Connector failover

Caution: Manufacturers such as Pepperl+Fuchs, Endress+Hauser, and Honeywell may only allow a single connection to a configured endpoint on the HART gateway. Therefore, check with the HART gateway manufacturer to verify support for simultaneous connections to the HART gateway. In some cases, the HART gateway may require multiple endpoints in order to support multiple connections. In this case, the connector failover pairs will require the data source to be configured with different endpoints so that each member of the failover pair can communicate with the same HART gateway.

With warm failover, each connector instance connects with the HART gateway defined in the configured datasource(s). Each connector instance actively retrieves HART gateway information so that the connector is able to assume the role of Active. However, only the connector instance in the Active role will actively retrieve real-time data to send to the PI System. The connector instance in the Backup role will actively check the HART gateway configuration to keep its objects up to date, but will not retrieve real-time data to send to the PI System. Having both connector instances simultaneously retrieve gateway configuration will put a slight load on the HART gateway. The HART gateway configuration calls are inexpensive in comparison to real-time data collections calls to the HART gateway. Therefore, warm failover should provide adequate performance during a failover scenario while minimizing the load on the HART gateway.

For failover to function properly, the connector must be able to notify the failover mechanism as to the connection status of the connector relative to the configured data source(s). PI Connector for HART-IP supports multiple data source configurations. A data source is considered connected if the connector can communicate with the HART gateway defined for the data source. Communication with the gateway means that the connector can discover the HART gateway contents. The connector does not need to be actively collecting real-time measurements from the datasource to be considered connected. The connector is considered connected if the percentage of connected data sources is greater than or equal to the value of the PercentUp field defined in the global configuration file (ConnectorGlobal.config.json). The connector is considered Disconnected if the percentage of connected data sources is less than the value of the PercentUp field defined in the global configuration file (ConnectorGlobal.config.json). The default PercentUp value is set to 100 percent.

The connector creates a PI AF element representing the connector instance failover configuration and status under the PI AF path of connector_root\Connector Installations\Failover. By default, the connector instance failover configuration and status PI AF element is not created. However, element creation can be enabled by setting the CreateFailoverStatusElements field in the global configuration file (ConnectorGlobal.config.json) to true.

Note: If this option is enabled, the PI AF element representing the connector instance failover configuration and status element, and any associated PI points, will not be created or updated while the connector instance is in the Backup role. Therefore, the failover element of the connector instance in the Backup role is not reliable and cannot be used to determine failover status. The failover element of the connector instance in the Active role is reliable and should be used monitor failover configuration and status.

The connector PI AF element representing the connector instance failover configuration and status contains the following attributes:

The PI AF object representing the connector instance failover configuration and status for the TestHost:9876 connector instance is shown below.

Note: Users should refer to the Failover configuration page in the connector UI to determine connector instance failover status.