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Throttler

The Throttler Pattern allows you to ensure that a specific endpoint does not get overloaded, or that we don't exceed an agreed SLA with some external service.

Options

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Name

Default Value

Description

maximumRequestsPerPeriod

 

Maximum number of requests per period to throttle. This option must be provided and a positive number.

timePeriodMillis

1000

The time period in millis, in which the throttler will allow at most maximumRequestsPerPeriod number of messages.

asyncDelayed

false

Camel 2.4: If enabled then any messages which is delayed 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.

Examples

Using the Fluent Builders

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So the above example will throttle messages all messages received on seda:a before being sent to mock:result ensuring that a maximum of 3 messages are sent in any 10 second window. Note that typically you would often use the default time period of a second. So to throttle requests at 100 requests per second between two endpoints it would look more like this...

from("seda:a").throttle(100).to("seda:b");

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

Using the Spring XML Extensions

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Asynchronous delaying

Available as of Camel 2.4

You can let the Throttler 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("seda:a").throttle(100).asyncDelayed().to("seda:b");

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.

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