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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Checkout which dependencies are required by Camel for logging purpose.
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From Camel 2.12
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: the CamelContext must be explicitly configured for tracing:
- XML:
<camelContext trace="true" ...>
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- Java
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- :
camelContext.setTracing(true)
.
Options
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Option | Default | Description |
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| 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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| Enable/disable the tracer. |
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| Sets the Trace Formatter to use. 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, OFF
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logName
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| Camel 2.3: Fully qualified class name for a custom |
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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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traceOutExchanges
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false
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For example you can use your custom JPA @Entity class to store traced information in a database according to your schema layout. | ||
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| The logging level to use: |
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| The log name to use. Default: |
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Controls whether the stack trace of a traced exception should be logged |
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. |
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If |
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are logged. |
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| An Exchange Predicate to filter the tracing. |
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| Enable/disable tracing of interceptors. |
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| Enable/disable tracing of an exception thrown during the processing of an Exchange. |
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| Camel 2.3: To use a custom |
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useJpa
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false
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To use a JpaTraceEventMessage
from camel-jpa component as the TraceEventMessage
. This requires that camel-jpa.jar is on the classpath.
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destinationUri
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null
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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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| Camel 2.3: |
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To use a custom Default: |
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| ||
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| Enable/disable fine grained tracing, using a callback, for both By default only one trace callback is executed. |
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| To use a |
Formatting
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traceHandler
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null
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Camel 2.3: To use a custom org.apache.camel.processor.interceptor.TraceEventHandler
where you can control what happens when a trace event occurs.
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traceInterceptorFactory
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null
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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
.
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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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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
.
The tracer uses by default the org.apache.camel.processor.interceptor.DefaultTraceFormatter
to format the log line.
DefaultTraceFormatter
has the following options:
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class | confluenceTableSmall |
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Option
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Default
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Description
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breadCrumbLength
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Option | Default | Description |
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| Fixed length of the bread crumb.
Setting a value to e.g. |
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| Limits the number of chars logged per line. From Camel 2.9: the default value is |
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| Camel 2.18: If |
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| Fixed length of the |
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node.
Setting a value to e.g. |
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0
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| Output the | |
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| Output the |
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. | ||
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| Outputs the unique |
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UnitOfWork for the exchange. |
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Can be used for correlation |
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to identify a particular Exchange. |
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Output the exception if the processing of an Exchange has failed. | |
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Enable/disable the output of an Exchange's unique Currently the breadcrumb is sufficient. |
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To output the unique exchange id in short form, without the hostname.
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showProperties
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false
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Output the exchange properties
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Output the Message Exchange Pattern (MEP). | ||
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| Output |
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the |
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showBodyType
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true
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Output the in body Java type
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showBody
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true
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Output the in body
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. | ||
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| Previous and destination node. Displayed as: |
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| Output |
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the |
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body. | ||
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| Output |
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the |
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| Output |
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the |
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message headers. |
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showExchangePattern
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true
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Output the exchange pattern
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| Output the Exchange's properties. |
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showException
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true
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| Camel 2.8: |
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output the |
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Is used to limit the number of chars logged per line. The default value is 10000
from Camel 2.9 onwards.
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| To output the Exchange's unique |
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From Camel 2.8: the Camel Tracer will by default not log stream or files bodies
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. To force Camel to log
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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.
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- Always displayed.
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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 Showing from
and 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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:
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or
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and the tracer will be activeactivated.
Enabling
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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 one a particular route.
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Configuring
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in Java
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The tracer Tracer options can be configured from the Java DSL like this:
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in Java as follows:
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Using
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Predicates to
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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
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in Spring XML
There is now a 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 XML
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.
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:
Enable
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Tracing of OUT
Messages
To trace the You can trace messages coming out of processing steps . To enable this, configure the tracer as follows
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:
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or
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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
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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TraceFormatter
.
Example:
And here we have our custom logger that implements the TraceFormatter
interface where we can construct the log message how we like:
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Using a Destination for
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Custom Processing and
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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.
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- 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 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:
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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 the IN
body with our String instead of the TraceEventMessage
.
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Using JPA as
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a Datastore for Trace Messages
See Tracer Example for complete documentation and how to use this feature.
Traced
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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:
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And then our custom error processor where we can handle the exception and figure out at which node the exception occurred.
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