Redundant polling
It is possible to create an element that is configured with a redundant connection. When the primary connection is no longer responding (i.e. a timeout occurs on this connection), DataMiner will automatically switch to the secondary connection (and vice versa).
In the protocol, you need to define the 2 connections and specify that redundant polling has to be used:
<Type communicationOptions="redundantPolling" relativeTimers="true" advanced="snmp:Secondary">snmp</Type>
The option redundantPolling in the communicationOptions attribute is required to activate the redundant polling mechanism.
Note
Redundant polling is supported with protocols that define exactly two connections of the same type. The following is supported: two SNMP, two serial, two smart-serial, or two HTTP connections.
Note that for smart-serial connections, in order to get a timeout (enabling the redundant polling connections to switch) the pair must contain a response. Alternatively, you can implement logic to set the communication state using the NT_CHANGE_COMMUNICATION_STATE (249) Notify call.
Scenarios that trigger redundant polling switching
This section describes when this feature will switch between polling interfaces during an element's runtime.
On timeout after retries of a single group
When polling for a group goes into timeout, DataMiner will try to poll that group again on the same connection. The wait time for a timeout to be called and the number of retries are based on the configurations in the element settings. After all retries are exhausted, DataMiner will switch to the other interface and poll for the next group in the queue.
Note
During an interface switch, the element will not go into timeout. It will only do so when both interfaces are inaccessible and no data has been retrieved for an extended period of time as defined in the element settings.
SNMP polling of invalid parameters
If the polled SNMP parameter returns an error such as NO SUCH NAME, DataMiner will switch between the polling interfaces and poll the next group in the queue. In such corner cases, DataMiner will switch back and forth between interfaces depending on how frequently these invalid parameters are polled.
Other polling scenarios
This section describes how redundant polling will behave with other connection configurations that can be made in the protocol.
SNMP polling of specific interfaces using the ipid attribute
Switching of interfaces is triggered on timeout after retries on that specific group/parameter. After this, DataMiner will proceed to poll for the next group in the queue.
See also: ipid attribute
On SNMP Get through QActions
When NT_SNMP_GET or NT_SNMP_RAW_GET are used in a QAction, switching of interfaces is not triggered.
See also:
SNMP polling of specific interfaces through the connection attribute in a Group
In this case, switching of interfaces is not triggered. When the group goes into timeout on a specific connection, DataMiner will try to poll the group again until all retries are exhausted. After this, DataMiner will proceed to poll for the next group in the queue.
See also: connection attribute