Delayer
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Delayer

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

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The expression is a value in millis to wait from the current time, so the expression should just be 3000.
However you can use a long value for a fixed value to indicate the delay in millis.
See the Spring DSL samples for Delayer.

Using Delayer in Java DSL

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Options

Name

Default Value

Description

asyncDelayed

false

Camel 2.4: If enabled then delayed messages happens asynchronously using a scheduled thread pool.

executorServiceRef

 

Camel 2.4: Refers to a custom Thread Pool to be used if asyncDelay has been enabled.

callerRunsWhenRejected

true

Camel 2.4: Is used if asyncDelayed was enabled. This controls if the caller thread should execute the task if the thread pool rejected the task.

Using the Fluent Builders

The example below will delay all messages received on seda:b 1 second before sending them to mock:result.

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

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

You can of course use many different Expression languages such as XPath, XQuery, SQL or various Scripting Languages. For example to delay the message for the time period specified in the header, use the following syntax:

And to delay processing using the Simple language you can use the following DSL:

Spring DSL

The sample below demonstrates the delay in Spring DSL:

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

Asynchronous delaying

Available as of Camel 2.4

You can let the Delayer use non blocking asynchronous delaying, which means Camel will use a scheduler to schedule a task to be executed in the future. The task will then continue routing. This allows the caller thread to not block and be able to service other messages etc.

From Java DSL

You use the asyncDelayed() to enable the async behavior.

From Spring XML

You use the asyncDelayed="true" attribute to enable the async behavior.

Creating a custom delay

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

then the bean would look like this...

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.

See Also

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