set root cause as the exception_name in micrometer tags

core/src/main/java/feign/utils/ExceptionUtils.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2012-2022 The Feign Authors
+ *
+ * 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
+ *
+ * http://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 feign.utils;
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class ExceptionUtils {
+  /**
+   * Introspects the {@link Throwable} to obtain the root cause.
+   *
+   * <p>
+   * This method walks through the exception chain to the last element, "root" of the tree, using
+   * {@link Throwable#getCause()}, and returns that exception.
+   *
+   * @param throwable the throwable to get the root cause for, may be null
+   * @return the root cause of the {@link Throwable}, {@code null} if null throwable input
+   */
+  public static Throwable getRootCause(Throwable throwable) {
+    if (throwable == null) {
+      return null;
+    }
+    Throwable rootCause = throwable;
+    // this is to avoid infinite loops for recursive cases
+    final Set<Throwable> seenThrowables = new HashSet<>();
+    seenThrowables.add(rootCause);
+    while ((rootCause.getCause() != null && !seenThrowables.contains(rootCause.getCause()))) {
+      seenThrowables.add(rootCause.getCause());
+      rootCause = rootCause.getCause();
+    }
+    return rootCause;
+  }
+}

core/src/test/java/feign/utils/ExceptionUtilsTest.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2012-2022 The Feign Authors
+ *
+ * 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
+ *
+ * http://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 feign.utils;
+
+import org.junit.Test;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class ExceptionUtilsTest {
+  @Test
+  public void rootCauseOfNullIsNull() {
+    Throwable e = null;
+    Throwable rootCause = ExceptionUtils.getRootCause(e);
+    assertThat(rootCause).isNull();
+  }
+
+  @Test
+  public void rootCauseIsSelf() {
+    Throwable e = new Exception();
+    Throwable rootCause = ExceptionUtils.getRootCause(e);
+    assertThat(rootCause).isSameAs(e);
+  }
+
+  @Test
+  public void rootCauseIsDifferent() {
+    Throwable rootCause = new Exception();
+    Throwable e = new Exception(rootCause);
+    Throwable actualRootCause = ExceptionUtils.getRootCause(e);
+    assertThat(actualRootCause).isSameAs(rootCause);
+  }
+}

dropwizard-metrics4/src/main/java/feign/metrics4/BaseMeteredClient.java

@@ -18,6 +18,7 @@
 import feign.FeignException;
 import feign.RequestTemplate;
 import feign.Response;
+import feign.utils.ExceptionUtils;
 
 class BaseMeteredClient {
 
@@ -64,7 +65,7 @@ protected void recordFailure(RequestTemplate template, FeignException e) {
             MetricRegistry.name(
                 httpResponseCode(template),
                 "exception_name",
-                e.getClass().getSimpleName(),
+                ExceptionUtils.getRootCause(e).getClass().getSimpleName(),
                 "status_group",
                 e.status() / 100 + "xx",
                 "http_status",
@@ -81,7 +82,7 @@ protected void recordFailure(RequestTemplate template, Exception e) {
             MetricRegistry.name(
                 httpResponseCode(template),
                 "exception_name",
-                e.getClass().getSimpleName(),
+                ExceptionUtils.getRootCause(e).getClass().getSimpleName(),
                 "uri",
                 template.methodMetadata().template().path()),
             metricSuppliers.meters())

dropwizard-metrics5/src/main/java/feign/metrics5/BaseMeteredClient.java

@@ -17,6 +17,7 @@
 import feign.FeignException;
 import feign.RequestTemplate;
 import feign.Response;
+import feign.utils.ExceptionUtils;
 import io.dropwizard.metrics5.MetricName;
 import io.dropwizard.metrics5.MetricRegistry;
 import io.dropwizard.metrics5.Timer;
@@ -59,7 +60,7 @@ protected void recordFailure(RequestTemplate template, FeignException e) {
     metricRegistry
         .counter(
             httpResponseCode(template)
-                .tagged("exception_name", e.getClass().getSimpleName())
+                .tagged("exception_name", ExceptionUtils.getRootCause(e).getClass().getSimpleName())
                 .tagged("http_status", String.valueOf(e.status()))
                 .tagged("status_group", e.status() / 100 + "xx")
                 .tagged("uri", template.methodMetadata().template().path()))
@@ -70,7 +71,7 @@ protected void recordFailure(RequestTemplate template, Exception e) {
     metricRegistry
         .counter(
             httpResponseCode(template)
-                .tagged("exception_name", e.getClass().getSimpleName())
+                .tagged("exception_name", ExceptionUtils.getRootCause(e).getClass().getSimpleName())
                 .tagged("uri", template.methodMetadata().template().path()))
         .inc();
   }

dropwizard-metrics5/src/main/java/feign/metrics5/MeteredDecoder.java

@@ -21,6 +21,7 @@
 import feign.Response;
 import feign.codec.DecodeException;
 import feign.codec.Decoder;
+import feign.utils.ExceptionUtils;
 import io.dropwizard.metrics5.MetricRegistry;
 import io.dropwizard.metrics5.Timer.Context;
 
@@ -63,14 +64,14 @@ public Object decode(Response response, Type type)
     } catch (IOException | RuntimeException e) {
       metricRegistry.meter(
           metricName.metricName(template.methodMetadata(), template.feignTarget(), "error_count")
-              .tagged("exception_name", e.getClass().getSimpleName())
+              .tagged("exception_name", ExceptionUtils.getRootCause(e).getClass().getSimpleName())
               .tagged("uri", template.methodMetadata().template().path()),
           metricSuppliers.meters()).mark();
       throw e;
     } catch (Exception e) {
       metricRegistry.meter(
           metricName.metricName(template.methodMetadata(), template.feignTarget(), "error_count")
-              .tagged("exception_name", e.getClass().getSimpleName())
+              .tagged("exception_name", ExceptionUtils.getRootCause(e).getClass().getSimpleName())
               .tagged("uri", template.methodMetadata().template().path()),
           metricSuppliers.meters()).mark();
       throw new IOException(e);

dropwizard-metrics5/src/main/java/feign/metrics5/MeteredInvocationHandleFactory.java

@@ -14,6 +14,7 @@
 package feign.metrics5;
 
 
+import feign.utils.ExceptionUtils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import java.lang.reflect.InvocationHandler;
@@ -86,7 +87,8 @@ public InvocationHandler create(Target target, Map<Method, MethodHandler> dispat
         metricRegistry
             .meter(metricName.metricName(clientClass, method, target.url())
                 .resolve("exception")
-                .tagged("exception_name", e.getClass().getSimpleName()),
+                .tagged("exception_name",
+                    ExceptionUtils.getRootCause(e).getClass().getSimpleName()),
                 metricSuppliers.meters())
             .mark();
 

micrometer/src/main/java/feign/micrometer/FeignMetricTagResolver.java

@@ -15,6 +15,7 @@
 
 import feign.MethodMetadata;
 import feign.Target;
+import feign.utils.ExceptionUtils;
 import io.micrometer.core.instrument.Tag;
 import io.micrometer.core.instrument.Tags;
 import java.lang.reflect.Method;
@@ -49,7 +50,7 @@ public Tags tag(Class<?> targetType, Method method, String url, Throwable e, Tag
     tags.add(Tag.of("method", method.getName()));
     tags.add(Tag.of("host", extractHost(url)));
     if (e != null) {
-      tags.add(Tag.of("exception_name", e.getClass().getSimpleName()));
+      tags.add(Tag.of("exception_name", ExceptionUtils.getRootCause(e).getClass().getSimpleName()));
     }
     tags.addAll(Arrays.asList(extraTags));
     return Tags.of(tags);
@@ -72,4 +73,5 @@ private String extractHost(final String targetUrl) {
         ? targetUrl
         : targetUrl.substring(0, 20);
   }
+
 }

micrometer/src/main/java/feign/micrometer/MeteredDecoder.java

@@ -18,6 +18,7 @@
 import feign.RequestTemplate;
 import feign.Response;
 import feign.codec.Decoder;
+import feign.utils.ExceptionUtils;
 import io.micrometer.core.instrument.*;
 import java.io.IOException;
 import java.lang.reflect.Type;
@@ -95,7 +96,7 @@ protected Counter createExceptionCounter(Response response, Type type, Exception
     final RequestTemplate template = response.request().requestTemplate();
     final Tags allTags = metricTagResolver.tag(template.methodMetadata(), template.feignTarget(),
         Tag.of("uri", template.methodMetadata().template().path()),
-        Tag.of("exception_name", e.getClass().getSimpleName()))
+        Tag.of("exception_name", ExceptionUtils.getRootCause(e).getClass().getSimpleName()))
         .and(extraTags);
     return meterRegistry.counter(metricName.name("error_count"), allTags);
   }