[[MetricsComponent-MetricsComponent]]
Metrics Component
~~~~~~~~~~~~~~~~~

*Available as of Camel 2.14*

The **metrics:** component allows to collect various metrics directly
from Camel routes. Supported metric types
are link:#MetricsComponent-counter[counter], link:#MetricsComponent-histogram[histogram],
link:#MetricsComponent-meter[meter] and link:#MetricsComponent-timer[timer]. http://metrics.dropwizard.io[Metrics] provides
simple way to measure behaviour of application. Configurable
reporting backend is enabling different integration options for
collecting and visualizing statistics. The component also provides
a `MetricsRoutePolicyFactory` which allows to expose route statistics
using Dropwizard Metrics, see bottom of page for details.

Maven users will need to add the following dependency to their `pom.xml`
for this component:

[source,xml]
----
<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-metrics</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>
----

[[MetricsComponent-URIformat]]
URI format
^^^^^^^^^^

[source]
----
metrics:[ meter | counter | histogram | timer ]:metricname[?options]
----

[[MetricsComponent-registryMetricRegistry]]
[[MetricsComponent-registry]]Metric Registry
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Camel Metrics component uses by default a `MetricRegistry` instance with
a `Slf4jReporter` that has a 60 second reporting interval.
This default registry can be replaced with a custom one by providing
a `MetricRegistry` bean. If multiple `MetricRegistry` beans exist in the
application, the one with name `metricRegistry` is used.

For example using Spring Java Configuration:

[source,java]
----
@Configuration
public static class MyConfig extends SingleRouteCamelConfiguration {

    @Bean
    @Override
    public RouteBuilder route() {
        return new RouteBuilder() {
            @Override
            public void configure() throws Exception {
                // define Camel routes here
            }
        };
    }

    @Bean(name = MetricsComponent.METRIC_REGISTRY_NAME)
    public MetricRegistry getMetricRegistry() {
        MetricRegistry registry = ...;
        return registry;
    }
}
----

Or using CDI:
[source,java]
----
class MyBean extends RouteBuilder {

    @Override
    public void configure() {
      from("...")
          // Register the 'my-meter' meter in the MetricRegistry below
          .to("metrics:meter:my-meter");
    }

    @Produces
    // If multiple MetricRegistry beans
    // @Named(MetricsComponent.METRIC_REGISTRY_NAME)
    MetricRegistry registry() {
        MetricRegistry registry = new MetricRegistry();
        // ...
        return registry;
    }
}
----

CAUTION: `MetricRegistry` uses internal thread(s) for reporting. There is no
public API in version `3.0.1` for users to clean up on exit. Thus using
Camel Metrics Component leads to Java classloader leak and my cause
`OutOfMemoryErrors` in some cases.

[[MetricsComponent-Usage]]
Usage
^^^^^

Each metric has type and name. Supported types are
link:#MetricsComponent-counter[counter],
link:#MetricsComponent-histogram[histogram], link:#MetricsComponent-meter[meter] and
link:#MetricsComponent-timer[timer]. Metric name is simple string. If
metric type is not provided then type meter is used by default.

[[MetricsComponent-Headers]]
Headers
+++++++

Metric name defined in URI can be overridden by using header with name
`CamelMetricsName`.

For example

[source,java]
----
from("direct:in")
    .setHeader(MetricsConstants.HEADER_METRIC_NAME, constant("new.name"))
    .to("metrics:counter:name.not.used")
    .to("direct:out");
----

will update counter with name `new.name` instead of `name.not.used`.

All Metrics specific headers are removed from the message once Metrics
endpoint finishes processing of exchange. While processing exchange
Metrics endpoint will catch all exceptions and write log entry using
level `warn`.

[[MetricsComponent-counterMetricstypecounter]]
[[MetricsComponent-counter]]Metrics type counter
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[source]
----
metrics:counter:metricname[?options]
----

[[MetricsComponent-Options]]
Options
+++++++

[width="100%",cols="10%,10%,80%",options="header",]
|=====================================================
|Name |Default |Description
|increment  |- |Long value to add to the counter
|decrement |- |Long value to subtract from the counter
|=====================================================

If neither `increment` or `decrement` is defined then counter value will
be incremented by one. If `increment` and `decrement` are both defined
only increment operation is called. 

[source,java]
----
// update counter simple.counter by 7
from("direct:in")
    .to("metric:counter:simple.counter?increment=7")
    .to("direct:out");
----

[source,java]
----
// increment counter simple.counter by 1
from("direct:in")
    .to("metric:counter:simple.counter")
    .to("direct:out");
----

[source,java]
----
// decrement counter simple.counter by 3
from("direct:in")
    .to("metric:counter:simple.counter?decrement=3")
    .to("direct:out");
----

[[MetricsComponent-Headers.1]]
Headers
+++++++

Message headers can be used to override `increment` and `decrement`
values specified in Metrics component URI.

[width="100%",cols="10%,80%,10%",options="header",]
|====================================================================
|Name |Description |Expected type
|CamelMetricsCounterIncrement  |Override increment value in URI |Long
|CamelMetricsCounterDecrement  |Override decrement value in URI |Long
|====================================================================

[source,java]
----
// update counter simple.counter by 417
from("direct:in")
    .setHeader(MetricsConstants.HEADER_COUNTER_INCREMENT, constant(417L))
    .to("metric:counter:simple.counter?increment=7")
    .to("direct:out");
----

[source,java]
----
// updates counter using simple language to evaluate body.length
from("direct:in")
    .setHeader(MetricsConstants.HEADER_COUNTER_INCREMENT, simple("${body.length}"))
    .to("metrics:counter:body.length")
    .to("mock:out");

----

[[MetricsComponent-histogramMetrictypehistogram]]
[[MetricsComponent-histogram]]Metric type histogram
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[source]
----
metrics:histogram:metricname[?options]
----

[[MetricsComponent-Options.1]]
Options
+++++++

[width="100%",cols="10%,10%,80%",options="header",]
|===================================
|Name |Default |Description
|value |- |Value to use in histogram
|===================================

If no `value` is not set nothing is added to histogram and warning is
logged.

[source,java]
----
// adds value 9923 to simple.histogram
from("direct:in")
    .to("metric:histogram:simple.histogram?value=9923")
    .to("direct:out");
----

[source,java]
----
// nothing is added to simple.histogram; warning is logged
from("direct:in")
    .to("metric:histogram:simple.histogram")
    .to("direct:out");

----

[[MetricsComponent-Headers.2]]
Headers
+++++++

Message header can be used to override value specified in Metrics
component URI.

[width="100%",cols="10%,80%,10%",options="header",]
|=================================================================
|Name |Description |Expected type
|CamelMetricsHistogramValue |Override histogram value in URI |Long
|=================================================================

[source,java]
----
// adds value 992 to simple.histogram
from("direct:in")
    .setHeader(MetricsConstants.HEADER_HISTOGRAM_VALUE, constant(992L))
    .to("metric:histogram:simple.histogram?value=700")
    .to("direct:out")

----

[[MetricsComponent-meterMetrictypemeter]]
[[MetricsComponent-meter]]Metric type meter
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[source]
----
metrics:meter:metricname[?options]
----

[[MetricsComponent-Options.2]]
Options
+++++++

[width="100%",cols="10%,10%,80%",options="header",]
|===================================
|Name |Default |Description
|mark  |- |Long value to use as mark
|===================================

If `mark` is not set then `meter.mark()` is called without argument.

[source,java]
----
// marks simple.meter without value
from("direct:in")
    .to("metric:simple.meter")
    .to("direct:out");
----

[source,java]
----
// marks simple.meter with value 81
from("direct:in")
    .to("metric:meter:simple.meter?mark=81")
    .to("direct:out");
----

[[MetricsComponent-Headers.3]]
Headers
+++++++

Message header can be used to override `mark` value specified in Metrics
component URI.

[width="100%",cols="10%,80%,10%",options="header",]
|=======================================================
|Name |Description |Expected type
|CamelMetricsMeterMark |Override mark value in URI |Long
|=======================================================

[source,java]
----
// updates meter simple.meter with value 345
from("direct:in")
    .setHeader(MetricsConstants.HEADER_METER_MARK, constant(345L))
    .to("metric:meter:simple.meter?mark=123")
    .to("direct:out");
----

[[MetricsComponent-timerMetricstypetimer]]
[[MetricsComponent-timer]]Metrics type timer
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[source]
----
metrics:timer:metricname[?options]
----

[[MetricsComponent-Options.3]]
Options
+++++++

[width="100%",cols="10%,10%,80%",options="header",]
|==========================
|Name |Default |Description
|action |- |start or stop
|==========================

If no `action` or invalid value is provided then warning is logged
without any timer update. If action `start` is called on already running
timer or `stop` is called on not running timer then nothing is updated
and warning is logged.

[source,java]
----
// measure time taken by route "calculate"
from("direct:in")
    .to("metrics:timer:simple.timer?action=start")
    .to("direct:calculate")
    .to("metrics:timer:simple.timer?action=stop");
----

`TimerContext` objects are stored as Exchange properties between
different Metrics component calls.

[[MetricsComponent-Headers.4]]
Headers
+++++++

Message header can be used to override action value specified in Metrics
component URI.

[width="100%",cols="10%,80%,10%",options="header",]
|=======================================================================
|Name |Description |Expected type
|CamelMetricsTimerAction |Override timer action in URI
|`org.apache.camel.component.metrics.timer.TimerEndpoint.TimerAction`
|=======================================================================

[source,java]
----
// sets timer action using header
from("direct:in")
    .setHeader(MetricsConstants.HEADER_TIMER_ACTION, TimerAction.start)
    .to("metric:timer:simple.timer")
    .to("direct:out");
----

[[MetricsComponent-MetricsRoutePolicyFactory]]
MetricsRoutePolicyFactory
^^^^^^^^^^^^^^^^^^^^^^^^^

This factory allows to add a link:routepolicy.html[RoutePolicy] for each
route which exposes route utilization statistics using Dropwizard metrics.
This factory can be used in Java and XML as the examples below
demonstrates. 

NOTE: Instead of using the MetricsRoutePolicyFactory you can define a
MetricsRoutePolicy per route you want to instrument, in case you only
want to instrument a few selected routes.

From Java you just add the factory to the `CamelContext` as shown below:

[source,java]
----
context.addRoutePolicyFactory(new MetricsRoutePolicyFactory());
----

And from XML DSL you define a <bean> as follows:

[source,xml]
----
  <!-- use camel-metrics route policy to gather metrics for all routes -->
  <bean id="metricsRoutePolicyFactory" class="org.apache.camel.component.metrics.routepolicy.MetricsRoutePolicyFactory"/>
----

The `MetricsRoutePolicyFactory` and `MetricsRoutePolicy` supports the
following options:

[width="100%",cols="10%,10%,80%",options="header",]
|=======================================================================
|Name |Default |Description
|useJmx |false |Whether to report fine grained statistics to JMX by
using the `com.codahale.metrics.JmxReporter`. +
Notice that if JMX is enabled on link:camelcontext.html[CamelContext]
then a `MetricsRegistryService` mbean is enlisted under the services
type in the JMX tree. That mbean has a single operation to output the
statistics using json. Setting `useJmx` to true is only needed if you
want fine grained mbeans per statistics type.

|jmxDomain |org.apache.camel.metrics |The JMX domain name

|prettyPrint |false |Whether to use pretty print when outputting
statistics in json format

|metricsRegistry |  |Allow to use a shared
`com.codahale.metrics.MetricRegistry`. If none is provided then Camel
will create a shared instance used by the this CamelContext.

|rateUnit |TimeUnit.SECONDS |The unit to use for rate in the metrics
reporter or when dumping the statistics as json.

|durationUnit |TimeUnit.MILLISECONDS |The unit to use for duration in
the metrics reporter or when dumping the statistics as json.

|namePattern |`##name##.##routeId##.##type##` |*Camel 2.17:* The name
pattern to use. Uses dot as separators, but you can change that. The
values `##name##`, `##routeId##`, and `##type##` will be replaced with actual
value. Where `###name###` is the name of the CamelContext. `###routeId###`
is the name of the route. And `###type###` is the value of responses.
|=======================================================================

 

From Java code tou can get hold of
the `com.codahale.metrics.MetricRegistry` from the
`org.apache.camel.component.metrics.routepolicy.MetricsRegistryService`
as shown below:

[source,java]
----
MetricRegistryService registryService = context.hasService(MetricsRegistryService.class);
if (registryService != null) {
  MetricsRegistry registry = registryService.getMetricsRegistry();
  ...
}
----

[[MetricsComponent-MetricsMessageHistoryFactory]]
MetricsMessageHistoryFactory
^^^^^^^^^^^^^^^^^^^^^^^^^^^^

*Available as of Camel 2.17*

This factory allows to use metrics to
capture link:message-history.html[Message History] performance
statistics while routing messages. It works by using a metrics Timer for
each node in all the routes. This factory can be used in Java and XML as
the examples below demonstrates. 

From Java you just set the factory to the `CamelContext` as shown below:

[source,java]
----
context.setMessageHistoryFactory(new MetricsMessageHistoryFactory());
----

And from XML DSL you define a <bean> as follows:

[source,xml]
----
  <!-- use camel-metrics message history to gather metrics for all messages being routed -->
  <bean id="metricsMessageHistoryFactory" class="org.apache.camel.component.metrics.messagehistory.MetricsMessageHistoryFactory"/>
----

The following options is supported on the factory:

[width="100%",cols="10%,10%,80%",options="header",]
|=======================================================================
|Name |Default |Description
|useJmx |false |Whether to report fine grained statistics to JMX by
using the `com.codahale.metrics.JmxReporter`. +
Notice that if JMX is enabled on link:camelcontext.html[CamelContext]
then a `MetricsRegistryService` mbean is enlisted under the services
type in the JMX tree. That mbean has a single operation to output the
statistics using json. Setting `useJmx` to true is only needed if you
want fine grained mbeans per statistics type.

|jmxDomain |org.apache.camel.metrics |The JMX domain name

|prettyPrint |false |Whether to use pretty print when outputting
statistics in json format

|metricsRegistry |  |Allow to use a shared
`com.codahale.metrics.MetricRegistry`. If none is provided then Camel
will create a shared instance used by the this CamelContext.

|rateUnit |TimeUnit.SECONDS |The unit to use for rate in the metrics
reporter or when dumping the statistics as json.

|durationUnit |TimeUnit.MILLISECONDS |The unit to use for duration in
the metrics reporter or when dumping the statistics as json.

|namePattern |`##name##.##routeId##.###id###.##type##` |The name pattern
to use. Uses dot as separators, but you can change that. The values
`##name##`, `##routeId##`, `##type##`, and `###id###` will be replaced with
actual value. Where `###name###` is the name of the CamelContext.
`###routeId###` is the name of the route. The `###id###` pattern represents
the node id. And `###type###` is the value of history.
|=======================================================================

At runtime the metrics can be accessed from Java API or JMX which allows
to gather the data as json output.

From Java code you can do get the service from the CamelContext as
shown:

[source,java]
----
MetricsMessageHistoryService service = context.hasService(MetricsMessageHistoryService.class);
String json = service.dumpStatisticsAsJson();
----

And the JMX API the MBean is registered in the `type=services` tree
with `name=MetricsMessageHistoryService`.

[[MetricsComponent-SeeAlso]]
See Also
^^^^^^^^

* The `camel-example-cdi-metrics` example that illustrates the integration
  between Camel, Metrics and CDI.
