What is meant by the Status warning "Discarded prior ACK"?

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asked Oct 7, 2020 by lewis-s-9714 (1,020 points)
We're posting to a webservice and sometimes we get the warning "Discarded prior ACK" when the message is sent more than once. Does this mean that if we, for instance, made the call twice and got two ACK messages that the first ACK was ignored? What concerns should we have when this warning occurs?

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If a web service sender sends the message and then the ACK is received it is recorded immediatly, but if it is rejected due to any error, the sender tries to send again according to the error management policy on the sender itself.

If a second attempt works, then the sender records the ACK from the second attempt.  Because the original ACK was already recorded, this warning is indicating that the first ACK will be discarded and the second ACK recorded with the message.

The warning is simply giving you a record of the first ACK.  If you review the logs and determine that the first ACK was indeed not correct or was an error, and the second call to the web service was required, then the warning can be ignored.  If this was unexpected behavior, then more troubleshooting can be done to determine how to avoid the two calls to the web service in the future.
answered Oct 8, 2020 by ben-s-7515 (11,910 points)
selected Oct 8, 2020 by lewis-s-9714