BacklogTracer Interceptor
Available as of Camel 2.11
Camel supports a backlog tracer interceptor that is used for capturing a trace message of each message as they are routed in Camel.
The trace message is stored in a backlog queue, which contains the last N messages for each node in the routes (by default 10).
The BacklogTracer is an InterceptStrategy which can be applied to a DefaultCamelContext or SpringCamelContext to ensure that there is a TracerInterceptor created for every node in the DSL.
You can enable or disable the BacklogTracer's logging dynamically, by calling the backlogTracer's setEnabled method.
 | What is the difference between BacklogTracer and Tracer
Camel also provides a Tracer which has similar capabilities as this backlog tracer. The difference is that the backlog tracer is storing
a capture of the message in an internal backlog queue. Where as the Tracer is event based and logs the messages as they happen (or route to another Camel destination). Also the Tracer has more fine grained events where it dives into EIPs such as the Content Based Router and traces the when/otherwise(s). Though the Tracer has much more complicated logic to handle this (there is some edge-cases where this may not work). The BacklogTracer allows you to pull the messages from the backlog queues on demand. The BacklogTracer works better with JMX capable tooling as it is simpler and allow to bulk dump all its traced messages in either a POJO or XML format. And there is a Karaf command for the BacklogTracer which allows you to control the tracing from a Karaf shell. |
Options
| Option | Default | Description |
|---|
| enabled | false | Flag to enable or disable this tracer |
| backlogSize | 1000 | Maximum number of total traced messages to keep in the backlog (FIFO queue). |
| tracePattern | null | Allows to filter tracing using a pattern that matches against the node id and route id. For example use "to1,to2" to match only nodes with either the name "to1", or "to2". You can use * for wildcards. So you can do "to*" to match any to. Or use "route-foo*" to match any foo routes. |
| traceFilter | null | Allow to configure a filter as a Predicate using any of the Camel Languages. But default the Simple language is used. For example to filter on messages with a given header, use ${header.foo} != null. To use Groovy then prefix the value with "groovy:". And similar for the other languages. |
| removeOnDump | true | Whether to remove the traced messages that was returned when invoking the dump methods. |
| bodyMaxChars | 128kb | To limit the message body to a maximum size in the traced message. Use 0 or negative value to use unlimited size. |
| bodyIncludeStreams | false | Whether to include the message body of stream based messages. If enabled then beware the stream may not be re-readable later. See more about Stream caching. |
| bodyIncludeFiles | true | Whether to include the message body of file based messages. The overhead is that the file content has to be read from the file. |
Operations
| Option | Type | Description |
|---|
| getTraceCounter | long | Gets the total number of traced messages. |
| resetTraceCounter | void | To reset the trace counter. |
| dumpTracedMessages(nodeOrRouteId) | List<BacklogTracerEventMessage> | To dump the traced messages from the give node or route id. |
| dumpTracedMessagesAsXml(nodeOrRouteId) | String | To dump the traced messages from the give node or route id in XML format. |
| dumpAllTracedMessages | List<BacklogTracerEventMessage> | To dump all the traced messages |
| dumpAllTracedMessagesAsXml | String | To dump all the traced messages in XML format. |
Enabling
You would need to enable this using the JMX API.
See Also