Saga pattern

pom.xml

@@ -183,6 +183,8 @@
         <module>data-locality</module>
         <module>subclass-sandbox</module>
         <module>circuit-breaker</module>
+        <module>role-object</module>
+		<module>saga</module>
         <module>double-buffer</module>
         <module>sharding</module>
     </modules>

role-object/src/main/java/com/iluwatar/roleobject/InvestorRole.java

@@ -43,6 +43,6 @@ public void setAmountToInvest(long amountToInvest) {
     }
 
     public String invest() {
-        return String.format("Investor  %s has invested %d dollars", name, amountToInvest);
+        return String.format("Investor %s has invested %d dollars", name, amountToInvest);
     }
 }

saga/README.md

@@ -0,0 +1,46 @@
+---
+layout: pattern
+title: Saga
+folder: saga
+permalink: /patterns/saga/
+categories: Behavioral
+tags:
+ - Java
+ - Difficulty-Expert
+ - Idiom
+ - Distributed communication
+---
+
+## Also known as
+This pattern has a similar goal with two-phase commit (XA transaction)
+
+## Intent
+This pattern is used in distributed services to perform a group of operations atomically.
+This is an analog of transaction in a database but in terms of microservices architecture this is executed 
+in a distributed environment
+
+## Explanation
+A saga is a sequence of local transactions in a certain context. If one transaction fails for some reason, 
+the saga executes compensating transactions(rollbacks) to undo the impact of the preceding transactions.
+There are two types of Saga:
+
+- Choreography-Based Saga. 
+In this approach, there is no central orchestrator. 
+Each service participating in the Saga performs their transaction and publish events. 
+The other services act upon those events and perform their transactions. 
+Also, they may or not publish other events based on the situation.
+
+- Orchestration-Based Saga
+In this approach, there is a Saga orchestrator that manages all the transactions and directs 
+the participant services to execute local transactions based on events. 
+This orchestrator can also be though of as a Saga Manager.
+
+## Applicability
+Use the Saga pattern, if:
+- you need to perform a group of operations related to different microservices atomically
+- you need to rollback changes in different places in case of failure one of the operation
+- you need to take care of data consistency in different places including different databases
+- you can not use 2PC(two phase commit)
+
+## Credits
+- [Pattern: Saga](https://microservices.io/patterns/data/saga.html)

saga/pom.xml

@@ -0,0 +1,45 @@
+<?xml version="1.0"?>
+<!--
+
+    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 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
+         xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>com.iluwatar</groupId>
+        <artifactId>java-design-patterns</artifactId>
+        <version>1.22.0-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>saga</artifactId>
+    <dependencies>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+</project>

saga/src/main/java/com/iluwatar/saga/choreography/ChoreographyChapter.java

@@ -0,0 +1,65 @@
+/*
+ * 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.saga.choreography;
+
+
+/**
+ * ChoreographyChapter is an interface representing a contract for an external service.
+ * In that case, a service needs to make a decision what to do further
+ * hence the server needs to get all context representing {@link Saga}
+ */
+public interface ChoreographyChapter {
+
+  /**
+   * In that case, every method is responsible to make a decision on what to do then.
+   *
+   * @param saga incoming saga
+   * @return saga result
+   */
+  Saga execute(Saga saga);
+
+  /**
+   * get name method.
+   * @return service name.
+   */
+  String getName();
+
+  /**
+   * The operation executed in general case.
+   *
+   * @param saga incoming saga
+   * @return result {@link Saga}
+   */
+  Saga process(Saga saga);
+
+  /**
+   * The operation executed in rollback case.
+   *
+   * @param saga incoming saga
+   * @return result {@link Saga}
+   */
+  Saga rollback(Saga saga);
+
+
+}

saga/src/main/java/com/iluwatar/saga/choreography/FlyBookingService.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.saga.choreography;
+
+
+/**
+ * Class representing a service to book a fly.
+ */
+public class FlyBookingService extends Service {
+  public FlyBookingService(ServiceDiscoveryService service) {
+    super(service);
+  }
+
+  @Override
+  public String getName() {
+    return "booking a Fly";
+  }
+}

saga/src/main/java/com/iluwatar/saga/choreography/HotelBookingService.java

@@ -0,0 +1,41 @@
+/*
+ * 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.saga.choreography;
+
+
+/**
+ * Class representing a service to book a hotel.
+ */
+public class HotelBookingService extends Service {
+  public HotelBookingService(ServiceDiscoveryService service) {
+    super(service);
+  }
+
+  @Override
+  public String getName() {
+    return "booking a Hotel";
+  }
+
+
+}

saga/src/main/java/com/iluwatar/saga/choreography/OrderService.java

@@ -0,0 +1,40 @@
+/*
+ * 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.saga.choreography;
+
+
+/**
+ * Class representing a service to init a new order.
+ */
+public class OrderService extends Service {
+
+  public OrderService(ServiceDiscoveryService service) {
+    super(service);
+  }
+
+  @Override
+  public String getName() {
+    return "init an order";
+  }
+}