Apache-Camel, ActiveMQ, camel-jms and Fuse -> why do I need them?

Question

I am still struggling with undertsanding some of Camel's main features and limitations.

My objective is to implement a demo application that can migrate camel endpoints. To achieve this everyone suggested that I should use the camel load-balancer pattern with the failover construct.

To achieve this objective people have suggested Fuse and ActiveMQ. Some have even suggested JBoss, but I am lost.

I understand that Camel needs the an implementation of a JMS server. To achieve this I can use ActiveMQ - a free implementation of a JMS server.

However camel also provies the jms-component. What is this? Is this a client implementation of JMS? If so, should I not be using an ActiveMQ client for JMS? Could someone provide a working example?

With ActiveMQ and JMS understood I can then try to find out why people suggest Fuse. I want my implementation to be as simple as possible. Why do I need Fuse? The Camel+ActiveMQ combination has the load balancer pattern with the failover mechanism right?

I am lost in this sea of new technologies, if someone could give a direction I would be thankful.

Answer 1

Camel provides two components. The first is the jms component, which is a generic API for working against JMS servers. The other is the activemq component, which uses the activemq API for working with activemq message brokers. The activemq component is the default component within things like servicemix/fuse, using an internal broker (not a networked/external broker).

If you are connecting to activemq, you can use either the activemq component or the jms component. The jms component will not start up a broker automatically, you would need to do this yourself.

Fusesource == JBoss Fuse == Apache ServiceMix + some addons. For argument sake, i'm going to refer to all three of these as ServiceMix.

ServiceMix is an enterprise service bus, you can lookup the term on wikipedia if you're not familiar with the concept. It uses Apache Camel to define routes between your components, implementing a number of integration patterns as you so need. ServiceMix deploys by default with Apache CXF, for JAX-RS and JAX-WS services and Apache ActiveMQ, a JMS message broker. Using Camel, you can tell service mix that when a REST API is called, do a series of steps, each step decoupled from the one before it.

JBoss Fuse (the enterprisey, costs money edition) comes with some additional components around fail over. Some of these are present in servicemix (namely, you can run servicemix in a hot stand by mode, waiting for the primary to go down). The Camel load balancer pattern doesn't really mean anything around replication, except that a message coming from one endpoint can be delivered to any of a set of a N endpoints. http://camel.apache.org/load-balancer.html

On the flipside, take a look at ServiceMix's failover http://servicemix.apache.org/docs/4.4.x/users-guide/failover.html

I think based on your question you're referring to system failure failover (needing to work against a new instance), and not a Camel Loadbalancer component (which is likely where the confusion is coming from, on the community side and your side).

Answer 2

start by reading these...Camel In Action, ActiveMQ In Action