add saga init dsc

saga/README.md

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+---
+layout: pattern
+title: Saga
+folder: Communication
+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 performed 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 description](https://microservices.io/patterns/data/saga.html)

saga/pom.xml

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+<?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>