In certain situations, an installation may have two parallel data sources presenting the exact same information under normal circumstances. This could be in a "Main/Backup" configuration or "Primary/Secondary" or "Main/Check" or any other terminology. In the EtaPRO environment, there is no differentiation between the two sources in terms of hierarchy. Both sources are equally capable of presenting the same data and neither is given preferential treatment over the other.
To support a situation such as this, administrators can take advantage of the EtaPRO Data Interface Redundancy. EtaPRO Data Interface Redundancy will only support the situation where there are two independent data sources presenting the same information.
Upon successful configuration, EtaPRO will accept data from either the interface configured on 'Server A' or 'Server B' depending on which sends good data first. When the configured 'heartbeat' tag is observed to be beyond the 'Failover Threshold', EtaPRO will switch and begin listening to the other interface. In summary, there are two interfaces installed and configured. One interface is installed on 'Server A' and the other installed on 'Server B'. Both of the interfaces have the same Instance Name and both are running and both are sending data to the EtaPRO Server.
For information on installation and configuration of the EtaPRO Data Interface, please see the EtaPRO Data Interface Configuration Manual.
Please do not proceed unless BOTH Interfaces have been correctly configured and tested.
Ensure that both interfaces are configured with the exact same Instance Name. The EtaPRO Data Interface Redundancy is keyed off of the Instance Name.
It is highly recommended that each EtaPRO Data Interface be configured with a useful 'Friendly Name' to help identify which interface is currently active. The friendly name is configured at the EtaPRO Data Interface. The recommended convention is to set the 'Friendly Name' the same as the computer name where the EtaPRO Data Interface is installed.
Once both Interfaces have been setup, open the EtaPRO Client and go to Configuration Tools | Data Interface Tools. EtaPRO Administration rights and Edit Mode is required for these steps. Click on New to setup a new Data Interface Redundancy.
Type in the same Interface Instance Name as was configured on both interfaces and then click OK.
Set the Failover Threshold and the Heartbeat Tag Id.
- Failover Threshold - The number of seconds before an interface instance is considered failed and can accept data from a redundant instance.
- Heartbeat Tag Id - The unique identifier of the tag that will represent the viability of the interface instance.
Click OK or Apply to set the Interface Redundancy Configuration.
For information about which Interface is currently active, as well as when was the last time it sent any values, click on the Status tab for a running log of information received from the EtaPRO Data Interfaces.
The Failover Threshold should be set large enough so that it isn't triggered just because of a single missed update. If the Heartbeat Tag is set to read at once a minute, set the Failover Threshold at just over two updates (two and a half minutes or 150 seconds).
The Heartbeat Tag Id can be selected by clicking on the "..." button in the cell to bring up a list of all of the acquired points in the system. It is up to the administrator to either select an already configured tag to be the Heartbeat Tag or setup a dedicated Heartbeat Tag.
A good Heartbeat Tag is a point which is setup to read a piece of data that is constantly changing, cannot turn off, and is expected to produce good reliable data every day all day. In addition, it is recommended that the Exception Deviation, Exception Deviation Percent, Exception Maximum Time and Exception Minimum Time, all be set to 0.