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The MQTT Transmision Edge side client can publish historic data either in-order (synchronously) or asynchronously
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When configured for In-Order History, MQTT Transmission will ensure that after the client reconnects, all historical data will be flushed before live data updates are resumed. Until the historical data is completely flushed, any new updates will continue to be written to the history store to ensure the in-order delivery of data. When publishing in this mode, MQTT Engine should be configured to write historical tag changes to the tag. In other words, 'Store Historical Events' in the MQTT Engine General configuration should be unchecked.
Under the MQTT Transmission Settings for your transmitter, navigate to the History Settings to disable the In-Order History configuration parameter.
MQTT Transmission History Store supports both In-Memory and Disk-Backed types. There are advantages/disadvantages to each:
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The Flush Period is a the delay between acquisition and publishing of the historical data. MQTT Transmission queries the history store and builds up a publish, and publishes it, and then delays by the Flush Period. The actual message publish frequency is not deterministic as the time to gather the publish from the history store can vary depending on the frequency tag change events occurring, disk speed, CPU availability, etc. For example, if it takes 5s to gather up and publish that payload, the actual message publish frequency will be it will be 5s + the flush period |
In the MQTT Transmitter provider, under each of the History Store folders for each Transmitter, a tag tree will be created with the tag path of GroupID > EdgeID and/or > DeviceID.
The tags are updated every 30 seconds
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If data is missing data at the Historian, then the next trouble-shooting troubleshooting steps are to adjust the MQTT Transmission Flush Quantity and Flush Period until you have a stable system when the messages published by MQTT Transmission are reliably consumed by your historian.
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