diff --git a/.gitignore b/.gitignore
index bf3e9b4..dcf033c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,5 +9,4 @@
 /.classpath
 /.project
 /.gradle
-/build
-/plugins
\ No newline at end of file
+build
diff --git a/build.gradle b/build.gradle
index 6fce17d..103dce9 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1,66 +1,108 @@
 
 plugins {
-    id "org.sonarqube" version "2.6.1"
-    id "io.codearte.nexus-staging" version "0.11.0"
+    id "org.sonarqube" version "2.8"
+    id "io.codearte.nexus-staging" version "0.21.1"
 }
 
-printf "Host: %s\nOS: %s %s %s\nJVM: %s %s %s %s\nGroovy: %s\nGradle: %s\n" +
-        "Build: group: ${project.group} name: ${project.name} version: ${project.version}\n",
-        InetAddress.getLocalHost(),
-        System.getProperty("os.name"),
-        System.getProperty("os.arch"),
-        System.getProperty("os.version"),
-        System.getProperty("java.version"),
-        System.getProperty("java.vm.version"),
-        System.getProperty("java.vm.vendor"),
-        System.getProperty("java.vm.name"),
-        GroovySystem.getVersion(),
-        gradle.gradleVersion
+subprojects {
 
-apply plugin: 'java'
-apply plugin: 'maven'
-apply plugin: 'signing'
+    apply plugin: 'java'
+    apply plugin: 'maven'
 
-apply from: 'gradle/ext.gradle'
+    dependencies {
+        testCompile "junit:junit:${project.property('junit.version')}"
+        testCompile "org.apache.logging.log4j:log4j-core:${project.property('log4j.version')}"
+        testCompile "org.apache.logging.log4j:log4j-slf4j-impl:${project.property('log4j.version')}"
+    }
 
-configurations {
-    wagon
-}
+    compileJava {
+        sourceCompatibility = JavaVersion.VERSION_11
+        targetCompatibility = JavaVersion.VERSION_11
+    }
+    compileTestJava {
+        sourceCompatibility = JavaVersion.VERSION_11
+        targetCompatibility = JavaVersion.VERSION_11
+    }
+    tasks.withType(JavaCompile) {
+        options.compilerArgs << "-Xlint:all"
+    }
+    
+    task javadocJar(type: Jar, dependsOn: classes) {
+        from javadoc
+        classifier 'javadoc'
+    }
+    
+    task sourcesJar(type: Jar, dependsOn: classes) {
+        from sourceSets.main.allSource
+        classifier 'sources'
+    }
+    
+    artifacts {
+        archives javadocJar, sourcesJar
+    }
 
-dependencies {
-    testCompile "junit:junit:4.12"
-    testCompile "org.apache.logging.log4j:log4j-core:2.10.0"
-    testCompile "org.apache.logging.log4j:log4j-slf4j-impl:2.10.0"
-    wagon 'org.apache.maven.wagon:wagon-ssh:3.0.0'
-}
+    ext {
+        user = 'jprante'
+        name = 'metrics'
+        description = 'A stripped-down and modified version of Coda Hale Metrics'
+        scmUrl = 'https://github.com/' + user + '/' + name
+        scmConnection = 'scm:git:git://github.com/' + user + '/' + name + '.git'
+        scmDeveloperConnection = 'scm:git:git://github.com/' + user + '/' + name + '.git'
+    }
 
-sourceCompatibility = 1.8
-targetCompatibility = 1.8
-
-tasks.withType(JavaCompile) {
-    options.compilerArgs << "-Xlint:all" << "-profile" << "compact3"
-}
-
-task javadocJar(type: Jar, dependsOn: classes) {
-    from javadoc
-    into "build/tmp"
-    classifier 'javadoc'
-}
-
-task sourcesJar(type: Jar, dependsOn: classes) {
-    from sourceSets.main.allSource
-    into "build/tmp"
-    classifier 'sources'
-}
-
-artifacts {
-    archives javadocJar, sourcesJar
-}
-
-if (project.hasProperty('signing.keyId')) {
-    signing {
-        sign configurations.archives
+    task sonaTypeUpload(type: Upload) {
+        group = 'publish'
+        configuration = configurations.archives
+        uploadDescriptor = true
+        repositories {
+            if (project.hasProperty('ossrhUsername')) {
+                mavenDeployer {
+                    beforeDeployment { MavenDeployment deployment -> signing.signPom(deployment) }
+                    repository(url: 'https://oss.sonatype.org/service/local/staging/deploy/maven2') {
+                        authentication(userName: ossrhUsername, password: ossrhPassword)
+                    }
+                    snapshotRepository(url: 'https://oss.sonatype.org/content/repositories/snapshots') {
+                        authentication(userName: ossrhUsername, password: ossrhPassword)
+                    }
+                    pom.project {
+                        groupId project.group
+                        artifactId project.name
+                        version project.version
+                        name project.name
+                        description description
+                        packaging 'jar'
+                        inceptionYear '2016'
+                        url scmUrl
+                        organization {
+                            name 'xbib'
+                            url 'http://xbib.org'
+                        }
+                        developers {
+                            developer {
+                                id user
+                                name 'Jörg Prante'
+                                email 'joergprante@gmail.com'
+                                url 'https://github.com/jprante'
+                            }
+                        }
+                        scm {
+                            url scmUrl
+                            connection scmConnection
+                            developerConnection scmDeveloperConnection
+                        }
+                        licenses {
+                            license {
+                                name 'The Apache License, Version 2.0'
+                                url 'http://www.apache.org/licenses/LICENSE-2.0.txt'
+                            }
+                        }
+                    }
+                }
+            }
+        }
     }
 }
 
-apply from: 'gradle/publish.gradle'
+nexusStaging {
+    packageGroup = "org.xbib"
+}
diff --git a/gradle.properties b/gradle.properties
index 8056dc3..d240468 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -1,6 +1,7 @@
 group = org.xbib
 name = metrics
-version = 1.1.0
+version = 2.0.0
 
+# test
+log4j.version = 2.12.1
 junit.version = 4.12
-wagon.version = 3.0.0
diff --git a/gradle/ext.gradle b/gradle/ext.gradle
deleted file mode 100644
index 3b01be1..0000000
--- a/gradle/ext.gradle
+++ /dev/null
@@ -1,8 +0,0 @@
-ext {
-    user = 'jprante'
-    name = 'metrics'
-    description = 'A stripped-down and modified version of Coda Hale Metrics'
-    scmUrl = 'https://github.com/' + user + '/' + name
-    scmConnection = 'scm:git:git://github.com/' + user + '/' + name + '.git'
-    scmDeveloperConnection = 'scm:git:git://github.com/' + user + '/' + name + '.git'
-}
diff --git a/gradle/publish.gradle b/gradle/publish.gradle
deleted file mode 100644
index 376f190..0000000
--- a/gradle/publish.gradle
+++ /dev/null
@@ -1,72 +0,0 @@
-
-task xbibUpload(type: Upload) {
-    group = 'publish'
-    configuration = configurations.archives
-    uploadDescriptor = true
-    repositories {
-        if (project.hasProperty("xbibUsername")) {
-            mavenDeployer {
-                configuration = configurations.wagon
-                repository(url: project.property('xbibUrl')) {
-                    authentication(userName: xbibUsername, privateKey: xbibPrivateKey)
-                }
-            }
-        }
-    }
-}
-
-task sonaTypeUpload(type: Upload) {
-    group = 'publish'
-    configuration = configurations.archives
-    uploadDescriptor = true
-    repositories {
-        if (project.hasProperty('ossrhUsername')) {
-            mavenDeployer {
-                beforeDeployment { MavenDeployment deployment -> signing.signPom(deployment) }
-                repository(url: 'https://oss.sonatype.org/service/local/staging/deploy/maven2') {
-                    authentication(userName: ossrhUsername, password: ossrhPassword)
-                }
-                snapshotRepository(url: 'https://oss.sonatype.org/content/repositories/snapshots') {
-                    authentication(userName: ossrhUsername, password: ossrhPassword)
-                }
-                pom.project {
-                    groupId project.group
-                    artifactId project.name
-                    version project.version
-                    name project.name
-                    description description
-                    packaging 'jar'
-                    inceptionYear '2016'
-                    url scmUrl
-                    organization {
-                        name 'xbib'
-                        url 'http://xbib.org'
-                    }
-                    developers {
-                        developer {
-                            id user
-                            name 'Jörg Prante'
-                            email 'joergprante@gmail.com'
-                            url 'https://github.com/jprante'
-                        }
-                    }
-                    scm {
-                        url scmUrl
-                        connection scmConnection
-                        developerConnection scmDeveloperConnection
-                    }
-                    licenses {
-                        license {
-                            name 'The Apache License, Version 2.0'
-                            url 'http://www.apache.org/licenses/LICENSE-2.0.txt'
-                        }
-                    }
-                }
-            }
-        }
-    }
-}
-
-nexusStaging {
-    packageGroup = "org.xbib"
-}
diff --git a/gradle/sonarqube.gradle b/gradle/sonarqube.gradle
deleted file mode 100644
index 6d4c3fa..0000000
--- a/gradle/sonarqube.gradle
+++ /dev/null
@@ -1,41 +0,0 @@
-tasks.withType(FindBugs) {
-    ignoreFailures = true
-    reports {
-        xml.enabled = true
-        html.enabled = false
-    }
-}
-tasks.withType(Pmd) {
-    ignoreFailures = true
-    reports {
-        xml.enabled = true
-        html.enabled = true
-    }
-}
-tasks.withType(Checkstyle) {
-    ignoreFailures = true
-    reports {
-        xml.enabled = true
-        html.enabled = true
-    }
-}
-
-jacocoTestReport {
-    reports {
-        xml.enabled true
-        csv.enabled false
-        xml.destination "${buildDir}/reports/jacoco-xml"
-        html.destination "${buildDir}/reports/jacoco-html"
-    }
-}
-
-sonarqube {
-    properties {
-        property "sonar.projectName", "${project.group} ${project.name}"
-        property "sonar.sourceEncoding", "UTF-8"
-        property "sonar.tests", "src/test/java"
-        property "sonar.scm.provider", "git"
-        property "sonar.java.coveragePlugin", "jacoco"
-        property "sonar.junit.reportsPath", "build/test-results/test/"
-    }
-}
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
index 8252d7e..5c2d1cf 100644
Binary files a/gradle/wrapper/gradle-wrapper.jar and b/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index eac7de5..80c4ad3 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,5 +1,6 @@
+#Thu Nov 07 15:59:31 CET 2019
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.2-all.zip
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.6-rc-1-bin.zip
-zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
diff --git a/gradlew b/gradlew
index cccdd3d..83f2acf 100755
--- a/gradlew
+++ b/gradlew
@@ -1,5 +1,21 @@
 #!/usr/bin/env sh
 
+#
+# Copyright 2015 the original author or authors.
+#
+# 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
+#
+#      https://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.
+#
+
 ##############################################################################
 ##
 ##  Gradle start up script for UN*X
@@ -28,7 +44,7 @@ APP_NAME="Gradle"
 APP_BASE_NAME=`basename "$0"`
 
 # Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
-DEFAULT_JVM_OPTS=""
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
 
 # Use the maximum available, or set MAX_FD != -1 to use that value.
 MAX_FD="maximum"
@@ -109,8 +125,8 @@ if $darwin; then
     GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
 fi
 
-# For Cygwin, switch paths to Windows format before running java
-if $cygwin ; then
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if [ "$cygwin" = "true" -o "$msys" = "true" ] ; then
     APP_HOME=`cygpath --path --mixed "$APP_HOME"`
     CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
     JAVACMD=`cygpath --unix "$JAVACMD"`
diff --git a/gradlew.bat b/gradlew.bat
index e95643d..24467a1 100644
--- a/gradlew.bat
+++ b/gradlew.bat
@@ -1,3 +1,19 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
 @if "%DEBUG%" == "" @echo off
 @rem ##########################################################################
 @rem
@@ -14,7 +30,7 @@ set APP_BASE_NAME=%~n0
 set APP_HOME=%DIRNAME%
 
 @rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
-set DEFAULT_JVM_OPTS=
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
 
 @rem Find java.exe
 if defined JAVA_HOME goto findJavaFromJavaHome
diff --git a/metrics-api/src/main/java/org/xbib/metrics/api/Clock.java b/metrics-api/src/main/java/org/xbib/metrics/api/Clock.java
new file mode 100644
index 0000000..459b1a6
--- /dev/null
+++ b/metrics-api/src/main/java/org/xbib/metrics/api/Clock.java
@@ -0,0 +1,21 @@
+package org.xbib.metrics.api;
+
+/**
+ * An interface for how time passes.
+ */
+public interface Clock {
+
+    /**
+     * Returns the current time tick.
+     *
+     * @return time tick in nanoseconds
+     */
+    long getTick();
+
+    /**
+     * Returns the current time in milliseconds.
+     *
+     * @return time in milliseconds
+     */
+    long getTime();
+}
diff --git a/src/main/java/org/xbib/metrics/Count.java b/metrics-api/src/main/java/org/xbib/metrics/api/Count.java
similarity index 94%
rename from src/main/java/org/xbib/metrics/Count.java
rename to metrics-api/src/main/java/org/xbib/metrics/api/Count.java
index 6c885dd..4e0673f 100644
--- a/src/main/java/org/xbib/metrics/Count.java
+++ b/metrics-api/src/main/java/org/xbib/metrics/api/Count.java
@@ -1,4 +1,4 @@
-package org.xbib.metrics;
+package org.xbib.metrics.api;
 
 /**
  * An interface for metric types which have counts.
diff --git a/src/main/java/org/xbib/metrics/Gauge.java b/metrics-api/src/main/java/org/xbib/metrics/api/Gauge.java
similarity index 95%
rename from src/main/java/org/xbib/metrics/Gauge.java
rename to metrics-api/src/main/java/org/xbib/metrics/api/Gauge.java
index f3f53ad..0c8a3ff 100644
--- a/src/main/java/org/xbib/metrics/Gauge.java
+++ b/metrics-api/src/main/java/org/xbib/metrics/api/Gauge.java
@@ -1,4 +1,4 @@
-package org.xbib.metrics;
+package org.xbib.metrics.api;
 
 /**
  * A gauge metric is an instantaneous reading of a particular value. To instrument a queue's depth,
diff --git a/src/main/java/org/xbib/metrics/Metered.java b/metrics-api/src/main/java/org/xbib/metrics/api/Metered.java
similarity index 96%
rename from src/main/java/org/xbib/metrics/Metered.java
rename to metrics-api/src/main/java/org/xbib/metrics/api/Metered.java
index 476ef97..7f4c08b 100644
--- a/src/main/java/org/xbib/metrics/Metered.java
+++ b/metrics-api/src/main/java/org/xbib/metrics/api/Metered.java
@@ -1,4 +1,6 @@
-package org.xbib.metrics;
+package org.xbib.metrics.api;
+
+import org.xbib.metrics.api.Metric;
 
 /**
  * An object which maintains mean and exponentially-weighted rate.
diff --git a/src/main/java/org/xbib/metrics/Metric.java b/metrics-api/src/main/java/org/xbib/metrics/api/Metric.java
similarity index 57%
rename from src/main/java/org/xbib/metrics/Metric.java
rename to metrics-api/src/main/java/org/xbib/metrics/api/Metric.java
index 9679413..f1f05b6 100644
--- a/src/main/java/org/xbib/metrics/Metric.java
+++ b/metrics-api/src/main/java/org/xbib/metrics/api/Metric.java
@@ -1,4 +1,4 @@
-package org.xbib.metrics;
+package org.xbib.metrics.api;
 
 /**
  *
diff --git a/src/main/java/org/xbib/metrics/MetricFilter.java b/metrics-api/src/main/java/org/xbib/metrics/api/MetricFilter.java
similarity index 95%
rename from src/main/java/org/xbib/metrics/MetricFilter.java
rename to metrics-api/src/main/java/org/xbib/metrics/api/MetricFilter.java
index 0be8511..a6939d8 100644
--- a/src/main/java/org/xbib/metrics/MetricFilter.java
+++ b/metrics-api/src/main/java/org/xbib/metrics/api/MetricFilter.java
@@ -1,4 +1,4 @@
-package org.xbib.metrics;
+package org.xbib.metrics.api;
 
 /**
  * A filter used to determine whether or not a metric should be reported, among other things.
diff --git a/src/main/java/org/xbib/metrics/MetricName.java b/metrics-api/src/main/java/org/xbib/metrics/api/MetricName.java
similarity index 99%
rename from src/main/java/org/xbib/metrics/MetricName.java
rename to metrics-api/src/main/java/org/xbib/metrics/api/MetricName.java
index 0ef8668..a867102 100644
--- a/src/main/java/org/xbib/metrics/MetricName.java
+++ b/metrics-api/src/main/java/org/xbib/metrics/api/MetricName.java
@@ -1,4 +1,4 @@
-package org.xbib.metrics;
+package org.xbib.metrics.api;
 
 import java.util.Collections;
 import java.util.HashMap;
@@ -10,8 +10,11 @@ import java.util.TreeSet;
  * A metric name with the ability to include semantic tags.
  */
 public class MetricName implements Comparable<MetricName> {
+
     public static final String SEPARATOR = ".";
+
     public static final Map<String, String> EMPTY_TAGS = Collections.unmodifiableMap(new HashMap<String, String>());
+
     public static final MetricName EMPTY = new MetricName();
 
     private final String key;
diff --git a/src/main/java/org/xbib/metrics/MetricSet.java b/metrics-api/src/main/java/org/xbib/metrics/api/MetricSet.java
similarity index 77%
rename from src/main/java/org/xbib/metrics/MetricSet.java
rename to metrics-api/src/main/java/org/xbib/metrics/api/MetricSet.java
index 7a6ead4..0221f41 100644
--- a/src/main/java/org/xbib/metrics/MetricSet.java
+++ b/metrics-api/src/main/java/org/xbib/metrics/api/MetricSet.java
@@ -1,11 +1,9 @@
-package org.xbib.metrics;
+package org.xbib.metrics.api;
 
 import java.util.Map;
 
 /**
  * A set of named metrics.
- *
- * @see MetricRegistry#registerAll(MetricSet)
  */
 @FunctionalInterface
 public interface MetricSet extends Metric {
diff --git a/src/main/java/org/xbib/metrics/Reservoir.java b/metrics-api/src/main/java/org/xbib/metrics/api/Reservoir.java
similarity index 94%
rename from src/main/java/org/xbib/metrics/Reservoir.java
rename to metrics-api/src/main/java/org/xbib/metrics/api/Reservoir.java
index db3e6b6..4bc826b 100644
--- a/src/main/java/org/xbib/metrics/Reservoir.java
+++ b/metrics-api/src/main/java/org/xbib/metrics/api/Reservoir.java
@@ -1,4 +1,4 @@
-package org.xbib.metrics;
+package org.xbib.metrics.api;
 
 /**
  * A statistically representative reservoir of a data stream.
diff --git a/src/main/java/org/xbib/metrics/Sampling.java b/metrics-api/src/main/java/org/xbib/metrics/api/Sampling.java
similarity index 88%
rename from src/main/java/org/xbib/metrics/Sampling.java
rename to metrics-api/src/main/java/org/xbib/metrics/api/Sampling.java
index 793225e..6dfed5d 100644
--- a/src/main/java/org/xbib/metrics/Sampling.java
+++ b/metrics-api/src/main/java/org/xbib/metrics/api/Sampling.java
@@ -1,4 +1,4 @@
-package org.xbib.metrics;
+package org.xbib.metrics.api;
 
 /**
  * An object which samples values.
diff --git a/src/main/java/org/xbib/metrics/Snapshot.java b/metrics-api/src/main/java/org/xbib/metrics/api/Snapshot.java
similarity index 98%
rename from src/main/java/org/xbib/metrics/Snapshot.java
rename to metrics-api/src/main/java/org/xbib/metrics/api/Snapshot.java
index c6e1ca3..7450f11 100644
--- a/src/main/java/org/xbib/metrics/Snapshot.java
+++ b/metrics-api/src/main/java/org/xbib/metrics/api/Snapshot.java
@@ -1,4 +1,4 @@
-package org.xbib.metrics;
+package org.xbib.metrics.api;
 
 import java.io.OutputStream;
 
diff --git a/metrics-api/src/main/java/org/xbib/metrics/api/package-info.java b/metrics-api/src/main/java/org/xbib/metrics/api/package-info.java
new file mode 100644
index 0000000..772933d
--- /dev/null
+++ b/metrics-api/src/main/java/org/xbib/metrics/api/package-info.java
@@ -0,0 +1,4 @@
+/**
+ * API interfaces for metrics.
+ */
+package org.xbib.metrics.api;
diff --git a/metrics-common/build.gradle b/metrics-common/build.gradle
new file mode 100644
index 0000000..740edb1
--- /dev/null
+++ b/metrics-common/build.gradle
@@ -0,0 +1,3 @@
+dependencies {
+    compile project(':metrics-api')
+}
diff --git a/src/main/java/org/xbib/metrics/CountMetric.java b/metrics-common/src/main/java/org/xbib/metrics/common/CountMetric.java
similarity index 88%
rename from src/main/java/org/xbib/metrics/CountMetric.java
rename to metrics-common/src/main/java/org/xbib/metrics/common/CountMetric.java
index 4dd3aea..bf40573 100644
--- a/src/main/java/org/xbib/metrics/CountMetric.java
+++ b/metrics-common/src/main/java/org/xbib/metrics/common/CountMetric.java
@@ -1,4 +1,7 @@
-package org.xbib.metrics;
+package org.xbib.metrics.common;
+
+import org.xbib.metrics.api.Count;
+import org.xbib.metrics.api.Metric;
 
 import java.nio.charset.StandardCharsets;
 import java.util.HashMap;
@@ -49,7 +52,8 @@ public class CountMetric implements Metric, Count {
             checksumIn.put(index + "/" + type, crc32);
         }
         if (id != null) {
-            crc32.update(id.getBytes(StandardCharsets.UTF_8));
+            byte[] b = id.getBytes(StandardCharsets.UTF_8);
+            crc32.update(b, 0, b.length);
         }
     }
 
@@ -79,7 +83,8 @@ public class CountMetric implements Metric, Count {
             checksumOut.put(index + "/" + type, crc32);
         }
         if (id != null) {
-            crc32.update(id.getBytes(StandardCharsets.UTF_8));
+            byte[] b = id.getBytes(StandardCharsets.UTF_8);
+            crc32.update(b, 0, b.length);
         }
     }
 
diff --git a/src/main/java/org/xbib/metrics/CpuTimeClock.java b/metrics-common/src/main/java/org/xbib/metrics/common/CpuTimeClock.java
similarity index 87%
rename from src/main/java/org/xbib/metrics/CpuTimeClock.java
rename to metrics-common/src/main/java/org/xbib/metrics/common/CpuTimeClock.java
index 05a7669..3dcf61d 100644
--- a/src/main/java/org/xbib/metrics/CpuTimeClock.java
+++ b/metrics-common/src/main/java/org/xbib/metrics/common/CpuTimeClock.java
@@ -1,4 +1,6 @@
-package org.xbib.metrics;
+package org.xbib.metrics.common;
+
+import org.xbib.metrics.api.Clock;
 
 import java.lang.management.ManagementFactory;
 import java.lang.management.ThreadMXBean;
diff --git a/src/main/java/org/xbib/metrics/ExpWeightedMovingAverage.java b/metrics-common/src/main/java/org/xbib/metrics/common/ExpWeightedMovingAverage.java
similarity index 97%
rename from src/main/java/org/xbib/metrics/ExpWeightedMovingAverage.java
rename to metrics-common/src/main/java/org/xbib/metrics/common/ExpWeightedMovingAverage.java
index 4f30f24..fea9dde 100644
--- a/src/main/java/org/xbib/metrics/ExpWeightedMovingAverage.java
+++ b/metrics-common/src/main/java/org/xbib/metrics/common/ExpWeightedMovingAverage.java
@@ -1,4 +1,4 @@
-package org.xbib.metrics;
+package org.xbib.metrics.common;
 
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.LongAdder;
@@ -11,14 +11,22 @@ import java.util.concurrent.atomic.LongAdder;
  * Average</a>
  */
 public class ExpWeightedMovingAverage {
+
     private static final double M1_ALPHA = 1 - Math.exp(-5 / 60.0);
+
     private static final double M5_ALPHA = 1 - Math.exp(-5 / 60.0 / 5);
+
     private static final double M15_ALPHA = 1 - Math.exp(-5 / 60.0 / 15);
+
     private final LongAdder uncounted = new LongAdder();
+
     private final double alpha;
+
     private final double interval;
+
     private volatile boolean initialized = false;
-    private volatile double rate = 0.0;
+
+    private double rate = 0.0;
 
     /**
      * Create a new EWMA with a specific smoothing constant.
diff --git a/src/main/java/org/xbib/metrics/ExponentiallyDecayingReservoir.java b/metrics-common/src/main/java/org/xbib/metrics/common/ExponentiallyDecayingReservoir.java
similarity index 96%
rename from src/main/java/org/xbib/metrics/ExponentiallyDecayingReservoir.java
rename to metrics-common/src/main/java/org/xbib/metrics/common/ExponentiallyDecayingReservoir.java
index c0b2325..b1cd32f 100644
--- a/src/main/java/org/xbib/metrics/ExponentiallyDecayingReservoir.java
+++ b/metrics-common/src/main/java/org/xbib/metrics/common/ExponentiallyDecayingReservoir.java
@@ -1,4 +1,8 @@
-package org.xbib.metrics;
+package org.xbib.metrics.common;
+
+import org.xbib.metrics.api.Clock;
+import org.xbib.metrics.api.Reservoir;
+import org.xbib.metrics.api.Snapshot;
 
 import static java.lang.Math.exp;
 import static java.lang.Math.min;
@@ -24,7 +28,7 @@ public class ExponentiallyDecayingReservoir implements Reservoir {
     private static final double DEFAULT_ALPHA = 0.015;
     private static final long RESCALE_THRESHOLD = TimeUnit.HOURS.toNanos(1);
 
-    private final ConcurrentSkipListMap<Double, org.xbib.metrics.WeightedSnapshot.WeightedSample> values;
+    private final ConcurrentSkipListMap<Double, WeightedSnapshot.WeightedSample> values;
     private final ReentrantReadWriteLock lock;
     private final double alpha;
     private final int size;
@@ -50,7 +54,7 @@ public class ExponentiallyDecayingReservoir implements Reservoir {
      *              will be towards newer values
      */
     public ExponentiallyDecayingReservoir(int size, double alpha) {
-        this(size, alpha, Clock.defaultClock());
+        this(size, alpha, UserTimeClock.defaultClock());
     }
 
     /**
diff --git a/src/main/java/org/xbib/metrics/Histogram.java b/metrics-common/src/main/java/org/xbib/metrics/common/Histogram.java
similarity index 88%
rename from src/main/java/org/xbib/metrics/Histogram.java
rename to metrics-common/src/main/java/org/xbib/metrics/common/Histogram.java
index 4f4beda..1682f1e 100644
--- a/src/main/java/org/xbib/metrics/Histogram.java
+++ b/metrics-common/src/main/java/org/xbib/metrics/common/Histogram.java
@@ -1,4 +1,10 @@
-package org.xbib.metrics;
+package org.xbib.metrics.common;
+
+import org.xbib.metrics.api.Count;
+import org.xbib.metrics.api.Metric;
+import org.xbib.metrics.api.Reservoir;
+import org.xbib.metrics.api.Sampling;
+import org.xbib.metrics.api.Snapshot;
 
 import java.util.concurrent.atomic.LongAdder;
 
@@ -9,7 +15,9 @@ import java.util.concurrent.atomic.LongAdder;
  * variance</a>
  */
 public class Histogram implements Metric, Sampling, Count {
+
     private final Reservoir reservoir;
+
     private final LongAdder count;
 
     /**
diff --git a/src/main/java/org/xbib/metrics/Meter.java b/metrics-common/src/main/java/org/xbib/metrics/common/Meter.java
similarity index 95%
rename from src/main/java/org/xbib/metrics/Meter.java
rename to metrics-common/src/main/java/org/xbib/metrics/common/Meter.java
index 9b45fc1..29d5994 100644
--- a/src/main/java/org/xbib/metrics/Meter.java
+++ b/metrics-common/src/main/java/org/xbib/metrics/common/Meter.java
@@ -1,4 +1,7 @@
-package org.xbib.metrics;
+package org.xbib.metrics.common;
+
+import org.xbib.metrics.api.Clock;
+import org.xbib.metrics.api.Metered;
 
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledFuture;
@@ -38,7 +41,7 @@ public class Meter implements Metered {
      * @param executorService the executor service
      */
     public Meter(ScheduledExecutorService executorService) {
-        this(executorService, Clock.defaultClock());
+        this(executorService, UserTimeClock.defaultClock());
     }
 
     /**
diff --git a/src/main/java/org/xbib/metrics/MetricRegistry.java b/metrics-common/src/main/java/org/xbib/metrics/common/MetricRegistry.java
similarity index 79%
rename from src/main/java/org/xbib/metrics/MetricRegistry.java
rename to metrics-common/src/main/java/org/xbib/metrics/common/MetricRegistry.java
index 08001fd..20022de 100644
--- a/src/main/java/org/xbib/metrics/MetricRegistry.java
+++ b/metrics-common/src/main/java/org/xbib/metrics/common/MetricRegistry.java
@@ -1,4 +1,10 @@
-package org.xbib.metrics;
+package org.xbib.metrics.common;
+
+import org.xbib.metrics.api.Gauge;
+import org.xbib.metrics.api.Metric;
+import org.xbib.metrics.api.MetricFilter;
+import org.xbib.metrics.api.MetricName;
+import org.xbib.metrics.api.MetricSet;
 
 import java.util.Collections;
 import java.util.List;
@@ -20,8 +26,10 @@ import java.util.logging.Logger;
 public class MetricRegistry implements MetricSet {
 
     private static final Logger logger = Logger.getLogger(MetricRegistry.class.getName());
+
     private final ConcurrentMap<MetricName, Metric> metrics;
-    private final List<MetricRegistryListener> listeners;
+
+    private final List<Listener> listeners;
 
     /**
      * Creates a new {@link MetricRegistry}.
@@ -234,13 +242,13 @@ public class MetricRegistry implements MetricSet {
     }
 
     /**
-     * Adds a {@link MetricRegistryListener} to a collection of listeners that will be notified on
+     * Adds a {@link Listener} to a collection of listeners that will be notified on
      * metric creation.  Listeners will be notified in the order in which they are added.
      * The listener will be notified of all existing metrics when it first registers.
      *
      * @param listener the listener that will be notified
      */
-    public void addListener(MetricRegistryListener listener) {
+    public void addListener(Listener listener) {
         listeners.add(listener);
 
         for (Map.Entry<MetricName, Metric> entry : metrics.entrySet()) {
@@ -249,11 +257,11 @@ public class MetricRegistry implements MetricSet {
     }
 
     /**
-     * Removes a {@link MetricRegistryListener} from this registry's collection of listeners.
+     * Removes a {@link Listener} from this registry's collection of listeners.
      *
      * @param listener the listener that will be removed
      */
-    public void removeListener(MetricRegistryListener listener) {
+    public void removeListener(Listener listener) {
         listeners.remove(listener);
     }
 
@@ -397,12 +405,12 @@ public class MetricRegistry implements MetricSet {
     }
 
     private void onMetricAdded(MetricName name, Metric metric) {
-        for (MetricRegistryListener listener : listeners) {
+        for (Listener listener : listeners) {
             notifyListenerOfAddedMetric(listener, metric, name);
         }
     }
 
-    private void notifyListenerOfAddedMetric(MetricRegistryListener listener, Metric metric, MetricName name) {
+    private void notifyListenerOfAddedMetric(Listener listener, Metric metric, MetricName name) {
         if (metric instanceof Gauge) {
             listener.onGaugeAdded(name, (Gauge<?>) metric);
         } else if (metric instanceof CountMetric) {
@@ -419,12 +427,12 @@ public class MetricRegistry implements MetricSet {
     }
 
     private void onMetricRemoved(MetricName name, Metric metric) {
-        for (MetricRegistryListener listener : listeners) {
+        for (Listener listener : listeners) {
             notifyListenerOfRemovedMetric(name, metric, listener);
         }
     }
 
-    private void notifyListenerOfRemovedMetric(MetricName name, Metric metric, MetricRegistryListener listener) {
+    private void notifyListenerOfRemovedMetric(MetricName name, Metric metric, Listener listener) {
         if (metric instanceof Gauge) {
             listener.onGaugeRemoved(name);
         } else if (metric instanceof CountMetric) {
@@ -456,6 +464,132 @@ public class MetricRegistry implements MetricSet {
         return Collections.unmodifiableMap(metrics);
     }
 
+
+    /**
+     * Listeners for events from the registry.  Listeners must be thread-safe.
+     */
+    public interface Listener {
+        /**
+         * Called when a {@link Gauge} is added to the registry.
+         *
+         * @param name  the gauge's name
+         * @param gauge the gauge
+         */
+        void onGaugeAdded(MetricName name, Gauge<?> gauge);
+
+        /**
+         * Called when a {@link Gauge} is removed from the registry.
+         *
+         * @param name the gauge's name
+         */
+        void onGaugeRemoved(MetricName name);
+
+        /**
+         * Called when a {@link CountMetric} is added to the registry.
+         *
+         * @param name    the counter's name
+         * @param counter the counter
+         */
+        void onCounterAdded(MetricName name, CountMetric counter);
+
+        /**
+         * Called when a {@link CountMetric} is removed from the registry.
+         *
+         * @param name the counter's name
+         */
+        void onCounterRemoved(MetricName name);
+
+        /**
+         * Called when a {@link Histogram} is added to the registry.
+         *
+         * @param name      the histogram's name
+         * @param histogram the histogram
+         */
+        void onHistogramAdded(MetricName name, Histogram histogram);
+
+        /**
+         * Called when a {@link Histogram} is removed from the registry.
+         *
+         * @param name the histogram's name
+         */
+        void onHistogramRemoved(MetricName name);
+
+        /**
+         * Called when a {@link Meter} is added to the registry.
+         *
+         * @param name  the meter's name
+         * @param meter the meter
+         */
+        void onMeterAdded(MetricName name, Meter meter);
+
+        /**
+         * Called when a {@link Meter} is removed from the registry.
+         *
+         * @param name the meter's name
+         */
+        void onMeterRemoved(MetricName name);
+
+        /**
+         * Called when a {@link Sampler} is added to the registry.
+         *
+         * @param name    the sampler's name
+         * @param sampler the sampler
+         */
+        void onTimerAdded(MetricName name, Sampler sampler);
+
+        /**
+         * Called when a {@link Sampler} is removed from the registry.
+         *
+         * @param name the timer's name
+         */
+        void onTimerRemoved(MetricName name);
+    }
+
+    /**
+     * A no-op implementation of {@link Listener}.
+     */
+    abstract class Base implements Listener {
+        @Override
+        public void onGaugeAdded(MetricName name, Gauge<?> gauge) {
+        }
+
+        @Override
+        public void onGaugeRemoved(MetricName name) {
+        }
+
+        @Override
+        public void onCounterAdded(MetricName name, CountMetric counter) {
+        }
+
+        @Override
+        public void onCounterRemoved(MetricName name) {
+        }
+
+        @Override
+        public void onHistogramAdded(MetricName name, Histogram histogram) {
+        }
+
+        @Override
+        public void onHistogramRemoved(MetricName name) {
+        }
+
+        @Override
+        public void onMeterAdded(MetricName name, Meter meter) {
+        }
+
+        @Override
+        public void onMeterRemoved(MetricName name) {
+        }
+
+        @Override
+        public void onTimerAdded(MetricName name, Sampler sampler) {
+        }
+
+        @Override
+        public void onTimerRemoved(MetricName name) {
+        }
+    }
+
     /**
      * A quick and easy way of capturing the notion of default metrics.
      */
diff --git a/src/main/java/org/xbib/metrics/Sampler.java b/metrics-common/src/main/java/org/xbib/metrics/common/Sampler.java
similarity index 94%
rename from src/main/java/org/xbib/metrics/Sampler.java
rename to metrics-common/src/main/java/org/xbib/metrics/common/Sampler.java
index f4680db..3562ecd 100644
--- a/src/main/java/org/xbib/metrics/Sampler.java
+++ b/metrics-common/src/main/java/org/xbib/metrics/common/Sampler.java
@@ -1,4 +1,10 @@
-package org.xbib.metrics;
+package org.xbib.metrics.common;
+
+import org.xbib.metrics.api.Clock;
+import org.xbib.metrics.api.Metered;
+import org.xbib.metrics.api.Reservoir;
+import org.xbib.metrics.api.Sampling;
+import org.xbib.metrics.api.Snapshot;
 
 import java.io.Closeable;
 import java.util.concurrent.Callable;
@@ -12,7 +18,9 @@ import java.util.concurrent.TimeUnit;
 public class Sampler implements Metered, Sampling {
 
     private final Meter meter;
+
     private final Histogram histogram;
+
     private final Clock clock;
 
     /**
@@ -31,7 +39,7 @@ public class Sampler implements Metered, Sampling {
      * @param executorService the executor service
      */
     public Sampler(Reservoir reservoir, ScheduledExecutorService executorService) {
-        this(reservoir, Clock.defaultClock(), executorService);
+        this(reservoir, UserTimeClock.defaultClock(), executorService);
     }
 
     /**
diff --git a/src/main/java/org/xbib/metrics/UserTimeClock.java b/metrics-common/src/main/java/org/xbib/metrics/common/UserTimeClock.java
similarity index 55%
rename from src/main/java/org/xbib/metrics/UserTimeClock.java
rename to metrics-common/src/main/java/org/xbib/metrics/common/UserTimeClock.java
index 3b229d4..5ce51c0 100644
--- a/src/main/java/org/xbib/metrics/UserTimeClock.java
+++ b/metrics-common/src/main/java/org/xbib/metrics/common/UserTimeClock.java
@@ -1,10 +1,23 @@
-package org.xbib.metrics;
+package org.xbib.metrics.common;
+
+import org.xbib.metrics.api.Clock;
 
 /**
  * A clock implementation which returns the current time in epoch nanoseconds.
  */
 class UserTimeClock implements Clock {
 
+    /**
+     * The default clock to use.
+     *
+     * @return the default {@link Clock} instance
+     * @see UserTimeClock
+     */
+    static Clock defaultClock() {
+        return UserTimeClock.DEFAULT;
+    }
+
+
     static final Clock DEFAULT = new UserTimeClock();
 
     @Override
@@ -17,4 +30,4 @@ class UserTimeClock implements Clock {
         return System.currentTimeMillis();
     }
 
-}
\ No newline at end of file
+}
diff --git a/src/main/java/org/xbib/metrics/WeightedSnapshot.java b/metrics-common/src/main/java/org/xbib/metrics/common/WeightedSnapshot.java
similarity index 96%
rename from src/main/java/org/xbib/metrics/WeightedSnapshot.java
rename to metrics-common/src/main/java/org/xbib/metrics/common/WeightedSnapshot.java
index 493a291..9cfd1d5 100644
--- a/src/main/java/org/xbib/metrics/WeightedSnapshot.java
+++ b/metrics-common/src/main/java/org/xbib/metrics/common/WeightedSnapshot.java
@@ -1,4 +1,6 @@
-package org.xbib.metrics;
+package org.xbib.metrics.common;
+
+import org.xbib.metrics.api.Snapshot;
 
 import java.io.OutputStream;
 import java.io.OutputStreamWriter;
@@ -6,6 +8,7 @@ import java.io.PrintWriter;
 import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Comparator;
 
 /**
  * A statistical snapshot of a {@link WeightedSnapshot}.
@@ -13,7 +16,9 @@ import java.util.Collection;
 public class WeightedSnapshot implements Snapshot {
 
     private final long[] values;
+
     private final double[] normWeights;
+
     private final double[] quantiles;
 
     /**
@@ -24,15 +29,7 @@ public class WeightedSnapshot implements Snapshot {
     public WeightedSnapshot(Collection<WeightedSample> values) {
         final WeightedSample[] copy = values.toArray(new WeightedSample[]{});
 
-        Arrays.sort(copy, (o1, o2) -> {
-            if (o1.value > o2.value) {
-                return 1;
-            }
-            if (o1.value < o2.value) {
-                return -1;
-            }
-            return 0;
-        });
+        Arrays.sort(copy, Comparator.comparingLong(o -> o.value));
 
         this.values = new long[copy.length];
         this.normWeights = new double[copy.length];
diff --git a/metrics-common/src/main/java/org/xbib/metrics/common/package-info.java b/metrics-common/src/main/java/org/xbib/metrics/common/package-info.java
new file mode 100644
index 0000000..0915c7f
--- /dev/null
+++ b/metrics-common/src/main/java/org/xbib/metrics/common/package-info.java
@@ -0,0 +1,4 @@
+/**
+ * Implementation classes for metrics.
+ */
+package org.xbib.metrics.common;
diff --git a/settings.gradle b/settings.gradle
new file mode 100644
index 0000000..5a42197
--- /dev/null
+++ b/settings.gradle
@@ -0,0 +1,2 @@
+include 'metrics-api'
+include 'metrics-common'
\ No newline at end of file
diff --git a/src/main/java/org/xbib/metrics/Clock.java b/src/main/java/org/xbib/metrics/Clock.java
deleted file mode 100644
index 8562ac7..0000000
--- a/src/main/java/org/xbib/metrics/Clock.java
+++ /dev/null
@@ -1,32 +0,0 @@
-package org.xbib.metrics;
-
-/**
- * An interface for how time passes. It is passed to {@link Sampler} to track timing.
- */
-public interface Clock {
-
-    /**
-     * The default clock to use.
-     *
-     * @return the default {@link Clock} instance
-     * @see UserTimeClock
-     */
-    static Clock defaultClock() {
-        return UserTimeClock.DEFAULT;
-    }
-
-    /**
-     * Returns the current time tick.
-     *
-     * @return time tick in nanoseconds
-     */
-    long getTick();
-
-    /**
-     * Returns the current time in milliseconds.
-     *
-     * @return time in milliseconds
-     */
-    long getTime();
-
-}
diff --git a/src/main/java/org/xbib/metrics/MetricRegistryListener.java b/src/main/java/org/xbib/metrics/MetricRegistryListener.java
deleted file mode 100644
index 10de733..0000000
--- a/src/main/java/org/xbib/metrics/MetricRegistryListener.java
+++ /dev/null
@@ -1,128 +0,0 @@
-package org.xbib.metrics;
-
-import java.util.EventListener;
-
-/**
- * Listeners for events from the registry.  Listeners must be thread-safe.
- */
-public interface MetricRegistryListener extends EventListener {
-    /**
-     * Called when a {@link Gauge} is added to the registry.
-     *
-     * @param name  the gauge's name
-     * @param gauge the gauge
-     */
-    void onGaugeAdded(MetricName name, Gauge<?> gauge);
-
-    /**
-     * Called when a {@link Gauge} is removed from the registry.
-     *
-     * @param name the gauge's name
-     */
-    void onGaugeRemoved(MetricName name);
-
-    /**
-     * Called when a {@link CountMetric} is added to the registry.
-     *
-     * @param name    the counter's name
-     * @param counter the counter
-     */
-    void onCounterAdded(MetricName name, CountMetric counter);
-
-    /**
-     * Called when a {@link CountMetric} is removed from the registry.
-     *
-     * @param name the counter's name
-     */
-    void onCounterRemoved(MetricName name);
-
-    /**
-     * Called when a {@link Histogram} is added to the registry.
-     *
-     * @param name      the histogram's name
-     * @param histogram the histogram
-     */
-    void onHistogramAdded(MetricName name, Histogram histogram);
-
-    /**
-     * Called when a {@link Histogram} is removed from the registry.
-     *
-     * @param name the histogram's name
-     */
-    void onHistogramRemoved(MetricName name);
-
-    /**
-     * Called when a {@link Meter} is added to the registry.
-     *
-     * @param name  the meter's name
-     * @param meter the meter
-     */
-    void onMeterAdded(MetricName name, Meter meter);
-
-    /**
-     * Called when a {@link Meter} is removed from the registry.
-     *
-     * @param name the meter's name
-     */
-    void onMeterRemoved(MetricName name);
-
-    /**
-     * Called when a {@link Sampler} is added to the registry.
-     *
-     * @param name    the sampler's name
-     * @param sampler the sampler
-     */
-    void onTimerAdded(MetricName name, Sampler sampler);
-
-    /**
-     * Called when a {@link Sampler} is removed from the registry.
-     *
-     * @param name the timer's name
-     */
-    void onTimerRemoved(MetricName name);
-
-    /**
-     * A no-op implementation of {@link MetricRegistryListener}.
-     */
-    abstract class Base implements MetricRegistryListener {
-        @Override
-        public void onGaugeAdded(MetricName name, Gauge<?> gauge) {
-        }
-
-        @Override
-        public void onGaugeRemoved(MetricName name) {
-        }
-
-        @Override
-        public void onCounterAdded(MetricName name, CountMetric counter) {
-        }
-
-        @Override
-        public void onCounterRemoved(MetricName name) {
-        }
-
-        @Override
-        public void onHistogramAdded(MetricName name, Histogram histogram) {
-        }
-
-        @Override
-        public void onHistogramRemoved(MetricName name) {
-        }
-
-        @Override
-        public void onMeterAdded(MetricName name, Meter meter) {
-        }
-
-        @Override
-        public void onMeterRemoved(MetricName name) {
-        }
-
-        @Override
-        public void onTimerAdded(MetricName name, Sampler sampler) {
-        }
-
-        @Override
-        public void onTimerRemoved(MetricName name) {
-        }
-    }
-}
diff --git a/src/main/java/org/xbib/metrics/package-info.java b/src/main/java/org/xbib/metrics/package-info.java
deleted file mode 100644
index 0023339..0000000
--- a/src/main/java/org/xbib/metrics/package-info.java
+++ /dev/null
@@ -1,4 +0,0 @@
-/**
- * Classes for metrics.
- */
-package org.xbib.metrics;