Support filtered scrape for Prometheus

See gh-21545

spring-boot-project/spring-boot-actuator-autoconfigure/src/docs/asciidoc/endpoints/prometheus.adoc

@@ -15,3 +15,14 @@ include::{snippets}/prometheus/curl-request.adoc[]
 The resulting response is similar to the following:
 
 include::{snippets}/prometheus/http-response.adoc[]
+
+
+
+[[prometheus-retrieving-query-parameters]]
+=== Query Parameters
+
+The endpoint uses query parameters to limit the samples that it returns.
+The following table shows the supported query parameters:
+
+[cols="2,4"]
+include::{snippets}/prometheus/request-parameters.adoc[]

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/endpoint/web/documentation/PrometheusScrapeEndpointDocumentationTests.java

 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -28,6 +28,8 @@ import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
 
 import static org.springframework.restdocs.mockmvc.MockMvcRestDocumentation.document;
+import static org.springframework.restdocs.request.RequestDocumentation.parameterWithName;
+import static org.springframework.restdocs.request.RequestDocumentation.requestParameters;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
 
@@ -35,6 +37,7 @@ import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.
  * Tests for generating documentation describing the {@link PrometheusScrapeEndpoint}.
  *
  * @author Andy Wilkinson
+ * @author Johnny Lim
  */
 class PrometheusScrapeEndpointDocumentationTests extends MockMvcEndpointDocumentationTests {
 
@@ -43,6 +46,16 @@ class PrometheusScrapeEndpointDocumentationTests extends MockMvcEndpointDocument
 		this.mockMvc.perform(get("/actuator/prometheus")).andExpect(status().isOk()).andDo(document("prometheus"));
 	}
 
+	@Test
+	void filteredPrometheus() throws Exception {
+		this.mockMvc
+				.perform(get("/actuator/prometheus").param("includedNames",
+						"jvm_memory_used_bytes,jvm_memory_committed_bytes"))
+				.andExpect(status().isOk())
+				.andDo(document("prometheus", requestParameters(parameterWithName("includedNames")
+						.description("Restricts the samples to those that match the names. Optional.").optional())));
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	@Import(BaseDocumentationConfiguration.class)
 	static class TestConfiguration {

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/metrics/export/prometheus/PrometheusScrapeEndpoint.java

 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,19 +19,24 @@ package org.springframework.boot.actuate.metrics.export.prometheus;
 import java.io.IOException;
 import java.io.StringWriter;
 import java.io.Writer;
+import java.util.Enumeration;
+import java.util.Set;
 
+import io.prometheus.client.Collector.MetricFamilySamples;
 import io.prometheus.client.CollectorRegistry;
 import io.prometheus.client.exporter.common.TextFormat;
 
 import org.springframework.boot.actuate.endpoint.annotation.Endpoint;
 import org.springframework.boot.actuate.endpoint.annotation.ReadOperation;
 import org.springframework.boot.actuate.endpoint.web.annotation.WebEndpoint;
+import org.springframework.lang.Nullable;
 
 /**
  * {@link Endpoint @Endpoint} that outputs metrics in a format that can be scraped by the
  * Prometheus server.
  *
  * @author Jon Schneider
+ * @author Johnny Lim
  * @since 2.0.0
  */
 @WebEndpoint(id = "prometheus")
@@ -44,10 +49,13 @@ public class PrometheusScrapeEndpoint {
 	}
 
 	@ReadOperation(produces = TextFormat.CONTENT_TYPE_004)
-	public String scrape() {
+	public String scrape(@Nullable Set<String> includedNames) {
 		try {
 			Writer writer = new StringWriter();
-			TextFormat.write004(writer, this.collectorRegistry.metricFamilySamples());
+			Enumeration<MetricFamilySamples> samples = (includedNames != null)
+					? this.collectorRegistry.filteredMetricFamilySamples(includedNames)
+					: this.collectorRegistry.metricFamilySamples();
+			TextFormat.write004(writer, samples);
 			return writer.toString();
 		}
 		catch (IOException ex) {

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/metrics/export/prometheus/PrometheusScrapeEndpointIntegrationTests.java

 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,6 +17,7 @@
 package org.springframework.boot.actuate.metrics.export.prometheus;
 
 import io.micrometer.core.instrument.Clock;
+import io.micrometer.core.instrument.Counter;
 import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.prometheus.PrometheusMeterRegistry;
 import io.prometheus.client.CollectorRegistry;
@@ -28,17 +29,30 @@ import org.springframework.context.annotation.Configuration;
 import org.springframework.http.MediaType;
 import org.springframework.test.web.reactive.server.WebTestClient;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 /**
  * Tests for {@link PrometheusScrapeEndpoint}.
  *
  * @author Jon Schneider
+ * @author Johnny Lim
  */
 class PrometheusScrapeEndpointIntegrationTests {
 
 	@WebEndpointTest
 	void scrapeHasContentTypeText004(WebTestClient client) {
 		client.get().uri("/actuator/prometheus").exchange().expectStatus().isOk().expectHeader()
-				.contentType(MediaType.parseMediaType(TextFormat.CONTENT_TYPE_004));
+				.contentType(MediaType.parseMediaType(TextFormat.CONTENT_TYPE_004)).expectBody(String.class)
+				.value((body) -> assertThat(body).contains("counter1_total").contains("counter2_total")
+						.contains("counter3_total"));
+	}
+
+	@WebEndpointTest
+	void scrapeWithIncludedNames(WebTestClient client) {
+		client.get().uri("/actuator/prometheus?includedNames=counter1_total,counter2_total").exchange().expectStatus()
+				.isOk().expectHeader().contentType(MediaType.parseMediaType(TextFormat.CONTENT_TYPE_004))
+				.expectBody(String.class).value((body) -> assertThat(body).contains("counter1_total")
+						.contains("counter2_total").doesNotContain("counter3_total"));
 	}
 
 	@Configuration(proxyBeanMethods = false)
@@ -56,7 +70,11 @@ class PrometheusScrapeEndpointIntegrationTests {
 
 		@Bean
 		MeterRegistry registry(CollectorRegistry registry) {
-			return new PrometheusMeterRegistry((k) -> null, registry, Clock.SYSTEM);
+			PrometheusMeterRegistry meterRegistry = new PrometheusMeterRegistry((k) -> null, registry, Clock.SYSTEM);
+			Counter.builder("counter1").register(meterRegistry);
+			Counter.builder("counter2").register(meterRegistry);
+			Counter.builder("counter3").register(meterRegistry);
+			return meterRegistry;
 		}
 
 	}