Ignition 8.1: CirrusLink MQTT Transmission - Store and Forward?

Not sure if this is the right spot for this question or whether I should post this on the CirrusLink form.

I have a question regarding the “store and forward” function and how it is implemented within Ignition.

According to one of the docs I read:


The “History” page allows for the configuration of MQTT Transmission History Stores. In the event that a Transmitter loses it’s connection with the MQTT Server and is unable to reconnect, a History Store (if enabled) will store all messages corresponding to change events on the monitored tags. Once a connection with an MQTT server is reestablished the History Store will publish the stored messages with a flag set to indicate that the messages are “historical” to prevent confusion with live data values.

Does this imply that if you have multiple MQTT Engines receiving the same data from a MQTT Distributor (Broker) that is receiving data from a MQTT Transmission module, if one of the Engines goes off line does the Transmission module buffer (store) data and then when the Engine goes back on line the data is Published (forwarded) to the Broker and then to the Engine that went back on line?

  1. Will this work even though another Engine is work fine and receiving data?? (Essentially this is a one-to-many device to server scenario)
  2. How big is this buffer? Where can I see this buffer file when “Enable History Storage by Default” is selected and History Store is set to “Disk-Backed”? {In my experience testing this, it would appear that the buffer is a little “hit and miss” with restoring data. It seems to work for short duration interruptions, but anything beyond 5 mins seems to be a problem with restoring the time-series data into the MQTT Engine and any corresponding Historian collecting the data.

For others with similar questions: MQTT Transmission: Store & Forward - #2 by wes.johnson - MQTT Modules - Cirrus Link Forum