ControlBus
The Control Bus from the EIP patterns allows for the integration system to be monitored and managed from within the framework.
Use a Control Bus to manage an enterprise integration system. The Control Bus uses the same messaging mechanism used by the application data, but uses separate channels to transmit data that is relevant to the management of components involved in the message flow.
In Camel you can manage and monitor using JMX, or by using a Java API from the CamelContext, or from the org.apache.camel.api.management package,
or use the event notifier which has an example here.
From Camel 2.11: we have introduced a new ControlBus Component that allows you to send messages to a control bus Endpoint that reacts accordingly.
ControlBus Component
Available as of Camel 2.11
The controlbus: component provides easy management of Camel applications based on the Control Bus EIP pattern. For example, by sending a message to an Endpoint you can control the lifecycle of routes, or gather performance statistics.
controlbus:command[?options]
Where command can be any string to identify which type of command to use.
Commands
Command | Description |
|---|
route
| To control routes using the routeId and action parameter. |
language
| Allows you to specify a Language to use for evaluating the message body. The result, if any, is returned in the message body. |
Options
Name | Default Value | Description |
|---|
routeId
| null
| To specify a route by its id. The special keyword current indicates the current route. |
action
| null
| Can be one of: startstopsuspendresumestatusstats
To either start or stop a route, or to get the status of the route as output in the message body. From Camel 2.11.1: use suspend and resume to either suspend or resume a route or stats to get performance statistics, in XML format, for the route whose id is given by the routeId option. If routeId is not defined, then statistics for the entire CamelContext will be returned. |
async
| false
| Whether to execute the control bus task asynchronously. |
loggingLevel
| INFO
| Logging level used for logging when task is done, or if any exceptions occurred during processing the task. |
You can append query options to the URI in the following format, ?option=value&option=value&...
Examples
Using the route Command
The route command allows you to do common tasks on a given route very easily, for example to start a route, you can send an empty message to this endpoint:
template.sendBody("controlbus:route?routeId=foo&action=start", null);
To get the status of the route, you can do:
String status = template.requestBody("controlbus:route?routeId=foo&action=status", null, String.class);
Available as of Camel 2.11.1
This requires JMX to be enabled (is by default) then you can get the performance statics per route, or for the CamelContext. For example to get the statics for a route named foo, we can do:
String xml = template.requestBody("controlbus:route?routeId=foo&action=stats", null, String.class);
The returned statics is in XML format. Its the same data you can get from JMX with the dumpRouteStatsAsXml operation on the ManagedRouteMBean.
To get statics for the entire CamelContext you just omit the routeId parameter as shown below:
String xml = template.requestBody("controlbus:route?action=stats", null, String.class);
Using Simple language
You can use the Simple language with the control bus, for example to stop a specific route, you can send a message to the controlbus:language:simple endpoint containing the following message:
template.sendBody("controlbus:language:simple", "${camelContext.stopRoute('myRoute')}");
As this is a void operation, no result is returned. However, if you want the route status you can do:
String status = template.requestBody("controlbus:language:simple", "${camelContext.getRouteStatus('myRoute')}", String.class);
Notice: its easier to use the route command to control lifecycle of routes. The language command allows you to execute a language script that has stronger powers such as Groovy or to some extend the Simple language.
For example to shutdown Camel itself you can do:
template.sendBody("controlbus:language:simple?async=true", "${camelContext.stop()}");
Notice we use async=true to stop Camel asynchronously as otherwise we would be trying to stop Camel while it was in-flight processing the message we sent to the control bus component.
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.
