Sharding Pattern (#1056)

* Create sharding module

* Add Unit Tests

* Fix readme hyperlink

* Fix check-style issue

pom.xml

@@ -184,6 +184,7 @@
         <module>subclass-sandbox</module>
         <module>circuit-breaker</module>
         <module>double-buffer</module>
+        <module>sharding</module>
     </modules>
 
     <repositories>

sharding/README.md

@@ -0,0 +1,27 @@
+
+---  
+layout: pattern  
+title: Sharding 
+folder:  sharding  
+permalink: /patterns/sharding/  
+categories: Other  
+tags:  
+ - Java  
+ - Difficulty-Beginner  
+---  
+  
+## Intent  
+Sharding pattern means divide the data store into horizontal partitions or shards. Each shard has the same schema, but holds its own distinct subset of the data. 
+A shard is a data store in its own right (it can contain the data for many entities of different types), running on a server acting as a storage node.
+
+## Applicability  
+This pattern offers the following benefits:
+
+- You can scale the system out by adding further shards running on additional storage nodes.
+- A system can use off the shelf commodity hardware rather than specialized (and expensive) computers for each storage node.
+- You can reduce contention and improved performance by balancing the workload across shards.
+- In the cloud, shards can be located physically close to the users that will access the data.
+
+## Credits  
+  
+* [Cloud Design Patterns: Prescriptive Architecture Guidance for Cloud Applications - Sharding Pattern](https://docs.microsoft.com/en-us/previous-versions/msp-n-p/dn589797(v=pandp.10)?redirectedfrom=MSDN)

sharding/pom.xml

@@ -0,0 +1,45 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    The MIT License
+    Copyright © 2014-2019 Ilkka Seppälä
+
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in
+    all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+    THE SOFTWARE.
+
+-->
+<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">
+    <parent>
+        <artifactId>java-design-patterns</artifactId>
+        <groupId>com.iluwatar</groupId>
+        <version>1.22.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>sharding</artifactId>
+
+    <dependencies>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+        </dependency>
+    </dependencies>
+
+</project>

sharding/src/main/java/com/iluwatar/sharding/App.java

@@ -0,0 +1,88 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.sharding;
+
+/**
+ * Sharding pattern means dividing a data store into a set of horizontal partitions
+ * or shards. This pattern can improve scalability when storing and accessing large
+ * volumes of data.
+ */
+public class App {
+
+  /**
+   * Program main entry point.
+   * @param args program runtime arguments
+   */
+  public static void main(String[] args) {
+
+    var data1 = new Data(1, "data1", Data.DataType.type1);
+    var data2 = new Data(2, "data2", Data.DataType.type2);
+    var data3 = new Data(3, "data3", Data.DataType.type3);
+    var data4 = new Data(4, "data4", Data.DataType.type1);
+
+    var shard1 = new Shard(1);
+    var shard2 = new Shard(2);
+    var shard3 = new Shard(3);
+
+    ShardManager manager = new LookupShardManager();
+    manager.addNewShard(shard1);
+    manager.addNewShard(shard2);
+    manager.addNewShard(shard3);
+    manager.storeData(data1);
+    manager.storeData(data2);
+    manager.storeData(data3);
+    manager.storeData(data4);
+
+    shard1.clearData();
+    shard2.clearData();
+    shard3.clearData();
+
+    manager = new RangeShardManager();
+    manager.addNewShard(shard1);
+    manager.addNewShard(shard2);
+    manager.addNewShard(shard3);
+    manager.storeData(data1);
+    manager.storeData(data2);
+    manager.storeData(data3);
+    manager.storeData(data4);
+
+    shard1.clearData();
+    shard2.clearData();
+    shard3.clearData();
+
+    manager = new HashShardManager();
+    manager.addNewShard(shard1);
+    manager.addNewShard(shard2);
+    manager.addNewShard(shard3);
+    manager.storeData(data1);
+    manager.storeData(data2);
+    manager.storeData(data3);
+    manager.storeData(data4);
+
+    shard1.clearData();
+    shard2.clearData();
+    shard3.clearData();
+  }
+
+}

sharding/src/main/java/com/iluwatar/sharding/Data.java

@@ -0,0 +1,84 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.sharding;
+
+/**
+ * Basic data structure for each tuple stored in data shards.
+ */
+public class Data {
+
+  private int key;
+
+  private String value;
+
+  private DataType type;
+
+  /**
+   * Constructor of Data class.
+   * @param key data key
+   * @param value data vlue
+   * @param type data type
+   */
+  public Data(final int key, final String value, final DataType type) {
+    this.key = key;
+    this.value = value;
+    this.type = type;
+  }
+
+  public int getKey() {
+    return key;
+  }
+
+  public void setKey(final int key) {
+    this.key = key;
+  }
+
+  public String getValue() {
+    return value;
+  }
+
+  public void setValue(final String value) {
+    this.value = value;
+  }
+
+  public DataType getType() {
+    return type;
+  }
+
+  public void setType(DataType type) {
+    this.type = type;
+  }
+
+  enum DataType {
+    type1, type2, type3
+  }
+
+  @Override
+  public String toString() {
+    return "Data {" + "key="
+      + key + ", value='" + value
+      + '\'' + ", type=" + type + '}';
+  }
+}
+

sharding/src/main/java/com/iluwatar/sharding/HashShardManager.java

@@ -0,0 +1,55 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.sharding;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * ShardManager with hash strategy. The purpose of this strategy is to reduce the
+ * chance of hot-spots in the data. It aims to distribute the data across the shards
+ * in a way that achieves a balance between the size of each shard and the average
+ * load that each shard will encounter.
+ */
+public class HashShardManager extends ShardManager {
+
+  private static final Logger LOGGER = LoggerFactory.getLogger(HashShardManager.class);
+
+  @Override
+  public int storeData(Data data) {
+    var shardId = allocateShard(data);
+    var shard = shardMap.get(shardId);
+    shard.storeData(data);
+    LOGGER.info(data.toString() + " is stored in Shard " + shardId);
+    return shardId;
+  }
+
+  @Override
+  protected int allocateShard(Data data) {
+    var shardCount = shardMap.size();
+    var hash = data.getKey() % shardCount;
+    return hash == 0 ? hash + shardCount : hash;
+  }
+
+}

sharding/src/main/java/com/iluwatar/sharding/LookupShardManager.java

@@ -0,0 +1,66 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.sharding;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Random;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * ShardManager with lookup strategy. In this strategy the sharding logic implements
+ * a map that routes a request for data to the shard that contains that data by using
+ * the shard key.
+ */
+public class LookupShardManager extends ShardManager {
+
+  private static final Logger LOGGER = LoggerFactory.getLogger(LookupShardManager.class);
+
+  private Map<Integer, Integer> lookupMap = new HashMap<>();
+
+  @Override
+  public int storeData(Data data) {
+    var shardId = allocateShard(data);
+    lookupMap.put(data.getKey(), shardId);
+    var shard = shardMap.get(shardId);
+    shard.storeData(data);
+    LOGGER.info(data.toString() + " is stored in Shard " + shardId);
+    return shardId;
+  }
+
+  @Override
+  protected int allocateShard(Data data) {
+    var key = data.getKey();
+    if (lookupMap.containsKey(key)) {
+      return lookupMap.get(key);
+    } else {
+      var shardCount = shardMap.size();
+      var allocatedShardId = new Random().nextInt(shardCount - 1) + 1;
+      return allocatedShardId;
+    }
+  }
+
+}

sharding/src/main/java/com/iluwatar/sharding/RangeShardManager.java

@@ -0,0 +1,66 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.sharding;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * ShardManager with range strategy. This strategy groups related items together
+ * in the same shard, and orders them by shard key.
+ */
+public class RangeShardManager extends ShardManager {
+
+  private static final Logger LOGGER = LoggerFactory.getLogger(RangeShardManager.class);
+
+  @Override
+  public int storeData(Data data) {
+    var shardId = allocateShard(data);
+    var shard = shardMap.get(shardId);
+    shard.storeData(data);
+    LOGGER.info(data.toString() + " is stored in Shard " + shardId);
+    return shardId;
+  }
+
+  @Override
+  protected int allocateShard(Data data) {
+    var type = data.getType();
+    var shardId = -1;
+    switch (type) {
+      case type1:
+        shardId = 1;
+        break;
+      case type2:
+        shardId = 2;
+        break;
+      case type3:
+        shardId = 3;
+        break;
+      default:
+        break;
+    }
+    return shardId;
+  }
+
+}

sharding/src/main/java/com/iluwatar/sharding/Shard.java

@@ -0,0 +1,59 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.sharding;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * The Shard class stored data in a HashMap.
+ */
+public class Shard {
+
+  private final int id;
+
+  private Map<Integer, Data> dataStore;
+
+  public Shard(final int id) {
+    this.id = id;
+    this.dataStore = new HashMap<>();
+  }
+
+  public void storeData(Data data) {
+    dataStore.put(data.getKey(), data);
+  }
+
+  public void clearData() {
+    dataStore.clear();
+  }
+
+  public Data getDataById(final int id) {
+    return dataStore.get(id);
+  }
+
+  public int getId() {
+    return id;
+  }
+
+}

sharding/src/main/java/com/iluwatar/sharding/ShardManager.java

@@ -0,0 +1,103 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.sharding;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Abstract class for ShardManager.
+ */
+public abstract class ShardManager {
+
+  private static final Logger LOGGER = LoggerFactory.getLogger(ShardManager.class);
+
+  protected Map<Integer, Shard> shardMap;
+
+  public ShardManager() {
+    shardMap = new HashMap<>();
+  }
+
+  /**
+   * Add a provided shard instance to shardMap.
+   *
+   * @param shard new shard instance.
+   * @return {@code true} if succeed to add the new instance.
+   *         {@code false} if the shardId is already existed.
+   */
+  public boolean addNewShard(final Shard shard) {
+    var shardId = shard.getId();
+    if (!shardMap.containsKey(shardId)) {
+      shardMap.put(shardId, shard);
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  /**
+   * Remove a shard instance by provided Id.
+   *
+   * @param shardId Id of shard instance to remove.
+   * @return {@code true} if removed. {@code false} if the shardId is not existed.
+   */
+  public boolean removeShardById(final int shardId) {
+    if (shardMap.containsKey(shardId)) {
+      shardMap.remove(shardId);
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  /**
+   * Get shard instance by provided shardId.
+   *
+   * @param shardId id of shard instance to get
+   * @return required shard instance
+   */
+  public Shard getShardById(final int shardId) {
+    return shardMap.get(shardId);
+  }
+
+  /**
+   * Store data in proper shard instance.
+   *
+   * @param data new data
+   * @return id of shard that the data is stored in
+   */
+  public abstract int storeData(final Data data);
+
+  /**
+   * Allocate proper shard to provided data.
+   *
+   * @param data new data
+   * @return id of shard that the data should be stored
+   */
+  protected abstract int allocateShard(final Data data);
+
+}

sharding/src/test/java/com/iluwatar/sharding/AppTest.java

@@ -0,0 +1,39 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.sharding;
+
+import org.junit.Test;
+
+/**
+ * Unit tests for App class.
+ */
+public class AppTest {
+
+  @Test
+  public void testMain() {
+    String[] args = {};
+    App.main(args);
+  }
+
+}

sharding/src/test/java/com/iluwatar/sharding/HashShardManagerTest.java

@@ -0,0 +1,64 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.sharding;
+
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+/**
+ * Unit tests for HashShardManager class.
+ */
+public class HashShardManagerTest {
+
+  private HashShardManager hashShardManager;
+
+  /**
+   * Initialize hashShardManager instance.
+   */
+  @Before
+  public void setup() {
+    hashShardManager = new HashShardManager();
+    var shard1 = new Shard(1);
+    var shard2 = new Shard(2);
+    var shard3 = new Shard(3);
+    hashShardManager.addNewShard(shard1);
+    hashShardManager.addNewShard(shard2);
+    hashShardManager.addNewShard(shard3);
+  }
+
+  @After
+  public void tearDown() {
+
+  }
+
+  @Test
+  public void testStoreData() {
+    var data = new Data(1, "test", Data.DataType.type1);
+    hashShardManager.storeData(data);
+    Assert.assertEquals(data, hashShardManager.getShardById(1).getDataById(1));
+  }
+
+}

sharding/src/test/java/com/iluwatar/sharding/LookupShardManagerTest.java

@@ -0,0 +1,68 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.sharding;
+
+import java.util.Map;
+
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+/**
+ * Unit tests for LookupShardManager class.
+ */
+public class LookupShardManagerTest {
+
+  private LookupShardManager lookupShardManager;
+
+  /**
+   * Initialize lookupShardManager instance.
+   */
+  @Before
+  public void setup() {
+    lookupShardManager = new LookupShardManager();
+    var shard1 = new Shard(1);
+    var shard2 = new Shard(2);
+    var shard3 = new Shard(3);
+    lookupShardManager.addNewShard(shard1);
+    lookupShardManager.addNewShard(shard2);
+    lookupShardManager.addNewShard(shard3);
+  }
+
+  @Test
+  public void testStoreData() {
+    try {
+      var data = new Data(1, "test", Data.DataType.type1);
+      lookupShardManager.storeData(data);
+      var field = LookupShardManager.class.getDeclaredField("lookupMap");
+      field.setAccessible(true);
+      Map<Integer, Integer> lookupMap = (Map<Integer, Integer>) field.get(lookupShardManager);
+      var shardId = lookupMap.get(1);
+      var shard = lookupShardManager.getShardById(shardId);
+      Assert.assertEquals(data, shard.getDataById(1));
+    } catch (NoSuchFieldException | IllegalAccessException e) {
+      Assert.fail("Fail to modify field access.");
+    }
+  }
+}

sharding/src/test/java/com/iluwatar/sharding/RangeShardManagerTest.java

@@ -0,0 +1,58 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.sharding;
+
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+/**
+ * Unit tests for RangeShardManager class.
+ */
+public class RangeShardManagerTest {
+
+  private RangeShardManager rangeShardManager;
+
+  /**
+   * Initialize rangeShardManager instance.
+   */
+  @Before
+  public void setup() {
+    rangeShardManager = new RangeShardManager();
+    var shard1 = new Shard(1);
+    var shard2 = new Shard(2);
+    var shard3 = new Shard(3);
+    rangeShardManager.addNewShard(shard1);
+    rangeShardManager.addNewShard(shard2);
+    rangeShardManager.addNewShard(shard3);
+  }
+
+  @Test
+  public void testStoreData() {
+    var data = new Data(1, "test", Data.DataType.type1);
+    rangeShardManager.storeData(data);
+    Assert.assertEquals(data, rangeShardManager.getShardById(1).getDataById(1));
+  }
+
+}

sharding/src/test/java/com/iluwatar/sharding/ShardManagerTest.java

@@ -0,0 +1,104 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.sharding;
+
+import java.util.Map;
+
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+/**
+ * Unit tests for ShardManager class.
+ */
+public class ShardManagerTest {
+
+  private ShardManager shardManager;
+
+  /**
+   * Initialize shardManager instance.
+   */
+  @Before
+  public void setup() {
+    shardManager = new TestShardManager();
+  }
+
+  @After
+  public void tearDown() {
+
+  }
+
+  @Test
+  public void testAddNewShard() {
+    try {
+      var shard = new Shard(1);
+      shardManager.addNewShard(shard);
+      var field = ShardManager.class.getDeclaredField("shardMap");
+      field.setAccessible(true);
+      Map<Integer, Shard> map = (Map<Integer, Shard>) field.get(shardManager);
+      Assert.assertEquals(1, map.size());
+      Assert.assertEquals(shard, map.get(1));
+    } catch (NoSuchFieldException | IllegalAccessException e) {
+      Assert.fail("Fail to modify field access.");
+    }
+  }
+
+  @Test
+  public void testRemoveShardById() {
+    try {
+      var shard = new Shard(1);
+      shardManager.addNewShard(shard);
+      boolean flag = shardManager.removeShardById(1);
+      var field = ShardManager.class.getDeclaredField("shardMap");
+      field.setAccessible(true);
+      Map<Integer, Shard> map = (Map<Integer, Shard>) field.get(shardManager);
+      Assert.assertEquals(true, flag);
+      Assert.assertEquals(0, map.size());
+    } catch (IllegalAccessException | NoSuchFieldException e) {
+      Assert.fail("Fail to modify field access.");
+    }
+  }
+
+  @Test
+  public void testGetShardById() {
+    Shard shard = new Shard(1);
+    shardManager.addNewShard(shard);
+    Shard tmpShard = shardManager.getShardById(1);
+    Assert.assertEquals(shard, tmpShard);
+  }
+
+  class TestShardManager extends ShardManager {
+
+    @Override
+    public int storeData(Data data) {
+      return 0;
+    }
+
+    @Override
+    protected int allocateShard(Data data) {
+      return 0;
+    }
+  }
+}

sharding/src/test/java/com/iluwatar/sharding/ShardTest.java

@@ -0,0 +1,83 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.sharding;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+
+/**
+ * Unit tests for Shard class.
+ */
+public class ShardTest {
+
+  private Data data;
+
+  private Shard shard;
+
+  @Before
+  public void setup() {
+    data = new Data(1, "test", Data.DataType.type1);
+    shard = new Shard(1);
+  }
+
+  @After
+  public void tearDown() {}
+
+  @Test
+  public void testStoreData() {
+    try {
+      shard.storeData(data);
+      var field = Shard.class.getDeclaredField("dataStore");
+      field.setAccessible(true);
+      Map<Integer, Data> dataMap = (Map<Integer, Data>) field.get(shard);
+      Assert.assertEquals(1, dataMap.size());
+      Assert.assertEquals(data, dataMap.get(1));
+    } catch (NoSuchFieldException | IllegalAccessException e) {
+      Assert.fail("Fail to modify field access.");
+    }
+
+  }
+
+  @Test
+  public void testClearData() {
+    try {
+      Map<Integer, Data> dataMap = new HashMap<>();
+      dataMap.put(1, data);
+      var field = Shard.class.getDeclaredField("dataStore");
+      field.setAccessible(true);
+      field.set(shard, dataMap);
+      shard.clearData();
+      dataMap = (Map<Integer, Data>) field.get(shard);
+      Assert.assertEquals(0, dataMap.size());
+    } catch (NoSuchFieldException | IllegalAccessException e) {
+      Assert.fail("Fail to modify field access.");
+    }
+  }
+}