THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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h2. Kestrel Component
The Kestrel component allows messages to be sent to a [Kestrel|https://github.com/robey/kestrel] queue, or messages to be consumed from a Kestrel queue. This component uses the [spymemcached|http://code.google.com/p/spymemcached/] client for memcached protocol communication with Kestrel servers.
h3. URI format
{code}
kestrel://[addresslist/]queuename[?options]
{code}
Where *queuename* is the name of the queue on Kestrel. The *addresslist* part of the URI may include one or more {{host:port}} pairs. For example, to connect to the queue {{foo}} on {{kserver01:22133}}, use:
{code}
kestrel://kserver01:22133/foo
{code}
If the addresslist is omitted, {{localhost:22133}} is assumed, i.e.:
{code}
kestrel://foo
{code}
Likewise, if a port is omitted from a {{host:port}} pair in addresslist, the default port 22133 is assumed, i.e.:
{code}
kestrel://kserver01/foo
{code}
Here is an example of a Kestrel endpoint URI used for producing to a clustered queue:
{code}
kestrel://kserver01:22133,kserver02:22133,kserver03:22133/massive
{code}
Here is an example of a Kestrel endpoint URI used for consuming concurrently from a queue:
{code}
kestrel://kserver03:22133/massive?concurrentConsumers=25&waitTimeMs=500
{code}
h3. Options
You can configure properties on each Kestrel endpoint individually by specifying them in the {{?parameters}} portion of the endpoint URI. Any {{?parameters}} that are omitted will default to what is configured on the KestrelComponent's base KestrelConfiguration. The following properties may be set on KestrelConfiguration and/or each individual endpoint:
{div:class=confluenceTableSmall}
|| Option || Default Value || Description ||
| {{concurrentConsumers}} | {{1}} | Specifies the number of concurrent consumer threads. |
| {{waitTimeMs}} | {{100}} | Specifies the {{/t=...}} wait time passed to Kestrel on GET requests. |
{div}
*NOTE:* If *waitTimeMs* is set to zero (or negative), the {{/t=...}} specifier does *not* get passed to the server on GET requests. When a queue is empty, the GET call returns immediately with no value. In order to prevent "tight looping" in the polling phase, this component will do a {{Thread.sleep(100)}} whenever nothing is returned from the GET request (only when nothing is returned). You are *highly encouraged* to configure a positive non-zero value for waitTimeMs.
h3. Configuring the Kestrel component using Spring XML
The simplest form of explicit configuration is as follows:
{code:xml}
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd">
<bean id="kestrel" class="org.apache.camel.component.kestrel.KestrelComponent"/>
<camelContext xmlns="http://camel.apache.org/schema/spring">
</camelContext>
</beans>
{code}
That will enable the Kestrel component with all default settings, i.e. it will use {{localhost:22133}}, 100ms wait time, and a single non-concurrent consumer by default.
To use specific options in the base configuration (which supplies configuration to endpoints whose {{?properties}} are not specified), you can set up a KestrelConfiguration POJO as follows:
{code:xml}
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd">
<bean id="kestrelConfiguration" class="org.apache.camel.component.kestrel.KestrelConfiguration">
<property name="addresses" value="kestrel01:22133"/>
<property name="waitTimeMs" value="100"/>
<property name="concurrentConsumers" value="1"/>
</bean>
<bean id="kestrel" class="org.apache.camel.component.kestrel.KestrelComponent">
<property name="configuration" ref="kestrelConfiguration"/>
</bean>
<camelContext xmlns="http://camel.apache.org/schema/spring">
</camelContext>
</beans>
{code}
h3. Usage Examples
h4. Example 1: Consuming
{code}
from("kestrel://kserver02:22133/massive?concurrentConsumers=10&waitTimeMs=500")
.bean("myConsumer", "onMessage");
{code}
{code}
public class MyConsumer {
public void onMessage(String message) {
...
}
}
{code}
h4. Example 2: Producing
{code}
public class MyProducer {
@EndpointInject(uri = "kestrel://kserver01:22133,kserver02:22133/myqueue")
ProducerTemplate producerTemplate;
public void produceSomething() {
producerTemplate.sendBody("Hello, world.");
}
}
{code}
h4. Example 3: Spring XML Configuration
{code:xml}
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="kestrel://ks01:22133/sequential?concurrentConsumers=1&waitTimeMs=500"/>
<to uri="log:something"/>
</route>
<route>
<from uri="direct:start"/>
<to uri="kestrel://ks02:22133/stuff"/>
</route>
</camelContext>
{code}
{code}
public class MyBean {
public void onMessage(String message) {
...
}
}
{code}
h3. Dependencies
The Kestrel component has the following dependencies:
- {{spymemcached}} 2.5 (or greater)
h4. spymemcached
You *must* have the {{spymemcached}} jar on your classpath. Here is a snippet you can use in your pom.xml:
{code}
<dependency>
<groupId>spy</groupId>
<artifactId>memcached</artifactId>
<version>2.5</version>
</dependency>
{code}
Alternatively, you can [download the jar|http://code.google.com/p/spymemcached/downloads/list] directly.
{warning:title=Limitations}
*NOTE:* The spymemcached client library does *not* work properly with kestrel when JVM assertions are enabled. There is a known issue with spymemcached when assertions are enabled and a requested key contains the {{/t=...}} extension (i.e. if you're using the {{waitTimeMs}} option on an endpoint URI, which is highly encouraged).
Fortunately, JVM assertions are *disabled by default*, unless you [explicitly enable them|http://download.oracle.com/javase/1.4.2/docs/guide/lang/assert.html], so this should not present a problem under normal circumstances.
Something to note is that Maven's Surefire test plugin *enables* assertions. If you're using this component in a Maven test environment, you may need to set {{enableAssertions}} to {{false}}. Please refer to the [surefire:test reference|http://maven.apache.org/plugins/maven-surefire-plugin/test-mojo.html] for details.
{warning}
{include:Endpoint See Also} |