Failover scenarios

Failover may occur in the following scenarios.

Starting and stopping the connector

Upon startup each connector attempts to communicate with its peer. If communication is successful, the connector communicates its own status to the other connector. As long as both connector instances have reliable data source communication, one of the connectors assumes the active role and other takes a backup role. The active connector sends data to both PI and PI AF servers and the backup connector discards the collected data.

When one connector is stopped or shut down, it sends a stopped state to its peer, and the peer connector assumes the active role. When the stopped connector is started again, it takes the backup role. The connectors do not support automatic fail-back to the connector that was previously active.

Data source connection loss

When an active connector loses its data source connection, it sends the backup the information about its own data source status to the backup connector. Upon receiving the data source disconnection status from the active connector, the backup connector assumes the active role provided it has a good data source connection. If the backup connector does not have a reliable data source connection, both connectors continue in the same role until one of them resumes a reliable data source connection.

Force transition to active role

When two connectors are in an active and backup role, you can transition the backup connector into an active role by clicking the Make node active button. The button is disabled if the connector is in an active role already or if the backup connector does not have a reliable data source connection.

Connection loss between connectors

When connector peers cannot communicate with each other, both become active connectors. In this scenario, duplicate data might be sent to PI and PI AF. When the connection resumes, both connectors negotiate their data source status and eventually one connector relinquishes the active role and becomes the backup.