Durable Notifications

Due to the asynchronous nature of notification delivery, when a primary space fails right after replicating an operation to the backup space and before sending the notification to the registered client, the backup space might not be able to send the missing notifications, since it is in the process of moving to active mode. This means that during this very short period of time, the registered client might not receive events that occurred in the primary space and were replicated to the backup space. Durable notifications use the replication mechanism to handle the above case. In addition, in case there are short network disconnections, the events that occurred during this period will not be lost and will be sent to the client.

Because durable notifications are based on the replication mechanism, there exists some different semantics regarding other EventSessionConfig parameters. These differences are described in the following sections.

Configuration

Using the com.gigaspaces.events.EventSessionConfig set the durable notifications flag to true.

EventSessionConfig config = new EventSessionConfig();
config.setDurableNotifications(true);
DataEventSession session = space.newDataEventSession(config);

Batch Parameters

Durable notifications are always sent as batches over the network (even if the client will receive them one by one), so tuning these parameters might be beneficial in certain cases.

EventSessionConfig#setBatch(int size, long delay, int pendingThreshold)

EventSessionConfig config = new EventSessionConfig();
config.setDurableNotifications(true);
config.setBatch(5000, 10, 100);

Disconnection Notifications

In order to receive a notification upon disconnection, use the following:

setAutoRenew(boolean renew, net.jini.lease.LeaseListener listener)

setAutoRenew(boolean renew, net.jini.lease.LeaseListener listener, long renewExpiration, long renewDuration, long renewRTT)

An example of a LeaseListener implementation:

public class MyLeaseListener implements LeaseListener {

    DataEventSession session;

    public MyLeaseListener (DataEventSession session) {
        this.session = session;
    }

    // Called when renewDuration elapsed after initial disconnection and no re-connection occurred
    public void notify(LeaseRenewalEvent event) {
        System.out.println("Disconnected - try to re-register");
        session.addListener(new MyData(), this, Lease.FOREVER, null, null, NotifyActionType.NOTIFY_ALL);
        System.out.println("Notify Re-registration Done!");
    }
}

Note that when adding a listener to the session with a specified lease, the maximum value between the session lease and the listener lease will be used.

Limitations and Requirements

• Durable Notification does not support an embedded Space Where GigaSpaces data is stored. It is the logical cache that holds data objects in memory and might also hold them in layered in tiering. Data is hosted from multiple SoRs, consolidated as a unified data model., it can only be used with a remote proxy. Use a Polling container as an alternative.
• The durable notifications feature is available only for primary backup topologies.
• Notifications are always sent as batches over the network. (even if the client will receive them one by one)
• Only Unicast communication type is supported.
• IDelegationFilter is not supported.
• Listener template must be replicable.
• Notify template is always replicated to backup space. (this is the default)
• Notify template cannot be triggered at backup space. (this is the default)

Notes

• Durable Notifications are always in FIFO FIFO is an acronym for first in, first out, a method for organizing the manipulation of a data structure where the oldest entry, or "head" of the queue, is processed first. ordering.
• The applicable replication parameters are described in the Replication Parameters section of the Administration guide.