Used in: packet-publisher.


The notification-queueing element is used to specificy the timing of notifications packets sent to other cluster nodes. Notification packets are used to acknowledge the receipt of packets which require confirmation.

Batched Acknowledgments

Rather then sending an individual ACK for each received packet which requires confirmation, Coherence will batch a series of acknowledgments for a given sender into a single ACK. The ack-delay-milliseconds specifies the maximum amount of time that an acknowledgment will be delayed before an ACK notification is sent. By batching the acknowledgments Coherence avoids wasting network bandwidth with many small ACK packets.

Negative Acknowledgments

When enabled cluster nodes will utilize packet ordering to perform early packet loss detection. This allows Coherence to identify a packet as likely being lost and retransmit it well before the packets scheduled resend time.


The following table describes the elements you can define within the notification-queueing element.

Element Required/Optional Description
<ack-delay-milliseconds> Required Specifies the maximum number of milliseconds that the packet publisher will delay before sending an ACK packet. The ACK packet may be transmitted earlier if number of batched acknowledgments fills the ACK packet.

This value should be substantially lower then the remote node's packet-delivery resend timeout, to allow ample time for the ACK to be received and processed by the remote node before the resend timeout expires.

Default value is 16.
<nack-delay-milliseconds> Required Specifies the number of milliseconds that the packet publisher will delay before sending a NACK packet.

Default value is 1.