Hot Standby

Scheduling failback

The failback command (/Gateway:failback) can scheduled like any other internal command. This could be useful to schedule an automatic failback outside of business hours should a secondary take over the role of primary at some point.

A suggested XPath for the target that would ensure that the command is only run on an active secondary in a manual-failback mode is shown below:

/geneos/gateway/directory[(param("HotStandbyRole")="Secondary")][(param("HotStandbyManualFailbackActive")="true")][(rparam("HotStandbyState")="Active")

Hot Standby with secure ports

To use secure ports with Gateways, configure the Gateway with a secure listen port in operatingEnvironment > listenPorts. The port for both the primary and secondary Gateway must match the secure port set. If you are using different secure ports on the primary and secondary Gateways, see Using different ports for primary and secondary Gateways.

Note: It is possible to specify both secure and insecure ports with Hot Standby. However, if you do specify both secure and insecure ports, you cannot specify different ports for primary and secondary Gateways.

Paired operation

It is recommended that primary and secondary Gateways run on different hosts. Therefore, failure of the host (or network connectivity of the host) does affect the secondary Gateway and monitoring can continue unaffected.

Once the hot-standby configuration is completed, the setup file should be copied from the primary to the secondary host. This setup should then be applied to the primary Gateway first, and then to the secondary Gateway.

The primary Gateway must be started first because the secondary Gateway attempts to connect to it to synchronise operation. This connection is maintained while both Gateways are in operation. Should the connection fail, the secondary Gateway becomes active after a brief time and takes over monitoring duties from the failed primary Gateway.

While the secondary Gateway is active, you should not notice a difference in services between Gateways.

In particular it is still possible to alter the Gateway setup. When the primary Gateway is running again the synchronisation between Gateways will ensure that the primary Gateway receives an up-to-date copy of the setup file before it takes up monitoring operations again.

When the primary Gateway is reactivated there will be a short period when the secondary Gateway releases control of Netprobes and the primary Gateway acquires them again during which monitoring is paused. It is possible to remove this period by switching the (active) secondary Gateway to a primary role by altering the Gateway setup, before the primary Gateway is restarted. When performing this switch, please ensure that the setup for the old primary Gateway is also edited so that it runs as a secondary Gateway.

A parameter, HotStandbyRole and a runtime parameter HotStandbyState are available on the directory object. These can be used to alert when hot standby failovers occur. The following rule is an example of how this could be used.

Target:

/geneos/gateway/directory

Rule:

if param "HotStandbyRole" = "Secondary" and rparam "HotStandbyState" = "Active" then
run "myFailoverAction"
endif	                      

Parameter HotStandbyRole and runtime parameter HotStandbyState can be described as follows:

Configuration

Basic configuration for a Hot Standby pair of Gateways consists of specifying the hostname and port for each Gateway.

Hostnames can be specified as either the machine hostname (obtained by running the hostname command), as an IP address, or as a fully qualified domain name (e.g. "somehost.somedomain.com").

When Hot Standby Gateway setup is applied, a Gateway determines whether it is running as the primary or secondary host. It does this by comparing first the primary then the secondary hostname with the identity of the host the Gateway is running on. The first match found determines the Gateway role; if no settings match the Gateway will run as Stand Alone.

Each comparison is performed in the following order:

• First, the Gateway checks if a configured hostname is an IP address (e.g. 192.168.1.135); this is then compared with the IP address(es) of the host.
• Second, if a configured hostname is a fully qualified domain name (e.g. "somehost.somedomain.com"), the whole name as given and then the first part of the configured hostname is compared with the Gateway host name. For example, "somehost.somedomain.com" matches if the Gateway host name is also "somehost.somedomain.com", or "somehost" but not if the Gateway host name is "somehost.anotherdomain.com".
• Otherwise, the Gateway compares the configured hostname with the full Gateway host name and then with the first part of its name. Therefore, if the configured host name is "somehost", it matches if the Gateway host name is "somehost.somedomain.com" or "somehost", as well as "somehost.anotherdomain.com".

A secondary Gateway attempts to connect to the primary Gateway on the configured hostname and port. If the hostname is not specified as an IP address, Gateway attempts to resolve this using a forward DNS lookup.

When the primary Gateway receives a connection from another Gateway, it attempts to authenticate this Gateway by matching the incoming connection against the configured secondary Gateway. The way this is done is controlled by the hotStandby > primarySecurityCheck setting, which by default resolves the connecting IP to a hostname using a reverse DNS lookup (if required) and match this against the secondary Gateway configuration.

Basic tab

These settings are found under the Basic tab.