Apache Camel: Delayer

Delayer

The Delayer Pattern allows you to delay the delivery of messages to some destination.

from("seda:a").delayer(header("JMSTimestamp"), 3000).to("mock:result");

So the above example will delay all messages received on queue:a until the JMSTimestamp plus 3 seconds before sending them to mock:result.

You can of course use many different Expression languages such as XPath, XQuery, SQL or various Scripting Languages. You can just delay things a fixed amount of time from the point at which the delayer receives the message. For example to delay things 2 seconds

delayer(2000)

The above assume that the delivery order is maintained and that the messages are delivered in delay order. If you want to reorder the messages based on delivery time, you can use the Resequencer with this pattern. For example

from("activemq:someQueue").resequencer(header("MyDeliveryTime")).delay("MyRedeliveryTime").to("activemq:aDelayedQueue");

For further examples of this pattern in use you could look at the junit test case

Creating a custom delay

You can use an expression to determine when to send a message using something like this

from("activemq:foo").
  delay().method("someBean", "sendAtTime").
  to("activemq:bar");

then the bean would look like this...

public class SomeBean {
  public long sendAtTime(@Header("MyDelayHeader") long delay) { 
    if (delay <= 0) delay = 3000;
    return System.currentTimeMillis() + delay;
 }
}

which would look for the MyDelayHeader on the message and use that as the delay.

Using This Pattern

If you would like to use this EIP Pattern then please read the Getting Started, you may also find the Architecture useful particularly the description of Endpoint and URIs. Then you could try out some of the Examples first before trying this pattern out.

Delayer

Creating a custom delay

Using This Pattern

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