Polish 'Support OpenMetrics text format with Prometheus'

Closes gh-25564

Author: philwebb

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

@@ -24,14 +24,12 @@
 
 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.WebEndpointResponse;
 import org.springframework.boot.actuate.endpoint.web.annotation.WebEndpoint;
 import org.springframework.lang.Nullable;
-import org.springframework.util.MimeType;
 
 /**
  * {@link Endpoint @Endpoint} that outputs metrics in a format that can be scraped by the
@@ -50,30 +48,19 @@ public PrometheusScrapeEndpoint(CollectorRegistry collectorRegistry) {
 		this.collectorRegistry = collectorRegistry;
 	}
 
-	@ReadOperation(produces = { TextFormat.CONTENT_TYPE_004, TextFormat.CONTENT_TYPE_OPENMETRICS_100 })
-	public WebEndpointResponse<String> scrape(ProducibleTextFormat producibleTextFormat,
-			@Nullable Set<String> includedNames) {
+	@ReadOperation(producesFrom = TextOutputFormat.class)
+	public WebEndpointResponse<String> scrape(TextOutputFormat format, @Nullable Set<String> includedNames) {
 		try {
 			Writer writer = new StringWriter();
 			Enumeration<MetricFamilySamples> samples = (includedNames != null)
 					? this.collectorRegistry.filteredMetricFamilySamples(includedNames)
 					: this.collectorRegistry.metricFamilySamples();
-			MimeType contentType = producibleTextFormat.getMimeType();
-			if (producibleTextFormat == ProducibleTextFormat.CONTENT_TYPE_004) {
-				TextFormat.write004(writer, samples);
-			}
-			else if (producibleTextFormat == ProducibleTextFormat.CONTENT_TYPE_OPENMETRICS_100) {
-				TextFormat.writeOpenMetrics100(writer, samples);
-			}
-			else {
-				throw new RuntimeException("Unsupported text format '" + producibleTextFormat.getMimeType() + "'");
-			}
-			return new WebEndpointResponse<>(writer.toString(), contentType);
+			format.write(writer, samples);
+			return new WebEndpointResponse<>(writer.toString(), format);
 		}
 		catch (IOException ex) {
-			// This actually never happens since StringWriter::write() doesn't throw any
-			// IOException
-			throw new RuntimeException("Writing metrics failed", ex);
+			// This actually never happens since StringWriter doesn't throw an IOException
+			throw new IllegalStateException("Writing metrics failed", ex);
 		}
 	}
 

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/metrics/export/prometheus/ProducibleTextFormat.java renamed to spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/metrics/export/prometheus/TextOutputFormat.java

@@ -16,39 +16,60 @@
 
 package org.springframework.boot.actuate.metrics.export.prometheus;
 
+import java.io.IOException;
+import java.io.Writer;
+import java.util.Enumeration;
+
+import io.prometheus.client.Collector.MetricFamilySamples;
 import io.prometheus.client.exporter.common.TextFormat;
 
-import org.springframework.boot.actuate.endpoint.http.Producible;
+import org.springframework.boot.actuate.endpoint.annotation.Producible;
 import org.springframework.util.MimeType;
 import org.springframework.util.MimeTypeUtils;
 
 /**
- * A {@link Producible} for Prometheus's {@link TextFormat}.
+ * A {@link Producible} enum for supported Prometheus {@link TextFormat}.
  *
  * @author Andy Wilkinson
  * @since 2.5.0
  */
-public enum ProducibleTextFormat implements Producible<ProducibleTextFormat> {
+public enum TextOutputFormat implements Producible<TextOutputFormat> {
 
 	/**
 	 * Openmetrics text version 1.0.0.
 	 */
-	CONTENT_TYPE_OPENMETRICS_100(TextFormat.CONTENT_TYPE_OPENMETRICS_100),
+	CONTENT_TYPE_OPENMETRICS_100(TextFormat.CONTENT_TYPE_OPENMETRICS_100) {
+
+		@Override
+		void write(Writer writer, Enumeration<MetricFamilySamples> samples) throws IOException {
+			TextFormat.writeOpenMetrics100(writer, samples);
+		}
+
+	},
 
 	/**
 	 * Prometheus text version 0.0.4.
 	 */
-	CONTENT_TYPE_004(TextFormat.CONTENT_TYPE_004);
+	CONTENT_TYPE_004(TextFormat.CONTENT_TYPE_004) {
+
+		@Override
+		void write(Writer writer, Enumeration<MetricFamilySamples> samples) throws IOException {
+			TextFormat.write004(writer, samples);
+		}
+
+	};
 
 	private final MimeType mimeType;
 
-	ProducibleTextFormat(String mimeType) {
+	TextOutputFormat(String mimeType) {
 		this.mimeType = MimeTypeUtils.parseMimeType(mimeType);
 	}
 
 	@Override
-	public MimeType getMimeType() {
+	public MimeType getProducedMimeType() {
 		return this.mimeType;
 	}
 
+	abstract void write(Writer writer, Enumeration<MetricFamilySamples> samples) throws IOException;
+
 }