AppEngine reconnect configuration for objects linked to the telemetry server

If an object with an attribute linked to a Telemetry Server is undeployed and then redeployed, you may see a gap in the timestamps that are historized by the Historian for the data collected between the undeployment and redeployment times. This can happen, even when buffering is enabled. Note that all data values are accurately preserved, but the timestamps for the values will not be accurate. This is a function of the behavior of the Historian and the default configuration of the AppEngine.

When an AppEngine or objects connected to it are undeployed and then redeployed, all values from the Telemetry Server are collected and sent to the Historian upon redeployment. The Historian gives the current timestamp to the first value received after redeployment. This leaves a gap between undeployment and redeployment times. The Historian adds 5 ms from the time of redeployment to all timestamps for values (after the first value) that were collected during the undeployed time. Thus, subsequent values have timestamps of redeploy time + 5 ms, redeploy time + 10 ms, etc.

To eliminate this gap in timestamp values for data collected during undeployment, configure the Reconnect setting under Data management in the AppEngine that contains the object. When the Reconnect setting is enabled, all values will be historized with the correct timestamp.

To configure the AppEngine Reconnect setting

1. Locate the AppEngine that contains the object with the Telemetry Server-connected attribute.

2. Open the AppEngine for editing.

3. In the General tab, expand Advanced Settings.

   

4. Under Data management, enable the setting, Reconnect as soon as possible & do not mark disconnects.

5. Save and close the AppEngine object.