Chapter 16. Control Bus
Only producer is supported
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.
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.
16.1. Commands
| Command | Description |
|---|---|
|
|
To control routes using the |
|
| Allows you to specify a to use for evaluating the message body. If there is any result from the evaluation, then the result is put in the message body. |
16.2. Configuring Options
Camel components are configured on two separate levels:
- component level
- endpoint level
16.2.1. Configuring Component Options
The component level is the highest level which holds general and common configurations that are inherited by the endpoints. For example a component may have security settings, credentials for authentication, urls for network connection and so forth.
Some components only have a few options, and others may have many. Because components typically have pre configured defaults that are commonly used, then you may often only need to configure a few options on a component; or none at all.
Configuring components can be done with the Component DSL, in a configuration file (application.properties|yaml), or directly with Java code.
16.2.2. Configuring Endpoint Options
Where you find yourself configuring the most is on endpoints, as endpoints often have many options, which allows you to configure what you need the endpoint to do. The options are also categorized into whether the endpoint is used as consumer (from) or as a producer (to), or used for both.
Configuring endpoints is most often done directly in the endpoint URI as path and query parameters. You can also use the Endpoint DSL as a type safe way of configuring endpoints.
A good practice when configuring options is to use Property Placeholders, which allows to not hardcode urls, port numbers, sensitive information, and other settings. In other words placeholders allows to externalize the configuration from your code, and gives more flexibility and reuse.
The following two sections lists all the options, firstly for the component followed by the endpoint.
16.3. Component Options
The Control Bus component supports 2 options, which are listed below.
| Name | Description | Default | Type |
|---|---|---|---|
| lazyStartProducer (producer) | Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing. | false | boolean |
| autowiredEnabled (advanced) | Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc. | true | boolean |
16.4. Endpoint Options
The Control Bus endpoint is configured using URI syntax:
controlbus:command:language
with the following path and query parameters:
16.4.1. Path Parameters (2 parameters)
| Name | Description | Default | Type |
|---|---|---|---|
| command (producer) | Required Command can be either route or language. Enum values:
| String | |
| language (producer) | Allows you to specify the name of a Language to use for evaluating the message body. If there is any result from the evaluation, then the result is put in the message body. Enum values:
| Language |
16.4.1.1. Query Parameters (6 parameters)
| Name | Description | Default | Type |
|---|---|---|---|
| action (producer) | To denote an action that can be either: start, stop, or status. To either start or stop a route, or to get the status of the route as output in the message body. You can use suspend and resume from Camel 2.11.1 onwards to either suspend or resume a route. And from Camel 2.11.1 onwards you can use stats to get performance statics returned in XML format; the routeId option can be used to define which route to get the performance stats for, if routeId is not defined, then you get statistics for the entire CamelContext. The restart action will restart the route. Enum values:
| String | |
| async (producer) | Whether to execute the control bus task asynchronously. Important: If this option is enabled, then any result from the task is not set on the Exchange. This is only possible if executing tasks synchronously. | false | boolean |
| lazyStartProducer (producer) | Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing. | false | boolean |
| loggingLevel (producer) | Logging level used for logging when task is done, or if any exceptions occurred during processing the task. Enum values:
| INFO | LoggingLevel |
| restartDelay (producer) | The delay in millis to use when restarting a route. | 1000 | int |
| routeId (producer) | To specify a route by its id. The special keyword current indicates the current route. | String |
16.5. Using 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);16.6. Getting performance statistics
This requires JMX to be enabled (is by default) then you can get the performance statistics per route, or for the CamelContext. For example to get the statistics for a route named foo, we can do:
String xml = template.requestBody("controlbus:route?routeId=foo&action=stats", null, String.class);
The returned statistics is in XML format. Its the same data you can get from JMX with the dumpRouteStatsAsXml operation on the ManagedRouteMBean.
To get statistics for the entire CamelContext you just omit the routeId parameter as shown below:
String xml = template.requestBody("controlbus:route?action=stats", null, String.class);16.7. 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", "${camelContext.getRouteController().stopRoute('myRoute')}");As this is a void operation, no result is returned. However, if you want the route status you can do:
String status = template.requestBody("controlbus:language:simple", "${camelContext.getRouteStatus('myRoute')}", String.class);
It’s 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()}");
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.
You can also use other languages such as Groovy, etc.
16.8. Spring Boot Auto-Configuration
When using controlbus with Spring Boot make sure to use the following Maven dependency to have support for auto configuration:
<dependency> <groupId>org.apache.camel.springboot</groupId> <artifactId>camel-controlbus-starter</artifactId> </dependency>
The component supports 3 options, which are listed below.
| Name | Description | Default | Type |
|---|---|---|---|
| camel.component.controlbus.autowired-enabled | Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc. | true | Boolean |
| camel.component.controlbus.enabled | Whether to enable auto configuration of the controlbus component. This is enabled by default. | Boolean | |
| camel.component.controlbus.lazy-start-producer | Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing. | false | Boolean |
