arbitrator:

Log in to the primary CLC.
Enter the following command to register an arbitrator:
```
/usr/sbin/euca_conf --register-arbitrator --partition <ID>
 --component <ID> --host <target_host>
```
where:
- <ID> is a globally unique ID that identifies an Arbitrator. Note that you must use the same <ID> as both a partition and component ID.
- <target_host> is the IP or hostname running the Eucalyptus component that will run the Arbitrator.
For example:
```
euca_conf --register-arbitrator --partition EXAMPLE_ARB --component EXAMPLE_ARB --host 192.168.1.10
```
Repeat for the secondary CLC and for both Walrus servers.
Define the gateway for each Arbitrator:
```
/usr/sbin/euca-modify-property -p <ID>.arbitrator.gatewayhost=<gateway>
```
where:
- <ID> is the globally unique ID of the registered Arbitrator.
- <gateway> is an external hostname or IP address used to approximate connectivity to the end user.
For example:
```
euca-modify-property -p EXAMPLE_ARB.arbitrator.gatewayhost=192.168.1.1
```
Repeat for each registered Arbitrator.
To register on each CC, log in to the primary CC, and open the /etc/eucalyptus/eucalyptus.conf file.
Provide a list of Arbitrators (up to three) as values for the CC_ARBITRATORS property. For example:
```
CC_ARBITRATORS="192.168.48.11 192.168.48.12"
```
Save the file and restart the CC.
```
service eucalyptus-cc restart 
```
Repeat on the secondary CC.

Example

In the following example, the primary CLC is on <CLC_host_p>, the secondary CLC is on <CLC_host_s>, the primary Walrus is on <Walrus_host_p>, and the secondary Walrus is on <Walrus_host_s>.

/usr/sbin/euca_conf --register-arbitrator --host <CLC_host_p> --component ARB00 --partition ARB00
/usr/sbin/euca_conf --register-arbitrator --host <CLC_host_p> --component ARB01 --partition ARB01
/usr/sbin/euca_conf --register-arbitrator --host <Walrus_host_p> --component ARB02 --partition ARB02
/usr/sbin/euca_conf --register-arbitrator --host <Walrus_host_p> --component ARB03 --partition ARB03
/usr/sbin/euca_conf --register-arbitrator --host <CLC_host_s> --component ARB04 --partition ARB04
/usr/sbin/euca_conf --register-arbitrator --host <CLC_host_s> --component ARB05 --partition ARB05
/usr/sbin/euca_conf --register-arbitrator --host <Walrus_host_s> --component ARB06 --partition ARB06
/usr/sbin/euca_conf --register-arbitrator --host <Walrus_host_s> --component ARB07 --partition ARB07