Overriden the Metric data collection

Three of the Metric in the yammer library are based on data that is
pushed to them: Counter, Histogram and Meter.

This patch modify the specific functionality by inherit the original
Meter, keeping its functionality and API, and modify the way the data is
collected.

For Counter: A call to count will be implementing by calling the API to
retreive a value.

For Meter: A call to count will be implementing by calling the API to
retreive a value, similiar to count, but the timer aspect of the Meter
remains the same.

For histogram: Histogram uses an internal sample container. To mimic the
behaviour, a call to any of the historgram get functionality will update
the sample container first. A timestamp of the last update limits the
number of updates that will be done by the histogram.

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

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

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+package com.yammer.metrics.core;
+/*
+ * Copyright 2015 Cloudius Systems
+ *
+ * Modified by Cloudius Systems
+ */
+
+import com.cloudius.urchin.api.APIClient;
+import com.yammer.metrics.core.Counter;
+
+public class APICounter extends Counter {
+    String url;
+    private APIClient c = new APIClient();
+    
+    public APICounter(String _url) {
+        super();
+        url = _url;
+    }
+    /**
+     * Returns the counter's current value.
+     *
+     * @return the counter's current value
+     */
+    public long count() {
+        return c.getLongValue(url);
+    }
+
+
+}

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

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+package com.yammer.metrics.core;
+
+/*
+ * Copyright 2015 Cloudius Systems
+ *
+ * Modified by Cloudius Systems
+ */
+
+import com.cloudius.urchin.api.APIClient;
+import com.yammer.metrics.stats.Sample;
+import com.yammer.metrics.stats.Snapshot;
+
+public class APIHistogram extends Histogram {
+    long last_update = 0;
+    static final long UPDATE_INTERVAL = 50;
+    String url;
+    private APIClient c = new APIClient();
+
+    public APIHistogram(String _url, Sample sample) {
+        super(sample);
+        url = _url;
+    }
+
+    public APIHistogram(String _url, SampleType type) {
+        super(type);
+        url = _url;
+    }
+
+    public void update() {
+        long now = System.currentTimeMillis();
+        if (now - last_update < UPDATE_INTERVAL) {
+            return;
+        }
+        last_update = now;
+        clear();
+        long[] vals = c.getLongArrValue(url);
+        for (long v : vals) {
+            update(v);
+        }
+    }
+
+    /**
+     * Returns the number of values recorded.
+     *
+     * @return the number of values recorded
+     */
+    public long count() {
+        update();
+        return super.count();
+    }
+
+    /*
+     * (non-Javadoc)
+     * 
+     * @see com.yammer.metrics.core.Summarizable#max()
+     */
+    @Override
+    public double max() {
+        update();
+        return super.max();
+    }
+
+    /*
+     * (non-Javadoc)
+     * 
+     * @see com.yammer.metrics.core.Summarizable#min()
+     */
+    @Override
+    public double min() {
+        update();
+        return super.min();
+    }
+
+    /*
+     * (non-Javadoc)
+     * 
+     * @see com.yammer.metrics.core.Summarizable#mean()
+     */
+    @Override
+    public double mean() {
+        update();
+        return super.mean();
+    }
+
+    /*
+     * (non-Javadoc)
+     * 
+     * @see com.yammer.metrics.core.Summarizable#stdDev()
+     */
+    @Override
+    public double stdDev() {
+        update();
+        return super.stdDev();
+    }
+
+    /*
+     * (non-Javadoc)
+     * 
+     * @see com.yammer.metrics.core.Summarizable#sum()
+     */
+    @Override
+    public double sum() {
+        update();
+        return super.sum();
+    }
+
+    @Override
+    public Snapshot getSnapshot() {
+        update();
+        return super.getSnapshot();
+    }
+}

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

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+package com.yammer.metrics.core;
+
+/*
+ * Copyright 2015 Cloudius Systems
+ *
+ * Modified by Cloudius Systems
+ */
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+import com.cloudius.urchin.api.APIClient;
+
+public class APIMeter extends Meter {
+    String url;
+    private APIClient c = new APIClient();
+
+    public APIMeter(String _url, ScheduledExecutorService tickThread,
+            String eventType, TimeUnit rateUnit, Clock clock) {
+        super(tickThread, eventType, rateUnit, clock);
+        // TODO Auto-generated constructor stub
+        url = _url;
+    }
+
+    @Override
+    public long count() {
+        return c.getLongValue(url);
+    }
+
+}