Adding Timer creation to APIMetricsRegistry

This adds a Timer creation methods to the APIMetricsRegistry, the
newTimer method would create an APITimer and would pass it the url for
quering.

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

src/main/java/com/yammer/metrics/core/APIMetricsRegistry.java

@@ -263,4 +263,100 @@ public class APIMetricsRegistry extends MetricsRegistry {
         return getOrAdd(metricName, new APIHistogram(url,
                 biased ? SampleType.BIASED : SampleType.UNIFORM));
     }
+
+    /**
+     * Creates a new {@link 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 Timer}
+     */
+    public Timer newTimer(String url, Class<?> klass, String name) {
+        return newTimer(url, klass, name, null, TimeUnit.MILLISECONDS,
+                TimeUnit.SECONDS);
+    }
+
+    /**
+     * Creates a new {@link 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 Timer}
+     */
+    public Timer newTimer(String url, Class<?> klass, String name,
+            TimeUnit durationUnit, TimeUnit rateUnit) {
+        return newTimer(url, klass, name, null, durationUnit, rateUnit);
+    }
+
+    /**
+     * Creates a new {@link 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 Timer}
+     */
+    public Timer newTimer(String url, Class<?> klass, String name, String scope) {
+        return newTimer(url, klass, name, scope, TimeUnit.MILLISECONDS,
+                TimeUnit.SECONDS);
+    }
+
+    /**
+     * Creates a new {@link 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 Timer}
+     */
+    public Timer newTimer(String url, Class<?> klass, String name,
+            String scope, TimeUnit durationUnit, TimeUnit rateUnit) {
+        return newTimer(url, createName(klass, name, scope), durationUnit,
+                rateUnit);
+    }
+
+    /**
+     * Creates a new {@link 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 Timer}
+     */
+    public Timer newTimer(String url, MetricName metricName,
+            TimeUnit durationUnit, TimeUnit rateUnit) {
+        final Metric existingMetric = getMetrics().get(metricName);
+        if (existingMetric != null) {
+            return (Timer) existingMetric;
+        }
+        return getOrAdd(metricName, new APITimer(url, newMeterTickThreadPool(),
+                durationUnit, rateUnit, getClock()));
+    }
+
 }