Every event that the correlator sends to one of its receivers has a sequence number. After a receiver processes an event, it sends the event’s sequence number back to the correlator as an acknowledgment that the receiver processed that event. By default, if the correlator does not receive an acknowledgment within 10 seconds after the correlator sent the event, the correlator marks that receiver as being slow to consume events.

You can control the length of time within which the receiver must acknowledge an event before it is marked as a slow receiver. When you start the correlator, you can specify the -m (or --maxoutstandingack) option and specify a number.

For example:

If you start the correlator with this command, the correlator marks a receiver as slow if the correlator does not receive an acknowledgment within 15 seconds. If you do not specify the -m option, the default is 10 seconds. You should not specify a value under 1 second because doing so raises the risk that the correlator might designate a receiver as slow when it is in fact not slow.

The mechanism that flags a receiver as slow is not precise. If a receiver does not acknowledge an event sequence after 10 seconds (the default setting), the correlator does not immediately designate the receiver as slow. Typically, the designation happens within the next 5 seconds. If you change the value of the -m option, the slow designation takes effect between 1 and 1.5 times the value of the -m option.