Each message received and inserted into a local table must contain some identity information to uniquely identify each message received from a source.
This message identity or state is usually a timestamp; but can also be a sequence or identity number. This timestamp or number must strictly monotonically increase with each message emitted by a source.
The message identity is used to discard any duplicate messages received from the same source and for message synchronisation between instance nodes under the same edge node.
Duplicate messages may arise because a message broker guarantees to deliver each message at least once, but not exactly once.
Note that if the message identity information does not strictly monotonically increase with each message emitted by a source, you are likely to see the following messages in the edge server log:
ERROR: Duplicate state detected for source ... - data discarded
ERROR: Non advancing state detected for source ... - data discarded