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MDC logging

Available as of Camel 2.7

In Camel 2.7 we migrated to use slf4j as the logging framework in Camel. This allows us to support MDC logging.
See more details about MDC logging in the logback manual.

The log kit in use must support MDC, such as:

See the log kit documentation how to configure and use MDC.

Enabling in Camel

To enable MDC logging in Camel you can do it as follows:

CamelContext context = ...
context.setUseMDCLogging(true);
...

In XML you enable it using the useMDCLogging attribute as follows:

<camelContext xmlns="http://camel.apache.org/schema/spring" useMDCLogging="true">
  ...
</camelContext>

MDC information

Camel provides the following context information available for MDC:

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Key

Description

exchangeId

The exchange id

correlationId

The correlation id of the exchange if it's correlated. For example a sub message from the Splitter EIP

transactionKey

The id of the transaction for transacted exchanges. Note the id is not unique, but its the id of the transaction template that marks the transaction boundary for the given transaction. Hence we decided to name the key transactionKey and not transactionID to point out this fact.

routeId

The id of the route, in which the exchange is currently being routed

The keys are subject to change as we want to align and leverage MDC across other Apache products such as ActiveMQ, ServiceMix and Karaf.

Example using log4j

If you use log4j you can configure MDC in the log4j.properties file as shown:

log4j.appender.out.layout.ConversionPattern=%d [%-15.15t] %-5p %-30.30c{1} - %-10.10X{exchangeId} - %-10.10X{routeId} - %m%n

Camel will log on startup if MDC is enabled or not

INFO  SpringCamelContext             -            -            -            - MDC logging is enabled on CamelContext: camel-1

The follow snippet is from an unit test which shows MDC in use. Notice the exchange id and route id is displayed in their respective columns in the log file:

INFO  SpringCamelContext -            -            - Apache Camel  (CamelContext: camel-1) started in 1.228 seconds
INFO  foo                - 358739-0-2 - route-a    - Exchange[ExchangePattern:InOnly, BodyType:String, Body:Hello World]
INFO  bar                - 358739-0-2 - route-b    - Exchange[ExchangePattern:InOnly, BodyType:String, Body:Hello World]
INFO  MockEndpoint       -            -            - Asserting: Endpoint[mock://result] is satisfied
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