Camel SCR component tries to add component to context twice if route builder includes an errorHandler

Question

I am using Camel in Karaf using SCR to process messages from ActiveMQ

Versions:

• Camel: 2.16.0
• Karaf: 4.0.7
• ActiveMQ 5.14.1

When I deploy the following Camel route to Karaf all works fine:

package com.test;
import org.apache.camel.builder.RouteBuilder;

public class TestRoute extends RouteBuilder {
    @Override
    public void configure() throws Exception {

        from("activemq:queue:TEST.IN")
        .routeId("test-route")
        .log("Message picked up from IN queue");
    }
}

Here is my SCR Runner class:

package com.test;

import java.util.ArrayList;
import java.util.List;

import org.apache.activemq.ActiveMQConnectionFactory;
import org.apache.activemq.camel.component.ActiveMQComponent;
import org.apache.activemq.pool.PooledConnectionFactory;
import org.apache.camel.RoutesBuilder;
import org.apache.camel.component.jms.JmsConfiguration;
import org.apache.camel.scr.AbstractCamelRunner;
import org.apache.camel.spi.ComponentResolver;
import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.Properties;
import org.apache.felix.scr.annotations.Property;
import org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.ReferenceCardinality;
import org.apache.felix.scr.annotations.ReferencePolicy;
import org.apache.felix.scr.annotations.ReferencePolicyOption;
import org.apache.felix.scr.annotations.References;
import org.osgi.framework.BundleContext;

@Component(label = TestRunner.COMPONENT_LABEL, description = TestRunner.COMPONENT_DESCRIPTION, immediate = true, metatype = true)
@Properties({
    @Property(name = "camelContextId", value = "test-context"),
    @Property(name = "active", value = "true"),
})
@References({
    @Reference(name = "camelComponent",referenceInterface = ComponentResolver.class,
        cardinality = ReferenceCardinality.MANDATORY_MULTIPLE, policy = ReferencePolicy.DYNAMIC,
        policyOption = ReferencePolicyOption.GREEDY, bind = "gotCamelComponent", unbind = "lostCamelComponent")
})
public class TestRunner extends AbstractCamelRunner {

    public static final String COMPONENT_LABEL = "TestRunner";
    public static final String COMPONENT_DESCRIPTION = "This is the description for the test runner";

    @Override
    protected List<RoutesBuilder> getRouteBuilders() {
        List<RoutesBuilder> routesBuilders = new ArrayList<RoutesBuilder>();
        routesBuilders.add(new TestRoute());
        return routesBuilders;
    }

    @Override
    protected void setupCamelContext(BundleContext bundleContext, String camelContextId)throws Exception{
        super.setupCamelContext(bundleContext, camelContextId);

        // Add Active MQ connection factory
        ActiveMQConnectionFactory amqConnectionFactory = new ActiveMQConnectionFactory("tcp://c3m-activemq:61616");
        amqConnectionFactory.setUserName("admin");
        amqConnectionFactory.setPassword("admin");

        // Create Pooled Connection Factory
        PooledConnectionFactory amqPooledConnectionFactory = new PooledConnectionFactory(amqConnectionFactory);
        amqPooledConnectionFactory.setMaxConnections(5);
        amqPooledConnectionFactory.setMaximumActiveSessionPerConnection(5);

        // Create JMS Configuration
        JmsConfiguration consumerJmsConfig = new JmsConfiguration(amqPooledConnectionFactory);
        consumerJmsConfig.setConcurrentConsumers(5);

        // Create the ActiveMQ Component
        ActiveMQComponent activemq = ActiveMQComponent.activeMQComponent();
        activemq.setConfiguration(consumerJmsConfig);

        // Add activeMQ component to the Camel Context
        getContext().addComponent("activemq", activemq);            

        // Use MDC logging
        getContext().setUseMDCLogging(true);

        // Use breadcrumb logging
        getContext().setUseBreadcrumb(true);
    }
}

However, if I add an errorHandler to my routeBuilder then things fail.

Here's the same route with the errorHandler added:

public void configure() throws Exception {
    errorHandler(deadLetterChannel("activemq:queue:TEST.DLQ").useOriginalMessage());

    from("activemq:queue:TEST.IN")
    .routeId("test-route")
    .log("Message picked up from IN queue");
}

What happens: - When installing the bundle on Karaf the following error is given:

2016-12-20 09:49:58,248 | ERROR | nsole user karaf | router | 124 - com.test.router - 1.1.0.SNAPSHOT | [com.test.TestRunner(7)] The activate method has thrown an exception java.lang.IllegalArgumentException: Cannot add component as its already previously added: activemq at org.apache.camel.impl.DefaultCamelContext.addComponent(DefaultCamelContext.java:369) at com.test.TestRunner.setupCamelContext(TestRunner.java:75)[124:com.test.router:1.1.0.SNAPSHOT] at org.apache.camel.scr.AbstractCamelRunner.prepare(AbstractCamelRunner.java:90)[72:org.apache.camel.camel-scr:2.16.0] at org.apache.camel.scr.AbstractCamelRunner.activate(AbstractCamelRunner.java:79)[72:org.apache.camel.camel-scr:2.16.0] ...

And then the Camel route is NOT deployed in Karaf.

I'll proceed with some more troubleshooting, but perhaps someone understand more fully what's going wrong here

Answer 1

In your own TestRunner class then only add the component if its not already registered, you can use

if (context.hasComponent("activemq") != null) {
  ... add component
}

Answer 2

In the end I solved the problem with the following hack: If the component already exists, I first remove it and then add it back.

Here's the code:

// If activemq component already exists, remove it
// Note: This is a bit of a hack, but if we keep the one that is there
// Camel throws a security exception.
if (getContext().hasComponent("activemq") != null) {
    getContext().removeComponent("activemq");
}

// Create the ActiveMQ Component
ActiveMQComponent activemq = ActiveMQComponent.activeMQComponent();
activemq.setConfiguration(consumerJmsConfig);
getContext().addComponent("activemq", activemq);

Not pretty, but if I don't remove it, and deploy the route, camel gives a security exception, almost as if the existing component "lost" the credentials of the broker.

Thanks for the help Claus!