ADX can now ingest Event Hub data that existed before the creation of an Event Hub data connection in your ADX cluster.
You can use this feature by entering the Event retrieval start date (under "Advanced settings") on the ADX's Event Hub data connection page of Azure portal, on the Kusto Web UI ingestion wizard (One-Click) , or by using the properties.retrievalStartDate of the data confection REST API.
Note that the feature can only retrieve events retained by the Event hub, based on its retention period.
If no time is specified, the default value is the time at which the data connection is created.
Changing the default time might cause ingestion latency while older records are ingested. For existing data connections, this might ingest events previously ingested.
For more information, visit the documentation page