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See the Ignition documentation Configuring Tag History for additional help.
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| historicaleventprocessing |
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| historicaleventprocessing |
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Historical Event ProcessingThere are two ways that MQTT Engine historical event processing can result in insert historical inserts into the databasedata into Ignition’s Tag Historian Module:
- Engine is configured to write historical events directly to the database, via the Historian, bypassing the Tag.
- Engine is configured to write historical events to the Tag instead of directly to the Historian.
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If you do not select In-Order History, data will be lost/ignored at MQTT engine because Ignition will ignore writes to the Tag if the timestamp on the Tag change is older that the current value. |
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Whilst the history flush is in progress, all new change events are written to the history store until it has been completely flushed. If the tag change rate at the Edge is faster than the MQTT Transmission Flush Period this can cause a build up of data in history store(s) and prevent the publishing of live data. |
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| engine-tag-persist-history-config |
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| engine-tag-persist-history-config |
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History Configuration Persistence
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Configuring history on tags indirectly referencing MQTT Engine tags will work properly if the referencing tag is a Reference tag only. Derived, Expression and OPC tags (expose MQTT Engine tag provider through OPCUA server) will not properly store history when MQTT Engine tags are updated with historical data at a high rate of speed. This is a limitation within the Ignition platform and may be addressed in a future release.
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If using an Ignition release before v8.1.4 with MQTT Engine - In order for historical tag changes at the MQTT Engine tag to propagate to the referencing tag, MQTT Engine must be configured to write historical data directly to its tags and MQTT Transmission must be configured to flush history in-order. See this section above for more details on these configuration requirements. |
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If using an Ignition v8.1.4 or later with MQTT Engine - Historical back-fill support was added in Ignition which allows Reference Tags in Ignition to be updated even if history arrives out of order. See the following document for details: MQTT History Back-Fill with Reference Tags |
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| flushing-history-metrics |
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| flushing-history-metrics |
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History Stores Metrics & Flushing HistoryOne can determine the current size of the History Store by examining the History Store metric tags under [MQTT Transmission]Transmission Info/History Store. These tags will show the number of historical metrics stored per edgenode/device and how much memory/disk is being consumed by these metrics. These tags update live (count down) as historical data is flushed.
Review Determining the settings for an MQTT Transmission History Store for help in determining the correct configuration for your History Store
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| CLD80:FAQ: Ignition Modules |
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| CLD80:FAQ: Ignition Modules |
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nopanel | true |
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