Fix all Javadoc warnings, fix SignalFx tag key naming convention

implementations/micrometer-registry-atlas/src/main/java/io/micrometer/atlas/AtlasMeterRegistry.java

@@ -162,8 +162,8 @@ protected <T> io.micrometer.core.instrument.Gauge newGauge(Meter.Id id, @Nullabl
     }
 
     @Override
-    protected <T> FunctionCounter newFunctionCounter(Meter.Id id, T obj, ToDoubleFunction<T> valueFunction) {
-        FunctionCounter fc = new StepFunctionCounter<>(id, clock, atlasConfig.step().toMillis(), obj, valueFunction);
+    protected <T> FunctionCounter newFunctionCounter(Meter.Id id, T obj, ToDoubleFunction<T> countFunction) {
+        FunctionCounter fc = new StepFunctionCounter<>(id, clock, atlasConfig.step().toMillis(), obj, countFunction);
         newMeter(id, Meter.Type.COUNTER, fc.measure());
         return fc;
     }

implementations/micrometer-registry-datadog/src/main/java/io/micrometer/datadog/DatadogConfig.java

@@ -20,7 +20,7 @@
 import io.micrometer.core.lang.Nullable;
 
 /**
- * Configuration for Datadog exporting.
+ * Configuration for {@link DatadogMeterRegistry}.
  *
  * @author Jon Schneider
  */
@@ -37,18 +37,22 @@ default String prefix() {
 
     default String apiKey() {
         String v = get(prefix() + ".apiKey");
-        if(v == null)
+        if (v == null)
             throw new MissingRequiredConfigurationException("apiKey must be set to report metrics to Datadog");
         return v;
     }
 
+    /**
+     * @return The Datadog application key. This is only required if you care for metadata like base units, description,
+     * and meter type to be published to Datadog.
+     */
     @Nullable
     default String applicationKey() {
         return get(prefix() + ".applicationKey");
     }
 
     /**
-     * The tag that will be mapped to "host" when shipping metrics to datadog, or {@code null} if
+     * @return The tag that will be mapped to "host" when shipping metrics to datadog, or {@code null} if
      * host should be omitted on publishing.
      */
     @Nullable
@@ -58,7 +62,7 @@ default String hostTag() {
     }
 
     /**
-     * The URI to ship metrics to. If you need to publish metrics to an internal proxy en route to
+     * @return The URI to ship metrics to. If you need to publish metrics to an internal proxy en route to
      * datadoghq, you can define the location of the proxy with this.
      */
     default String uri() {
@@ -67,13 +71,11 @@ default String uri() {
     }
 
     /**
-     * {@code true} if meter descriptions should be sent to Datadog.
+     * @return {@code true} if meter descriptions should be sent to Datadog.
      * Turn this off to minimize the amount of data sent on each scrape.
      */
     default boolean descriptions() {
         String v = get(prefix() + ".descriptions");
         return v == null || Boolean.valueOf(v);
     }
-
-
 }

implementations/micrometer-registry-ganglia/src/main/java/io/micrometer/ganglia/GangliaConfig.java

@@ -22,6 +22,8 @@
 import java.util.concurrent.TimeUnit;
 
 /**
+ * Configuration for {@link GangliaMeterRegistry}.
+ *
  * @author Jon Schneider
  */
 public interface GangliaConfig extends DropwizardConfig {
@@ -33,16 +35,14 @@ public interface GangliaConfig extends DropwizardConfig {
     /**
      * Get the value associated with a key.
      *
-     * @param key
-     *     Key to lookup in the config.
-     * @return
-     *     Value for the key or null if no key is present.
+     * @param key Key to lookup in the config.
+     * @return Value for the key or null if no key is present.
      */
     @Nullable
     String get(String key);
 
     /**
-     * Property prefix to prepend to configuration names.
+     * @return Property prefix to prepend to configuration names.
      */
     default String prefix() {
         return "ganglia";
@@ -60,19 +60,19 @@ default TimeUnit durationUnits() {
 
     default String protocolVersion() {
         String v = get(prefix() + ".protocolVersion");
-        if(v == null)
+        if (v == null)
             return "3.1";
-        if(!v.equals("3.1") && !v.equals("3.0")) {
+        if (!v.equals("3.1") && !v.equals("3.0")) {
             throw new IllegalArgumentException("Ganglia version must be one of 3.1 or 3.0 (check property " + prefix() + ".protocolVersion)");
         }
         return v;
     }
 
     default GMetric.UDPAddressingMode addressingMode() {
         String v = get(prefix() + ".addressingMode");
-        if(v == null)
+        if (v == null)
             return GMetric.UDPAddressingMode.MULTICAST;
-        if(!v.equalsIgnoreCase("unicast") && !v.equalsIgnoreCase("multicast")) {
+        if (!v.equalsIgnoreCase("unicast") && !v.equalsIgnoreCase("multicast")) {
             throw new IllegalArgumentException("Ganglia UDP addressing mode must be one of 'unicast' or 'multicast' (check property " + prefix() + ".addressingMode)");
         }
         return GMetric.UDPAddressingMode.valueOf(v.toUpperCase());
@@ -94,7 +94,7 @@ default int port() {
     }
 
     /**
-     * Returns true if publishing is enabled. Default is {@code true}.
+     * @return {@code true} if publishing is enabled. Default is {@code true}.
      */
     default boolean enabled() {
         String v = get(prefix() + ".enabled");

implementations/micrometer-registry-graphite/src/main/java/io/micrometer/graphite/GraphiteConfig.java

@@ -21,6 +21,8 @@
 import java.util.concurrent.TimeUnit;
 
 /**
+ * Configuration for {@link GraphiteMeterRegistry}.
+ *
  * @author Jon Schneider
  */
 public interface GraphiteConfig extends DropwizardConfig {
@@ -32,23 +34,21 @@ public interface GraphiteConfig extends DropwizardConfig {
     /**
      * Get the value associated with a key.
      *
-     * @param key
-     *     Key to lookup in the config.
-     * @return
-     *     Value for the key or null if no key is present.
+     * @param key Key to lookup in the config.
+     * @return Value for the key or null if no key is present.
      */
     @Nullable
     String get(String key);
 
     /**
-     * Property prefix to prepend to configuration names.
+     * @return Property prefix to prepend to configuration names.
      */
     default String prefix() {
         return "graphite";
     }
 
     /**
-     * For the default naming convention, turn the specified tag keys into
+     * @return For the default naming convention, turn the specified tag keys into
      * part of the metric prefix.
      */
     default String[] tagsAsPrefix() {
@@ -76,24 +76,24 @@ default int port() {
     }
 
     /**
-     * Returns true if publishing is enabled. Default is {@code true}.
+     * @return {@code true} if publishing is enabled. Default is {@code true}.
      */
     default boolean enabled() {
         String v = get(prefix() + ".enabled");
         return v == null || Boolean.valueOf(v);
     }
 
     /**
-     * Protocol to use while shipping data to Graphite.
+     * @return Protocol to use while shipping data to Graphite.
      */
     default GraphiteProtocol protocol() {
         String v = get(prefix() + ".protocol");
 
-        if(v == null)
+        if (v == null)
             return GraphiteProtocol.PICKLED;
 
         for (GraphiteProtocol flavor : GraphiteProtocol.values()) {
-            if(flavor.toString().equalsIgnoreCase(v))
+            if (flavor.toString().equalsIgnoreCase(v))
                 return flavor;
         }
 

implementations/micrometer-registry-influx/src/main/java/io/micrometer/influx/InfluxConfig.java

@@ -19,6 +19,8 @@
 import io.micrometer.core.lang.Nullable;
 
 /**
+ * Configuration for {@link InfluxMeterRegistry}.
+ *
  * @author Jon Schneider
  */
 public interface InfluxConfig extends StepRegistryConfig {
@@ -33,28 +35,26 @@ default String prefix() {
     }
 
     /**
-     * The db to send metrics to. Defaults to "mydb".
+     * @return The db to send metrics to. Defaults to "mydb".
      */
     default String db() {
         String v = get(prefix() + ".db");
         return v == null ? "mydb" : v;
     }
 
     /**
-     * Sets the write consistency for each point. The Influx default is 'one'. Must
-     * be one of 'any', 'one', 'quorum', or 'all'.
-     *
-     * Only available for InfluxEnterprise clusters.
+     * @return Sets the write consistency for each point. The Influx default is 'one'. Must
+     * be one of 'any', 'one', 'quorum', or 'all'. Only available for InfluxEnterprise clusters.
      */
     default InfluxConsistency consistency() {
         String v = get(prefix() + ".consistency");
-        if(v == null)
+        if (v == null)
             return InfluxConsistency.ONE;
         return InfluxConsistency.valueOf(v.toUpperCase());
     }
 
     /**
-     * Authenticate requests with this user. By default is {@code null}, and the registry will not
+     * @return Authenticate requests with this user. By default is {@code null}, and the registry will not
      * attempt to present credentials to Influx.
      */
     @Nullable
@@ -63,7 +63,7 @@ default String userName() {
     }
 
     /**
-     * Authenticate requests with this password. By default is {@code null}, and the registry will not
+     * @return Authenticate requests with this password. By default is {@code null}, and the registry will not
      * attempt to present credentials to Influx.
      */
     @Nullable
@@ -72,16 +72,15 @@ default String password() {
     }
 
     /**
-     * Influx writes to the DEFAULT retention policy if one is not specified.
+     * @return Influx writes to the DEFAULT retention policy if one is not specified.
      */
     @Nullable
     default String retentionPolicy() {
         return get(prefix() + ".retentionPolicy");
     }
 
     /**
-     * Returns the URI for the Influx backend. The default is
-     * {@code http://localhost:8086/write}.
+     * @return The URI for the Influx backend. The default is {@code http://localhost:8086}.
      */
     default String uri() {
         String v = get(prefix() + ".uri");

implementations/micrometer-registry-new-relic/src/main/java/io/micrometer/newrelic/NewRelicConfig.java

@@ -18,6 +18,11 @@
 import io.micrometer.core.instrument.config.MissingRequiredConfigurationException;
 import io.micrometer.core.instrument.step.StepRegistryConfig;
 
+/**
+ * Configuration for {@link NewRelicMeterRegistry}.
+ *
+ * @author Jon Schneider
+ */
 public interface NewRelicConfig extends StepRegistryConfig {
     /**
      * Accept configuration defaults
@@ -44,7 +49,7 @@ default String accountId() {
     }
 
     /**
-     * Returns the URI for the New Relic insights API. The default is
+     * @return The URI for the New Relic insights API. The default is
      * {@code https://insights-collector.newrelic.com}. If you need to pass through
      * a proxy, you can change this value.
      */

implementations/micrometer-registry-prometheus/src/main/java/io/micrometer/prometheus/PrometheusConfig.java

@@ -19,6 +19,11 @@
 
 import java.time.Duration;
 
+/**
+ * Configuration for {@link PrometheusMeterRegistry}.
+ *
+ * @author Jon Schneider
+ */
 public interface PrometheusConfig extends MeterRegistryConfig {
     /**
      * Accept configuration defaults
@@ -31,7 +36,7 @@ default String prefix() {
     }
 
     /**
-     * {@code true} if meter descriptions should be sent to Prometheus.
+     * @return {@code true} if meter descriptions should be sent to Prometheus.
      * Turn this off to minimize the amount of data sent on each scrape.
      */
     default boolean descriptions() {
@@ -40,7 +45,7 @@ default boolean descriptions() {
     }
 
     /**
-     * Returns the step size to use in computing windowed statistics like max. The default is 1 minute.
+     * @return The step size to use in computing windowed statistics like max. The default is 1 minute.
      * To get the most out of these statistics, align the step interval to be close to your scrape interval.
      */
     default Duration step() {

implementations/micrometer-registry-prometheus/src/main/java/io/micrometer/prometheus/PrometheusDistributionSummary.java

@@ -82,6 +82,8 @@ public int hashCode() {
     /**
      * For Prometheus we cannot use the histogram counts from HistogramSnapshot, as it is based on a
      * rolling histogram. Prometheus requires a histogram that accumulates values over the lifetime of the app.
+     *
+     * @return Cumulative histogram buckets.
      */
     public CountAtBucket[] histogramCounts() {
         return percentilesHistogram.takeSnapshot(0, 0, 0, true).histogramCounts();

implementations/micrometer-registry-prometheus/src/main/java/io/micrometer/prometheus/PrometheusMeterRegistry.java

@@ -67,7 +67,7 @@ public PrometheusMeterRegistry(PrometheusConfig config, CollectorRegistry regist
     }
 
     /**
-     * Content that should be included in the response body for an endpoint designate for
+     * @return Content that should be included in the response body for an endpoint designate for
      * Prometheus to scrape from.
      */
     public String scrape() {
@@ -263,9 +263,9 @@ protected <T> FunctionTimer newFunctionTimer(Meter.Id id, T obj, ToLongFunction<
     }
 
     @Override
-    protected <T> FunctionCounter newFunctionCounter(Meter.Id id, T obj, ToDoubleFunction<T> valueFunction) {
+    protected <T> FunctionCounter newFunctionCounter(Meter.Id id, T obj, ToDoubleFunction<T> countFunction) {
         MicrometerCollector collector = collectorByName(id, Collector.Type.COUNTER);
-        FunctionCounter fc = new CumulativeFunctionCounter<>(id, obj, valueFunction);
+        FunctionCounter fc = new CumulativeFunctionCounter<>(id, obj, countFunction);
         List<String> tagValues = tagValues(id);
 
         collector.add((conventionName, tagKeys) -> Stream.of(

implementations/micrometer-registry-prometheus/src/main/java/io/micrometer/prometheus/PrometheusTimer.java

@@ -17,8 +17,8 @@
 
 import io.micrometer.core.instrument.AbstractTimer;
 import io.micrometer.core.instrument.Clock;
-import io.micrometer.core.instrument.distribution.CountAtBucket;
 import io.micrometer.core.instrument.Timer;
+import io.micrometer.core.instrument.distribution.CountAtBucket;
 import io.micrometer.core.instrument.distribution.DistributionStatisticConfig;
 import io.micrometer.core.instrument.distribution.TimeWindowLatencyHistogram;
 import io.micrometer.core.instrument.distribution.pause.PauseDetector;
@@ -74,6 +74,8 @@ public double max(TimeUnit unit) {
     /**
      * For Prometheus we cannot use the histogram counts from HistogramSnapshot, as it is based on a
      * rolling histogram. Prometheus requires a histogram that accumulates values over the lifetime of the app.
+     *
+     * @return Cumulative histogram buckets.
      */
     public CountAtBucket[] histogramCounts() {
         return percentilesHistogram.takeSnapshot(0, 0, 0, true).histogramCounts();