Phillip Webb fa191d8c73 Align ReactiveWebApplicationContext with framework
Refactor `ReactiveWebApplicationContext` implementations to align closer
with the `WebApplicationContext` implementations defined in
Spring Framework.

The following classes are now provided:

  - `AnnotationConfigReactiveWebApplicationContext` -- A refreshable
    reactive web context with support for `@Configuration` classes.

  - `GenericReactiveWebApplicationContext` -- A non-refreshable reactive
    GenericApplicationContext.

  - `ReactiveWebServerApplicationContext` --  A non-refreshable reactive
    GenericApplicationContext with support for server discovery.

  - `AnnotationConfigReactiveWebServerApplicationContext` -- A
    non-refreshable reactive `GenericApplicationContext` with support
    for `@Configuration` classes and server discovery.

These classes roughly align to the following Servlet equivalents:

  - `AnnotationConfigWebApplicationContext` (Spring Framework)
  - `GenericWebApplicationContext` (Spring Framework)
  - `ServletWebServerApplicationContext` (Spring Boot)
  - `AnnotationConfigServletWebServerApplicationContext` (Spring Boot)

An additional `ConfigurableReactiveWebEnvironment` interface as also
been introduced, primarily for `@ConditionalOnWebApplication` to use.

Fixes gh-10852
2017-11-03 19:07:23 -07:00
..

= Spring Boot - Actuator

Spring Boot Actuator 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. The
http://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#production-ready[user guide]
covers the features in more detail.

== Enabling the Actuator
The simplest way to enable the features is to add a dependency to the
`spring-boot-starter-actuator` '`Starter`'. 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:

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

== Features
* **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. Run up a basic application and look at `/health` (and see `/mappings` for
  a list of other HTTP endpoints).
* **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). Metrics for all HTTP requests are automatically
  recorded, so if you hit the `metrics` endpoint should see a sensible response.
* **Audit** Spring Boot Actuator has a flexible audit framework that will publish events
  to an `AuditEventRepository`. Once Spring Security is in play it automatically publishes
  authentication events by default. This can be very useful for reporting, and also to
  implement a lock-out policy based on authentication failures.
* **Process Monitoring** In Spring Boot Actuator you can find `ApplicationPidFileWriter`
  which creates a file containing the application PID (by default in the application
  directory with a file name of `application.pid`).