A delayer is a processor that enables you to apply a relative time delay to incoming messages.
You can use the delay() command to add a relative time
delay, in units of milliseconds, to incoming messages. For example, the following route
delays all incoming messages by 2 seconds:
from("seda:a").delay(2000).to("mock:result");Alternatively, you can specify the time delay using an expression:
from("seda:a").delay(header("MyDelay")).to("mock:result");The DSL commands that follow delay() are interpreted as sub-clauses of
delay(). Hence, in some contexts it is necessary to terminate the sub-clauses
of delay() by inserting the end() command. For example, when
delay() appears inside an onException() clause, you would
terminate it as follows:
from("direct:start")
.onException(Exception.class)
.maximumRedeliveries(2)
.backOffMultiplier(1.5)
.handled(true)
.delay(1000)
.log("Halting for some time")
.to("mock:halt")
.end()
.end()
.to("mock:result");The following example demonstrates the delay in XML DSL:
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="seda:a"/>
<delay>
<header>MyDelay</header>
</delay>
<to uri="mock:result"/>
</route>
<route>
<from uri="seda:b"/>
<delay>
<constant>1000</constant>
</delay>
<to uri="mock:result"/>
</route>
</camelContext>You can use an expression combined with a bean to determine the delay as follows:
from("activemq:foo").
delay().expression().method("someBean", "computeDelay").
to("activemq:bar");Where the bean class could be defined as follows:
public class SomeBean {
public long computeDelay() {
long delay = 0;
// use java code to compute a delay value in millis
return delay;
}
}You can let the delayer use non-blocking asynchronous delaying, which means that Fuse Mediation Router schedules a task to be executed in the future. The task is responsible for processing the latter part of the route (after the delayer). This allows the caller thread to unblock and service further incoming messages. For example:
from("activemq:queue:foo")
.delay(1000)
.asyncDelayed()
.to("activemq:aDelayedQueue");The same route can be written in the XML DSL, as follows:
<route>
<from uri="activemq:queue:foo"/>
<delay asyncDelayed="true">
<constant>1000</constant>
</delay>
<to uri="activemq:aDealyedQueue"/>
</route>The delayer pattern supports the following 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. |
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