Track number of exception that happen while decoding payload (#1288)

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

@@ -59,6 +59,18 @@ public class MeteredDecoder implements Decoder {
                 metricSuppliers.timers())
             .time()) {
       decoded = decoder.decode(response, type);
+    } catch (IOException | RuntimeException e) {
+      metricRegistry.meter(
+          metricName.metricName(template.methodMetadata(), template.feignTarget(), "error_count")
+              .tagged("exception_name", e.getClass().getSimpleName()),
+          metricSuppliers.meters()).mark();
+      throw e;
+    } catch (Exception e) {
+      metricRegistry.meter(
+          metricName.metricName(template.methodMetadata(), template.feignTarget(), "error_count")
+              .tagged("exception_name", e.getClass().getSimpleName()),
+          metricSuppliers.meters()).mark();
+      throw new IOException(e);
     }
 
     if (body != null) {

micrometer/src/main/java/feign/micrometer/FeignMetricName.java

@@ -23,7 +23,7 @@ import java.util.List;
 import feign.MethodMetadata;
 import feign.Target;
 import io.micrometer.core.instrument.Tag;
-import io.micrometer.core.instrument.config.NamingConvention;
+import io.micrometer.core.instrument.Tags;
 
 public final class FeignMetricName {
 
@@ -43,17 +43,17 @@ public final class FeignMetricName {
     return meteredComponent.getName();
   }
 
-  public List<Tag> tag(MethodMetadata methodMetadata, Target<?> target, Tag... tags) {
+  public Tags tag(MethodMetadata methodMetadata, Target<?> target, Tag... tags) {
     return tag(methodMetadata.targetType(), methodMetadata.method(), target.url(), tags);
   }
 
-  public List<Tag> tag(Class<?> targetType, Method method, String url, Tag... extraTags) {
+  public Tags tag(Class<?> targetType, Method method, String url, Tag... extraTags) {
     List<Tag> tags = new ArrayList<>();
     tags.add(Tag.of("client", targetType.getName()));
     tags.add(Tag.of("method", method.getName()));
     tags.add(Tag.of("host", extractHost(url)));
     tags.addAll(Arrays.asList(extraTags));
-    return tags;
+    return Tags.of(tags);
   }
 
   private String extractHost(final String targetUrl) {

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

@@ -23,6 +23,7 @@ import feign.Response;
 import feign.codec.DecodeException;
 import feign.codec.Decoder;
 import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.Tag;
 
 /**
  * Warp feign {@link Decoder} with metrics.
@@ -56,8 +57,18 @@ public class MeteredDecoder implements Decoder {
               metricName.tag(template.methodMetadata(), template.feignTarget()))
           .recordCallable(() -> decoder.decode(meteredResponse, type));
     } catch (IOException | RuntimeException e) {
+      meterRegistry.counter(
+          metricName.name("error_count"),
+          metricName.tag(template.methodMetadata(), template.feignTarget())
+              .and(Tag.of("exception_name", e.getClass().getSimpleName())))
+          .count();
       throw e;
     } catch (Exception e) {
+      meterRegistry.counter(
+          metricName.name("error_count"),
+          metricName.tag(template.methodMetadata(), template.feignTarget())
+              .and(Tag.of("exception_name", e.getClass().getSimpleName())))
+          .count();
       throw new IOException(e);
     }