[ONOS-4127] Backup metric service to ganglia monitoring server

- Initial implementation of metric service reporter
- Unit test for metric service reporter
- Bump up metric lib from 3.1.0 to 3.1.2

Change-Id: Ia178df759d671dfc15cffaacb09d5279ad3d9ad8
diff --git a/apps/metricsreporter/features.xml b/apps/metricsreporter/features.xml
new file mode 100644
index 0000000..5bba72a
--- /dev/null
+++ b/apps/metricsreporter/features.xml
@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<!--
+  ~ Copyright 2016 Open Networking Laboratory
+  ~
+  ~ Licensed 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.
+  -->
+<features xmlns="http://karaf.apache.org/xmlns/features/v1.2.0" name="${project.artifactId}-${project.version}">
+    <feature name="${project.artifactId}" version="${project.version}"
+             description="${project.description}">
+        <feature>onos-api</feature>
+        <bundle>mvn:${project.groupId}/onos-app-metrics-reporter/${project.version}</bundle>
+        <bundle>mvn:io.dropwizard.metrics/metrics-core/3.1.2</bundle>
+        <bundle>mvn:io.dropwizard.metrics/metrics-ganglia/3.1.2</bundle>
+        <bundle>mvn:info.ganglia.gmetric4j/gmetric4j/1.0.10</bundle>
+        <bundle>mvn:org.acplt.remotetea/remotetea-oncrpc/1.1.3</bundle>
+    </feature>
+</features>
diff --git a/apps/metricsreporter/pom.xml b/apps/metricsreporter/pom.xml
new file mode 100644
index 0000000..53669c8
--- /dev/null
+++ b/apps/metricsreporter/pom.xml
@@ -0,0 +1,116 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ~ Copyright 2016 Open Networking Laboratory
+  ~
+  ~ Licensed 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.
+  -->
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>org.onosproject</groupId>
+        <artifactId>onos-apps</artifactId>
+        <version>1.6.0-SNAPSHOT</version>
+        <relativePath>../pom.xml</relativePath>
+    </parent>
+
+    <artifactId>onos-app-metrics-reporter</artifactId>
+    <packaging>bundle</packaging>
+
+    <description>Performance metric service reporter</description>
+
+    <properties>
+        <onos.app.name>org.onosproject.metrics.reporter</onos.app.name>
+        <onos.app.title>Metric Service Reporter</onos.app.title>
+        <onos.app.category>Monitoring</onos.app.category>
+        <onos.app.url>http://onosproject.org</onos.app.url>
+        <metrics.version>3.1.2</metrics.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.onosproject</groupId>
+            <artifactId>onlab-misc</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.onosproject</groupId>
+            <artifactId>onos-cli</artifactId>
+            <version>${project.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.osgi</groupId>
+            <artifactId>org.osgi.core</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.karaf.shell</groupId>
+            <artifactId>org.apache.karaf.shell.console</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-annotations</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.osgi</groupId>
+            <artifactId>org.osgi.compendium</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>io.dropwizard.metrics</groupId>
+            <artifactId>metrics-core</artifactId>
+            <version>${metrics.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>io.dropwizard.metrics</groupId>
+            <artifactId>metrics-json</artifactId>
+            <version>${metrics.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>io.dropwizard.metrics</groupId>
+            <artifactId>metrics-ganglia</artifactId>
+            <version>${metrics.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>info.ganglia.gmetric4j</groupId>
+            <artifactId>gmetric4j</artifactId>
+            <version>1.0.10</version>
+        </dependency>
+        <dependency>
+            <groupId>org.acplt.remotetea</groupId>
+            <artifactId>remotetea-oncrpc</artifactId>
+            <version>1.1.3</version>
+        </dependency>
+        <dependency>
+            <groupId>org.onosproject</groupId>
+            <artifactId>onlab-junit</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.easymock</groupId>
+            <artifactId>easymock</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.onosproject</groupId>
+            <artifactId>onos-api</artifactId>
+            <version>${project.version}</version>
+            <classifier>tests</classifier>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+</project>
diff --git a/apps/metricsreporter/src/main/java/org/onosproject/metrics/reporter/GangliaMetricsReporter.java b/apps/metricsreporter/src/main/java/org/onosproject/metrics/reporter/GangliaMetricsReporter.java
new file mode 100644
index 0000000..f2f48f4
--- /dev/null
+++ b/apps/metricsreporter/src/main/java/org/onosproject/metrics/reporter/GangliaMetricsReporter.java
@@ -0,0 +1,222 @@
+/*
+ * Copyright 2016 Open Networking Laboratory
+ *
+ * Licensed 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.
+ */
+package org.onosproject.metrics.reporter;
+
+import com.codahale.metrics.MetricRegistry;
+import com.codahale.metrics.ganglia.GangliaReporter;
+import info.ganglia.gmetric4j.gmetric.GMetric;
+import org.apache.commons.lang.StringUtils;
+import org.apache.felix.scr.annotations.Activate;
+import org.apache.felix.scr.annotations.Component;
+import org.apache.felix.scr.annotations.Deactivate;
+import org.apache.felix.scr.annotations.Modified;
+import org.apache.felix.scr.annotations.Property;
+import org.apache.felix.scr.annotations.Reference;
+import org.apache.felix.scr.annotations.ReferenceCardinality;
+import org.onlab.metrics.MetricsService;
+import org.onlab.util.Tools;
+import org.onosproject.cfg.ComponentConfigService;
+import org.onosproject.core.ApplicationId;
+import org.onosproject.core.CoreService;
+import org.osgi.service.component.ComponentContext;
+import org.slf4j.Logger;
+
+import java.io.IOException;
+import java.util.Dictionary;
+import java.util.concurrent.TimeUnit;
+
+import static org.slf4j.LoggerFactory.getLogger;
+
+/**
+ * A metric report that reports all metrics value to ganglia monitoring server.
+ */
+@Component(immediate = true)
+public class GangliaMetricsReporter implements MetricsReporter {
+    private final Logger log = getLogger(getClass());
+
+    // we will use uni-cast mode to transfer the metrics value by default
+    private static final GMetric.UDPAddressingMode GANGLIA_MODE =
+                         GMetric.UDPAddressingMode.UNICAST;
+    private static final int REPORT_PERIOD = 1;
+    private static final TimeUnit REPORT_TIME_UNIT = TimeUnit.MINUTES;
+
+    private static final String DEFAULT_ADDRESS = "localhost";
+    private static final int DEFAULT_PORT = 8649;
+    private static final int DEFAULT_TTL = 1;
+    private static final String DEFAULT_METRIC_NAMES = "default";
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected CoreService coreService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected MetricsService metricsService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected ComponentConfigService cfgService;
+
+    @Property(name = "monitorAll", boolValue = true,
+              label = "Enable to monitor all of metrics stored in metric registry default is true")
+    protected boolean monitorAll = true;
+
+    @Property(name = "metricNames", value = DEFAULT_METRIC_NAMES,
+              label = "Names of metric to be monitored; default metric names are 'default'")
+    protected String metricNames = DEFAULT_METRIC_NAMES;
+
+    @Property(name = "address", value = DEFAULT_ADDRESS,
+              label = "IP address of ganglia monitoring server; default is localhost")
+    protected String address = DEFAULT_ADDRESS;
+
+    @Property(name = "port", intValue = DEFAULT_PORT,
+              label = "Port number of ganglia monitoring server; default is 8649")
+    protected int port = DEFAULT_PORT;
+
+    @Property(name = "ttl", intValue = DEFAULT_TTL,
+              label = "TTL value of ganglia monitoring server; default is 1")
+    protected int ttl = DEFAULT_TTL;
+
+    private ApplicationId appId;
+    private GMetric ganglia;
+    private GangliaReporter gangliaReporter;
+
+    @Activate
+    public void activate() {
+        cfgService.registerProperties(getClass());
+        appId = coreService.registerApplication("org.onosproject.metrics.reporter");
+
+        startReport();
+        log.info("Started");
+    }
+
+    @Deactivate
+    public void deactivate() {
+        cfgService.unregisterProperties(getClass(), false);
+
+        stopReport();
+        log.info("Stopped");
+    }
+
+    @Modified
+    public void modified(ComponentContext context) {
+        readComponentConfiguration(context);
+        stopReport();
+        startReport();
+    }
+
+    @Override
+    public void startReport() {
+        try {
+            ganglia = new GMetric(address, port, GANGLIA_MODE, ttl);
+
+            MetricRegistry mr = metricsService.getMetricRegistry();
+
+            gangliaReporter = GangliaReporter.forRegistry(filter(mr))
+                    .convertRatesTo(TimeUnit.SECONDS)
+                    .convertDurationsTo(TimeUnit.MILLISECONDS)
+                    .build(ganglia);
+            gangliaReporter.start(REPORT_PERIOD, REPORT_TIME_UNIT);
+        } catch (IOException e) {
+            log.error("Fail to connect to given ganglia server!");
+        }
+    }
+
+    @Override
+    public void stopReport() {
+        gangliaReporter.stop();
+        ganglia = null;
+        gangliaReporter = null;
+    }
+
+    /**
+     * Filters the metrics to only include a set of the given metrics.
+     *
+     * @param metricRegistry original metric registry
+     * @return filtered metric registry
+     */
+    protected MetricRegistry filter(MetricRegistry metricRegistry) {
+        if (!monitorAll) {
+            final MetricRegistry filtered = new MetricRegistry();
+            metricRegistry.getNames().stream().filter(name ->
+                    containsName(name, metricNames)).forEach(name ->
+                    filtered.register(name, metricRegistry.getMetrics().get(name)));
+            return filtered;
+        } else {
+            return metricRegistry;
+        }
+    }
+
+    /**
+     * Looks up whether the metric name contains the given prefix keywords.
+     * Note that the keywords are separated with comma as delimiter
+     *
+     * @param full the original metric name that to be compared with
+     * @param prefixes the prefix keywords that are matched against with the metric name
+     * @return boolean value that denotes whether the metric name starts with the given prefix
+     */
+    protected boolean containsName(String full, String prefixes) {
+        String[] prefixArray = StringUtils.split(prefixes, ",");
+        for (String prefix : prefixArray) {
+            if (StringUtils.startsWith(full, StringUtils.trimToEmpty(prefix))) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Extracts properties from the component configuration context.
+     *
+     * @param context the component context
+     */
+    private void readComponentConfiguration(ComponentContext context) {
+        Dictionary<?, ?> properties = context.getProperties();
+
+        String addressStr = Tools.get(properties, "address");
+        address = addressStr != null ? addressStr : DEFAULT_ADDRESS;
+        log.info("Configured. Ganglia server address is {}", address);
+
+        String metricNameStr = Tools.get(properties, "metricNames");
+        metricNames = metricNameStr != null ? metricNameStr : DEFAULT_METRIC_NAMES;
+        log.info("Configured. Metric name is {}", metricNames);
+
+        Integer portConfigured = Tools.getIntegerProperty(properties, "port");
+        if (portConfigured == null) {
+            port = DEFAULT_PORT;
+            log.info("Ganglia port is not configured, default value is {}", port);
+        } else {
+            port = portConfigured;
+            log.info("Configured. Ganglia port is configured to {}", port);
+        }
+
+        Integer ttlConfigured = Tools.getIntegerProperty(properties, "ttl");
+        if (ttlConfigured == null) {
+            ttl = DEFAULT_TTL;
+            log.info("Ganglia TTL is not configured, default value is {}", ttl);
+        } else {
+            ttl = ttlConfigured;
+            log.info("Configured. Ganglia TTL is configured to {}", ttl);
+        }
+
+        Boolean monitorAllEnabled = Tools.isPropertyEnabled(properties, "monitorAll");
+        if (monitorAllEnabled == null) {
+            log.info("Monitor all metrics is not configured, " +
+                     "using current value of {}", monitorAll);
+        } else {
+            monitorAll = monitorAllEnabled;
+            log.info("Configured. Monitor all metrics is {}",
+                    monitorAll ? "enabled" : "disabled");
+        }
+    }
+}
diff --git a/apps/metricsreporter/src/main/java/org/onosproject/metrics/reporter/MetricsReporter.java b/apps/metricsreporter/src/main/java/org/onosproject/metrics/reporter/MetricsReporter.java
new file mode 100644
index 0000000..572e45c
--- /dev/null
+++ b/apps/metricsreporter/src/main/java/org/onosproject/metrics/reporter/MetricsReporter.java
@@ -0,0 +1,32 @@
+/*
+ * Copyright 2016 Open Networking Laboratory
+ *
+ * Licensed 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.
+ */
+package org.onosproject.metrics.reporter;
+
+/**
+ * A metric report that reports all metrics value to third party monitor.
+ */
+public interface MetricsReporter {
+
+    /**
+     * Starts to report a set of metrics to the monitoring server.
+     */
+    void startReport();
+
+    /**
+     * Stops reporting metrics.
+     */
+    void stopReport();
+}
diff --git a/apps/metricsreporter/src/main/java/org/onosproject/metrics/reporter/package-info.java b/apps/metricsreporter/src/main/java/org/onosproject/metrics/reporter/package-info.java
new file mode 100644
index 0000000..0acbcf3
--- /dev/null
+++ b/apps/metricsreporter/src/main/java/org/onosproject/metrics/reporter/package-info.java
@@ -0,0 +1,21 @@
+/*
+ * Copyright 2016 Open Networking Laboratory
+ *
+ * Licensed 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.
+ */
+
+/**
+ * Contains various reporters that backup all of the collected metrics
+ * to monitoring server.
+ */
+package org.onosproject.metrics.reporter;
diff --git a/apps/metricsreporter/src/test/java/org/onosproject/metrics/reporter/GangliaMetricsReporterTest.java b/apps/metricsreporter/src/test/java/org/onosproject/metrics/reporter/GangliaMetricsReporterTest.java
new file mode 100644
index 0000000..c0eeb1a
--- /dev/null
+++ b/apps/metricsreporter/src/test/java/org/onosproject/metrics/reporter/GangliaMetricsReporterTest.java
@@ -0,0 +1,112 @@
+/*
+ * Copyright 2016 Open Networking Laboratory
+ *
+ * Licensed 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.
+ */
+package org.onosproject.metrics.reporter;
+
+import com.codahale.metrics.MetricRegistry;
+import com.google.common.collect.ImmutableSet;
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Unit test for metrics reporter of ganglia.
+ */
+public class GangliaMetricsReporterTest {
+
+    private GangliaMetricsReporter gmr;
+
+    private static final String METRIC_NAME1 = "consistentMap.onos-app-ids.putIfAbsent";
+    private static final String METRIC_NAME2 = "consistentMap.onos-hosts.entrySet";
+    private static final String METRIC_NAME3 = "clusterCommunication.endpoint.*";
+    private static final String METRIC_NAME4 = "atomicCounter.onos-app-id-counter.*";
+
+    private static final String PREFIXES1 = "consistentMap";
+    private static final String PREFIXES2 = "topology";
+    private static final String PREFIXES3 = "consistentMap.onos-app-ids";
+    private static final String PREFIXES4 = "consistentMap, clusterCommunication, atomicCounter";
+
+    /**
+     * Initializes ganglia metrics reporter instance.
+     */
+    @Before
+    public void setUp() {
+        gmr = new GangliaMetricsReporter();
+    }
+
+    /**
+     * Tests whether the containsName method can always return the correct result
+     * with the given metric name and a set of prefixes.
+     */
+    @Test
+    public void testContainsName() {
+        assertTrue(gmr.containsName(METRIC_NAME1, PREFIXES1));
+        assertTrue(gmr.containsName(METRIC_NAME1, PREFIXES3));
+        assertTrue(gmr.containsName(METRIC_NAME1, PREFIXES4));
+        assertTrue(gmr.containsName(METRIC_NAME2, PREFIXES4));
+        assertTrue(gmr.containsName(METRIC_NAME3, PREFIXES4));
+        assertTrue(gmr.containsName(METRIC_NAME4, PREFIXES4));
+        assertFalse(gmr.containsName(METRIC_NAME1, PREFIXES2));
+    }
+
+    /**
+     * Tests whether the filter method can always return the correct result.
+     */
+    @Test
+    public void testFilter() {
+        MetricRegistry filtered;
+        MetricRegistry full = new MetricRegistry();
+        full.meter(METRIC_NAME1);
+        full.meter(METRIC_NAME2);
+        full.meter(METRIC_NAME3);
+        full.meter(METRIC_NAME4);
+
+        gmr.monitorAll = true;
+        filtered = gmr.filter(full);
+
+        assertTrue(filtered.getNames()
+                .containsAll(ImmutableSet.of(METRIC_NAME1, METRIC_NAME2,
+                                             METRIC_NAME3, METRIC_NAME4)));
+
+        gmr.monitorAll = false;
+        gmr.metricNames = PREFIXES1;
+        filtered = gmr.filter(full);
+
+        assertTrue(filtered.getNames()
+                .containsAll(ImmutableSet.of(METRIC_NAME1, METRIC_NAME2)));
+        assertFalse(filtered.getNames()
+                .containsAll(ImmutableSet.of(METRIC_NAME3, METRIC_NAME4)));
+
+        gmr.metricNames = PREFIXES2;
+        filtered = gmr.filter(full);
+
+        assertFalse(filtered.getNames().containsAll(ImmutableSet.of(METRIC_NAME1)));
+
+        gmr.metricNames = PREFIXES3;
+        filtered = gmr.filter(full);
+
+        assertTrue(filtered.getNames().containsAll(ImmutableSet.of(METRIC_NAME1)));
+        assertFalse(filtered.getNames().containsAll(ImmutableSet.of(METRIC_NAME2)));
+
+        gmr.metricNames = PREFIXES4;
+        filtered = gmr.filter(full);
+
+        assertTrue(filtered.getNames()
+                .containsAll(ImmutableSet.of(METRIC_NAME1, METRIC_NAME2,
+                        METRIC_NAME3, METRIC_NAME4)));
+    }
+}
diff --git a/apps/pom.xml b/apps/pom.xml
index 7abc49a..1505f76 100644
--- a/apps/pom.xml
+++ b/apps/pom.xml
@@ -38,6 +38,7 @@
         <module>sdnip</module>
         <module>optical</module>
         <module>metrics</module>
+        <module>metricsreporter</module>
         <module>routing</module>
         <module>routing-api</module>
         <module>reactive-routing</module>
diff --git a/features/features.xml b/features/features.xml
index 58750fb..01ea081 100644
--- a/features/features.xml
+++ b/features/features.xml
@@ -36,8 +36,8 @@
 
         <bundle>mvn:joda-time/joda-time/2.9</bundle>
 
-        <bundle>mvn:io.dropwizard.metrics/metrics-core/3.1.0</bundle>
-        <bundle>mvn:io.dropwizard.metrics/metrics-json/3.1.0</bundle>
+        <bundle>mvn:io.dropwizard.metrics/metrics-core/3.1.2</bundle>
+        <bundle>mvn:io.dropwizard.metrics/metrics-json/3.1.2</bundle>
         <bundle>mvn:com.eclipsesource.minimal-json/minimal-json/0.9.1</bundle>
 
         <bundle>mvn:com.esotericsoftware/kryo/3.0.0</bundle>
diff --git a/utils/misc/pom.xml b/utils/misc/pom.xml
index 25c404b..28573b5 100644
--- a/utils/misc/pom.xml
+++ b/utils/misc/pom.xml
@@ -31,6 +31,10 @@
 
     <description>Miscellaneous ON.Lab utilities</description>
 
+    <properties>
+        <metrics.version>3.1.2</metrics.version>
+    </properties>
+
     <dependencies>
         <dependency>
             <groupId>com.google.guava</groupId>
@@ -71,12 +75,12 @@
         <dependency>
             <groupId>io.dropwizard.metrics</groupId>
             <artifactId>metrics-core</artifactId>
-            <version>3.1.0</version>
+            <version>${metrics.version}</version>
         </dependency>
         <dependency>
             <groupId>io.dropwizard.metrics</groupId>
             <artifactId>metrics-json</artifactId>
-            <version>3.1.0</version>
+            <version>${metrics.version}</version>
         </dependency>
         <dependency>
             <groupId>org.apache.felix</groupId>
diff --git a/utils/misc/src/main/java/org/onlab/metrics/MetricsManager.java b/utils/misc/src/main/java/org/onlab/metrics/MetricsManager.java
index 6c9314a..64bf9ee 100644
--- a/utils/misc/src/main/java/org/onlab/metrics/MetricsManager.java
+++ b/utils/misc/src/main/java/org/onlab/metrics/MetricsManager.java
@@ -102,6 +102,16 @@
     }
 
     /**
+     * Fetches existing metric registry.
+     *
+     * @return metric registry
+     */
+    @Override
+    public MetricRegistry getMetricRegistry() {
+        return metricsRegistry;
+    }
+
+    /**
      * Generates a name for a Metric from its component and feature.
      *
      * @param component component the metric is defined in
diff --git a/utils/misc/src/main/java/org/onlab/metrics/MetricsService.java b/utils/misc/src/main/java/org/onlab/metrics/MetricsService.java
index 4f0d67a..7688da6 100644
--- a/utils/misc/src/main/java/org/onlab/metrics/MetricsService.java
+++ b/utils/misc/src/main/java/org/onlab/metrics/MetricsService.java
@@ -23,6 +23,7 @@
 import com.codahale.metrics.Meter;
 import com.codahale.metrics.Metric;
 import com.codahale.metrics.MetricFilter;
+import com.codahale.metrics.MetricRegistry;
 import com.codahale.metrics.Timer;
 
 /**
@@ -39,6 +40,13 @@
     MetricsComponent registerComponent(String name);
 
     /**
+     * Fetches existing metric registry.
+     *
+     * @return metric registry
+     */
+    MetricRegistry getMetricRegistry();
+
+    /**
      * Creates a Counter metric.
      *
      * @param component component the Counter is defined in
diff --git a/utils/misc/src/test/java/org/onlab/metrics/MetricsServiceAdapter.java b/utils/misc/src/test/java/org/onlab/metrics/MetricsServiceAdapter.java
index 9593feb..59e6116 100644
--- a/utils/misc/src/test/java/org/onlab/metrics/MetricsServiceAdapter.java
+++ b/utils/misc/src/test/java/org/onlab/metrics/MetricsServiceAdapter.java
@@ -19,6 +19,7 @@
 import com.codahale.metrics.Counter;
 import com.codahale.metrics.Histogram;
 import com.codahale.metrics.Meter;
+import com.codahale.metrics.MetricRegistry;
 import com.codahale.metrics.Timer;
 import com.codahale.metrics.Gauge;
 import com.codahale.metrics.Metric;
@@ -39,6 +40,11 @@
     }
 
     @Override
+    public MetricRegistry getMetricRegistry() {
+        return null;
+    }
+
+    @Override
     public Counter createCounter(MetricsComponent component,
                                  MetricsFeature feature, String metricName) {
         return null;