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Tracer Interceptor

Camel supports a tracer interceptor that is used for logging the route executions at INFO level.

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Implementing custom tracing via TracingInterceptor has been deprecated. However turning tracing on via setTracing(true) is okay.

Camel's tracer interceptor can be used for logging, by default at the INFO level, a route's execution. The tracer is an instance of org.apache.camel.spi.InterceptStrategy. It can be applied to either a DefaultCamelContext or a The Tracer is an InterceptStrategy which can be applied to a DefaultCamelContext or SpringCamelContext to ensure that there is a a TracerInterceptor created for every node in the DSL.You can enable or disable the Tracerroute. The tracer's logging can be enabled/disabled dynamically , by calling the tracer's its setEnabled method.

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The org.apache.camel.processor.interceptor.TraceFormatter has been rename to org.apache.camel.processor.interceptor.DefaultTraceFormatter in Camel 2.0.

Users of Camel 1.x should use TraceFormatter whereas 2.x users should use DefaultTraceFormatter.

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Checkout which dependencies are required by Camel for logging purpose.

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From Camel 2.12: the CamelContext must be explicitly configured for tracing:

• XML:  <camelContext trace="true" ...>
• Java: camelContext.setTracing(true).

Options

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Options

Trace has been improved in Camel 1.5 to be more configurable with these options:

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Option

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Default

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true

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Flag to enable or disable this tracer

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logLevel

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INFO

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The logging level to use: FATAL, ERROR, WARN, INFO, DEBUG, TRACE

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logName

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traceFilter

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null

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An exchange Predicate to filter the tracing.

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traceInterceptors

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false

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Flag to enable or disable tracing of interceptors

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traceExceptions

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true

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Flag to enable or disable tracing of thrown exception during processing of the exchange

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destinationUri

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null

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Camel 2.0: Optional destination uri to route TraceEventExchange containing TraceEventMessage with details about the trace. Can be used for custom processing to store traces in database using JPA.

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Formatting

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TraceFormatter has the following options:

Example:

ID-claus-acer/4412-1222625653890/2-0 -> to(mock:a)                , Pattern:InOnly , Headers:{to=James} , BodyType:String , Body:Hello London

{{ID-claus-acer/3690-1214458315718/2-0}} is the breadcrumb with the unique correlation id.
{{node3}} is the id of the node in the route path. Is always shown.
{{To\[mock:a\]}} is the destination node.
{{InOnly}} is the exchange pattern. Is always shown.
Then the rest is properties, headers and the body.

Showing from and to

In Camel 2.0 the trace log will output both the from and to so you can see where the Exchange came from, such as:

>>> direct:start --> process(MyProcessor)
>>> process(MyProcessor) --> to(mock:a)
>>> to(mock:a) --> to(mock:b)

Enabling

To enable tracer from the main run

java org.apache.camel.spring.Main -t

or

java org.apache.camel.spring.Main -trace

and the tracer will be active.

Enabling from Java DSL

The tracer can be enabled by adding it to the interceptor chain to the camel context. This is demonstrated in the unit test below.
Notice: We could have changed the properties on the Tracer object before adding it, if we e.g. don't like the default settings.

{snippet:id=e1|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/TraceInterceptorTest.java}

Running the test we get the trace information logged at INFO level:

INFO  TraceInterceptor     - ID-claus-acer/4412-1222625653890/2-0 -> process(MyProcessor)      , Pattern:InOnly , Headers:{to=James} , BodyType:String , Body:Hello London 
INFO  TraceInterceptor     - ID-claus-acer/4412-1222625653890/2-0 -> to(mock:a)                , Pattern:InOnly , Headers:{to=James} , BodyType:String , Body:Hello London 
INFO  TraceInterceptor     - ID-claus-acer/4412-1222625653890/2-0 -> to(mock:b)                , Pattern:InOnly , Headers:{to=James} , BodyType:String , Body:Hello London 
INFO  TraceInterceptor     - ID-claus-acer/4412-1222625653890/2-1 -> process(MyProcessor)      , Pattern:InOnly , Headers:{from=Claus} , BodyType:String , Body:This is Copenhagen calling 
INFO  TraceInterceptor     - ID-claus-acer/4412-1222625653890/2-1 -> to(mock:a)                , Pattern:InOnly , Headers:{from=Claus} , BodyType:String , Body:This is Copenhagen calling 
INFO  TraceInterceptor     - ID-claus-acer/4412-1222625653890/2-1 -> to(mock:b)                , Pattern:InOnly , Headers:{from=Claus} , BodyType:String , Body:This is Copenhagen calling 

Configuring from Java DSL

The tracer options can be configured from the Java DSL like this:

    public void configure() throws Exception {
        // add tracer as an interceptor so it will log the exchange executions at runtime
        // this can aid us to understand/see how the exchanges is routed etc.
        Tracer tracer = new Tracer();
        tracer.getFormatter().setShowBreadCrumb(false);
        tracer.getFormatter().setShowNode(false);
        ...
        getContext().addInterceptStrategy(tracer);

Using predicates to filter exchanges

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Formatting

The tracer formats the execution of exchanges to log lines. They are logged at INFO level in the log category: org.apache.camel.processor.interceptor.TraceInterceptor. By default the tracer uses: org.apache.camel.processor.interceptor.DefaultTraceFormatter to format the log line.

DefaultTraceFormatter has the following options:

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From Camel 2.8: the Camel Tracer will by default not log stream or files bodies. To force Camel to log these set the following property on the CamelContext properties:

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Example:

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where:

• ID-claus-acer/3690-1214458315718/2-0 is the breadcrumb with the unique correlation id.
• node3 is the id of the node in the route path. Always displayed.
• To[mock:a] is the destination node.
• InOnly is the exchange pattern. Is always shown.
• Then the rest is properties, headers and the body.

Showing from and to

The trace log will output both the from and to so you can see where the Exchange came from, such as:

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Enabling

To enable tracer from the main run:

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or

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and the tracer will be activated.

Enabling in Java

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You can configure tracing at a higher granularity as you can configure it on camel context and then override and set it per route as well. For instance you could just enable the tracer for a particular route.

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Configuring in Java

Tracer options can be configured in Java as follows:

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Using Predicates to Filter Exchanges

In the code below we want the tracer only to trace if the body contains the text London. As this is just an example can of course set any Predicate that matches your criteria:

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Enabling in Spring XML

There is now a 

Enabling from Spring XML

There is now a trace attribute you can specify on the *the <camelContext/> for example.

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Example:

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You can see this in action with the SpringTraceTest and its spring.xml file

Another option is to just include a spring XML which defines the Tracer bean such as the one that is automatically included if you run the Main with -t above.

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Configuring in Spring

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XML

You In Camel 1.5 you can configure the tracer as a Spring bean. Just add a bean with the bean class org.apache.camel.processor.interceptor.Tracer and Camel will use it as the Tracer.

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tracer.{snippet:id=e1|lang=xml|url=camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/interceptor/tracerConfigurationTest.xml}

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Formatting from Spring

You In Camel 1.5 you can configure the formatting of tracer as a Spring bean. Just add a bean with the the id="traceFormatter" and Camel will lookup this this id and use the formatter, as the example below illustrates:

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associated formatter.

Example:{snippet:id=e1|lang=xml|url=camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/interceptor/traceFormatterTest.xml}

Enable

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Tracing of OUT Messages

To trace the

Available as of Camel 2.0

You can now trace messages coming out of processing steps . To enable this, configure the tracer as follows

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:{snippet:id=tracingOutExchanges|title=Java

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DSL|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/TraceInterceptorWithOutBodyTraceTest.java} 

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or

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{snippet:id=tracingOutExchanges|title=Spring

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DSL|lang=xml|url=camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/processor/traceInterceptorWithOutBodyTrace.xml} 

Running with With these options , you'll get output similar to:

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the output will look like:

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Using a Custom Formatter

Avaiable as of Camel 2.0

You can now implement your own To create a custom formatter create a class that implements the interface org.apache.camel.processor.interceptor.TraceFormatter to be used for logging trace messages to the log.

The sample below shows how to configure a Tracer from Java DSL using custom formatter:

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Example:{snippet:

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id=e1|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/interceptor

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And here we have our custom logger that implements the TraceFormatter interface where we can construct the log message how we like:

/TraceFormatterTest.java} 

And here we have our custom logger that implements the TraceFormatter interface where we can construct the log message how we like:{snippet:id=e2|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/interceptor/TraceFormatterTest.java}

Using a Destination for Custom Processing and Routing

Tracer supports custom processing of trace events. This can be used to route a trace event to a JPA endpoint for persistence in a database.

This works by Camel creates a new TraceEventMessage containing:

• snapshot of the original traced Exchange as a immutable TraceEventMessage containing String values of the fields, when the interception occurred. This ensures the fields contains the exact data at the given time of interception.
• the original Exchange can in some implementations be accessed using getTracedExchange() (though with JPA based tracer you cannot get the original Exchange).

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Beware to access the original Exchange to avoid causing any side effects or alter its state. Prefer to access the information from TraceEventMessage

Camel routes the TraceEventMessage synchronously from the point of interception. When its completed Camel will continue routing the original Exchange.

The sample below demonstrates this feature, where we route traced Exchanges to the direct:traced route:{snippet:id=e1

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|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/interceptor/

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TraceInterceptorDestinationTest.java

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Using Destination for custom processing and routing

Avaiable as of Camel 2.0

Tracer now supports custom processing of trace events. This can be used to route a trace event to a JPA endpoint for persistence in a database.

This works by Camel creates a new TraceEventExchange containing:

• snapshot of the original traced Exchange as a immutable TraceEventMessage containing String values of the fields, when the interception occurred. This ensures the fields contains the exact data at the given time of interception.
• the original Exchange can be accessed using getTracedExchange()

Camel routes the TraceEventExchange synchronously from the point of interception. When its completed Camel will continue routing the original Exchange.

The sample below demonstrates this feature, where we route traced Exchanges to the ((direct:traced)) route:

} 

Then we can configure a route for the traced messages:

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And our processor where we can process the TraceEventMessage. Here we want to create a CSV format of the trace event to be stored as a file. We do this by constructing the CSV String and the replace the IN body with our String instead of the TraceEventMessage.{snippet:id=e2|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/interceptor/TraceInterceptorDestinationTest.java}

Using JPA as a Datastore for Trace Messages

See Tracer Example for complete documentation and how to use this feature.

Traced Route Path During Runtime

Tracer also traces the actual route path taken during runtime. Camel will store the route path taken on the UnitOfWork when Tracer is enabled. The example below demonstrates how we can use that for error handling where we can determine at which node in the route graph the error triggered.

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First we define our route:

{snippet:id=e1|lang=java|url=camel/trunk/camel-core/src/test/java/org

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Then we can configure a route for the traced messages:

   from("direct:traced").process(new MyTraceMessageProcessor()).to("file://myapp/logs/trace);

And our /apache/camel/processor/TraceableUnitOfWorkTest.java}And then our custom error processor where we can process the TraceEventMessage. Here we want to create a CSV format of the trace event to be stored as a file. We do this by constructing the CSV String and the replace the IN body with our String instead of the TraceEventMessage.

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handle the exception and figure out at which node the exception occurred.{snippet:id=e2|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/

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TraceableUnitOfWorkTest.java}

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Using JPA as datastore for trace messages

Avaiable as of Camel 2.0

See Tracer Example for complete documentation and how to use this feature.

See Also

• Tracer Example
• Debugger
• Delay Interceptor
• Log