Adding the APIMetrics

This is a copy of the Metrics class from yammer, with two differences:
Add a url Metrics that needs it to retrieve data and uses the
APIMetricsRegistry as the Metric factory.

Signed-off-by: Amnon Heiman <amnon@cloudius-systems.com>

src/main/java/com/cloudius/urchin/metrics/APIMetrics.java

@@ -0,0 +1,397 @@
+package com.cloudius.urchin.metrics;
+
+/*
+ * Copyright 2015 Cloudius Systems
+ *
+ * Modified by Cloudius Systems
+ */
+
+import java.util.concurrent.TimeUnit;
+
+import com.yammer.metrics.core.APIMetricsRegistry;
+import com.yammer.metrics.core.Counter;
+import com.yammer.metrics.core.Gauge;
+import com.yammer.metrics.core.Histogram;
+import com.yammer.metrics.core.Meter;
+import com.yammer.metrics.core.MetricName;
+import com.yammer.metrics.core.Timer;
+import com.yammer.metrics.reporting.JmxReporter;
+
+public class APIMetrics {
+    private static final APIMetricsRegistry DEFAULT_REGISTRY = new APIMetricsRegistry();
+    private static final Thread SHUTDOWN_HOOK = new Thread() {
+        public void run() {
+            JmxReporter.shutdownDefault();
+        }
+    };
+
+    static {
+        JmxReporter.startDefault(DEFAULT_REGISTRY);
+        Runtime.getRuntime().addShutdownHook(SHUTDOWN_HOOK);
+    }
+
+    private APIMetrics() { /* unused */
+    }
+
+    /**
+     * Given a new {@link com.yammer.metrics.core.Gauge}, registers it under the
+     * given class and name.
+     *
+     * @param klass
+     *            the class which owns the metric
+     * @param name
+     *            the name of the metric
+     * @param metric
+     *            the metric
+     * @param <T>
+     *            the type of the value returned by the metric
+     * @return {@code metric}
+     */
+    public static <T> Gauge<T> newGauge(Class<?> klass, String name,
+            Gauge<T> metric) {
+        return DEFAULT_REGISTRY.newGauge(klass, name, metric);
+    }
+
+    /**
+     * Given a new {@link com.yammer.metrics.core.Gauge}, registers it under the
+     * given class and name.
+     *
+     * @param klass
+     *            the class which owns the metric
+     * @param name
+     *            the name of the metric
+     * @param scope
+     *            the scope of the metric
+     * @param metric
+     *            the metric
+     * @param <T>
+     *            the type of the value returned by the metric
+     * @return {@code metric}
+     */
+    public static <T> Gauge<T> newGauge(Class<?> klass, String name,
+            String scope, Gauge<T> metric) {
+        return DEFAULT_REGISTRY.newGauge(klass, name, scope, metric);
+    }
+
+    /**
+     * Given a new {@link com.yammer.metrics.core.Gauge}, registers it under the
+     * given metric name.
+     *
+     * @param metricName
+     *            the name of the metric
+     * @param metric
+     *            the metric
+     * @param <T>
+     *            the type of the value returned by the metric
+     * @return {@code metric}
+     */
+    public static <T> Gauge<T> newGauge(MetricName metricName, Gauge<T> metric) {
+        return DEFAULT_REGISTRY.newGauge(metricName, metric);
+    }
+
+    /**
+     * Creates a new {@link com.yammer.metrics.core.Counter} and registers it
+     * under the given class and name.
+     *
+     * @param klass
+     *            the class which owns the metric
+     * @param name
+     *            the name of the metric
+     * @return a new {@link com.yammer.metrics.core.Counter}
+     */
+    public static Counter newCounter(String url, Class<?> klass, String name) {
+        return DEFAULT_REGISTRY.newCounter(url, klass, name);
+    }
+
+    /**
+     * Creates a new {@link com.yammer.metrics.core.Counter} and registers it
+     * under the given class and name.
+     *
+     * @param klass
+     *            the class which owns the metric
+     * @param name
+     *            the name of the metric
+     * @param scope
+     *            the scope of the metric
+     * @return a new {@link com.yammer.metrics.core.Counter}
+     */
+    public static Counter newCounter(String url, Class<?> klass, String name,
+            String scope) {
+        return DEFAULT_REGISTRY.newCounter(url, klass, name, scope);
+    }
+
+    /**
+     * Creates a new {@link com.yammer.metrics.core.Counter} and registers it
+     * under the given metric name.
+     *
+     * @param metricName
+     *            the name of the metric
+     * @return a new {@link com.yammer.metrics.core.Counter}
+     */
+    public static Counter newCounter(String url, MetricName metricName) {
+        return DEFAULT_REGISTRY.newCounter(url, metricName);
+    }
+
+    /**
+     * Creates a new {@link com.yammer.metrics.core.Histogram} and registers it
+     * under the given class and name.
+     *
+     * @param klass
+     *            the class which owns the metric
+     * @param name
+     *            the name of the metric
+     * @param biased
+     *            whether or not the histogram should be biased
+     * @return a new {@link com.yammer.metrics.core.Histogram}
+     */
+    public static Histogram newHistogram(Class<?> klass, String name,
+            boolean biased) {
+        return DEFAULT_REGISTRY.newHistogram(klass, name, biased);
+    }
+
+    /**
+     * Creates a new {@link com.yammer.metrics.core.Histogram} and registers it
+     * under the given class, name, and scope.
+     *
+     * @param klass
+     *            the class which owns the metric
+     * @param name
+     *            the name of the metric
+     * @param scope
+     *            the scope of the metric
+     * @param biased
+     *            whether or not the histogram should be biased
+     * @return a new {@link com.yammer.metrics.core.Histogram}
+     */
+    public static Histogram newHistogram(Class<?> klass, String name,
+            String scope, boolean biased) {
+        return DEFAULT_REGISTRY.newHistogram(klass, name, scope, biased);
+    }
+
+    /**
+     * Creates a new {@link com.yammer.metrics.core.Histogram} and registers it
+     * under the given metric name.
+     *
+     * @param metricName
+     *            the name of the metric
+     * @param biased
+     *            whether or not the histogram should be biased
+     * @return a new {@link com.yammer.metrics.core.Histogram}
+     */
+    public static Histogram newHistogram(MetricName metricName, boolean biased) {
+        return DEFAULT_REGISTRY.newHistogram(metricName, biased);
+    }
+
+    /**
+     * Creates a new non-biased {@link com.yammer.metrics.core.Histogram} and
+     * registers it under the given class and name.
+     *
+     * @param klass
+     *            the class which owns the metric
+     * @param name
+     *            the name of the metric
+     * @return a new {@link com.yammer.metrics.core.Histogram}
+     */
+    public static Histogram newHistogram(Class<?> klass, String name) {
+        return DEFAULT_REGISTRY.newHistogram(klass, name);
+    }
+
+    /**
+     * Creates a new non-biased {@link com.yammer.metrics.core.Histogram} and
+     * registers it under the given class, name, and scope.
+     *
+     * @param klass
+     *            the class which owns the metric
+     * @param name
+     *            the name of the metric
+     * @param scope
+     *            the scope of the metric
+     * @return a new {@link com.yammer.metrics.core.Histogram}
+     */
+    public static Histogram newHistogram(Class<?> klass, String name,
+            String scope) {
+        return DEFAULT_REGISTRY.newHistogram(klass, name, scope);
+    }
+
+    /**
+     * Creates a new non-biased {@link com.yammer.metrics.core.Histogram} and
+     * registers it under the given metric name.
+     *
+     * @param metricName
+     *            the name of the metric
+     * @return a new {@link com.yammer.metrics.core.Histogram}
+     */
+    public static Histogram newHistogram(MetricName metricName) {
+        return newHistogram(metricName, false);
+    }
+
+    /**
+     * Creates a new {@link com.yammer.metrics.core.Meter} and registers it
+     * under the given class and name.
+     *
+     * @param klass
+     *            the class which owns the metric
+     * @param name
+     *            the name of the metric
+     * @param eventType
+     *            the plural name of the type of events the meter is measuring
+     *            (e.g., {@code "requests"})
+     * @param unit
+     *            the rate unit of the new meter
+     * @return a new {@link com.yammer.metrics.core.Meter}
+     */
+    public static Meter newMeter(String url, Class<?> klass, String name,
+            String eventType, TimeUnit unit) {
+        return DEFAULT_REGISTRY.newMeter(url, klass, name, eventType, unit);
+    }
+
+    /**
+     * Creates a new {@link com.yammer.metrics.core.Meter} and registers it
+     * under the given class, name, and scope.
+     *
+     * @param klass
+     *            the class which owns the metric
+     * @param name
+     *            the name of the metric
+     * @param scope
+     *            the scope of the metric
+     * @param eventType
+     *            the plural name of the type of events the meter is measuring
+     *            (e.g., {@code "requests"})
+     * @param unit
+     *            the rate unit of the new meter
+     * @return a new {@link com.yammer.metrics.core.Meter}
+     */
+    public static Meter newMeter(String url, Class<?> klass, String name,
+            String scope, String eventType, TimeUnit unit) {
+        return DEFAULT_REGISTRY.newMeter(url, klass, name, scope, eventType,
+                unit);
+    }
+
+    /**
+     * Creates a new {@link com.yammer.metrics.core.Meter} and registers it
+     * under the given metric name.
+     *
+     * @param metricName
+     *            the name of the metric
+     * @param eventType
+     *            the plural name of the type of events the meter is measuring
+     *            (e.g., {@code "requests"})
+     * @param unit
+     *            the rate unit of the new meter
+     * @return a new {@link com.yammer.metrics.core.Meter}
+     */
+    public static Meter newMeter(String url, MetricName metricName,
+            String eventType, TimeUnit unit) {
+        return DEFAULT_REGISTRY.newMeter(url, metricName, eventType, unit);
+    }
+
+    /**
+     * Creates a new {@link com.yammer.metrics.core.Timer} and registers it
+     * under the given class and name.
+     *
+     * @param klass
+     *            the class which owns the metric
+     * @param name
+     *            the name of the metric
+     * @param durationUnit
+     *            the duration scale unit of the new timer
+     * @param rateUnit
+     *            the rate scale unit of the new timer
+     * @return a new {@link com.yammer.metrics.core.Timer}
+     */
+    public static Timer newTimer(Class<?> klass, String name,
+            TimeUnit durationUnit, TimeUnit rateUnit) {
+        return DEFAULT_REGISTRY.newTimer(klass, name, durationUnit, rateUnit);
+    }
+
+    /**
+     * Creates a new {@link com.yammer.metrics.core.Timer} and registers it
+     * under the given class and name, measuring elapsed time in milliseconds
+     * and invocations per second.
+     *
+     * @param klass
+     *            the class which owns the metric
+     * @param name
+     *            the name of the metric
+     * @return a new {@link com.yammer.metrics.core.Timer}
+     */
+    public static Timer newTimer(Class<?> klass, String name) {
+        return DEFAULT_REGISTRY.newTimer(klass, name);
+    }
+
+    /**
+     * Creates a new {@link com.yammer.metrics.core.Timer} and registers it
+     * under the given class, name, and scope.
+     *
+     * @param klass
+     *            the class which owns the metric
+     * @param name
+     *            the name of the metric
+     * @param scope
+     *            the scope of the metric
+     * @param durationUnit
+     *            the duration scale unit of the new timer
+     * @param rateUnit
+     *            the rate scale unit of the new timer
+     * @return a new {@link com.yammer.metrics.core.Timer}
+     */
+    public static Timer newTimer(Class<?> klass, String name, String scope,
+            TimeUnit durationUnit, TimeUnit rateUnit) {
+        return DEFAULT_REGISTRY.newTimer(klass, name, scope, durationUnit,
+                rateUnit);
+    }
+
+    /**
+     * Creates a new {@link com.yammer.metrics.core.Timer} and registers it
+     * under the given class, name, and scope, measuring elapsed time in
+     * milliseconds and invocations per second.
+     *
+     * @param klass
+     *            the class which owns the metric
+     * @param name
+     *            the name of the metric
+     * @param scope
+     *            the scope of the metric
+     * @return a new {@link com.yammer.metrics.core.Timer}
+     */
+    public static Timer newTimer(Class<?> klass, String name, String scope) {
+        return DEFAULT_REGISTRY.newTimer(klass, name, scope);
+    }
+
+    /**
+     * Creates a new {@link com.yammer.metrics.core.Timer} and registers it
+     * under the given metric name.
+     *
+     * @param metricName
+     *            the name of the metric
+     * @param durationUnit
+     *            the duration scale unit of the new timer
+     * @param rateUnit
+     *            the rate scale unit of the new timer
+     * @return a new {@link com.yammer.metrics.core.Timer}
+     */
+    public static Timer newTimer(MetricName metricName, TimeUnit durationUnit,
+            TimeUnit rateUnit) {
+        return DEFAULT_REGISTRY.newTimer(metricName, durationUnit, rateUnit);
+    }
+
+    /**
+     * Returns the (static) default registry.
+     *
+     * @return the metrics registry
+     */
+    public static APIMetricsRegistry defaultRegistry() {
+        return DEFAULT_REGISTRY;
+    }
+
+    /**
+     * Shuts down all thread pools for the default registry.
+     */
+    public static void shutdown() {
+        DEFAULT_REGISTRY.shutdown();
+        JmxReporter.shutdownDefault();
+        Runtime.getRuntime().removeShutdownHook(SHUTDOWN_HOOK);
+    }
+
+}