[[production-ready]]
= Spring Boot Actuator: Production-ready features

[partintro]
--
Spring Boot includes a number of additional features to help you monitor and manage your
application when it's pushed to production. You can choose to manage and monitor your
application using HTTP endpoints, with JMX or even by remote shell (SSH or Telnet).
Auditing, health and metrics gathering can be automatically applied to your application.
--



[[production-ready-enabling]]
== Enabling production-ready features.
The {github-code}/spring-boot-actuator[`spring-boot-actuator`] module provides all of
Spring Boot's production-ready features. The simplest way to enable the features is to add
a dependency to the `spring-boot-starter-actuator` '`Starter POM`'.

.Definition of Actuator
****
An actuator is a manufacturing term, referring to a mechanical device for moving or
controlling something. Actuators can generate a large amount of motion from a small
change.
****

To add the actuator to a Maven based project, add the following '`starter`'
dependency:

[source,xml,indent=0]
----
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-actuator</artifactId>
		</dependency>
	</dependencies>
----

For Gradle, use the declaration:

[source,groovy,indent=0]
----
	dependencies {
		compile("org.springframework.boot:spring-boot-starter-actuator")
	}
----



[[production-ready-endpoints]]
== Endpoints
Actuator endpoints allow you to monitor and interact with your application. Spring Boot
includes a number of built-in endpoints and you can also add your own. For example the
`health` endpoint provides basic application health information.

The way that endpoints are exposed will depend on the type of technology that you choose.
Most applications choose HTTP monitoring, where the ID of the endpoint is mapped
to a URL. For example, by default, the `health` endpoint will be mapped to `/health`.

The following endpoints are available:

[cols="2,5,1"]
|===
| ID | Description | Sensitive

|`autoconfig`
|Displays an auto-configuration report showing all auto-configuration candidates and the
 reason why they '`were`' or '`were not`' applied.
|true

|`beans`
|Displays a complete list of all the Spring Beans in your application.
|true

|`configprops`
|Displays a collated list of all `@ConfigurationProperties`.
|true

|`dump`
|Performs a thread dump.
|true

|`env`
|Exposes properties from Spring's `ConfigurableEnvironment`.
|true

|`health`
|Shows application health information (a simple '`status`' when accessed over an
unauthenticated connection or full message details when authenticated).
|false

|`info`
|Displays arbitrary application info.
|false

|`metrics`
|Shows '`metrics`' information for the current application.
|true

|`mappings`
|Displays a collated list of all `@RequestMapping` paths.
|true

|`shutdown`
|Allows the application to be gracefully shutdown (not enabled by default).
|true

|`trace`
|Displays trace information (by default the last few HTTP requests).
|true
|===

NOTE: Depending on how an endpoint is exposed, the `sensitive` parameter may be used as
a security hint. For example, sensitive endpoints will require a username/password when
they are accessed over HTTP (or simply disabled if web security is not enabled).



[[production-ready-customizing-endpoints]]
=== Customizing endpoints
Endpoints can be customized using Spring properties. You can change if an endpoint is
`enabled`, if it is considered `sensitive` and even its `id`.

For example, here is an `application.properties` that changes the sensitivity and id
of the `beans` endpoint and also enables `shutdown`.

[source,properties,indent=0]
----
	endpoints.beans.id=springbeans
	endpoints.beans.sensitive=false
	endpoints.shutdown.enabled=true
----

NOTE: The prefix ‟`endpoints` + `.` + `name`” is used to uniquely identify the endpoint
that is being configured.

By default, all endpoints except for `shutdown` are enabled. If you prefer to
specifically "`opt-in`" endpoint enablement you can use the `endpoints.enabled` property.
For example, the following will disable _all_ endpoints except for `info`:

[source,properties,indent=0]
----
	endpoints.enabled=false
	endpoints.info.enabled=true
----



[[production-ready-health]]
=== Health information
Health information can be used to check the status of your running application. It is
often used by monitoring software to alert someone if a production system goes down.
The default information exposed by the `health` endpoint depends on how it is accessed.
For an insecure unauthenticated connection a simple '`status`' message is returned, for a
secure or authenticated connection additional details are also displayed (see
<<production-ready-health-access-restrictions>> for HTTP details).

Health information is collected from all
{sc-spring-boot-actuator}/health/HealthIndicator.{sc-ext}[`HealthIndicator`] beans defined
in your `ApplicationContext`. Spring Boot includes a number of auto-configured
`HealthIndicators` and you can also write your own.



=== Security with HealthIndicators
Information returned by `HealthIndicators` is often somewhat sensitive in nature. For
example, you probably don't want to publish details of your database server to the
world. For this reason, by default, only the health status is exposed over an
unauthenticated HTTP connection. If you are happy for complete health information to always
be exposed you can set `endpoints.health.sensitive` to `false`.

Health responses are also cached to prevent "`denial of service`" attacks. Use the
`endpoints.health.time-to-live` property if you want to change the default cache period
of 1000 milliseconds.



==== Auto-configured HealthIndicators
The following `HealthIndicators` are auto-configured by Spring Boot when appropriate:

[cols="1,4"]
|===
|Name |Description

|{sc-spring-boot-actuator}/health/DiskSpaceHealthIndicator.{sc-ext}[`DiskSpaceHealthIndicator`]
|Checks for low disk space.

|{sc-spring-boot-actuator}/health/DataSourceHealthIndicator.{sc-ext}[`DataSourceHealthIndicator`]
|Checks that a connection to `DataSource` can be obtained.

|{sc-spring-boot-actuator}/health/MongoHealthIndicator.{sc-ext}[`MongoHealthIndicator`]
|Checks that a Mongo database is up.

|{sc-spring-boot-actuator}/health/RabbitHealthIndicator.{sc-ext}[`RabbitHealthIndicator`]
|Checks that a Rabbit server is up.

|{sc-spring-boot-actuator}/health/RedisHealthIndicator.{sc-ext}[`RedisHealthIndicator`]
|Checks that a Redis server is up.

|{sc-spring-boot-actuator}/health/SolrHealthIndicator.{sc-ext}[`SolrHealthIndicator`]
|Checks that a Solr server is up.
|===



==== Writing custom HealthIndicators
To provide custom health information you can register Spring beans that implement the
{sc-spring-boot-actuator}/health/HealthIndicator.{sc-ext}[`HealthIndicator`] interface.
You need to provide an implementation of the `health()` method and return a `Health`
response. The `Health` response should include a status and can optionally include
additional details to be displayed.

[source,java,indent=0]
----
	import org.springframework.boot.actuate.health.HealthIndicator;
	import org.springframework.stereotype.Component;

	@Component
	public class MyHealth implements HealthIndicator {

		@Override
		public Health health() {
			int errorCode = check(); // perform some specific health check
			if (errorCode != 0) {
				return Health.down().withDetail("Error Code", errorCode).build();
			}
			return Health.up().build();
		}

	}
----

In addition to Spring Boot's predefined {sc-spring-boot-actuator}/health/Status.{sc-ext}[`Status`]
types, it is also possible for `Health` to return a custom `Status` that represents a
new system state. In such cases a custom implementation of the
{sc-spring-boot-actuator}/health/HealthAggregator.{sc-ext}[`HealthAggregator`]
interface also needs to be provided, or the default implementation has to be configured
using the `management.health.status.order` configuration property.

For example, assuming a new `Status` with code `FATAL` is being used in one of your
`HealthIndicator` implementations. To configure the severity order add the following
to your application properties:

[source,properties,indent=0]
----
	management.health.status.order: DOWN, OUT_OF_SERVICE, UNKNOWN, UP
----

You might also want to register custom status mappings with the `HealthMvcEndpoint`
if you access the health endpoint over HTTP. For example you could map `FATAL` to
`HttpStatus.SERVICE_UNAVAILABLE`.



[[production-ready-application-info]]
=== Custom application info information
You can customize the data exposed by the `info` endpoint by setting `+info.*+` Spring
properties. All `Environment` properties under the info key will be automatically
exposed. For example, you could add the following to your `application.properties`:

[source,properties,indent=0]
----
	info.app.name=MyService
	info.app.description=My awesome service
	info.app.version=1.0.0
----



[[production-ready-application-info-automatic-expansion]]
==== Automatically expand info properties at build time
Rather than hardcoding some properties that are also specified in your project's build
configuration, you can automatically expand info properties using the existing build
configuration instead. This is possible in both Maven and Gradle.



[[production-ready-application-info-automatic-expansion-maven]]
===== Automatic property expansion using Maven
You can automatically expand info properties from the Maven project using resource
filtering. If you use the `spring-boot-starter-parent` you can then refer to your
Maven '`project properties`' via `@..@` placeholders, e.g.

[source,properties,indent=0]
----
	project.artifactId=myproject
	project.name=Demo
	project.version=X.X.X.X
	project.description=Demo project for info endpoint
	info.build.artifact=@project.artifactId@
	info.build.name=@project.name@
	info.build.description=@project.description@
	info.build.version=@project.version@
----

NOTE: In the above example we used `+project.*+` to set some values to be used as
fallbacks if the Maven resource filtering has not been switched on for some reason.

NOTE: If you don't use the starter parent, in your `pom.xml` you need (inside the `<build/>` element):

[source,xml,indent=0]
----
    <resources>
        <resource>
            <directory>src/main/resources</directory>
            <filtering>true</filtering>
        </resource>
    </resources>
----

and (inside `<plugins/>`):

[source,xml,indent=0]
----
	<plugin>
		<groupId>org.apache.maven.plugins</groupId>
		<artifactId>maven-resources-plugin</artifactId>
		<version>2.6</version>
		<configuration>
			<delimiters>
				<delimiter>@</delimiter>
			</delimiters>
		</configuration>
	</plugin>
----

[[production-ready-application-info-automatic-expansion-gradle]]
===== Automatic property expansion using Gradle
You can automatically expand info properties from the Gradle project by configuring
the Java plugin's `processResources` task to do so:

[source,groovy,indent=0]
----
	processResources {
		expand(project.properties)
	}
----

You can then refer to your Gradle project's properties via placeholders, e.g.

[source,properties,indent=0]
----
	info.build.name=${name}
	info.build.description=${description}
	info.build.version=${version}
----



[[production-ready-git-commit-information]]
==== Git commit information
Another useful feature of the `info` endpoint is its ability to publish information
about the state of your `git` source code repository when the project was built. If a
`git.properties` file is contained in your jar the `git.branch` and `git.commit`
properties will be loaded.

For Maven users the `spring-boot-starter-parent` POM includes a pre-configured plugin to
generate a `git.properties` file. Simply add the following declaration to your POM:

[source,xml,indent=0]
----
	<build>
		<plugins>
			<plugin>
				<groupId>pl.project13.maven</groupId>
				<artifactId>git-commit-id-plugin</artifactId>
			</plugin>
		</plugins>
	</build>
----

A similar https://github.com/ajoberstar/gradle-git[`gradle-git`] plugin is also available
for Gradle users, although a little more work is required to generate the properties file.



[[production-ready-monitoring]]
== Monitoring and management over HTTP
If you are developing a Spring MVC application, Spring Boot Actuator will auto-configure
all enabled endpoints to be exposed over HTTP. The default convention is to use the
`id` of the endpoint as the URL path. For example, `health` is exposed as `/health`.



[[production-ready-sensitive-endpoints]]
=== Securing sensitive endpoints
If you add '`Spring Security`' to your project, all sensitive endpoints exposed over HTTP
will be protected. By default '`basic`' authentication will be used with the username
`user` and a generated password (which is printed on the console when the application
starts).

TIP: Generated passwords are logged as the application starts. Search for '`Using default
security password`'.

You can use Spring properties to change the username and password and to change the
security role required to access the endpoints. For example, you might set the following
in your `application.properties`:

[source,properties,indent=0]
----
	security.user.name=admin
	security.user.password=secret
	management.security.role=SUPERUSER
----

TIP: If you don't use Spring Security and your HTTP endpoints are exposed publicly,
you should carefully consider which endpoints you enable. See
<<production-ready-customizing-endpoints>> for details of how you can set
`endpoints.enabled` to `false` then "`opt-in`" only specific endpoints.


[[production-ready-customizing-management-server-context-path]]
=== Customizing the management server context path
Sometimes it is useful to group all management endpoints under a single path. For example,
your application might already use `/info` for another purpose. You can use the
`management.contextPath` property to set a prefix for your management endpoint:

[source,properties,indent=0]
----
	management.context-path=/manage
----

The `application.properties` example above will change the endpoint from `/{id}` to
`/manage/{id}` (e.g. `/manage/info`).



[[production-ready-customizing-management-server-port]]
=== Customizing the management server port
Exposing management endpoints using the default HTTP port is a sensible choice for cloud
based deployments. If, however, your application runs inside your own data center you
may prefer to expose endpoints using a different HTTP port.

The `management.port` property can be used to change the HTTP port.

[source,properties,indent=0]
----
	management.port=8081
----

Since your management port is often protected by a firewall, and not exposed to the public
you might not need security on the management endpoints, even if your main application is
secure. In that case you will have Spring Security on the classpath, and you can disable
management security like this:

[source,properties,indent=0]
----
	management.security.enabled=false
----

(If you don't have Spring Security on the classpath then there is no need to explicitly
disable the management security in this way, and it might even break the application.)



[[production-ready-customizing-management-server-address]]
=== Customizing the management server address
You can customize the address that the management endpoints are available on by
setting the `management.address` property. This can be useful if you want to
listen only on an internal or ops-facing network, or to only listen for connections from
`localhost`.

NOTE: You can only listen on a different address if the port is different to the
main server port.

Here is an example `application.properties` that will not allow remote management
connections:

[source,properties,indent=0]
----
	management.port=8081
	management.address=127.0.0.1
----



[[production-ready-disabling-http-endpoints]]
=== Disabling HTTP endpoints
If you don't want to expose endpoints over HTTP you can set the management port to `-1`:

[source,properties,indent=0]
----
	management.port=-1
----



[[production-ready-health-access-restrictions]]
=== HTTP Health endpoint access restrictions
The information exposed by the health endpoint varies depending on whether or not it's
accessed anonymously. By default, when accessed anonymously, any details about the
server's health are hidden and the endpoint will simply indicate whether or not the server
is up or down. Furthermore, when accessed anonymously, the response is cached for a
configurable period to prevent the endpoint being used in a denial of service attack.
The `endpoints.health.time-to-live` property is used to configure the caching period in
milliseconds. It defaults to 1000, i.e. one second.

The above-described restrictions can be disabled, thereby allowing anonymous users full
access to the health endpoint. To do so, set `endpoints.health.sensitive` to `false`.



[[production-ready-jmx]]
== Monitoring and management over JMX
Java Management Extensions (JMX) provide a standard mechanism to monitor and manage
applications. By default Spring Boot will expose management endpoints as JMX MBeans
under the `org.springframework.boot` domain.



[[production-ready-custom-mbean-names]]
=== Customizing MBean names
The name of the MBean is usually generated from the `id` of the endpoint. For example
the `health` endpoint is exposed as `org.springframework.boot/Endpoint/HealthEndpoint`.

If your application contains more than one Spring `ApplicationContext` you may find that
names clash. To solve this problem you can set the `endpoints.jmx.uniqueNames` property
to `true` so that MBean names are always unique.

You can also customize the JMX domain under which endpoints are exposed. Here is an
example `application.properties`:

[source,properties,indent=0]
----
	endpoints.jmx.domain=myapp
	endpoints.jmx.uniqueNames=true
----



[[production-ready-disable-jmx-endpoints]]
=== Disabling JMX endpoints
If you don't want to expose endpoints over JMX you can set the `spring.jmx.enabled`
property to `false`:

[source,properties,indent=0]
----
	spring.jmx.enabled=false
----



[[production-ready-jolokia]]
=== Using Jolokia for JMX over HTTP
Jolokia is a JMX-HTTP bridge giving an alternative method of accessing JMX beans. To
use Jolokia, simply include a dependency to `org.jolokia:jolokia-core`. For example,
using Maven you would add the following:

[source,xml,indent=0]
----
	<dependency>
		<groupId>org.jolokia</groupId>
		<artifactId>jolokia-core</artifactId>
 	</dependency>
----

Jolokia can then be accessed using `/jolokia` on your management HTTP server.



[[production-ready-customizing-jolokia]]
==== Customizing Jolokia
Jolokia has a number of settings that you would traditionally configure using servlet
parameters. With Spring Boot you can use your `application.properties`, simply prefix the
parameter with `jolokia.config.`:

[source,properties,indent=0]
----
	jolokia.config.debug=true
----



[[production-ready-disabling-jolokia]]
==== Disabling Jolokia
If you are using Jolokia but you don't want Spring Boot to configure it, simply set the
`endpoints.jolokia.enabled` property to `false`:

[source,properties,indent=0]
----
	endpoints.jolokia.enabled=false
----



[[production-ready-remote-shell]]
== Monitoring and management using a remote shell
Spring Boot supports an integrated Java shell called '`CRaSH`'. You can use CRaSH to
`ssh` or `telnet` into your running application. To enable remote shell support add a
dependency to `spring-boot-starter-remote-shell`:

[source,xml,indent=0]
----
	<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-remote-shell</artifactId>
 	</dependency>
----

TIP: If you want to also enable telnet access your will additionally need a dependency
on `org.crsh:crsh.shell.telnet`.



[[production-ready-connecting-to-the-remote-shell]]
=== Connecting to the remote shell
By default the remote shell will listen for connections on port `2000`. The default user
is `user` and the default password will be randomly generated and displayed in the log
output. If your application is using Spring Security, the shell will use
<<boot-features-security, the same configuration>> by default. If not, a simple
authentication will be applied and you should see a message like this:

[indent=0]
----
	Using default password for shell access: ec03e16c-4cf4-49ee-b745-7c8255c1dd7e
----

Linux and OSX users can use `ssh` to connect to the remote shell, Windows users can
download and install http://www.putty.org/[PuTTY].

[indent=0,subs="attributes"]
----
	$ ssh -p 2000 user@localhost

	user@localhost's password:
	  .   ____          _            __ _ _
	 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
	( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
	 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
	  '  |____| .__|_| |_|_| |_\__, | / / / /
	 =========|_|==============|___/=/_/_/_/
	 :: Spring Boot ::  (v{spring-boot-version}) on myhost
----

Type `help` for a list of commands. Spring boot provides `metrics`, `beans`, `autoconfig`
and `endpoint` commands.



[[production-ready-remote-shell-credentials]]
==== Remote shell credentials
You can use the `shell.auth.simple.user.name` and `shell.auth.simple.user.password` properties
to configure custom connection credentials. It is also possible to use a
'`Spring Security`' `AuthenticationManager` to handle login duties. See the
{dc-spring-boot-actuator}/autoconfigure/CrshAutoConfiguration.{dc-ext}[`CrshAutoConfiguration`]
and {dc-spring-boot-actuator}/autoconfigure/ShellProperties.{dc-ext}[`ShellProperties`]
Javadoc for full details.



[[production-ready-extending-the-remote-shell]]
=== Extending the remote shell
The remote shell can be extended in a number of interesting ways.



[[production-ready-remote-commands]]
==== Remote shell commands
You can write additional shell commands using Groovy or Java (see the CRaSH documentation
for details). By default Spring Boot will search for commands in the following locations:

* `+classpath*:/commands/**+`
* `+classpath*:/crash/commands/**+`

TIP: You can change the search path by settings a `shell.commandPathPatterns` property.

Here is a simple '`hello world`' command that could be loaded from
`src/main/resources/commands/hello.groovy`

[source,groovy,indent=0]
----
	package commands

	import org.crsh.cli.Usage
	import org.crsh.cli.Command

	class hello {

		@Usage("Say Hello")
		@Command
		def main(InvocationContext context) {
			return "Hello"
		}

	}
----

Spring Boot adds some additional attributes to `InvocationContext` that you can access
from your command:

[cols="2,3"]
|===
| Attribute Name | Description

|`spring.boot.version`
|The version of Spring Boot

|`spring.version`
|The version of the core Spring Framework

|`spring.beanfactory`
|Access to the Spring `BeanFactory`

|`spring.environment`
|Access to the Spring `Environment`
|===



[[production-ready-remote-shell-plugins]]
==== Remote shell plugins
In addition to new commands, it is also possible to extend other CRaSH shell features.
All Spring Beans that extend `org.crsh.plugin.CRaSHPlugin` will be automatically
registered with the shell.

For more information please refer to the http://www.crashub.org/[CRaSH reference
documentation].



[[production-ready-metrics]]
== Metrics
Spring Boot Actuator includes a metrics service with '`gauge`' and '`counter`' support.
A '`gauge`' records a single value; and a '`counter`' records a delta (an increment or
decrement). Spring Boot Actuator also provides a
{sc-spring-boot-actuator}/endpoint/PublicMetrics.{sc-ext}[`PublicMetrics`] interface that
you can implement to expose metrics that you cannot record via one of those two
mechanisms. Look at {sc-spring-boot-actuator}/endpoint/SystemPublicMetrics.{sc-ext}[`SystemPublicMetrics`]
for an example.

Metrics for all HTTP requests are automatically recorded, so if you hit the `metrics`
endpoint you should see a response similar to this:

[source,json,indent=0]
----
	{
		"counter.status.200.root": 20,
		"counter.status.200.metrics": 3,
		"counter.status.200.star-star": 5,
		"counter.status.401.root": 4,
		"gauge.response.star-star": 6,
		"gauge.response.root": 2,
		"gauge.response.metrics": 3,
		"classes": 5808,
		"classes.loaded": 5808,
		"classes.unloaded": 0,
		"heap": 3728384,
		"heap.committed": 986624,
		"heap.init": 262144,
		"heap.used": 52765,
		"mem": 986624,
		"mem.free": 933858,
		"processors": 8,
		"threads": 15,
		"threads.daemon": 11,
		"threads.peak": 15,
		"uptime": 494836,
		"instance.uptime": 489782,
		"datasource.primary.active": 5,
		"datasource.primary.usage": 0.25
	}
----

Here we can see basic `memory`, `heap`, `class loading`, `processor` and `thread pool`
information along with some HTTP metrics. In this instance the `root` ('`/`') and `/metrics`
URLs have returned `HTTP 200` responses `20` and `3` times respectively. It also appears
that the `root` URL returned `HTTP 401` (unauthorized) `4` times. The double asterix (`star-star`)
comes from a request matched by Spring MVC as `+/**+` (normally a static resource).

The `gauge` shows the last response time for a request. So the last request to `root` took
`2ms` to respond and the last to `/metrics` took `3ms`.

NOTE: In this example we are actually accessing the endpoint over HTTP using the
`/metrics` URL, this explains why `metrics` appears in the response.



[[production-ready-system-metrics]]
=== System metrics
The following system metrics are exposed by Spring Boot:

* The total system memory in Kb (`mem`)
* The amount of free memory in Kb (`mem.free`)
* The number of processors (`processors`)
* The system uptime in milliseconds (`uptime`)
* The application context uptime in milliseconds (`instance.uptime`)
* The average system load (`systemload.average`)
* Heap information in Kb (`heap`, `heap.committed`, `heap.init`, `heap.used`)
* Thread information (`threads`, `thread.peak`, `thead.daemon`)
* Class load information (`classes`, `classes.loaded`, `classes.unloaded`)
* Garbage collection information (`gc.xxx.count`, `gc.xxx.time`)



[[production-ready-datasource-metrics]]
=== DataSource metrics
The following metrics are exposed for each supported `DataSource` defined in your
application:

* The maximum number connections (`datasource.xxx.max`).
* The minimum number of connections (`datasource.xxx.min`).
* The number of active connections (`datasource.xxx.active`)
* The current usage of the connection pool (`datasource.xxx.usage`).

All data source metrics share the `datasource.` prefix. The prefix is further qualified
for each data source:

* If the data source is the primary data source (that is either the only available data
  source or the one flagged `@Primary` amongst the existing ones), the prefix is
  `datasource.primary`.
* If the data source bean name ends with `dataSource`, the prefix is the name of the bean
  without `dataSource` (i.e. `datasource.batch` for `batchDataSource`).
* In all other cases, the name of the bean is used.

It is possible to override part or all of those defaults by registering a bean with a
customized version of `DataSourcePublicMetrics`. By default, Spring Boot provides metadata
for all  supported datasources; you can add additional `DataSourcePoolMetadataProvider`
beans if your favorite data source isn't supported out of the box. See
`DataSourcePoolMetadataProvidersConfiguration` for examples.



[[production-ready-session-metrics]]
=== Tomcat session metrics
If you are using Tomcat as your embedded servlet container, session metrics will
automatically be exposed. The `httpsessions.active` and `httpsessions.max` keys provide
the number of active and maximum sessions.



[[production-ready-recording-metrics]]
=== Recording your own metrics
To record your own metrics inject a
{sc-spring-boot-actuator}/metrics/CounterService.{sc-ext}[`CounterService`] and/or
{sc-spring-boot-actuator}/metrics/GaugeService.{sc-ext}[`GaugeService`] into
your bean. The `CounterService` exposes `increment`, `decrement` and `reset` methods; the
`GaugeService` provides a `submit` method.

Here is a simple example that counts the number of times that a method is invoked:

[source,java,indent=0]
----
	import org.springframework.beans.factory.annotation.Autowired;
	import org.springframework.boot.actuate.metrics.CounterService;
	import org.springframework.stereotype.Service;

	@Service
	public class MyService {

		private final CounterService counterService;

		@Autowired
		public MyService(CounterService counterService) {
			this.counterService = counterService;
		}

		public void exampleMethod() {
			this.counterService.increment("services.system.myservice.invoked");
		}

	}
----

TIP: You can use any string as a metric name but you should follow guidelines of your chosen
store/graphing technology. Some good guidelines for Graphite are available on
http://matt.aimonetti.net/posts/2013/06/26/practical-guide-to-graphite-monitoring/[Matt Aimonetti's Blog].



[[production-ready-public-metrics]]
=== Adding your own public metrics
To add additional metrics that are computed every time the metrics endpoint is invoked,
simply register additional `PublicMetrics` implementation bean(s). By default, all such
beans are gathered by the endpoint. You can easily change that by defining your own
`MetricsEndpoint`.



[[production-ready-metric-repositories]]
=== Metric repositories
Metric service implementations are usually bound to a
{sc-spring-boot-actuator}/metrics/repository/MetricRepository.{sc-ext}[`MetricRepository`].
A `MetricRepository` is responsible for storing and retrieving metric information. Spring
Boot provides an `InMemoryMetricRepository` and a `RedisMetricRepository` out of the
box (the in-memory repository is the default) but you can also write your own. The
`MetricRepository` interface is actually composed of higher level `MetricReader` and
`MetricWriter` interfaces. For full details refer to the
{dc-spring-boot-actuator}/metrics/repository/MetricRepository.{dc-ext}[Javadoc].

There's nothing to stop you hooking a `MetricRepository` with back-end storage directly
into your app, but we recommend using the default `InMemoryMetricRepository`
(possibly with a custom `Map` instance if you are worried about heap usage) and
populating a back-end repository through a scheduled export job. In that way you get
some buffering in memory of the metric values and you can reduce the network
chatter by exporting less frequently or in batches. Spring Boot provides
an `Exporter` interface and a few basic implementations for you to get started with that.


[[production-ready-code-hale-metrics]]
=== Dropwizard Metrics
User of the https://dropwizard.github.io/metrics/[Dropwizard '`Metrics`' library] will
automatically find that Spring Boot metrics are published to
`com.codahale.metrics.MetricRegistry`. A default `com.codahale.metrics.MetricRegistry`
Spring bean will be created when you declare a dependency to the
`io.dropwizard.metrics:metrics-core` library; you can also register you own `@Bean`
instance if you need customizations. Metrics from the `MetricRegistry` are also
automatically exposed via the `/metrics` endpoint

Users can create Dropwizard metrics by prefixing their metric names with the appropriate
type (e.g. `+histogram.*+`, `+meter.*+`).



[[production-ready-metrics-message-channel-integration]]
=== Message channel integration
If the '`Spring Messaging`' jar is on your classpath a `MessageChannel` called
`metricsChannel` is automatically created (unless one already exists). All metric update
events are additionally published as '`messages`' on that channel. Additional analysis or
actions can be taken by clients subscribing to that channel.



[[production-ready-auditing]]
== Auditing
Spring Boot Actuator has a flexible audit framework that will publish events once Spring
Security is in play ('`authentication success`', '`failure`' and '`access denied`'
exceptions by default). This can be very useful for reporting, and also to implement a
lock-out policy based on authentication failures.

You can also choose to use the audit services for your own business events. To do that
you can either inject the existing `AuditEventRepository` into your own components and
use that directly, or you can simply publish `AuditApplicationEvent` via the Spring
`ApplicationEventPublisher` (using `ApplicationEventPublisherAware`).



[[production-ready-tracing]]
== Tracing
Tracing is automatically enabled for all HTTP requests. You can view the `trace` endpoint
and obtain basic information about the last few requests:

[source,json,indent=0]
----
	[{
		"timestamp": 1394343677415,
		"info": {
			"method": "GET",
			"path": "/trace",
			"headers": {
				"request": {
					"Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
					"Connection": "keep-alive",
					"Accept-Encoding": "gzip, deflate",
					"User-Agent": "Mozilla/5.0 Gecko/Firefox",
					"Accept-Language": "en-US,en;q=0.5",
					"Cookie": "_ga=GA1.1.827067509.1390890128; ..."
					"Authorization": "Basic ...",
					"Host": "localhost:8080"
				},
				"response": {
					"Strict-Transport-Security": "max-age=31536000 ; includeSubDomains",
					"X-Application-Context": "application:8080",
					"Content-Type": "application/json;charset=UTF-8",
					"status": "200"
				}
			}
		}
	},{
		"timestamp": 1394343684465,
		...
    }]
----



[[production-ready-custom-tracing]]
=== Custom tracing
If you need to trace additional events you can inject a
{sc-spring-boot-actuator}/trace/TraceRepository.{sc-ext}[`TraceRepository`] into your
Spring Beans. The `add` method accepts a single `Map` structure that will be converted to
JSON and logged.

By default an `InMemoryTraceRepository` will be used that stores the last 100 events. You
can define your own instance of the `InMemoryTraceRepository` bean if you need to expand
the capacity. You can also create your own alternative `TraceRepository` implementation
if needed.


[[production-ready-process-monitoring]]
== Process monitoring
In Spring Boot Actuator you can find a couple of classes to create files that are useful
for process monitoring:

* `ApplicationPidFileWriter` creates a file containing the application PID (by default in
  the application directory with the file name `application.pid`).
* `EmbeddedServerPortFileWriter` creates a file (or files) containing the ports of the
  embedded server (by default in the application directory with the file name
  `application.port`).

These writers are not activated by default, but you can enable them in one of the ways
described below.



[[production-ready-process-monitoring-configuration]]
=== Extend configuration
In `META-INF/spring.factories` file you have to activate the listener(s):

[indent=0]
----
	org.springframework.context.ApplicationListener=\
	org.springframework.boot.actuate.system.ApplicationPidFileWriter,
	org.springframework.boot.actuate.system.EmbeddedServerPortFileWriter
----



[[production-ready-process-monitoring-programmatically]]
=== Programmatically
You can also activate a listener by invoking the `SpringApplication.addListeners(...)`
method and passing the appropriate `Writer` object. This method also allows you to
customize the file name and path via the `Writer` constructor.



[[production-ready-whats-next]]
== What to read next
If you want to explore some of the concepts discussed in this chapter, you can take a
look at the actuator {github-code}/spring-boot-samples[sample applications]. You also
might want to read about graphing tools such as http://graphite.wikidot.com/[Graphite].

Otherwise, you can continue on, to read about <<cloud-deployment.adoc#cloud-deployment,
'`cloud deployment options`'>> or jump ahead
for some in-depth information about Spring Boot's
_<<build-tool-plugins.adoc#build-tool-plugins, build tool plugins>>_.
