RATIS-1710. Refactor metrics api and implementation to separated modules.

pom.xml

@@ -83,7 +83,8 @@
 
     <module>ratis-examples</module>
     <module>ratis-replicated-map</module>
-    <module>ratis-metrics</module>
+    <module>ratis-metrics-api</module>
+    <module>ratis-metrics-default</module>
     <module>ratis-tools</module>
     <module>ratis-shell</module>
     <module>ratis-assembly</module>
@@ -271,16 +272,21 @@
         <version>${project.version}</version>
       </dependency>
       <dependency>
-       <artifactId>ratis-metrics</artifactId>
-       <groupId>org.apache.ratis</groupId>
-       <version>${project.version}</version>
+        <artifactId>ratis-metrics-api</artifactId>
+        <groupId>org.apache.ratis</groupId>
+        <version>${project.version}</version>
+      </dependency>
+      <dependency>
+        <artifactId>ratis-metrics-default</artifactId>
+        <groupId>org.apache.ratis</groupId>
+        <version>${project.version}</version>
       </dependency>
       <dependency>
-       <artifactId>ratis-metrics</artifactId>
-       <groupId>org.apache.ratis</groupId>
-       <version>${project.version}</version>
-       <type>test-jar</type>
-       <scope>test</scope>
+        <artifactId>ratis-metrics-default</artifactId>
+        <groupId>org.apache.ratis</groupId>
+        <version>${project.version}</version>
+        <type>test-jar</type>
+        <scope>test</scope>
       </dependency>
       <dependency>
         <artifactId>ratis-tools</artifactId>

ratis-assembly/pom.xml

@@ -291,7 +291,11 @@
 
     <dependency>
       <groupId>org.apache.ratis</groupId>
-      <artifactId>ratis-metrics</artifactId>
+      <artifactId>ratis-metrics-api</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.apache.ratis</groupId>
+      <artifactId>ratis-metrics-default</artifactId>
     </dependency>
     <dependency>
       <groupId>org.apache.ratis</groupId>

ratis-assembly/src/main/assembly/bin.xml

@@ -39,7 +39,8 @@
         <include>org.apache.ratis:ratis-server-api</include>
         <include>org.apache.ratis:ratis-server</include>
         <include>org.apache.ratis:ratis-test</include>
-        <include>org.apache.ratis:ratis-metrics</include>
+        <include>org.apache.ratis:ratis-metrics-api</include>
+        <include>org.apache.ratis:ratis-metrics-default</include>
         <include>org.apache.ratis:ratis-tools</include>
         <include>org.apache.ratis:ratis-resource-bundle</include>
       </includes>

ratis-assembly/src/main/assembly/src.xml

@@ -42,7 +42,8 @@
         <include>org.apache.ratis:ratis-server</include>
         <include>org.apache.ratis:ratis-shell</include>
         <include>org.apache.ratis:ratis-test</include>
-        <include>org.apache.ratis:ratis-metrics</include>
+        <include>org.apache.ratis:ratis-metrics-api</include>
+        <include>org.apache.ratis:ratis-metrics-default</include>
         <include>org.apache.ratis:ratis-tools</include>
         <include>org.apache.ratis:ratis-resource-bundle</include>
       </includes>

ratis-examples/pom.xml

@@ -64,6 +64,11 @@
       <type>test-jar</type>
     </dependency>
 
+    <dependency>
+      <artifactId>ratis-metrics-default</artifactId>
+      <groupId>org.apache.ratis</groupId>
+    </dependency>
+
     <dependency>
       <artifactId>ratis-grpc</artifactId>
       <groupId>org.apache.ratis</groupId>

ratis-metrics-api/pom.xml

@@ -0,0 +1,38 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  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. See accompanying LICENSE file.
+-->
+<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/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <artifactId>ratis</artifactId>
+    <groupId>org.apache.ratis</groupId>
+    <version>3.0.0-SNAPSHOT</version>
+  </parent>
+
+  <artifactId>ratis-metrics-api</artifactId>
+  <name>Apache Ratis Metrics API</name>
+
+  <dependencies>
+    <dependency>
+      <artifactId>ratis-common</artifactId>
+      <groupId>org.apache.ratis</groupId>
+    </dependency>
+
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>slf4j-api</artifactId>
+    </dependency>
+  </dependencies>
+</project>

ratis-metrics/src/main/java/org/apache/ratis/metrics/MetricRegistryFactory.java → ratis-metrics-api/src/main/java/org/apache/ratis/metrics/MetricRegistryFactory.java

@@ -1,5 +1,4 @@
-/**
- *
+/*
  * 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
@@ -16,8 +15,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-
-
 package org.apache.ratis.metrics;
 
 /**

ratis-metrics/src/main/java/org/apache/ratis/metrics/MetricRegistryInfo.java → ratis-metrics-api/src/main/java/org/apache/ratis/metrics/MetricRegistryInfo.java

@@ -18,23 +18,25 @@
 
 package org.apache.ratis.metrics;
 
-import org.apache.ratis.thirdparty.com.codahale.metrics.MetricRegistry;
+import org.apache.ratis.util.JavaUtils;
+import org.apache.ratis.util.MemoizedSupplier;
 
 import java.util.Objects;
+import java.util.function.Supplier;
 
 /**
- *
- * This class holds the name and description and JMX related context names for such group of
- * metrics.
+ * This class holds the name, description and JMX related context names for such group of metrics.
+ * <p>
+ * This class is immutable.
  */
 public class MetricRegistryInfo {
-
   private final String prefix;
   private final String metricsDescription;
   private final String metricsComponentName;
-  private final String fullName;
   private final String applicationName;
 
+  private final Supplier<Integer> hash = MemoizedSupplier.valueOf(this::computeHash);
+
   /**
    * @param prefix   className or component name this metric registry collects metric for
    * @param applicationName application Name needs to be in small case as it is used for hadoop2metrics
@@ -48,7 +50,6 @@ public MetricRegistryInfo(String prefix, String applicationName, String metricsC
     this.applicationName = applicationName;
     this.metricsComponentName = metricsComponentName;
     this.metricsDescription = metricsDescription;
-    this.fullName = MetricRegistry.name(applicationName, metricsComponentName, prefix);
   }
 
   public String getApplicationName() {
@@ -79,21 +80,33 @@ public String getPrefix() {
 
   @Override
   public boolean equals(Object obj) {
-    if (obj instanceof MetricRegistryInfo) {
-      return this.hashCode() == obj.hashCode();
-    } else {
+    if (this == obj) {
+      return true;
+    } else if (!(obj instanceof MetricRegistryInfo)) {
       return false;
     }
+    final MetricRegistryInfo that = (MetricRegistryInfo) obj;
+    return Objects.equals(prefix, that.prefix)
+        && Objects.equals(metricsDescription, that.metricsDescription)
+        && Objects.equals(metricsComponentName, that.metricsComponentName)
+        && Objects.equals(applicationName, that.applicationName);
   }
 
   @Override
   public int hashCode() {
-    return Objects.hash(prefix, metricsDescription, metricsComponentName);
+    return hash.get();
   }
 
-  public String getName() {
-    return fullName;
+  private Integer computeHash() {
+    return Objects.hash(prefix, metricsDescription, metricsComponentName);
   }
 
-
+  @Override
+  public String toString() {
+    return JavaUtils.getClassSimpleName(getClass())
+        + ": applicationName=" + getApplicationName()
+        + ", metricsComponentName=" + getMetricsComponentName()
+        + ", prefix=" + getPrefix()
+        + ", metricsDescription=" + getMetricsDescription();
+  }
 }

ratis-metrics/src/main/java/org/apache/ratis/metrics/RatisMetrics.java → ratis-metrics-api/src/main/java/org/apache/ratis/metrics/RatisMetrics.java

@@ -59,9 +59,7 @@ protected static <T extends Enum<T>> Map<T, Timekeeper> newTimerMap(
   protected static RatisMetricRegistry create(MetricRegistryInfo info) {
     Optional<RatisMetricRegistry> metricRegistry = MetricRegistries.global().get(info);
     return metricRegistry.orElseGet(() -> {
-      if (LOG.isDebugEnabled()) {
-        LOG.debug("Creating Metrics Registry : {}", info.getName());
-      }
+      LOG.debug("Creating {}", info);
       return MetricRegistries.global().create(info);
     });
   }
@@ -74,9 +72,7 @@ protected RatisMetrics(RatisMetricRegistry registry) {
 
   public void unregister() {
     MetricRegistryInfo info = registry.getMetricRegistryInfo();
-    if (LOG.isDebugEnabled()) {
-      LOG.debug("Unregistering Metrics Registry : {}", info.getName());
-    }
+    LOG.debug("Unregistering {}", info);
     Optional<RatisMetricRegistry> metricRegistry = MetricRegistries.global().get(info);
     if (metricRegistry.isPresent()) {
       MetricRegistries.global().remove(info);

ratis-metrics/pom.xml → ratis-metrics-default/pom.xml

@@ -21,10 +21,14 @@
     <version>3.0.0-SNAPSHOT</version>
   </parent>
 
-  <artifactId>ratis-metrics</artifactId>
-  <name>Apache Ratis Metrics</name>
+  <artifactId>ratis-metrics-default</artifactId>
+  <name>Apache Ratis Metrics Default Implementation</name>
 
   <dependencies>
+    <dependency>
+      <artifactId>ratis-metrics-api</artifactId>
+      <groupId>org.apache.ratis</groupId>
+    </dependency>
     <dependency>
       <artifactId>ratis-proto</artifactId>
       <groupId>org.apache.ratis</groupId>

ratis-metrics/src/main/java/org/apache/ratis/metrics/impl/RatisMetricRegistryImpl.java → ratis-metrics-default/src/main/java/org/apache/ratis/metrics/impl/RatisMetricRegistryImpl.java

@@ -32,6 +32,7 @@
 import org.apache.ratis.thirdparty.com.google.common.annotations.VisibleForTesting;
 
 import java.util.Map;
+import java.util.Objects;
 import java.util.SortedMap;
 import java.util.function.Supplier;
 
@@ -49,13 +50,14 @@ static RatisMetricRegistryImpl cast(RatisMetricRegistry registry) {
   private final MetricRegistry metricRegistry = new MetricRegistry();
 
   private final MetricRegistryInfo info;
+  private final String namePrefix;
 
   private JmxReporter jmxReporter;
   private ConsoleReporter consoleReporter;
 
   public RatisMetricRegistryImpl(MetricRegistryInfo info) {
-    super();
-    this.info = info;
+    this.info = Objects.requireNonNull(info, "info == null");
+    this.namePrefix = MetricRegistry.name(info.getApplicationName(), info.getMetricsComponentName(), info.getPrefix());
   }
 
   @Override
@@ -111,7 +113,7 @@ public Metric get(String shortName) {
   }
 
   private String getMetricName(String shortName) {
-    return MetricRegistry.name(info.getName(), shortName);
+    return MetricRegistry.name(namePrefix, shortName);
   }
 
   private <T extends Metric> T register(String name, T metric) throws IllegalArgumentException {

ratis-metrics/src/test/java/org/apache/ratis/metrics/TestMetricRegistriesLoader.java → ratis-metrics-default/src/test/java/org/apache/ratis/metrics/TestMetricRegistriesLoader.java

@@ -1,4 +1,4 @@
-/**
+/*
  * 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

ratis-server/pom.xml

@@ -82,15 +82,15 @@
     </dependency>
     <dependency>
       <groupId>org.apache.ratis</groupId>
-      <artifactId>ratis-metrics</artifactId>
+      <artifactId>ratis-metrics-api</artifactId>
     </dependency>
     <dependency>
       <groupId>org.apache.ratis</groupId>
-      <artifactId>ratis-metrics</artifactId>
-      <type>test-jar</type>
+      <artifactId>ratis-metrics-default</artifactId>
       <scope>test</scope>
     </dependency>
 
+
     <dependency>
       <groupId>com.github.spotbugs</groupId>
       <artifactId>spotbugs-annotations</artifactId>

ratis-test/pom.xml

@@ -54,6 +54,12 @@
       <type>test-jar</type>
     </dependency>
 
+    <dependency>
+      <artifactId>ratis-metrics-default</artifactId>
+      <groupId>org.apache.ratis</groupId>
+      <scope>test</scope>
+    </dependency>
+
     <dependency>
       <artifactId>ratis-netty</artifactId>
       <groupId>org.apache.ratis</groupId>