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h3. Options
{div:class=confluenceTableSmall}
|| Option || Default || Description ||
| formatter | | Sets the Trace Formatter to use. Will default use {{org.apache.camel.processor.interceptor.DefaultTraceFormatter}}. |
| enabled | true | Flag to enable or disable this tracer |
| logLevel | {{INFO}} | The logging level to use: FATAL, ERROR, WARN, INFO, DEBUG, TRACE, OFF |
| logName | | The log name to use. Will default use {{org.apache.camel.processor.interceptor.TraceInterceptor}}.
| traceFilter | null | An exchange [Predicate] to filter the tracing. |
| traceInterceptors | false | Flag to enable or disable tracing of interceptors |
| traceExceptions | true| Flag to enable or disable tracing of thrown exception during processing of the exchange |
| traceOutExchanges | false | Flag to enable fine grained tracing with a callback for both IN (before) and OUT (after). Is disabled by default which means there is only one trace callback executed. | 
| logStackTrace | false | When tracing exception you can control whether the stack trace should be logged also. If *not* then only the exception class and message is logged. |
| useJpa | false | To use a {{JpaTraceEventMessage}} from *camel-jpa* component as the {{TraceEventMessage}}. This requires that *camel-jpa.jar* is on the classpath. |
| destinationUri | null | Optional destination uri to route [TraceEventExchange|http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/processor/interceptor/TraceEventExchange.html] containing [TraceEventMessage|http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/processor/interceptor/TraceEventMessage.html] with details about the trace. Can be used for custom processing to store traces in database using [JPA]. |
| jpaTraceEventMessageClassName | null | *Camel 2.3:* Fully class name for a custom  {{org.apache.camel.processor.interceptor.TraceEventMessage}} class which contains the traced information. For example you can use your custom JPA @Entity class to store traced information in a database according to your schema layout. |
| traceHandler | null | *Camel 2.3:* To use a custom {{org.apache.camel.processor.interceptor.TraceEventHandler}} where you can control what happens when a trace event occurs. |
| traceInterceptorFactory | null | *Camel 2.3:* To use a custom {{org.apache.camel.processor.interceptor.TraceInterceptorFactory}} where you can create the runtime trace instance which does the actual tracing. It should be a {{Processor}} instance. The default tracer is implemented in the class {{org.apache.camel.processor.interceptor.TraceInterceptor}}. |
{div}

h3. Formatting
The tracer formats the execution of exchanges to log lines. They are logged at INFO level in the log category: {{

{{DefaultTraceFormatter}} has the following options:
{div:class=confluenceTableSmall}
|| Option || Default || Description ||
| breadCrumbLength | 0 | Fixed length of the bread crumb. 0 = no fixed length. Setting a value to e.g. 80 allows the tracer logs to be aligned for easier reading. | 
| nodeLength | 0 | Fixed length of the node. 0 = no fixed length. Setting a value to e.g. 40 allows the tracer logs to be aligned for easier reading.
| showBreadCrumb | true | Outputs the unique unit of work for the exchange. To be used for correlation so you can identify the same exchange. |
| showNode | true | Previous and destination node, so you can see from -> to. |
| showExchangeId | false | To output the unique exchange id. Currently the breadcrumb is sufficient. |
| showShortExchangeId | false | To output the unique exchange id in short form, without the hostname. |
| showProperties | false | Output the exchange properties |
| showHeaders | true | Output the in message headers |
| showBodyType | true | Output the in body Java type |
| showBody | true | Output the in body |
| showOutHeaders | false | Output the out (if any) message headers |
| showOutBodyType | false | Output the out (if any) body Java type |
| showOutBody | false | Output the out (if any) body |
| showExchangePattern | true | Output the exchange pattern |
| showException | true | Output the exception if the exchange has failed |
| showRouteId | true | *Camel 2.8:* Output the id of the route |
| maxChars | | Is used to limit the number of chars logged per line. The default value is {{10000}} from *Camel 2.9* onwards. |
{div}

{

{code}

h3. Enabling

To enable tracer from the main run

{code}
java org.apache.camel.spring.Main -t

{code}
or 
{code}
java org.apache.camel.spring.Main -trace
{code}
  
and the tracer will be active.

h3. Enabling from Java 

DSL

{code}
context.setTracing(true);
{

code}

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 tracer for one particular route.

{code}
INFO  TraceInterceptor     - ID-davsclaus-local-54403-1246038742624-0-0 >>> from(direct:start) --> MyProcessor     , Pattern:InOnly, Headers:{to=James}, BodyType:String, Body:Hello London
INFO  TraceInterceptor     - ID-davsclaus-local-54403-1246038742624-0-0 >>> MyProcessor --> mock:a                 , Pattern:InOnly, Headers:{to=James}, BodyType:String, Body:Hello London
INFO  TraceInterceptor     - ID-davsclaus-local-54403-1246038742624-0-0 >>> mock:a --> mock:b                      , Pattern:InOnly, Headers:{to=James}, BodyType:String, Body:Hello London
...
INFO  TraceInterceptor     - ID-davsclaus-local-54403-1246038742624-0-1 >>> from(direct:start) --> MyProcessor     , Pattern:InOnly, Headers:{from=Claus}, BodyType:String, Body:This is Copenhagen calling
INFO  TraceInterceptor     - ID-davsclaus-local-54403-1246038742624-0-1 >>> MyProcessor --> mock:a                 , Pattern:InOnly, Headers:{from=Claus}, BodyType:String, Body:This is Copenhagen calling
INFO  TraceInterceptor     - ID-davsclaus-local-54403-1246038742624-0-1 >>> mock:a --> mock:b                      , Pattern:InOnly, Headers:{from=Claus}, BodyType:String, Body:This is Copenhagen calling

{code}

h3. Configuring from Java DSL
The tracer options can be configured from the Java DSL like this:
{code}
    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();
        formatter.getDefaultTraceFormatter().setShowBreadCrumb(false);
        formatter.getDefaultTraceFormatter().setShowNode(false);
        ...
        getContext().addInterceptStrategy(tracer);
{code}

h4. 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:
{code:java}

    Tracer tracer = new Tracer();
    // set the level to FATAL so we can easily spot it
    tracer.setLogLevel(LoggingLevel.FATAL);
    // and only trace if the body contains London as text
    tracer.setTraceFilter(body().contains(constant("London")));
{code}

h3. Enabling from Spring XML

There is now a *trace* attribute you can specify on the 

{snippet:id=e1|lang=xml|url= [SpringTraceTest|http://svn.apache.org/repos/asf/camel/trunk/components/camel-spring/src/test/java/org/apache/camel/spring/processor/SpringTraceTest.java] and its [spring.xml file|http://svn.apache.org/repos/asf/camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/processorinterceptor/SpringTraceTest-context.xml]

Another option is to just include a spring XML which defines the Tracer bean such as the [one that is automatically included if tracerConfigurationTest.xml}

{snippet:id=e1|lang=xml|url=you run the Main with -t above|http://svn.apache.org/repos/asf/camel/trunk/components/camel-spring/src/maintest/resources/META-INF/services/org/apache/camel/spring/interceptor/traceFormatterTest.xml}

{snippet:id=tracingOutExchanges|title=Java DSL|lang=java|url=camel/trunk/camel-core/src/test/javatrace.xml].

h3. Configuration from Spring
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.

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

You can configure the formatting of tracer as a Spring bean. Just add a bean with the id *traceFormatter* and Camel will lookup this id and use the formatterjava}

{snippet:id=tracingOutExchanges|title=Spring DSL|lang=xml, as the example below illustrates:

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

h3. Enable tracing of out messages

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

{snippet:id=tracingOutExchanges|title=Java DSL|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/TraceInterceptorWithOutBodyTraceTest.java}
or
{snippet:id=tracingOutExchanges|title=Spring DSL|lang=xml|url=camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/processor/traceInterceptorWithOutBodyTrace.xml}

Running with these options, you'll get output similar to:
{code}
INFO  TraceInterceptor - ID-mojo/59899-1225474989226/2-0 -> transform(body) , Pattern:InOnly , Headers:{to=James} , BodyType:String , Body:Hello London
INFO  TraceInterceptor - transform(body) -> ID-mojo/59899-1225474989226/2-0 , Pattern:InOnly , Headers:{to=James} , BodyType:String , Body:Hello London , OutBodyType:String , OutBody:Hello London
{code}

h3. Using Custom Formatter

You can now implement your own {{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:
{snippet:id=e1|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/interceptor/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/components/camel-corespring/src/test/javaresources/org/apache/camel/spring/processor/interceptor/TraceFormatterTesttraceInterceptorWithOutBodyTrace.java}

h3. Using 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 xml}

INFO  TraceInterceptor - ID-mojo/59899-1225474989226/2-0 -> transform(body) , Pattern:InOnly , Headers:{to=James} , BodyType:String , Body:Hello London
INFO  TraceInterceptor - transform(body) -> ID-mojo/59899-1225474989226/2-0 , Pattern:InOnly , Headers:{to=James} , BodyType:String , Body:Hello London , OutBodyType:String , OutBody:Hello London

{snippet:id=e1|lang=java|url=camel/trunk/camel-core/src/test/javaCamel creates a new [TraceEventMessage|http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/processor/interceptor/TraceFormatterTest.java}

{snippet:id=e2|lang=java|url=camel/trunk/TraceEventMessage.html] containing:
- snapshot of the original traced Exchange as a immutable [TraceEventMessage|http://camel.apache.org/maven/current/camel-core/apidocssrc/test/java/org/apache/camel/processor/interceptor/TraceFormatterTest.java}

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

TraceEventMessage.html] 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).

{warning}
Beware to access the original Exchange to avoid causing any side effects or alter its state. Prefer to access the information from [TraceEventMessage|http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/processor/interceptor/TraceEventMessage.html]
{warning}

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

}}.
{snippet:id=e2|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/interceptor/TraceInterceptorDestinationTest.java}

h3. Using [JPA] as datastore for trace messages

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

h3. 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.
First we define our route:
{snippet:id=e1|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/TraceableUnitOfWorkTest.java}

{snippet:id=e2|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/TraceableUnitOfWorkTest.java}

h3.