The FD discovery protocol requires each node periodically sends are-you-alive messages to its neighbor. If the neighbor fails to respond, the calling node sends a SUSPECT message to the cluster. The current group coordinator double checks that the suspect node is indeed dead and updates the cluster's view. Here is an example FD configuration.
<FD timeout="2000"
max_tries="3"
shun="true"/>
The available attributes in the FD element are listed below.
timeout specifies the maximum number of milliseconds to wait for the responses to the are-you-alive messages.
max_tries specifies the number of missed are-you-alive messages from a node before the node is suspected.
shun specifies whether a failed node will be shunned. Once shunned, the node will be expelled from the cluster even if it comes back later. The shunned node would have to re-join the cluster through the discovery process.
Regular traffic from a node counts as if it is a live. So, the are-you-alive messages are only sent when there is no regular traffic to the node for sometime.