Adding the CommitLogMetrics

This Adds the CommitLogMetrics object.
The implementation is based on the API, that define in commitlog.json

After this patch, it will be possible to connect with jconsole and see
the CommitLogMetrics.

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

src/main/java/org/apache/cassandra/db/commitlog/CommitLog.java

@@ -29,6 +29,8 @@ import java.util.*;
 import javax.management.MBeanServer;
 import javax.management.ObjectName;
 
+import org.apache.cassandra.metrics.CommitLogMetrics;
+
 import com.cloudius.urchin.api.APIClient;
 
 /*
@@ -37,6 +39,7 @@ import com.cloudius.urchin.api.APIClient;
  */
 public class CommitLog implements CommitLogMBean {
 
+    CommitLogMetrics metrics = new CommitLogMetrics();
     private static final java.util.logging.Logger logger = java.util.logging.Logger
             .getLogger(CommitLog.class.getName());
 

src/main/java/org/apache/cassandra/metrics/CommitLogMetrics.java

@@ -0,0 +1,87 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * Copyright 2015 Cloudius Systems
+ *
+ * Modified by Cloudius Systems
+ */
+package org.apache.cassandra.metrics;
+
+import com.cloudius.urchin.api.APIClient;
+import com.cloudius.urchin.metrics.APIMetrics;
+import com.cloudius.urchin.metrics.DefaultNameFactory;
+import com.cloudius.urchin.metrics.MetricNameFactory;
+import com.yammer.metrics.core.Gauge;
+import com.yammer.metrics.core.Timer;
+
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Metrics for commit log
+ */
+public class CommitLogMetrics {
+    public static final MetricNameFactory factory = new DefaultNameFactory(
+            "CommitLog");
+    private APIClient c = new APIClient();
+
+    /** Number of completed tasks */
+    public final Gauge<Long> completedTasks;
+    /** Number of pending tasks */
+    public final Gauge<Long> pendingTasks;
+    /** Current size used by all the commit log segments */
+    public final Gauge<Long> totalCommitLogSize;
+    /**
+     * Time spent waiting for a CLS to be allocated - under normal conditions
+     * this should be zero
+     */
+    public final Timer waitingOnSegmentAllocation;
+    /**
+     * The time spent waiting on CL sync; for Periodic this is only occurs when
+     * the sync is lagging its sync interval
+     */
+    public final Timer waitingOnCommit;
+
+    public CommitLogMetrics() {
+        completedTasks = APIMetrics.newGauge(
+                factory.createMetricName("CompletedTasks"), new Gauge<Long>() {
+                    public Long value() {
+                        return c.getLongValue("/commitlog/metrics/completed_tasks");
+                    }
+                });
+        pendingTasks = APIMetrics.newGauge(
+                factory.createMetricName("PendingTasks"), new Gauge<Long>() {
+                    public Long value() {
+                        return c.getLongValue("/commitlog/metrics/pending_tasks");
+                    }
+                });
+        totalCommitLogSize = APIMetrics.newGauge(
+                factory.createMetricName("TotalCommitLogSize"),
+                new Gauge<Long>() {
+                    public Long value() {
+                        return c.getLongValue("/commitlog/metrics/total_commit_log_size");
+                    }
+                });
+        waitingOnSegmentAllocation = APIMetrics.newTimer(
+                factory.createMetricName("WaitingOnSegmentAllocation"),
+                TimeUnit.MICROSECONDS, TimeUnit.SECONDS);
+        waitingOnCommit = APIMetrics.newTimer(
+                factory.createMetricName("WaitingOnCommit"),
+                TimeUnit.MICROSECONDS, TimeUnit.SECONDS);
+    }
+}