iluwatar#1627 adding readme

Author: karthikbhat13

fanout-fanin/README.md

@@ -0,0 +1,33 @@
+---
+layout: pattern
+title: FanOut-FanIn 
+folder: fanout-fanin
+permalink: /patterns/fanout-fanin/
+categories: Concurrency
+language: en
+tags:
+- Cloud distributed
+- Performance
+---
+
+## Intent
+The pattern that refers to executing multiple instances of the activity function concurrently. Generally "FanOut" 
+process is splitting the data into multiple chunks that would be passed to the activity function. "FanIn" process is 
+basically aggregating the result from individual instance of activity function and forming a single final result. <br />
+
+Each activity function is a long-running process that takes in a chunk of data. A callback function, or a Consumer 
+is passed to the activity function, that will be called when the long-running process gets over. The consumer will 
+process the individual return value from activity function as they are done running into a final result.
+
+## Class diagram
+![alt-text](./etc/fanout-fanin.png)
+
+## Applicability
+
+Use this pattern when you can chunk the workload or load into multiple chunks that can be dealt with separately.
+
+## Credits
+
+* [Understanding Azure Durable Functions - Part 8: The Fan Out/Fan In Pattern](http://dontcodetired.com/blog/post/Understanding-Azure-Durable-Functions-Part-8-The-Fan-OutFan-In-Pattern)
+* [Fan-out/fan-in scenario in Durable Functions - Cloud backup example](https://docs.microsoft.com/en-us/azure/azure-functions/durable/durable-functions-cloud-backup)
+* [Understanding the Fan-Out/Fan-In API Integration Pattern](https://dzone.com/articles/understanding-the-fan-out-fan-in-api-integration-p)

fanin-fanout/etc/fanout-fanin.png renamed to fanout-fanin/etc/fanout-fanin.png

@@ -9,7 +9,7 @@
     </parent>
     <modelVersion>4.0.0</modelVersion>
 
-    <artifactId>fanin-fanout</artifactId>
+    <artifactId>fanout-fanin</artifactId>
 
     <dependencies>
         <dependency>

fanin-fanout/etc/fanin-fanout.urm.puml renamed to fanout-fanin/etc/fanout-fanin.urm.puml

@@ -9,7 +9,7 @@
 
 
 /**
- * FanOut/FanIn pattern is a behavioral pattern that refers to executing multiple instances of the
+ * FanOut/FanIn pattern is a concurrency pattern that refers to executing multiple instances of the
  * activity function concurrently. The "fan out" part is essentially splitting the data into
  * multiple chunks and then calling the activity function multiple times, passing the chunks.
  *

fanin-fanout/pom.xml renamed to fanout-fanin/pom.xml

@@ -24,6 +24,7 @@ public static Long fanOutFanIn(
 
     ExecutorService service = Executors.newFixedThreadPool(requests.size());
 
+    // fanning out
     List<CompletableFuture<Void>> futures =
         requests.stream()
             .map(