Jetty Client instrumentation with Observation API (#3416)

Allow configuring an ObservationRegistry so that the JettyClientMetrics can instrument with Observation API in addition to its prior instrumentation with `Timer`.

micrometer-core/src/main/java/io/micrometer/core/instrument/binder/http/Outcome.java

@@ -15,6 +15,7 @@
  */
 package io.micrometer.core.instrument.binder.http;
 
+import io.micrometer.common.KeyValue;
 import io.micrometer.core.instrument.Tag;
 
 /**
@@ -57,8 +58,11 @@ public enum Outcome {
 
     private final Tag tag;
 
+    private final KeyValue keyValue;
+
     Outcome() {
         this.tag = Tag.of("outcome", name());
+        this.keyValue = KeyValue.of("outcome", name());
     }
 
     /**
@@ -69,6 +73,15 @@ public Tag asTag() {
         return this.tag;
     }
 
+    /**
+     * Returns the {@code Outcome} as a {@link KeyValue} named {@code outcome}.
+     * @return the {@code outcome} {@code KeyValue}
+     * @since 1.11.0
+     */
+    public KeyValue asKeyValue() {
+        return this.keyValue;
+    }
+
     /**
      * Return the {@code Outcome} for the given HTTP {@code status} code.
      * @param status the HTTP status code

micrometer-core/src/main/java/io/micrometer/core/instrument/binder/jetty/DefaultJettyClientObservationConvention.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2022 VMware, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.micrometer.core.instrument.binder.jetty;
+
+import io.micrometer.common.KeyValues;
+import org.eclipse.jetty.client.api.Request;
+import org.eclipse.jetty.client.api.Result;
+
+/**
+ * Default implementation of {@link JettyClientObservationConvention}.
+ *
+ * @since 1.11.0
+ */
+public class DefaultJettyClientObservationConvention implements JettyClientObservationConvention {
+
+    public static DefaultJettyClientObservationConvention INSTANCE = new DefaultJettyClientObservationConvention();
+
+    @Override
+    public KeyValues getLowCardinalityKeyValues(JettyClientContext context) {
+        Request request = context.getCarrier();
+        Result result = context.getResponse();
+        return KeyValues.of(JettyClientKeyValues.method(request), JettyClientKeyValues.host(request),
+                JettyClientKeyValues.uri(request, result, context.getUriPatternFunction()),
+                JettyClientKeyValues.exception(result), JettyClientKeyValues.status(result),
+                JettyClientKeyValues.outcome(result));
+    }
+
+    @Override
+    public String getName() {
+        return JettyClientMetrics.DEFAULT_JETTY_CLIENT_REQUESTS_TIMER_NAME;
+    }
+
+}

micrometer-core/src/main/java/io/micrometer/core/instrument/binder/jetty/JettyClientContext.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2022 VMware, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.micrometer.core.instrument.binder.jetty;
+
+import io.micrometer.observation.transport.RequestReplySenderContext;
+import org.eclipse.jetty.client.api.Request;
+import org.eclipse.jetty.client.api.Result;
+
+import java.util.Objects;
+import java.util.function.BiFunction;
+
+/**
+ * Context to use when instrumenting Jetty client metrics with the Observation API.
+ *
+ * @since 1.11.0
+ * @see JettyClientMetrics
+ */
+public class JettyClientContext extends RequestReplySenderContext<Request, Result> {
+
+    private final BiFunction<Request, Result, String> uriPatternFunction;
+
+    public JettyClientContext(Request request, BiFunction<Request, Result, String> uriPatternFunction) {
+        super((carrier, key, value) -> Objects.requireNonNull(carrier).header(key, value));
+        this.uriPatternFunction = uriPatternFunction;
+        setCarrier(request);
+    }
+
+    public BiFunction<Request, Result, String> getUriPatternFunction() {
+        return uriPatternFunction;
+    }
+
+}

micrometer-core/src/main/java/io/micrometer/core/instrument/binder/jetty/JettyClientKeyValues.java

@@ -0,0 +1,163 @@
+/*
+ * Copyright 2022 VMware, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.micrometer.core.instrument.binder.jetty;
+
+import io.micrometer.common.KeyValue;
+import io.micrometer.common.lang.Nullable;
+import io.micrometer.common.util.StringUtils;
+import io.micrometer.core.instrument.binder.http.Outcome;
+import org.eclipse.jetty.client.api.Request;
+import org.eclipse.jetty.client.api.Result;
+import org.eclipse.jetty.http.HttpStatus;
+
+import java.util.function.BiFunction;
+import java.util.regex.Pattern;
+
+/**
+ * Factory methods for {@link KeyValue} associated with a request-response exchange that
+ * is handled by Jetty {@link org.eclipse.jetty.client.HttpClient}.
+ *
+ * @author Jon Schneider
+ * @since 1.11.0
+ */
+public final class JettyClientKeyValues {
+
+    private static final KeyValue URI_NOT_FOUND = KeyValue.of("uri", "NOT_FOUND");
+
+    private static final KeyValue URI_REDIRECTION = KeyValue.of("uri", "REDIRECTION");
+
+    private static final KeyValue URI_ROOT = KeyValue.of("uri", "root");
+
+    private static final KeyValue EXCEPTION_NONE = KeyValue.of("exception", "None");
+
+    private static final KeyValue EXCEPTION_UNKNOWN = KeyValue.of("exception", "UNKNOWN");
+
+    private static final KeyValue METHOD_UNKNOWN = KeyValue.of("method", "UNKNOWN");
+
+    private static final KeyValue HOST_UNKNOWN = KeyValue.of("host", "UNKNOWN");
+
+    public static final KeyValue STATUS_UNKNOWN = KeyValue.of("status", "UNKNOWN");
+
+    private static final Pattern TRAILING_SLASH_PATTERN = Pattern.compile("/$");
+
+    private static final Pattern MULTIPLE_SLASH_PATTERN = Pattern.compile("//+");
+
+    private static final KeyValue OUTCOME_UNKNOWN = KeyValue.of("outcome", "UNKNOWN");
+
+    private JettyClientKeyValues() {
+    }
+
+    /**
+     * Creates a {@code method} KeyValue based on the {@link Request#getMethod() method}
+     * of the given {@code request}.
+     * @param request the request
+     * @return the method KeyValue whose value is a capitalized method (e.g. GET).
+     */
+    public static KeyValue method(Request request) {
+        return (request != null) ? KeyValue.of("method", request.getMethod()) : METHOD_UNKNOWN;
+    }
+
+    /**
+     * Creates a {@code host} KeyValue based on the {@link Request#getHost()} of the given
+     * {@code request}.
+     * @param request the request
+     * @return the host KeyValue derived from request
+     * @since 1.7.0
+     */
+    public static KeyValue host(Request request) {
+        return (request != null) ? KeyValue.of("host", request.getHost()) : HOST_UNKNOWN;
+    }
+
+    /**
+     * Creates a {@code status} KeyValue based on the status of the given {@code result}.
+     * @param result the request result
+     * @return the status KeyValue derived from the status of the response
+     */
+    public static KeyValue status(@Nullable Result result) {
+        return result != null ? KeyValue.of("status", Integer.toString(result.getResponse().getStatus()))
+                : STATUS_UNKNOWN;
+    }
+
+    /**
+     * Creates a {@code uri} KeyValue based on the URI of the given {@code result}.
+     * {@code REDIRECTION} for 3xx responses, {@code NOT_FOUND} for 404 responses.
+     * @param result the request result
+     * @param successfulUriPattern successful URI pattern
+     * @return the uri KeyValue derived from the request result
+     */
+    public static KeyValue uri(Request request, @Nullable Result result,
+            BiFunction<Request, Result, String> successfulUriPattern) {
+        if (result != null && result.getResponse() != null) {
+            int status = result.getResponse().getStatus();
+            if (HttpStatus.isRedirection(status)) {
+                return URI_REDIRECTION;
+            }
+            if (status == 404) {
+                return URI_NOT_FOUND;
+            }
+        }
+
+        String matchingPattern = successfulUriPattern.apply(request, result);
+        matchingPattern = MULTIPLE_SLASH_PATTERN.matcher(matchingPattern).replaceAll("/");
+        if (matchingPattern.equals("/")) {
+            return URI_ROOT;
+        }
+        matchingPattern = TRAILING_SLASH_PATTERN.matcher(matchingPattern).replaceAll("");
+        return KeyValue.of("uri", matchingPattern);
+    }
+
+    /**
+     * Creates an {@code exception} KeyValue based on the {@link Class#getSimpleName()
+     * simple name} of the class of the given {@code exception}.
+     * @param result the request result
+     * @return the exception KeyValue derived from the exception
+     */
+    public static KeyValue exception(@Nullable Result result) {
+        if (result == null) {
+            return EXCEPTION_UNKNOWN;
+        }
+        Throwable exception = result.getFailure();
+        if (exception == null) {
+            return EXCEPTION_NONE;
+        }
+        if (result.getResponse() != null) {
+            int status = result.getResponse().getStatus();
+            if (status == 404 || HttpStatus.isRedirection(status)) {
+                return EXCEPTION_NONE;
+            }
+        }
+        if (exception.getCause() != null) {
+            exception = exception.getCause();
+        }
+        String simpleName = exception.getClass().getSimpleName();
+        return KeyValue.of("exception",
+                StringUtils.isNotEmpty(simpleName) ? simpleName : exception.getClass().getName());
+    }
+
+    /**
+     * Creates an {@code outcome} KeyValue based on the status of the given
+     * {@code result}.
+     * @param result the request result
+     * @return the outcome KeyValue derived from the status of the response
+     */
+    public static KeyValue outcome(@Nullable Result result) {
+        if (result == null) {
+            return OUTCOME_UNKNOWN;
+        }
+        return Outcome.forStatus(result.getResponse().getStatus()).asKeyValue();
+    }
+
+}