Attuatore Spring Boot

1. Panoramica

In questo articolo, presentiamo l'attuatore Spring Boot. Tratteremo prima le nozioni di base, quindi discuteremo in dettaglio cosa è disponibile in Spring Boot 2.x vs 1.x.

Impareremo come utilizzare, configurare ed estendere questo strumento di monitoraggio in Spring Boot 2.x e WebFlux, sfruttando il modello di programmazione reattivo. Quindi discuteremo come fare lo stesso usando Boot 1.x.

Spring Boot Actuator è disponibile da aprile 2014, insieme alla prima versione Spring Boot.

Con il rilascio di Spring Boot 2, Actuator è stato riprogettato e sono stati aggiunti nuovi entusiasmanti endpoint.

Abbiamo suddiviso questa guida in tre sezioni principali:

  • Cos'è un attuatore?
  • Attuatore Spring Boot 2.x
  • Attuatore Spring Boot 1.x

2. Cos'è un attuatore?

In sostanza, Actuator porta nella nostra applicazione funzionalità pronte per la produzione.

Il monitoraggio della nostra app, la raccolta di metriche, la comprensione del traffico o lo stato del nostro database diventano banali con questa dipendenza.

Il vantaggio principale di questa libreria è che possiamo ottenere strumenti di livello di produzione senza dover implementare effettivamente queste funzionalità da soli.

Actuator viene utilizzato principalmente per esporre le informazioni operative sull'applicazione in esecuzione : salute, metriche, informazioni, dump, env, ecc. Utilizza endpoint HTTP o bean JMX per consentirci di interagire con esso.

Una volta che questa dipendenza è sul classpath, diversi endpoint sono disponibili per noi immediatamente. Come con la maggior parte dei moduli Spring, possiamo facilmente configurarlo o estenderlo in molti modi.

2.1. Iniziare

Per attivare la primavera di avvio attuatore, abbiamo solo bisogno di aggiungere la primavera-boot-attuatore dipendenza al nostro gestore di pacchetti.

A Maven:

 org.springframework.boot spring-boot-starter-actuator 

Si noti che ciò rimane valido indipendentemente dalla versione di avvio, poiché le versioni sono specificate nella distinta materiali (BOM) di Spring Boot.

3. Attuatore Spring Boot 2.x

In 2.x, Actuator mantiene il suo intento fondamentale ma semplifica il suo modello, estende le sue capacità e incorpora impostazioni predefinite migliori.

Innanzitutto, questa versione diventa indipendente dalla tecnologia. Inoltre semplifica il suo modello di sicurezza fondendolo con quello dell'applicazione.

Tra le varie modifiche, è importante tenere presente che alcune di esse si stanno rompendo. Ciò include richieste e risposte HTTP, nonché API Java.

Infine, l'ultima versione ora supporta il modello CRUD rispetto al vecchio modello di lettura / scrittura.

3.1. Supporto tecnologico

Con la sua seconda versione principale, Actuator è ora indipendente dalla tecnologia mentre in 1.x era legato a MVC, quindi all'API Servlet.

In 2.x, Actuator definisce il suo modello come collegabile ed estensibile senza fare affidamento su MVC per questo.

Quindi, con questo nuovo modello, siamo in grado di sfruttare MVC e WebFlux come tecnologia web sottostante.

Inoltre, le tecnologie future potrebbero essere aggiunte implementando gli adattatori giusti.

Infine, JMX rimane supportato per esporre gli endpoint senza alcun codice aggiuntivo.

3.2. Cambiamenti importanti

A differenza delle versioni precedenti, Actuator viene fornito con la maggior parte degli endpoint disabilitati.

Pertanto, gli unici due disponibili per impostazione predefinita sono / health e / info .

Se vogliamo abilitarli tutti, potremmo impostare management.endpoints.web.exposure.include = * . In alternativa, possiamo elencare gli endpoint che dovrebbero essere abilitati.

Actuator ora condivide la configurazione di sicurezza con le normali regole di sicurezza dell'app, quindi il modello di sicurezza è notevolmente semplificato.

Pertanto, per modificare le regole di sicurezza dell'attuatore, potremmo semplicemente aggiungere una voce per / Actuator / ** :

@Bean public SecurityWebFilterChain securityWebFilterChain( ServerHttpSecurity http) { return http.authorizeExchange() .pathMatchers("/actuator/**").permitAll() .anyExchange().authenticated() .and().build(); }

Possiamo trovare ulteriori dettagli sui nuovissimi documenti ufficiali di Actuator.

Inoltre, per impostazione predefinita, tutti i punti finali dell'attuatore sono ora posizionati sotto il percorso / attuatore .

Come nella versione precedente, possiamo modificare questo percorso utilizzando la nuova proprietà management.endpoints.web.base-path .

3.3. Endpoint predefiniti

Diamo un'occhiata ad alcuni endpoint disponibili, la maggior parte dei quali erano già disponibili in 1.x.

Inoltre, alcuni endpoint sono stati aggiunti, alcuni rimossi e altri sono stati ristrutturati :

  • / auditevents elenca gli eventi relativi al controllo della sicurezza come il login / logout dell'utente. Inoltre, possiamo filtrare per principale o tipo tra gli altri campi.
  • / bean restituisce tutti i fagioli disponibili nella nostra BeanFactory . A differenza di / auditevents , non supporta il filtraggio.
  • / condition , precedentemente noto come / autoconfig , crea un report delle condizioni relative all'autoconfigurazione.
  • / configprops ci permette di recuperare tutti i bean @ConfigurationProperties .
  • /env returns the current environment properties. Additionally, we can retrieve single properties.
  • /flyway provides details about our Flyway database migrations.
  • /health summarizes the health status of our application.
  • /heapdump builds and returns a heap dump from the JVM used by our application.
  • /info returns general information. It might be custom data, build information or details about the latest commit.
  • /liquibase behaves like /flyway but for Liquibase.
  • /logfile returns ordinary application logs.
  • /loggers enables us to query and modify the logging level of our application.
  • /metrics details metrics of our application. This might include generic metrics as well as custom ones.
  • /prometheus returns metrics like the previous one, but formatted to work with a Prometheus server.
  • /scheduledtasks provides details about every scheduled task within our application.
  • /sessions lists HTTP sessions given we are using Spring Session.
  • /shutdown performs a graceful shutdown of the application.
  • /threaddump dumps the thread information of the underlying JVM.

3.4. Hypermedia for Actuator Endpoints

Spring Boot adds a discovery endpoint that returns links to all available actuator endpoints. This will facilitate discovering actuator endpoints and their corresponding URLs.

By default, this discovery endpoint is accessible through the /actuator endpoint.

Therefore, if we send a GET request to this URL, it'll return the actuator links for the various endpoints:

{ "_links": { "self": { "href": "//localhost:8080/actuator", "templated": false }, "features-arg0": { "href": "//localhost:8080/actuator/features/{arg0}", "templated": true }, "features": { "href": "//localhost:8080/actuator/features", "templated": false }, "beans": { "href": "//localhost:8080/actuator/beans", "templated": false }, "caches-cache": { "href": "//localhost:8080/actuator/caches/{cache}", "templated": true }, // truncated }

As shown above, the /actuator endpoint reports all available actuator endpoints under the _links field.

Moreover, if we configure a custom management base path, then we should use that base path as the discovery URL.

For instance, if we set the management.endpoints.web.base-path to /mgmt, then we should send a request to the /mgmt endpoint to see the list of links.

Quite interestingly, when the management base path is set to /, the discovery endpoint is disabled to prevent the possibility of a clash with other mappings.

3.5. Health Indicators

Just like in the previous version, we can add custom indicators easily. Opposite to other APIs, the abstractions for creating custom health endpoints remain unchanged. However, a new interface, ReactiveHealthIndicator, has been added to implement reactive health checks.

Let's have a look at a simple custom reactive health check:

@Component public class DownstreamServiceHealthIndicator implements ReactiveHealthIndicator { @Override public Mono health() { return checkDownstreamServiceHealth().onErrorResume( ex -> Mono.just(new Health.Builder().down(ex).build()) ); } private Mono checkDownstreamServiceHealth() { // we could use WebClient to check health reactively return Mono.just(new Health.Builder().up().build()); } }

A handy feature of health indicators is that we can aggregate them as part of a hierarchy.

So, following the previous example, we could group all downstream services under a downstream-services category. This category would be healthy as long as every nested service was reachable.

Check out our article on health indicators for a more in-depth look.

3.6. Health Groups

As of Spring Boot 2.2, we can organize health indicators into groups and apply the same configuration to all the group members.

For example, we can create a health group named custom by adding this to our application.properties:

management.endpoint.health.group.custom.include=diskSpace,ping

This way, the custom group contains the diskSpace and ping health indicators.

Now if we call the /actuator/health endpoint, it would tell us about the new health group in the JSON response:

{"status":"UP","groups":["custom"]}

With health groups, we can see the aggregated results of a few health indicators.

In this case, if we send a request to /actuator/health/custom, then:

{"status":"UP"}

We can configure the group to show more details via application.properties:

management.endpoint.health.group.custom.show-components=always management.endpoint.health.group.custom.show-details=always

Now if we send the same request to /actuator/health/custom, we'll see more details:

{ "status": "UP", "components": { "diskSpace": { "status": "UP", "details": { "total": 499963170816, "free": 91300069376, "threshold": 10485760 } }, "ping": { "status": "UP" } } }

It's also possible to show these details only for authorized users:

management.endpoint.health.group.custom.show-components=when_authorized management.endpoint.health.group.custom.show-details=when_authorized

We can also have a custom status mapping.

For instance, instead of an HTTP 200 OK response, it can return a 207 status code:

management.endpoint.health.group.custom.status.http-mapping.up=207

Here, we're telling Spring Boot to return a 207 HTTP status code if the custom group status is UP.

3.7. Metrics in Spring Boot 2

In Spring Boot 2.0, the in-house metrics were replaced with Micrometer support, so we can expect breaking changes. If our application was using metric services such as GaugeService or CounterService, they will no longer be available.

Instead, we're expected to interact with Micrometer directly. In Spring Boot 2.0, we'll get a bean of type MeterRegistry autoconfigured for us.

Furthermore, Micrometer is now part of Actuator's dependencies, so we should be good to go as long as the Actuator dependency is in the classpath.

Moreover, we'll get a completely new response from the /metrics endpoint:

{ "names": [ "jvm.gc.pause", "jvm.buffer.memory.used", "jvm.memory.used", "jvm.buffer.count", // ... ] }

As we can see, there are no actual metrics as we got in 1.x.

To get the actual value of a specific metric, we can now navigate to the desired metric, e.g., /actuator/metrics/jvm.gc.pause, and get a detailed response:

{ "name": "jvm.gc.pause", "measurements": [ { "statistic": "Count", "value": 3.0 }, { "statistic": "TotalTime", "value": 7.9E7 }, { "statistic": "Max", "value": 7.9E7 } ], "availableTags": [ { "tag": "cause", "values": [ "Metadata GC Threshold", "Allocation Failure" ] }, { "tag": "action", "values": [ "end of minor GC", "end of major GC" ] } ] }

Now metrics are much more thorough, including not only different values but also some associated metadata.

3.8. Customizing the /info Endpoint

The /info endpoint remains unchanged. As before, we can add git details using the respective Maven or Gradle dependency:

 pl.project13.maven git-commit-id-plugin 

Likewise, we could also include build information including name, group, and version using the Maven or Gradle plugin:

 org.springframework.boot spring-boot-maven-plugin    build-info    

3.9. Creating a Custom Endpoint

As we pointed out previously, we can create custom endpoints. However, Spring Boot 2 has redesigned the way to achieve this to support the new technology-agnostic paradigm.

Let's create an Actuator endpoint to query, enable, and disable feature flags in our application:

@Component @Endpoint(id = "features") public class FeaturesEndpoint { private Map features = new ConcurrentHashMap(); @ReadOperation public Map features() { return features; } @ReadOperation public Feature feature(@Selector String name) { return features.get(name); } @WriteOperation public void configureFeature(@Selector String name, Feature feature) { features.put(name, feature); } @DeleteOperation public void deleteFeature(@Selector String name) { features.remove(name); } public static class Feature { private Boolean enabled; // [...] getters and setters } }

To get the endpoint, we need a bean. In our example, we're using @Component for this. Also, we need to decorate this bean with @Endpoint.

The path of our endpoint is determined by the id parameter of @Endpoint. In our case, it'll route requests to /actuator/features.

Once ready, we can start defining operations using:

  • @ReadOperation: It'll map to HTTP GET.
  • @WriteOperation: It'll map to HTTP POST.
  • @DeleteOperation: It'll map to HTTP DELETE.

When we run the application with the previous endpoint in our application, Spring Boot will register it.

A quick way to verify this is to check the logs:

[...].WebFluxEndpointHandlerMapping: Mapped "{[/actuator/features/{name}], methods=[GET], produces=[application/vnd.spring-boot.actuator.v2+json || application/json]}" [...].WebFluxEndpointHandlerMapping : Mapped " application/json]" [...].WebFluxEndpointHandlerMapping : Mapped "{[/actuator/features/{name}], methods=[POST], consumes=[application/vnd.spring-boot.actuator.v2+json || application/json]}" [...].WebFluxEndpointHandlerMapping : Mapped "{[/actuator/features/{name}], methods=[DELETE]}"[...]

In the previous logs, we can see how WebFlux is exposing our new endpoint. If we switch to MVC, it'll simply delegate on that technology without having to change any code.

Also, we have a few important considerations to keep in mind with this new approach:

  • There are no dependencies with MVC.
  • All the metadata present as methods before (sensitive, enabled…) no longer exist. We can, however, enable or disable the endpoint using @Endpoint(id = “features”, enableByDefault = false).
  • Unlike in 1.x, there is no need to extend a given interface anymore.
  • In contrast with the old read/write model, we can now define DELETE operations using @DeleteOperation.

3.10. Extending Existing Endpoints

Let's imagine we want to make sure the production instance of our application is never a SNAPSHOT version.

We decide to do this by changing the HTTP status code of the Actuator endpoint that returns this information, i.e., /info. If our app happened to be a SNAPSHOT, we would get a different HTTP status code.

We can easily extend the behavior of a predefined endpoint using the @EndpointExtension annotations, or its more concrete specializations @EndpointWebExtension or @EndpointJmxExtension:

@Component @EndpointWebExtension(endpoint = InfoEndpoint.class) public class InfoWebEndpointExtension { private InfoEndpoint delegate; // standard constructor @ReadOperation public WebEndpointResponse info() { Map info = this.delegate.info(); Integer status = getStatus(info); return new WebEndpointResponse(info, status); } private Integer getStatus(Map info) { // return 5xx if this is a snapshot return 200; } }

3.11. Enable All Endpoints

In order to access the actuator endpoints using HTTP, we need to both enable and expose them.

By default, all endpoints but /shutdown are enabled. Only the /health and /info endpoints are exposed by default.

We need to add the following configuration to expose all endpoints:

management.endpoints.web.exposure.include=*

To explicitly enable a specific endpoint (e.g., /shutdown), we use:

management.endpoint.shutdown.enabled=true

To expose all enabled endpoints except one (e.g., /loggers), we use:

management.endpoints.web.exposure.include=* management.endpoints.web.exposure.exclude=loggers

4. Spring Boot 1.x Actuator

In 1.x, Actuator follows a read/write model, which means we can either read from it or write to it.

For example, we can retrieve metrics or the health of our application. Alternatively, we could gracefully terminate our app or change our logging configuration.

In order to get it working, Actuator requires Spring MVC to expose its endpoints through HTTP. No other technology is supported.

4.1. Endpoints

In 1.x, Actuator brings its own security model. It takes advantage of Spring Security constructs but needs to be configured independently from the rest of the application.

Also, most endpoints are sensitive — meaning they're not fully public, or most information will be omitted — while a handful are not, e.g., /info.

Here are some of the most common endpoints Boot provides out of the box:

  • /health shows application health information (a simple status when accessed over an unauthenticated connection or full message details when authenticated); it's not sensitive by default.
  • /info displays arbitrary application info; it's not sensitive by default.
  • /metrics shows metrics information for the current application; it's sensitive by default.
  • /trace displays trace information (by default the last few HTTP requests).

We can find the full list of existing endpoints over on the official docs.

4.2. Configuring Existing Endpoints

We can customize each endpoint with properties using the format endpoints.[endpoint name].[property to customize].

Three properties are available:

  • id: by which this endpoint will be accessed over HTTP
  • enabled: if true, then it can be accessed; otherwise not
  • sensitive: if true, then need the authorization to show crucial information over HTTP

For example, adding the following properties will customize the /beans endpoint:

endpoints.beans.id=springbeans endpoints.beans.sensitive=false endpoints.beans.enabled=true

4.3. /health Endpoint

The /health endpoint is used to check the health or state of the running application.

It's usually exercised by monitoring software to alert us if the running instance goes down or gets unhealthy for other reasons, e.g., connectivity issues with our DB, lack of disk space, etc.

By default, unauthorized users can only see status information when they access over HTTP:

{ "status" : "UP" } 

This health information is collected from all the beans implementing the HealthIndicator interface configured in our application context.

Some information returned by HealthIndicator is sensitive in nature, but we can configure endpoints.health.sensitive=false to expose more detailed information like disk space, messaging broker connectivity, custom checks, and more.

Note that this only works for Spring Boot versions below 1.5.0. For 1.5.0 and later versions, we should also disable security by setting management.security.enabled=false for unauthorized access.

We could also implement our own custom health indicator, which can collect any type of custom health data specific to the application and automatically expose it through the /health endpoint:

@Component("myHealthCheck") public class HealthCheck 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(); } public int check() { // Our logic to check health return 0; } } 

Here's how the output would look:

{ "status" : "DOWN", "myHealthCheck" : { "status" : "DOWN", "Error Code" : 1 }, "diskSpace" : { "status" : "UP", "free" : 209047318528, "threshold" : 10485760 } }

4.4. /info Endpoint

We can also customize the data shown by the /info endpoint:

info.app.name=Spring Sample Application info.app.description=This is my first spring boot application info.app.version=1.0.0

And the sample output:

{ "app" : { "version" : "1.0.0", "description" : "This is my first spring boot application", "name" : "Spring Sample Application" } }

4.5. /metrics Endpoint

The metrics endpoint publishes information about OS and JVM as well as application-level metrics. Once enabled, we get information such as memory, heap, processors, threads, classes loaded, classes unloaded, and thread pools along with some HTTP metrics as well.

Here's what the output of this endpoint looks like out of the box:

{ "mem" : 193024, "mem.free" : 87693, "processors" : 4, "instance.uptime" : 305027, "uptime" : 307077, "systemload.average" : 0.11, "heap.committed" : 193024, "heap.init" : 124928, "heap.used" : 105330, "heap" : 1764352, "threads.peak" : 22, "threads.daemon" : 19, "threads" : 22, "classes" : 5819, "classes.loaded" : 5819, "classes.unloaded" : 0, "gc.ps_scavenge.count" : 7, "gc.ps_scavenge.time" : 54, "gc.ps_marksweep.count" : 1, "gc.ps_marksweep.time" : 44, "httpsessions.max" : -1, "httpsessions.active" : 0, "counter.status.200.root" : 1, "gauge.response.root" : 37.0 } 

In order to gather custom metrics, we have support for gauges (single-value snapshots of data) and counters, i.e., incrementing/decrementing metrics.

Let's implement our own custom metrics into the /metrics endpoint.

We'll customize the login flow to record a successful and failed login attempt:

@Service public class LoginServiceImpl { private final CounterService counterService; public LoginServiceImpl(CounterService counterService) { this.counterService = counterService; } public boolean login(String userName, char[] password) { boolean success; if (userName.equals("admin") && "secret".toCharArray().equals(password)) { counterService.increment("counter.login.success"); success = true; } else { counterService.increment("counter.login.failure"); success = false; } return success; } }

Here's what the output might look like:

{ ... "counter.login.success" : 105, "counter.login.failure" : 12, ... } 

Note that login attempts and other security-related events are available out of the box in Actuator as audit events.

4.6. Creating a New Endpoint

In addition to using the existing endpoints provided by Spring Boot, we can also create an entirely new one.

First, we need to have the new endpoint implement the Endpoint interface:

@Component public class CustomEndpoint implements Endpoint
     
       { @Override public String getId() { return "customEndpoint"; } @Override public boolean isEnabled() { return true; } @Override public boolean isSensitive() { return true; } @Override public List invoke() { // Custom logic to build the output List messages = new ArrayList(); messages.add("This is message 1"); messages.add("This is message 2"); return messages; } }
     

In order to access this new endpoint, its id is used to map it. In other words we could exercise it hitting /customEndpoint.

Output:

[ "This is message 1", "This is message 2" ]

4.7. Further Customization

For security purposes, we might choose to expose the actuator endpoints over a non-standard port — the management.port property can easily be used to configure that.

Also, as we already mentioned, in 1.x. Actuator configures its own security model based on Spring Security but independent from the rest of the application.

Hence, we can change the management.address property to restrict where the endpoints can be accessed from over the network:

#port used to expose actuator management.port=8081 #CIDR allowed to hit actuator management.address=127.0.0.1 #Whether security should be enabled or disabled altogether management.security.enabled=false

Besides, all the built-in endpoints except /info are sensitive by default.

If the application is using Spring Security, we can secure these endpoints by defining the default security properties (username, password, and role) in the application.properties file:

security.user.name=admin security.user.password=secret management.security.role=SUPERUSER

5. Conclusion

In this article, we talked about Spring Boot Actuator. We began by defining what Actuator means and what it does for us.

Next, we focused on Actuator for the current Spring Boot version 2.x, discussing how to use it, tweak it, and extend it. We also talked about the important security changes that we can find in this new iteration. We discussed some popular endpoints and how they have changed as well.

Then we discussed Actuator in the earlier Spring Boot 1 version.

Lastly, we demonstrated how to customize and extend Actuator.

As always, the code used in this article can be found over on GitHub for both Spring Boot 2.x and Spring Boot 1.x.