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Add buffering ApplicationStartup variant

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As of spring-projects/spring-framework#24878, Spring Framework provides
an `ApplicationStartup` infrastructure that applications can use to
collect and track events during the application startup phase.

This commit adds a new `BufferingApplicationStartup` implementation that
buffer `StartupStep`s and tracks their execution time. Once buffered,
these steps can be pushed to an external metrics system or drained
through a web endpoint, to a file...

Closes gh-22603
This commit is contained in:
Brian Clozel
2020-09-07 18:04:31 +02:00
parent 17b6910208
commit fdf21da7ba
6 changed files with 593 additions and 0 deletions
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31
spring-boot-project/spring-boot-docs/src/docs/asciidoc/spring-boot-features.adoc
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@@ -443,6 +443,37 @@ This feature could also be useful for any service wrapper implementation.
TIP: If you want to know on which HTTP port the application is running, get the property with a key of `local.server.port`.
[[boot-features-application-startup-tracking]]
=== Application Startup tracking
During the application startup, the `SpringApplication` and the `ApplicationContext` perform many tasks related to the application lifecycle,
the beans lifecycle or even processing application events.
With {spring-framework-api}/core/metrics/ApplicationStartup.html[ApplicationStartup`], Spring Framework {spring-framework-docs}/core.html#context-functionality-startup[allows you track the application startup sequence with `StartupStep`s].
This data can be collected for profiling purposes, or just to have a better understanding of an application startup process.
You can choose a `ApplicationStartup` implementation when setting up the `SpringApplication` instance.
For example, to use the `BufferingApplicationStartup`, you could write:
[source,java,indent=0]
----
public static void main(String[] args) {
SpringApplication app = new SpringApplication(MySpringConfiguration.class);
app.setApplicationStartup(new BufferingApplicationStartup(2048));
app.run(args);
}
----
The first available implementation, `FlightRecorderApplicationStartup` is provided by Spring Framework.
It adds Spring-specific startup events to a Java Flight Recorder session and is meant for profiling applications and correlating their Spring context lifecycle with JVM events (such as allocations, GCs, class loading...).
Once configured, you can record data by running the application with the Flight Recorder enabled:
[source,bash,indent=0]
----
$ java -XX:StartFlightRecording:filename=recording.jfr,duration=10s -jar demo.jar
----
Spring Boot ships with the `BufferingApplicationStartup` variant; this implementation is meant for buffering the startup steps and draining them into an external metrics system.
Applications can ask for the bean of type `BufferingApplicationStartup` in any component.
Additionally, Spring Boot Actuator will <<production-ready-features.adoc#production-ready-endpoints, expose a `startup` endpoint to expose this information as a JSON document>>.
[[boot-features-external-config]]
== Externalized Configuration