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Camel leverages thread pools in the following places:

• several EIP patterns supports using thread pools for concurrency
• SEDA component for asynchronous connectivity
• Threads DSL in the Camel route
• ServicePool for pooling services
• And some component provide thread pools by nature such as JMS, Jetty

Thread pool profiles

By default when a thread pool is to be created then its based on the default thread pool profile which is:

    <threadPoolProfile id="defaultThreadPoolProfile" defaultProfile="true"
                       poolSize="10" maxPoolSize="20" maxQueueSize="1000" allowCoreThreadTimeOut="false"
                       rejectedPolicy="CallerRuns"/>

What that means is that for example when you use Multicast with parallelProcessing=true enabled, then it would create a thread pool based on the profile above. The rejectedPolicy has four options: Abort, CallerRuns, Discard, DiscardOldest which corresponds to the same four options provided out of the box in the JDK. Notice: option allowCoreThreadTimeOut is a new option from Camel 2.15 onwards.

You can define as many thread pool profiles as you like. But there must only one default profile. A custom thread pool profile will inherit from the default profile. Which means that any option you do not explicit define will fallback and use the option from the default profile.

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Suppose you want to use a custom thread pool profile for a Multicast EIP pattern in a Camel route you can do it using the executorServiceRef attribute as shown:

<camelContext ...>
    ...
    <threadPoolProfile id="fooProfile" 
                       poolSize="20" maxPoolSize="50" maxQueueSize="-1"/>
    ...

    <route>
       ...
       <multicast strategyRef="myStrategy" executorServiceRef="fooProfile">
          ...
       </multicast>
      ...
    <route>
</camelContext>

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The default pattern is for:

• Camel 2.9.x or older: Camel (${camelId}) thread #${counter} - ${name}
• Camel 2.10 onwards: Camel (#camelId#) thread ##counter# - #name#

Notice we renamed the tokens from Camel 2.10 onwards to not clash with tokens by the Property Placeholder.

In the pattern you can use the following placeholders

• ${camelId} Camel 2.6: is the CamelContext name
• ${counter} is a unique incrementing counter.
• ${name} is the regular thread name.
• ${longName} is the long thread name which can includes endpoint parameters etc.

Notice the pattern name has changed from Camel 2.10 onwards, use #name# instead.

In Camel 2.11 onwards its easier to set the thread name pattern on the CamelContext using the threadNamePattern attribute in the XML files as shown below:

  <camelContext xmlns="http://camel.apache.org/schema/spring" threadNamePattern="Riding the thread #counter#">
    <route>
      <from uri="seda:start"/>
      <to uri="log:result"/>
      <to uri="mock:result"/>
    </route>
  </camelContext>

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See Also

• Architecture
• Async