Support attaching base units to distribution summaries (issue #80)

micrometer-core/src/main/java/io/micrometer/core/instrument/AbstractMeterRegistry.java

@@ -206,6 +206,7 @@ private class DistributionSummaryBuilder implements DistributionSummary.Builder
         private Histogram<?> histogram;
         private final List<Tag> tags = new ArrayList<>();
         private String description;
+        private String baseUnit;
 
         private DistributionSummaryBuilder(String name) {
             this.name = name;
@@ -233,10 +234,17 @@ public DistributionSummary.Builder description(String description) {
             return this;
         }
 
+        @Override
+        public DistributionSummary.Builder baseUnit(String unit) {
+            this.baseUnit = unit;
+            return this;
+        }
+
         @Override
         public DistributionSummary create() {
             return registerMeterIfNecessary(DistributionSummary.class, name, tags, id ->
-                newDistributionSummary(id.getConventionName(Meter.Type.DistributionSummary), id.getTags(), description, quantiles, histogram));
+                newDistributionSummary(id.getConventionName(Meter.Type.DistributionSummary, baseUnit), id.getTags(),
+                    description, quantiles, histogram));
         }
     }
 
@@ -449,8 +457,12 @@ String getName() {
         /**
          * The formatted name matching this registry's naming convention
          */
+        String getConventionName(Meter.Type type, String baseUnit) {
+            return namingConvention.name(name, type, baseUnit);
+        }
+
         String getConventionName(Meter.Type type) {
-            return namingConvention.name(name, type);
+            return getConventionName(type, null);
         }
 
         /**

micrometer-core/src/main/java/io/micrometer/core/instrument/DistributionSummary.java

@@ -56,6 +56,8 @@ default Builder tags(String... tags) {
 
         Builder description(String description);
 
+        Builder baseUnit(String unit);
+
         DistributionSummary create();
     }
 

micrometer-core/src/main/java/io/micrometer/core/instrument/NamingConvention.java

@@ -34,7 +34,7 @@
 public interface NamingConvention {
     NamingConvention snakeCase = new NamingConvention() {
         @Override
-        public String name(String name, Meter.Type type) {
+        public String name(String name, Meter.Type type, String baseUnit) {
             return toSnakeCase(name);
         }
 
@@ -50,7 +50,7 @@ private String toSnakeCase(String value) {
 
     NamingConvention camelCase = new NamingConvention() {
         @Override
-        public String name(String name, Meter.Type type) {
+        public String name(String name, Meter.Type type, String baseUnit) {
             return toCamelCase(name);
         }
 
@@ -82,7 +82,11 @@ private String toCamelCase(String value) {
         }
     };
 
-    String name(String name, Meter.Type type);
+    default String name(String name, Meter.Type type) {
+        return name(name, type, null);
+    }
+
+    String name(String name, Meter.Type type, String baseUnit);
 
     default String tagKey(String key) { return key; }
     default String tagValue(String value) { return value; }

micrometer-core/src/main/java/io/micrometer/core/instrument/datadog/DatadogNamingConvention.java

@@ -29,8 +29,8 @@ public class DatadogNamingConvention implements NamingConvention {
      * all non-alphanumeric characters with '_'.
      */
     @Override
-    public String name(String name, Meter.Type type) {
-        String sanitized = NamingConvention.camelCase.name(name, type);
+    public String name(String name, Meter.Type type, String baseUnit) {
+        String sanitized = NamingConvention.camelCase.name(name, type, baseUnit);
 
         // Metrics that don't start with a letter get dropped on the floor by the Datadog publish API,
         // so we will prepend them with 'm_'.

micrometer-core/src/main/java/io/micrometer/core/instrument/graphite/GraphiteNamingConvention.java

@@ -29,7 +29,7 @@ public class GraphiteNamingConvention implements NamingConvention {
     private static final Pattern blacklistedChars = Pattern.compile("[{}(),=\\[\\]/]");
 
     @Override
-    public String name(String name, Meter.Type type) {
+    public String name(String name, Meter.Type type, String baseUnit) {
         return format(name);
     }
 

micrometer-core/src/main/java/io/micrometer/core/instrument/influx/InfluxNamingConvention.java

@@ -23,7 +23,7 @@
  */
 public class InfluxNamingConvention implements NamingConvention {
     @Override
-    public String name(String name, Meter.Type type) {
+    public String name(String name, Meter.Type type, String baseUnit) {
         return format(name.replace("=", "_"));
     }
 

micrometer-core/src/main/java/io/micrometer/core/instrument/prometheus/PrometheusNamingConvention.java

@@ -38,8 +38,8 @@ public class PrometheusNamingConvention implements NamingConvention {
      * [a-zA-Z_:][a-zA-Z0-9_:]*
      */
     @Override
-    public String name(String name, Meter.Type type) {
-        String conventionName = NamingConvention.snakeCase.name(name, type);
+    public String name(String name, Meter.Type type, String baseUnit) {
+        String conventionName = NamingConvention.snakeCase.name(name, type, baseUnit);
 
         switch (type) {
             case Counter:
@@ -51,6 +51,10 @@ public String name(String name, Meter.Type type) {
                 else if(!conventionName.endsWith("_seconds"))
                     conventionName += "_duration_seconds";
                 break;
+            case DistributionSummary:
+                if(baseUnit != null && !conventionName.endsWith("_" + baseUnit))
+                    conventionName += "_" + baseUnit;
+                break;
         }
 
         String sanitized = nameChars.matcher(conventionName).replaceAll("_");

micrometer-core/src/main/java/io/micrometer/core/instrument/stats/quantile/SlidingWindow.java

@@ -52,7 +52,7 @@ public SlidingWindow(Integer windowSize) {
             windowSize *= -1;
         }
         this.windowSize = windowSize;
-        this.elements = new LinkedList<Element<T>>();
+        this.elements = new LinkedList<>();
     }
 
     /**
@@ -63,7 +63,7 @@ public SlidingWindow(Integer windowSize) {
      * @param element
      */
     public void add(T element) {
-        Element<T> newElement = new Element<T>(element, this.windowSize, 0);
+        Element<T> newElement = new Element<>(element, this.windowSize, 0);
         this.elements.addFirst(newElement);
     }
 
@@ -85,7 +85,7 @@ public void add(T element, Integer size) {
             throw new RuntimeException("The size of an element can't be a negative integer.");
         }
 
-        Element<T> newElement = new Element<T>(element, this.windowSize - size, size);
+        Element<T> newElement = new Element<>(element, this.windowSize - size, size);
         this.elements.addFirst(newElement);
     }
 
@@ -156,7 +156,7 @@ public T getNewestElement() {
      * @return a {@link Collection} of element of type <b>T</b>
      */
     public Collection<T> getAll() {
-        Collection<T> elements = new LinkedList<T>();
+        Collection<T> elements = new LinkedList<>();
 
         for (int i = 0; i < this.elements.size(); i++) {
             elements.add(this.elements.get(i).getElement());
@@ -171,7 +171,7 @@ public Collection<T> getAll() {
      * @return a {@link Collection} of element of type {@link Integer}
      */
     public Collection<Integer> getAllLifeTimes() {
-        Collection<Integer> lifeTimes = new LinkedList<Integer>();
+        Collection<Integer> lifeTimes = new LinkedList<>();
 
         for (int i = 0; i < this.elements.size(); i++) {
             lifeTimes.add(this.elements.get(i).getTimeToLive());

micrometer-core/src/test/java/io/micrometer/core/instrument/datadog/DatadogNamingConventionTest.java

@@ -25,7 +25,7 @@ class DatadogNamingConventionTest {
 
     @Test
     void nameStartsWithLetter() {
-        assertThat(convention.name("123", Meter.Type.Gauge)).isEqualTo("m_123");
+        assertThat(convention.name("123", Meter.Type.Gauge, null)).isEqualTo("m_123");
     }
 
     @Test
@@ -35,6 +35,6 @@ void tagKeyStartsWithLetter() {
 
     @Test
     void dotNotationIsConvertedToCamelCase() {
-        assertThat(convention.name("gauge.size", Meter.Type.Gauge)).isEqualTo("gaugeSize");
+        assertThat(convention.name("gauge.size", Meter.Type.Gauge, null)).isEqualTo("gaugeSize");
     }
 }

micrometer-core/src/test/java/io/micrometer/core/instrument/prometheus/PrometheusNamingConventionTest.java

@@ -41,6 +41,12 @@ void unitsAreAppendedToTimers() {
         assertThat(convention.name("timer", Meter.Type.Timer)).isEqualTo("timer_duration_seconds");
     }
 
+    @Test
+    void unitsAreAppendedToDistributionSummaries() {
+        assertThat(convention.name("response.size", Meter.Type.DistributionSummary, "bytes")).isEqualTo("response_size_bytes");
+        assertThat(convention.name("summary", Meter.Type.DistributionSummary)).isEqualTo("summary");
+    }
+
     @Test
     void dotNotationIsConvertedToSnakeCase() {
         assertThat(convention.name("gauge.size", Meter.Type.Gauge)).isEqualTo("gauge_size");