Add HttpServer#metrics(boolean, Function<String, String>, Function<St…

…ring, String>)

Add HttpServer#metrics(boolean, Supplier<? extends ChannelMetricsRecorder>, Function<String, String>, Function<String, String>)

reactor-netty-http/src/main/java/reactor/netty/http/server/AbstractHttpServerMetricsHandler.java

@@ -59,9 +59,13 @@ abstract class AbstractHttpServerMetricsHandler extends ChannelDuplexHandler {
 
 	long dataSentTime;
 
+	final Function<String, String> methodTagValue;
 	final Function<String, String> uriTagValue;
 
-	protected AbstractHttpServerMetricsHandler(@Nullable Function<String, String> uriTagValue) {
+	protected AbstractHttpServerMetricsHandler(
+			@Nullable Function<String, String> methodTagValue,
+			@Nullable Function<String, String> uriTagValue) {
+		this.methodTagValue = methodTagValue == null ? Function.identity() : methodTagValue;
 		this.uriTagValue = uriTagValue;
 	}
 
@@ -72,6 +76,7 @@ protected AbstractHttpServerMetricsHandler(AbstractHttpServerMetricsHandler copy
 		this.dataReceivedTime = copy.dataReceivedTime;
 		this.dataSent = copy.dataSent;
 		this.dataSentTime = copy.dataSentTime;
+		this.methodTagValue = copy.methodTagValue;
 		this.uriTagValue = copy.uriTagValue;
 	}
 
@@ -140,7 +145,7 @@ public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise)
 						HttpServerOperations ops = (HttpServerOperations) channelOps;
 						try {
 							recordWrite(ops, uriTagValue == null ? ops.path : uriTagValue.apply(ops.path),
-									ops.method().name(), ops.status().codeAsText().toString());
+									methodTagValue.apply(ops.method().name()), ops.status().codeAsText().toString());
 						}
 						catch (RuntimeException e) {
 							// Allow request-response exchange to continue, unaffected by metrics problem
@@ -191,7 +196,7 @@ public void channelRead(ChannelHandlerContext ctx, Object msg) {
 				ChannelOperations<?, ?> channelOps = ChannelOperations.get(ctx.channel());
 				if (channelOps instanceof HttpServerOperations) {
 					HttpServerOperations ops = (HttpServerOperations) channelOps;
-					recordRead(ops, uriTagValue == null ? ops.path : uriTagValue.apply(ops.path), ops.method().name());
+					recordRead(ops, uriTagValue == null ? ops.path : uriTagValue.apply(ops.path), methodTagValue.apply(ops.method().name()));
 				}
 
 				dataReceived = 0;

reactor-netty-http/src/main/java/reactor/netty/http/server/ContextAwareHttpServerMetricsHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021-2022 VMware, Inc. or its affiliates, All Rights Reserved.
+ * Copyright (c) 2021-2023 VMware, Inc. or its affiliates, All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -29,9 +29,11 @@ final class ContextAwareHttpServerMetricsHandler extends AbstractHttpServerMetri
 
 	final ContextAwareHttpServerMetricsRecorder recorder;
 
-	ContextAwareHttpServerMetricsHandler(ContextAwareHttpServerMetricsRecorder recorder,
+	ContextAwareHttpServerMetricsHandler(
+			ContextAwareHttpServerMetricsRecorder recorder,
+			@Nullable Function<String, String> methodTagValue,
 			@Nullable Function<String, String> uriTagValue) {
-		super(uriTagValue);
+		super(methodTagValue, uriTagValue);
 		this.recorder = recorder;
 	}
 

reactor-netty-http/src/main/java/reactor/netty/http/server/HttpServer.java

@@ -624,6 +624,73 @@ else if (configuration().metricsRecorder() != null) {
 		}
 	}
 
+	/**
+	 * Whether to enable metrics to be collected and registered in Micrometer's
+	 * {@link io.micrometer.core.instrument.Metrics#globalRegistry globalRegistry}
+	 * under the name {@link reactor.netty.Metrics#HTTP_SERVER_PREFIX}.
+	 * <p>{@code uriTagValue} function receives the actual uri and returns the uri tag value
+	 * that will be used for the metrics with {@link reactor.netty.Metrics#URI} tag.
+	 * For example instead of using the actual uri {@code "/users/1"} as uri tag value, templated uri
+	 * {@code "/users/{id}"} can be used.
+	 * <p><strong>Note:</strong>
+	 * It is strongly recommended to provide template-like form for the URIs. Without a conversion to a template-like form,
+	 * each distinct URI leads to the creation of a distinct tag, which takes a lot of memory for the metrics.
+	 * <p><strong>Note:</strong>
+	 * It is strongly recommended applications to configure an upper limit for the number of the URI tags.
+	 * For example:
+	 * <pre class="code">
+	 * Metrics.globalRegistry
+	 *        .config()
+	 *        .meterFilter(MeterFilter.maximumAllowableTags(HTTP_SERVER_PREFIX, URI, 100, MeterFilter.deny()));
+	 * </pre>
+	 * <p>{@code methodTagValue} function receives the actual method name and returns the method tag value
+	 * that will be used for the metrics with {@link reactor.netty.Metrics#METHOD} tag.
+	 * <p>By default metrics are not enabled.
+	 *
+	 * @param enable true enables metrics collection; false disables it
+	 * @param uriTagValue a function that receives the actual uri and returns the uri tag value
+	 * that will be used for the metrics with {@link reactor.netty.Metrics#URI} tag
+	 * @param methodTagValue a function that receives the actual method name and returns the method tag value
+	 * that will be used for the metrics with {@link reactor.netty.Metrics#METHOD} tag
+	 * @return a new {@link HttpServer}
+	 * @since 1.0.39
+	 */
+	public final HttpServer metrics(boolean enable, Function<String, String> uriTagValue, Function<String, String> methodTagValue) {
+		if (enable) {
+			Objects.requireNonNull(methodTagValue, "methodTagValue");
+			if (!Metrics.isInstrumentationAvailable()) {
+				throw new UnsupportedOperationException(
+						"To enable metrics, you must add the dependency `io.micrometer:micrometer-core`" +
+								" to the class path first");
+			}
+			if (uriTagValue == Function.<String>identity()) {
+				log.debug("Metrics are enabled with [uriTagValue=Function#identity]. " +
+						"It is strongly recommended to provide template-like form for the URIs. " +
+						"Without a conversion to a template-like form, each distinct URI leads " +
+						"to the creation of a distinct tag, which takes a lot of memory for the metrics.");
+			}
+			if (methodTagValue == Function.<String>identity()) {
+				log.debug("Metrics are enabled with [methodTagValue=Function#identity]. " +
+						"It is strongly recommended to provide a function for transforming the method names.");
+			}
+			HttpServer dup = duplicate();
+			dup.configuration().metricsRecorder(() -> configuration().defaultMetricsRecorder());
+			dup.configuration().methodTagValue = methodTagValue;
+			dup.configuration().uriTagValue = uriTagValue;
+			return dup;
+		}
+		else if (configuration().metricsRecorder() != null) {
+			HttpServer dup = duplicate();
+			dup.configuration().metricsRecorder(null);
+			dup.configuration().methodTagValue = null;
+			dup.configuration().uriTagValue = null;
+			return dup;
+		}
+		else {
+			return this;
+		}
+	}
+
 	@Override
 	public final HttpServer metrics(boolean enable, Supplier<? extends ChannelMetricsRecorder> recorder) {
 		return super.metrics(enable, recorder);
@@ -663,6 +730,49 @@ else if (configuration().metricsRecorder() != null) {
 		}
 	}
 
+	/**
+	 * Specifies whether the metrics are enabled on the {@link HttpServer}.
+	 * All generated metrics are provided to the specified recorder which is only
+	 * instantiated if metrics are being enabled (the instantiation is not lazy,
+	 * but happens immediately, while configuring the {@link HttpServer}).
+	 * <p>{@code uriValue} function receives the actual uri and returns the uri value
+	 * that will be used when the metrics are propagated to the recorder.
+	 * For example instead of using the actual uri {@code "/users/1"} as uri value, templated uri
+	 * {@code "/users/{id}"} can be used.
+	 * <p>{@code methodValue} function receives the actual method name and returns the method value
+	 * that will be used when the metrics are propagated to the recorder.
+	 *
+	 * @param enable true enables metrics collection; false disables it
+	 * @param recorder a supplier for the metrics recorder that receives the collected metrics
+	 * @param uriValue a function that receives the actual uri and returns the uri value
+	 * that will be used when the metrics are propagated to the recorder.
+	 * @param methodValue a function that receives the actual method name and returns the method value
+	 * that will be used when the metrics are propagated to the recorder.
+	 * @return a new {@link HttpServer}
+	 * @since 1.0.39
+	 */
+	public final HttpServer metrics(boolean enable, Supplier<? extends ChannelMetricsRecorder> recorder,
+			Function<String, String> uriValue, Function<String, String> methodValue) {
+		if (enable) {
+			Objects.requireNonNull(methodValue, "methodTagValue");
+			HttpServer dup = duplicate();
+			dup.configuration().metricsRecorder(recorder);
+			dup.configuration().methodTagValue = methodValue;
+			dup.configuration().uriTagValue = uriValue;
+			return dup;
+		}
+		else if (configuration().metricsRecorder() != null) {
+			HttpServer dup = duplicate();
+			dup.configuration().metricsRecorder(null);
+			dup.configuration().methodTagValue = null;
+			dup.configuration().uriTagValue = null;
+			return dup;
+		}
+		else {
+			return this;
+		}
+	}
+
 	/**
 	 * Removes any previously applied SSL configuration customization.
 	 *