NMS.ActiveMQ Delay and Schedule Message Feature

ActiveMQ from version 5.4 has an optional persistent scheduler built into the ActiveMQ message broker. It is enabled by setting the broker schedulerSupport attribute to true in the xml configuration.

An ActiveMQ client can take advantage of a delayed delivery by using the following message properties:

Property name	type	description
`AMQ_SCHEDULED_DELAY`	long	The time in milliseconds that a message will wait before being scheduled to be delivered by the broker
`AMQ_SCHEDULED_PERIOD`	long	The time in milliseconds to wait after the start time to wait before scheduling the message again
`AMQ_SCHEDULED_REPEAT`	int	The number of times to repeat scheduling a message for delivery
`AMQ_SCHEDULED_CRON`	String	Use a Cron entry to set the schedule

For example, to have a message scheduled for delivery in 60 seconds - you would need to set the AMQ_SCHEDULED_DELAY property:

    IMessageProducer producer = session.CreateProducer(destination);
    ITextMessage message = session.CreateTextMessage("test msg");
    long time = 60 * 1000;
    message.Properties\["AMQ\_SCHEDULED\_DELAY"\] = time;
    producer.Send(message);

You can set a message to wait with an initial delay, and the repeat delivery 10 times, waiting 10 seconds between each re-delivery:

    IMessageProducer producer = session.CreateProducer(destination);
    ITextMessage message = session.CreateTextMessage("test msg");
    long delay = 30 * 1000;
    long period = 10 * 1000;
    int repeat = 9;
    message.Properties\["AMQ\_SCHEDULED\_DELAY"\] = delay;
    message.Properties\["AMQ\_SCHEDULED\_PERIOD"\] = period;
    message.Properties\["AMQ\_SCHEDULED\_REPEAT"\] = repeat;
    producer.Send(message);

You can also use CRON to schedule a message, for example, if you want a message scheduled to be delivered every hour, you would need to set the CRON entry to be - 0 * * * * - e.g.

    IMessageProducer producer = session.CreateProducer(destination);
    ITextMessage message = session.CreateTextMessage("test msg");
    message.Properties\["AMQ\_SCHEDULED\_CRON"\] = "0 * * * *";
    producer.Send(message);

CRON scheduling takes priority over using message delay - however, if a repeat and period is set with a CRON entry, the ActiveMQ scheduler will schedule delivery of the message for every time the CRON entry fires. Easier to explain with an example. Supposing that you want a message to be delivered 10 times, with a one second delay between each message - and you wanted this to happen every hour - you’d do this:

    IMessageProducer producer = session.CreateProducer(destination);
    ITextMessage message = session.CreateTextMessage("test msg");
    message.Properties\["AMQ\_SCHEDULED\_CRON"\] = "0 * * * *";
    message.Properties\["AMQ\_SCHEDULED\_DELAY"\] = 1000;
    message.Properties\["AMQ\_SCHEDULED\_PERIOD"\] = 1000;
    message.Properties\["AMQ\_SCHEDULED\_REPEAT"\] = 9;
    producer.Send(message);