feature: Claim check pattern azure (#1897)

* Archietecture Diagram added * Added pom.xml * Architecture Diagram Updated * Added Microservices and kafka * ReadME File Added * ReadME file Updated * #1329 ReadMe file updated and working pattern code added * #1329 readme file updated * #1329 readme file updated and java documentation added * #1329 repository merged * Update claim-check-pattern/ReadME.md #1329 Real world description updated Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com> * #1329 Update claim-check-pattern/ReadME.md Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com> * #1329 Applicability section in ReadMe file updated Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com> * #1329 Tutorial section in ReadMe file updated Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com> * #1329 Storage Data section in ReadMe File updated Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com> * #1329 workflow section Update claim-check-pattern/ReadME.md Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com> * #1329 Update claim-check-pattern/pom.xml Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com> * #1329 deleted mvnw.cmd file * #1329 deleted drawio file * #1329 deleted mvnw file * #1329 deleted mvnw file * #1329 mvnw.cmd file deleted * #1329 Update claim-check-pattern/usage-cost-processor/src/main/java/com/callusage/domain/MessageHeader.java Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com> * #1329 Update claim-check-pattern/usage-cost-processor/src/main/java/com/callusage/domain/UsageCostDetail.java Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com> * #1329 Update claim-check-pattern/usage-cost-processor/src/main/java/com/callusage/domain/UsageDetail.java Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com> * #1329 deleted mvnw file * #1329 deleted mvnw.cmd file * #1329 Update claim-check-pattern/usage-detail-sender/src/main/java/com/callusage/domain/Message.java Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com> * #1329 Update claim-check-pattern/ReadME.md Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com> * #1329 pom file dependencies fixed, readmeflie updated, removed unused imports * #1329 Readfile updated, class javadoc added * #1329 UML class diagrams added, readme file updated * #1329 lombok annotations used on model classes, common dependencies moved to parent pom * #1329 test cases added * include claim-check-pattern in parent pom * #1329 code smells fixed * #1329 code smells removed * #1329 security issues fixed * #1329 updated pom files and refactored packages name * #1329 checkstyle warning fixed * #1329 code coverage increased * #1329 minor changed. * checkpoint created with common utility * Claim-Check-Pattern | Shrirang97 | Implemented using Java Azure Functions * Claim-Check-Pattern | Shrirang97 | Updated Functions logic * Update MessageHandlerUtility.java * Update UsageCostProcessorFunction.java * claim-check-pattern | Shrirang97 | Added test cases * claim-check-pattern | Shrirang97 | Test cases for Azure functions fixed * Claim-Check-Pattern | Shrirang | Used string as request body * claim-check-pattern | Shrirang | Working test cases * claim-check-pattern | Shrirang | Issue fixed while deserializing * claim-check-pattern | Shrirang | removed unused import * claim-check-pattern | Shrirang | fixed refactoring * claim-chek-pattern | Shrirang | added lombok | fixed dependencies & test cases * Delete .DS_Store * claim-check-pattern | Shrirang | Fixed unrelated file * Update BookService.java * Update BookService.java * claim-check-pattern | Shrirang | Fixed unrelated files * claim-check-pattern | Shrirang | Fixed review comments * Update UsageCostProcessorFunction.java * Update ReadME.md * Rename ReadME.md to README.md * claim-check-pattern | Shrirang | Incorporated review comments. * Update cloud-claim-check-pattern/README.md Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com> * Update cloud-claim-check-pattern/README.md Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com> * Update cloud-claim-check-pattern/README.md Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com> * Update cloud-claim-check-pattern/README.md Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com> * Update cloud-claim-check-pattern/README.md Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com> * Update cloud-claim-check-pattern/README.md Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com> * Update cloud-claim-check-pattern/README.md Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com> * Updated readme file * Read me file updated | Added more description Co-authored-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com> Co-authored-by: Subhrodip Mohanta <hello@subho.xyz> Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>
2021-12-11 20:29:36 +05:30
parent b22c8bc32f
commit 9063336687
28 changed files with 2010 additions and 0 deletions
--- a/cloud-claim-check-pattern/call-usage-app/.gitignore
+++ b/cloud-claim-check-pattern/call-usage-app/.gitignore
@ -0,0 +1,38 @@
+# Build output
+target/
+*.class
+
+# Log file
+*.log
+
+# BlueJ files
+*.ctxt
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+
+# IDE
+.idea/
+*.iml
+.settings/
+.project
+.classpath
+
+# macOS
+.DS_Store
+
+# Azure Functions
+local.settings.json
+bin/
+obj/
--- a/cloud-claim-check-pattern/call-usage-app/etc/call-usage-app.urm.puml
+++ b/cloud-claim-check-pattern/call-usage-app/etc/call-usage-app.urm.puml
@ -0,0 +1,117 @@
+@startuml
+package com.iluwatar.claimcheckpattern.producer.calldetails.functions {
+  class UsageDetailPublisherFunction {
+    - eventHandlerUtility : EventHandlerUtility<MessageHeader>
+    - messageHandlerUtility : MessageHandlerUtility<UsageDetail>
+    + UsageDetailPublisherFunction()
+    + UsageDetailPublisherFunction(messageHandlerUtility : MessageHandlerUtility<UsageDetail>, eventHandlerUtility : EventHandlerUtility<MessageHeader>)
+    + run(request : HttpRequestMessage<Optional<String>>, context : ExecutionContext) : HttpResponseMessage
+  }
+}
+package com.iluwatar.claimcheckpattern.domain {
+  class Message<T> {
+    - messageBody : MessageBody<T>
+    - messageHeader : MessageHeader
+    + Message<T>()
+    + getMessageBody() : MessageBody<T>
+    + getMessageHeader() : MessageHeader
+    + setMessageBody(messageBody : MessageBody<T>)
+    + setMessageHeader(messageHeader : MessageHeader)
+  }
+  class MessageBody<T> {
+    - data : List<T>
+    + MessageBody<T>()
+    + getData() : List<T>
+    + setData(data : List<T>)
+  }
+  class MessageHeader {
+    - data : Object
+    - dataVersion : String
+    - eventTime : String
+    - eventType : String
+    - id : String
+    - subject : String
+    - topic : String
+    + MessageHeader()
+    + getData() : Object
+    + getDataVersion() : String
+    + getEventTime() : String
+    + getEventType() : String
+    + getId() : String
+    + getSubject() : String
+    + getTopic() : String
+    + setData(data : Object)
+    + setDataVersion(dataVersion : String)
+    + setEventTime(eventTime : String)
+    + setEventType(eventType : String)
+    + setId(id : String)
+    + setSubject(subject : String)
+    + setTopic(topic : String)
+  }
+  class MessageReference {
+    - dataFileName : String
+    - dataLocation : String
+    + MessageReference()
+    + MessageReference(dataLocation : String, dataFileName : String)
+    + getDataFileName() : String
+    + getDataLocation() : String
+    + setDataFileName(dataFileName : String)
+    + setDataLocation(dataLocation : String)
+  }
+  class UsageCostDetail {
+    - callCost : double
+    - dataCost : double
+    - userId : String
+    + UsageCostDetail()
+    + getCallCost() : double
+    + getDataCost() : double
+    + getUserId() : String
+    + setCallCost(callCost : double)
+    + setDataCost(dataCost : double)
+    + setUserId(userId : String)
+  }
+  class UsageDetail {
+    - data : int
+    - duration : int
+    - userId : String
+    + UsageDetail()
+    + getData() : int
+    + getDuration() : int
+    + getUserId() : String
+    + setData(data : int)
+    + setDuration(duration : int)
+    + setUserId(userId : String)
+  }
+}
+package com.iluwatar.claimcheckpattern.utility {
+  class EventHandlerUtility<T> {
+    - customEventClient : EventGridPublisherClient<BinaryData>
+    + EventHandlerUtility<T>()
+    + EventHandlerUtility<T>(customEventClient : EventGridPublisherClient<BinaryData>)
+    + publishEvent(customEvent : T, logger : Logger)
+  }
+  class MessageHandlerUtility<T> {
+    - blobServiceClient : BlobServiceClient
+    + MessageHandlerUtility<T>()
+    + MessageHandlerUtility<T>(blobServiceClient : BlobServiceClient)
+    + dropToPersistantStorage(message : Message<T>, logger : Logger)
+    + readFromPersistantStorage(messageReference : MessageReference, logger : Logger) : Message<T>
+  }
+}
+package com.iluwatar.claimcheckpattern.consumer.callcostprocessor.functions {
+  class UsageCostProcessorFunction {
+    - messageHandlerUtilityForUsageCostDetail : MessageHandlerUtility<UsageCostDetail>
+    - messageHandlerUtilityForUsageDetail : MessageHandlerUtility<UsageDetail>
+    + UsageCostProcessorFunction()
+    + UsageCostProcessorFunction(messageHandlerUtilityForUsageDetail : MessageHandlerUtility<UsageDetail>, messageHandlerUtilityForUsageCostDetail : MessageHandlerUtility<UsageCostDetail>)
+    - calculateUsageCostDetails(usageDetailsList : List<UsageDetail>) : List<UsageCostDetail>
+    + run(request : HttpRequestMessage<Optional<String>>, context : ExecutionContext) : HttpResponseMessage
+  }
+}
+UsageCostProcessorFunction -->  "-messageHandlerUtilityForUsageDetail" MessageHandlerUtility
+Message -->  "-messageBody" MessageBody
+UsageDetailPublisherFunction -->  "-eventHandlerUtility" EventHandlerUtility
+Builder ..+ HttpResponseMessage
+UsageDetailPublisherFunction -->  "-messageHandlerUtility" MessageHandlerUtility
+Message -->  "-messageHeader" MessageHeader
+@enduml
--- a/cloud-claim-check-pattern/call-usage-app/host.json
+++ b/cloud-claim-check-pattern/call-usage-app/host.json
@ -0,0 +1,7 @@
+{
+  "version": "2.0",
+  "extensionBundle": {
+    "id": "Microsoft.Azure.Functions.ExtensionBundle",
+    "version": "[1.*, 2.0.0)"
+  } 
+}
--- a/cloud-claim-check-pattern/call-usage-app/pom.xml
+++ b/cloud-claim-check-pattern/call-usage-app/pom.xml
@ -0,0 +1,150 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<!--
+
+    The MIT License
+    Copyright © 2014-2021 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">
+    <modelVersion>4.0.0</modelVersion>
+
+
+    <parent>
+	    <groupId>com.iluwatar</groupId>
+	    <artifactId>claim-check-pattern</artifactId>
+	    <version>1.25.0-SNAPSHOT</version>		
+	 </parent>
+    
+    <artifactId>call-usage-app</artifactId>
+    <name>call-usage-app</name>
+    <packaging>jar</packaging>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <azure.functions.maven.plugin.version>1.14.0</azure.functions.maven.plugin.version>
+        <azure.functions.java.library.version>1.4.2</azure.functions.java.library.version>
+        <functionAppName>CallUsageApp</functionAppName>
+    </properties>
+
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>com.azure</groupId>
+                <artifactId>azure-sdk-bom</artifactId>
+                <version>1.0.4</version>
+                <type>pom</type>
+                <scope>import</scope>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.microsoft.azure.functions</groupId>
+            <artifactId>azure-functions-java-library</artifactId>
+            <version>${azure.functions.java.library.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>com.azure</groupId>
+            <artifactId>azure-messaging-eventgrid</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.azure</groupId>
+            <artifactId>azure-storage-blob</artifactId>
+            <version>12.13.0</version>
+        </dependency>
+
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-simple</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <!-- Test -->
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>com.microsoft.azure</groupId>
+                <artifactId>azure-functions-maven-plugin</artifactId>
+                <version>${azure.functions.maven.plugin.version}</version>
+                <configuration>
+                    <!-- function app name -->
+                    <appName>${functionAppName}</appName>
+                    <!-- function app resource group -->
+                    <resourceGroup>java-functions-group</resourceGroup>
+                    <!-- function app service plan name -->
+                    <appServicePlanName>java-functions-app-service-plan</appServicePlanName>
+                    <!-- function app region-->
+                    <!-- refers https://github.com/microsoft/azure-maven-plugins/wiki/Azure-Functions:-Configuration-Details#supported-regions for all valid values -->
+                    <region>westus</region>
+                    <!-- function pricingTier, default to be consumption if not specified -->
+                    <!-- refers https://github.com/microsoft/azure-maven-plugins/wiki/Azure-Functions:-Configuration-Details#supported-pricing-tiers for all valid values -->
+                    <!-- <pricingTier></pricingTier> -->
+                    <!-- Whether to disable application insights, default is false -->
+                    <!-- refers https://github.com/microsoft/azure-maven-plugins/wiki/Azure-Functions:-Configuration-Details for all valid configurations for application insights-->
+                    <!-- <disableAppInsights></disableAppInsights> -->
+                    <runtime>
+                        <!-- runtime os, could be windows, linux or docker-->
+                        <os>windows</os>
+                        <javaVersion>11</javaVersion>
+                    </runtime>
+                    <appSettings>
+                        <property>
+                            <name>FUNCTIONS_EXTENSION_VERSION</name>
+                            <value>~3</value>
+                        </property>
+                    </appSettings>
+                </configuration>
+                <executions>
+                    <execution>
+                        <id>package-functions</id>
+                        <goals>
+                            <goal>package</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+            <!--Remove obj folder generated by .NET SDK in maven clean-->
+            <plugin>
+                <artifactId>maven-clean-plugin</artifactId>
+                <version>3.1.0</version>
+                <configuration>
+                    <filesets>
+                        <fileset>
+                            <directory>obj</directory>
+                        </fileset>
+                    </filesets>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</project>
--- a/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/consumer/callcostprocessor/functions/UsageCostProcessorFunction.java
+++ b/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/consumer/callcostprocessor/functions/UsageCostProcessorFunction.java
@ -0,0 +1,168 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 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.claimcheckpattern.consumer.callcostprocessor.functions;
+
+import com.azure.core.util.BinaryData;
+import com.azure.core.util.serializer.TypeReference;
+import com.azure.messaging.eventgrid.EventGridEvent;
+import com.azure.messaging.eventgrid.systemevents.SubscriptionValidationEventData;
+import com.azure.messaging.eventgrid.systemevents.SubscriptionValidationResponse;
+import com.iluwatar.claimcheckpattern.domain.Message;
+import com.iluwatar.claimcheckpattern.domain.MessageBody;
+import com.iluwatar.claimcheckpattern.domain.MessageHeader;
+import com.iluwatar.claimcheckpattern.domain.MessageReference;
+import com.iluwatar.claimcheckpattern.domain.UsageCostDetail;
+import com.iluwatar.claimcheckpattern.domain.UsageDetail;
+import com.iluwatar.claimcheckpattern.utility.MessageHandlerUtility;
+import com.microsoft.azure.functions.ExecutionContext;
+import com.microsoft.azure.functions.HttpMethod;
+import com.microsoft.azure.functions.HttpRequestMessage;
+import com.microsoft.azure.functions.HttpResponseMessage;
+import com.microsoft.azure.functions.HttpStatus;
+import com.microsoft.azure.functions.annotation.AuthorizationLevel;
+import com.microsoft.azure.functions.annotation.FunctionName;
+import com.microsoft.azure.functions.annotation.HttpTrigger;
+import java.time.OffsetDateTime;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+
+/**
+ * Azure Functions with HTTP Trigger.
+ * This is Consumer class.
+ */
+public class UsageCostProcessorFunction {
+
+  private MessageHandlerUtility<UsageDetail> messageHandlerUtilityForUsageDetail;
+  private MessageHandlerUtility<UsageCostDetail> messageHandlerUtilityForUsageCostDetail;
+
+  public UsageCostProcessorFunction() {
+    this.messageHandlerUtilityForUsageDetail = new MessageHandlerUtility<>();
+    this.messageHandlerUtilityForUsageCostDetail = new MessageHandlerUtility<>();
+  }
+
+  public UsageCostProcessorFunction(
+      MessageHandlerUtility<UsageDetail> messageHandlerUtilityForUsageDetail,
+      MessageHandlerUtility<UsageCostDetail> messageHandlerUtilityForUsageCostDetail) {
+    this.messageHandlerUtilityForUsageDetail = messageHandlerUtilityForUsageDetail;
+    this.messageHandlerUtilityForUsageCostDetail = messageHandlerUtilityForUsageCostDetail;
+  }
+
+  /**
+   * Azure function which gets triggered when event grid event send event to it.
+   * After receiving event, it read input file from blob storage, calculate call cost details.
+   * It creates new message with cost details and drop message to blob storage.
+   * @param request represents HttpRequestMessage
+   * @param context represents ExecutionContext
+   * @return HttpResponseMessage
+   */
+  @FunctionName("UsageCostProcessorFunction")
+  public HttpResponseMessage run(@HttpTrigger(name = "req", methods = { HttpMethod.GET,
+      HttpMethod.POST }, authLevel = AuthorizationLevel.ANONYMOUS)
+                                       HttpRequestMessage<Optional<String>> request,
+                                 final ExecutionContext context) {
+    try {
+      var eventGridEvents = EventGridEvent.fromString(request.getBody().get());
+      for (var eventGridEvent : eventGridEvents) {
+        // Handle system events
+        if (eventGridEvent.getEventType()
+            .equals("Microsoft.EventGrid.SubscriptionValidationEvent")) {
+          SubscriptionValidationEventData subscriptionValidationEventData = eventGridEvent.getData()
+              .toObject(SubscriptionValidationEventData.class);
+          // Handle the subscription validation event
+          var responseData = new SubscriptionValidationResponse();
+          responseData.setValidationResponse(subscriptionValidationEventData.getValidationCode());
+          return request.createResponseBuilder(HttpStatus.OK).body(responseData).build();
+
+        } else if (eventGridEvent.getEventType().equals("UsageDetail")) {
+          // Get message header and reference
+          var messageReference = eventGridEvent.getData()
+              .toObject(MessageReference.class);
+
+          // Read message from persistent storage
+          var message = this.messageHandlerUtilityForUsageDetail
+              .readFromPersistantStorage(messageReference, context.getLogger());
+
+          // Get Data and generate cost details
+          List<UsageDetail> usageDetailsList = BinaryData.fromObject(
+              message.getMessageBody().getData())
+              .toObject(new TypeReference<>() {
+              });
+          var usageCostDetailsList = calculateUsageCostDetails(usageDetailsList);
+
+          // Create message body
+          var newMessageBody = new MessageBody<UsageCostDetail>();
+          newMessageBody.setData(usageCostDetailsList);
+
+          // Create message header
+          var newMessageReference = new MessageReference("callusageapp",
+              eventGridEvent.getId() + "/output.json");
+          var newMessageHeader = new MessageHeader();
+          newMessageHeader.setId(eventGridEvent.getId());
+          newMessageHeader.setSubject("UsageCostProcessor");
+          newMessageHeader.setTopic("");
+          newMessageHeader.setEventType("UsageCostDetail");
+          newMessageHeader.setEventTime(OffsetDateTime.now().toString());
+          newMessageHeader.setData(newMessageReference);
+          newMessageHeader.setDataVersion("v1.0");
+
+          // Create entire message
+          var newMessage = new Message<UsageCostDetail>();
+          newMessage.setMessageHeader(newMessageHeader);
+          newMessage.setMessageBody(newMessageBody);
+
+          // Drop data to persistent storage
+          this.messageHandlerUtilityForUsageCostDetail.dropToPersistantStorage(newMessage,
+              context.getLogger());
+
+          context.getLogger().info("Message is dropped successfully");
+          return request.createResponseBuilder(HttpStatus.OK)
+              .body("Message is dropped successfully").build();
+        }
+      }
+    } catch (Exception e) {
+      context.getLogger().warning(e.getMessage());
+    }
+
+    return request.createResponseBuilder(HttpStatus.INTERNAL_SERVER_ERROR).body(null).build();
+  }
+
+  private List<UsageCostDetail> calculateUsageCostDetails(List<UsageDetail> usageDetailsList) {
+    if (usageDetailsList == null) {
+      return null;
+    }
+    var usageCostDetailsList = new ArrayList<UsageCostDetail>();
+
+    usageDetailsList.forEach(usageDetail -> {
+      var usageCostDetail = new UsageCostDetail();
+      usageCostDetail.setUserId(usageDetail.getUserId());
+      usageCostDetail.setCallCost(usageDetail.getDuration() * 0.30); // 0.30₹ per minute
+      usageCostDetail.setDataCost(usageDetail.getData() * 0.20); // 0.20₹ per MB
+
+      usageCostDetailsList.add(usageCostDetail);
+    });
+
+    return usageCostDetailsList;
+  }
+}
--- a/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/domain/Message.java
+++ b/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/domain/Message.java
@ -0,0 +1,43 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 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.claimcheckpattern.domain;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * It is the message which gets dropped or read by Producer or Consumer Azure functions.
+ * It is stored in the json format.
+ * @param <T> represents UsageDetail or UsageCostDetail
+ */
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class Message<T> {
+  private MessageHeader messageHeader;
+
+  private MessageBody<T> messageBody;
+
+}
--- a/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/domain/MessageBody.java
+++ b/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/domain/MessageBody.java
@ -0,0 +1,43 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 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.claimcheckpattern.domain;
+
+import java.util.List;
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * It is message body of the message.
+ * It stores actual data in our case UsageCostDetail or UsageDetail.
+ * @param <T> represents UsageDetail or UsageCostDetail
+ */
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class MessageBody<T> {
+
+  private List<T> data;
+
+}
--- a/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/domain/MessageHeader.java
+++ b/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/domain/MessageHeader.java
@ -0,0 +1,47 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 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.claimcheckpattern.domain;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * This is message header or event which is sent to Event Grid.
+ * Its structure is same as Azure Event Grid Event Class.
+ */
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class MessageHeader {
+
+  private String id;
+  private String subject;
+  private String topic;
+  private String eventType;
+  private String eventTime;
+  private Object data;
+  private String dataVersion;
+
+}
--- a/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/domain/MessageReference.java
+++ b/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/domain/MessageReference.java
@ -0,0 +1,45 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 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.claimcheckpattern.domain;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * This is claim/message reference class.
+ * It contains the information about data where it is stored in persistent storage
+ * and file name.
+ * dataLocation is blob storage container name.
+ * dataFileName is file name in above container.
+ */
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class MessageReference {
+
+  private String dataLocation;
+  private String dataFileName;
+
+}
--- a/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/domain/UsageCostDetail.java
+++ b/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/domain/UsageCostDetail.java
@ -0,0 +1,43 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 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.claimcheckpattern.domain;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * This is call cost details class.
+ * It stores userId of the caller, call duration cost and data cost.
+ */
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class UsageCostDetail {
+
+  private String userId;
+  private double callCost;
+  private double dataCost;
+
+}
--- a/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/domain/UsageDetail.java
+++ b/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/domain/UsageDetail.java
@ -0,0 +1,44 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 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.claimcheckpattern.domain;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * This is call usage detail calls.
+ * It stores userId of the caller, call duration and data used.
+ */
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class UsageDetail {
+
+  private String userId;
+
+  private int duration;
+
+  private int data;
+}
--- a/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/producer/calldetails/functions/UsageDetailPublisherFunction.java
+++ b/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/producer/calldetails/functions/UsageDetailPublisherFunction.java
@ -0,0 +1,146 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 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.claimcheckpattern.producer.calldetails.functions;
+
+import com.azure.messaging.eventgrid.EventGridEvent;
+import com.azure.messaging.eventgrid.systemevents.SubscriptionValidationEventData;
+import com.azure.messaging.eventgrid.systemevents.SubscriptionValidationResponse;
+import com.iluwatar.claimcheckpattern.domain.Message;
+import com.iluwatar.claimcheckpattern.domain.MessageBody;
+import com.iluwatar.claimcheckpattern.domain.MessageHeader;
+import com.iluwatar.claimcheckpattern.domain.MessageReference;
+import com.iluwatar.claimcheckpattern.domain.UsageDetail;
+import com.iluwatar.claimcheckpattern.utility.EventHandlerUtility;
+import com.iluwatar.claimcheckpattern.utility.MessageHandlerUtility;
+import com.microsoft.azure.functions.ExecutionContext;
+import com.microsoft.azure.functions.HttpMethod;
+import com.microsoft.azure.functions.HttpRequestMessage;
+import com.microsoft.azure.functions.HttpResponseMessage;
+import com.microsoft.azure.functions.HttpStatus;
+import com.microsoft.azure.functions.annotation.AuthorizationLevel;
+import com.microsoft.azure.functions.annotation.FunctionName;
+import com.microsoft.azure.functions.annotation.HttpTrigger;
+import java.time.OffsetDateTime;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+import java.util.Random;
+import java.util.UUID;
+
+/**
+ * Azure Functions with HTTP Trigger.
+ * This is Producer class.
+ */
+public class UsageDetailPublisherFunction {
+
+  private MessageHandlerUtility<UsageDetail> messageHandlerUtility;
+  private EventHandlerUtility<MessageHeader> eventHandlerUtility;
+
+  public UsageDetailPublisherFunction() {
+    this.messageHandlerUtility = new MessageHandlerUtility<>();
+    this.eventHandlerUtility = new EventHandlerUtility<>();
+  }
+
+  public UsageDetailPublisherFunction(MessageHandlerUtility<UsageDetail> messageHandlerUtility,
+      EventHandlerUtility<MessageHeader> eventHandlerUtility) {
+    this.messageHandlerUtility = messageHandlerUtility;
+    this.eventHandlerUtility = eventHandlerUtility;
+  }
+
+  /**
+   * Azure function which create message, drop it in persistent storage
+   * and publish the event to Event Grid topic.
+   * @param request represents HttpRequestMessage
+   * @param context represents ExecutionContext
+   * @return HttpResponseMessage
+   */
+  @FunctionName("UsageDetailPublisherFunction")
+  public HttpResponseMessage run(@HttpTrigger(name = "req", methods = {
+      HttpMethod.POST }, authLevel = AuthorizationLevel.ANONYMOUS)
+      HttpRequestMessage<Optional<String>> request,
+      final ExecutionContext context) {
+    try {
+
+      var eventGridEvents = EventGridEvent.fromString(request.getBody().get());
+
+      for (EventGridEvent eventGridEvent : eventGridEvents) {
+        // Handle system events
+        if (eventGridEvent.getEventType()
+            .equals("Microsoft.EventGrid.SubscriptionValidationEvent")) {
+          SubscriptionValidationEventData subscriptionValidationEventData = eventGridEvent.getData()
+              .toObject(SubscriptionValidationEventData.class);
+          // Handle the subscription validation event
+          var responseData = new SubscriptionValidationResponse();
+          responseData.setValidationResponse(subscriptionValidationEventData.getValidationCode());
+          return request.createResponseBuilder(HttpStatus.OK).body(responseData).build();
+
+        } else if (eventGridEvent.getEventType().equals("UsageDetail")) {
+          // Create message body
+          var messageBody = new MessageBody<UsageDetail>();
+          var usageDetailsList = new ArrayList<UsageDetail>();
+          var random = new Random();
+          for (int i = 0; i < 51; i++) {
+            var usageDetail = new UsageDetail();
+            usageDetail.setUserId("userId" + i);
+            usageDetail.setData(random.nextInt(500));
+            usageDetail.setDuration(random.nextInt(500));
+
+            usageDetailsList.add(usageDetail);
+          }
+          messageBody.setData(usageDetailsList);
+
+          // Create message header
+          var messageHeader = new MessageHeader();
+          messageHeader.setId(UUID.randomUUID().toString());
+          messageHeader.setSubject("UsageDetailPublisher");
+          messageHeader.setTopic("usagecostprocessorfunction-topic");
+          messageHeader.setEventType("UsageDetail");
+          messageHeader.setEventTime(OffsetDateTime.now().toString());
+          var messageReference = new MessageReference("callusageapp",
+              messageHeader.getId() + "/input.json");
+          messageHeader.setData(messageReference);
+          messageHeader.setDataVersion("v1.0");
+
+          // Create entire message
+          var message = new Message<UsageDetail>();
+          message.setMessageHeader(messageHeader);
+          message.setMessageBody(messageBody);
+
+          // Drop data to persistent storage
+          this.messageHandlerUtility.dropToPersistantStorage(message, context.getLogger());
+
+          // Publish event to event grid topic
+          eventHandlerUtility.publishEvent(messageHeader, context.getLogger());
+
+          context.getLogger().info("Message is dropped and event is published successfully");
+          return request.createResponseBuilder(HttpStatus.OK).body(message).build();
+        }
+      }
+    } catch (Exception e) {
+      context.getLogger().warning(e.getMessage());
+    }
+
+    return request.createResponseBuilder(HttpStatus.OK).body(null).build();
+  }
+}
--- a/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/utility/EventHandlerUtility.java
+++ b/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/utility/EventHandlerUtility.java
@ -0,0 +1,66 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 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.claimcheckpattern.utility;
+
+import com.azure.core.credential.AzureKeyCredential;
+import com.azure.core.util.BinaryData;
+import com.azure.messaging.eventgrid.EventGridPublisherClient;
+import com.azure.messaging.eventgrid.EventGridPublisherClientBuilder;
+import java.util.logging.Logger;
+
+/**
+ * This class is event publisher utility which published message header to Event Grid topic.
+ * @param <T> represents UsageDetail or UsageCostDetail
+ */
+public class EventHandlerUtility<T> {
+
+  private EventGridPublisherClient<BinaryData> customEventClient;
+
+  /** Default constructor.
+   */
+  public EventHandlerUtility() {
+    this.customEventClient = new EventGridPublisherClientBuilder()
+            .endpoint(System.getenv("EventGridURL"))
+        .credential(new AzureKeyCredential(System.getenv("EventGridKey")))
+            .buildCustomEventPublisherClient();
+  }
+
+  /**
+  Parameterized constructor.
+   */
+  public EventHandlerUtility(EventGridPublisherClient<BinaryData> customEventClient) {
+    this.customEventClient = customEventClient;
+  }
+
+  /**
+  Method for publishing event to Event Grid Topic.
+   */
+  public void publishEvent(T customEvent, Logger logger) {
+    try {
+      customEventClient.sendEvent(BinaryData.fromObject(customEvent));
+    } catch (Exception e) {
+      logger.info(e.getMessage());
+    }
+  }
+}
--- a/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/utility/MessageHandlerUtility.java
+++ b/cloud-claim-check-pattern/call-usage-app/src/main/java/com/iluwatar/claimcheckpattern/utility/MessageHandlerUtility.java
@ -0,0 +1,127 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 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.claimcheckpattern.utility;
+
+import com.azure.core.util.BinaryData;
+import com.azure.core.util.serializer.TypeReference;
+import com.azure.storage.blob.BlobClient;
+import com.azure.storage.blob.BlobContainerClient;
+import com.azure.storage.blob.BlobServiceClient;
+import com.azure.storage.blob.BlobServiceClientBuilder;
+import com.iluwatar.claimcheckpattern.domain.Message;
+import com.iluwatar.claimcheckpattern.domain.MessageReference;
+import java.util.logging.Logger;
+
+/**
+ * This class read and drop message from Azure blob storage.
+ * @param <T> represents UsageDetail or UsageCostDetail
+ */
+public class MessageHandlerUtility<T> {
+
+  private BlobServiceClient blobServiceClient;
+
+  /**
+   * Parameterized constructor.
+   * @param blobServiceClient represents BlobServiceClient
+   */
+  public MessageHandlerUtility(BlobServiceClient blobServiceClient) {
+    this.blobServiceClient = blobServiceClient;
+  }
+
+  /**
+   * Default constructor.
+   */
+  public MessageHandlerUtility() {
+    // Create a BlobServiceClient object which will be used to create a container
+    // client
+    this.blobServiceClient = new BlobServiceClientBuilder()
+        .connectionString(System.getenv("BlobStorageConnectionString")).buildClient();
+
+  }
+
+  /**
+   * Read message from blob storage.
+   * @param messageReference represents MessageReference
+   * @param logger represents Logger
+   * @return Message
+   */
+  public Message<T> readFromPersistantStorage(MessageReference messageReference, Logger logger) {
+    Message<T> message = null;
+    try {
+
+      // Get container name from message reference
+      String containerName = messageReference.getDataLocation();
+
+      // Get blob name from message reference
+      String blobName = messageReference.getDataFileName();
+
+      // Get container client
+      BlobContainerClient containerClient = blobServiceClient.getBlobContainerClient(containerName);
+
+      // Get a reference to a blob
+      BlobClient blobClient = containerClient.getBlobClient(blobName);
+
+      // download the blob
+      message = blobClient.downloadContent().toObject(new TypeReference<Message<T>>() {
+      });
+    } catch (Exception e) {
+      logger.info(e.getMessage());
+    }
+    return message;
+
+  }
+
+  /**
+   * Drop message to blob storage.
+   * @param message represents Message
+   * @param logger represents Logger
+   */
+  public void dropToPersistantStorage(Message<T> message, Logger logger) {
+    try {
+
+      // Get message reference
+      MessageReference messageReference = (MessageReference) message.getMessageHeader().getData();
+
+      // Create a unique name for the container
+      String containerName = messageReference.getDataLocation();
+
+      // Create the container and return a container client object
+      BlobContainerClient containerClient = this.blobServiceClient
+          .getBlobContainerClient(containerName);
+      if (!containerClient.exists()) {
+        containerClient.create();
+      }
+
+      // Get a reference to a blob
+      BlobClient blobClient = containerClient.getBlobClient(messageReference.getDataFileName());
+
+      // Upload the blob
+      blobClient.upload(BinaryData.fromObject(message));
+    } catch (Exception e) {
+      logger.info(e.getMessage());
+    }
+
+  }
+
+}
--- a/cloud-claim-check-pattern/call-usage-app/src/test/java/com/iluwatar/claimcheckpattern/HttpResponseMessageMock.java
+++ b/cloud-claim-check-pattern/call-usage-app/src/test/java/com/iluwatar/claimcheckpattern/HttpResponseMessageMock.java
@ -0,0 +1,105 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 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.claimcheckpattern;
+
+import com.microsoft.azure.functions.HttpResponseMessage;
+import com.microsoft.azure.functions.HttpStatus;
+import com.microsoft.azure.functions.HttpStatusType;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * The mock for HttpResponseMessage, can be used in unit tests to verify if the
+ * returned response by HTTP trigger function is correct or not.
+ */
+public class HttpResponseMessageMock implements HttpResponseMessage {
+    private int httpStatusCode;
+    private HttpStatusType httpStatus;
+    private Object body;
+    private Map<String, String> headers;
+
+    public HttpResponseMessageMock(HttpStatusType status, Map<String, String> headers, Object body) {
+        this.httpStatus = status;
+        this.httpStatusCode = status.value();
+        this.headers = headers;
+        this.body = body;
+    }
+
+    @Override
+    public HttpStatusType getStatus() {
+        return this.httpStatus;
+    }
+
+    @Override
+    public int getStatusCode() {
+        return httpStatusCode;
+    }
+
+    @Override
+    public String getHeader(String key) {
+        return this.headers.get(key);
+    }
+
+    @Override
+    public Object getBody() {
+        return this.body;
+    }
+
+    public static class HttpResponseMessageBuilderMock implements HttpResponseMessage.Builder {
+        private Object body;
+        private int httpStatusCode;
+        private Map<String, String> headers = new HashMap<>();
+        private HttpStatusType httpStatus;
+
+        public Builder status(HttpStatus status) {
+            this.httpStatusCode = status.value();
+            this.httpStatus = status;
+            return this;
+        }
+
+        @Override
+        public Builder status(HttpStatusType httpStatusType) {
+            this.httpStatusCode = httpStatusType.value();
+            this.httpStatus = httpStatusType;
+            return this;
+        }
+
+        @Override
+        public HttpResponseMessage.Builder header(String key, String value) {
+            this.headers.put(key, value);
+            return this;
+        }
+
+        @Override
+        public HttpResponseMessage.Builder body(Object body) {
+            this.body = body;
+            return this;
+        }
+
+        @Override
+        public HttpResponseMessage build() {
+            return new HttpResponseMessageMock(this.httpStatus, this.headers, this.body);
+        }
+    }
+}
--- a/cloud-claim-check-pattern/call-usage-app/src/test/java/com/iluwatar/claimcheckpattern/consumer/callcostprocessor/functions/UsageCostProcessorFunctionTest.java
+++ b/cloud-claim-check-pattern/call-usage-app/src/test/java/com/iluwatar/claimcheckpattern/consumer/callcostprocessor/functions/UsageCostProcessorFunctionTest.java
@ -0,0 +1,181 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 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.claimcheckpattern.consumer.callcostprocessor.functions;
+
+import com.iluwatar.claimcheckpattern.HttpResponseMessageMock;
+import com.iluwatar.claimcheckpattern.domain.Message;
+import com.iluwatar.claimcheckpattern.domain.MessageBody;
+import com.iluwatar.claimcheckpattern.domain.MessageHeader;
+import com.iluwatar.claimcheckpattern.domain.MessageReference;
+import com.iluwatar.claimcheckpattern.domain.UsageCostDetail;
+import com.iluwatar.claimcheckpattern.domain.UsageDetail;
+import com.iluwatar.claimcheckpattern.utility.MessageHandlerUtility;
+import com.microsoft.azure.functions.ExecutionContext;
+import com.microsoft.azure.functions.HttpRequestMessage;
+import com.microsoft.azure.functions.HttpResponseMessage;
+import com.microsoft.azure.functions.HttpStatus;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.invocation.InvocationOnMock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.mockito.stubbing.Answer;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.time.OffsetDateTime;
+import java.util.*;
+import java.util.logging.Logger;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.*;
+
+/**
+ * Unit test for Function class.
+ */
+@ExtendWith(MockitoExtension.class)
+public class UsageCostProcessorFunctionTest {
+
+    @Mock
+    MessageHandlerUtility<UsageDetail> mockMessageHandlerUtilityForUsageADetail;
+    @Mock
+    MessageHandlerUtility<UsageCostDetail> mockMessageHandlerUtilityForUsageCostDetail;
+    @Mock
+    ExecutionContext context;
+
+    Message<UsageCostDetail> messageToDrop;
+    Message<UsageDetail> messageToRead;
+    MessageReference messageReference;
+    @InjectMocks
+    UsageCostProcessorFunction usageCostProcessorFunction;
+
+    @BeforeEach
+    public void setUp() {
+        var messageBodyUsageDetail = new MessageBody<UsageDetail>();
+        var usageDetailsList = new ArrayList<UsageDetail>();
+
+        var messageBodyUsageCostDetail = new MessageBody<UsageCostDetail>();
+        var usageCostDetailsList = new ArrayList<UsageCostDetail>();
+        for (int i = 0; i < 2; i++) {
+            var usageDetail = new UsageDetail();
+            usageDetail.setUserId("userId" + i);
+            usageDetail.setData(i + 1);
+            usageDetail.setDuration(i + 1);
+            usageDetailsList.add(usageDetail);
+
+            var usageCostDetail = new UsageCostDetail();
+            usageCostDetail.setUserId(usageDetail.getUserId());
+            usageCostDetail.setDataCost(usageDetail.getData() * 0.20);
+            usageCostDetail.setCallCost(usageDetail.getDuration() * 0.30);
+            usageCostDetailsList.add(usageCostDetail);
+        }
+        messageBodyUsageDetail.setData(usageDetailsList);
+        messageBodyUsageCostDetail.setData(usageCostDetailsList);
+
+        // Create message header
+        var messageHeader = new MessageHeader();
+        messageHeader.setId(UUID.randomUUID().toString());
+        messageHeader.setSubject("UsageDetailPublisher");
+        messageHeader.setTopic("usagecostprocessorfunction-topic");
+        messageHeader.setEventType("UsageDetail");
+        messageHeader.setEventTime(OffsetDateTime.now().toString());
+        this.messageReference = new MessageReference("callusageapp", "d8284456-dfff-4bd4-9cef-ea99f70f4835/input.json");
+        messageHeader.setData(messageReference);
+        messageHeader.setDataVersion("v1.0");
+
+        // Create entire message
+        messageToRead = new Message<>();
+        messageToRead.setMessageHeader(messageHeader);
+        messageToRead.setMessageBody(messageBodyUsageDetail);
+
+        messageToDrop = new Message<>();
+        messageToDrop.setMessageHeader(messageHeader);
+        messageToDrop.setMessageBody(messageBodyUsageCostDetail);
+
+    }
+
+    /**
+     * Unit test for HttpTriggerJava method.
+     */
+    @Test
+    public void shouldTriggerHttpAzureFunctionJavaWithSubscriptionValidationEventType() throws Exception {
+
+        // Setup
+        @SuppressWarnings("unchecked")
+        final HttpRequestMessage<Optional<String>> req = mock(HttpRequestMessage.class);
+        String fileAbsolutePath = getClass().getResource("/subscriptionValidationEvent.json").getPath()
+                .replaceAll("%20", " "), jsonBody = Files.readString(Paths.get(fileAbsolutePath)).replaceAll("\n", " ");
+        doReturn(Optional.of(jsonBody)).when(req).getBody();
+        doAnswer(new Answer<HttpResponseMessage.Builder>() {
+            @Override
+            public HttpResponseMessage.Builder answer(InvocationOnMock invocation) {
+                HttpStatus status = (HttpStatus) invocation.getArguments()[0];
+                return new HttpResponseMessageMock.HttpResponseMessageBuilderMock().status(status);
+            }
+        }).when(req).createResponseBuilder(any(HttpStatus.class));
+
+        final ExecutionContext context = mock(ExecutionContext.class);
+
+        // Invoke
+        final HttpResponseMessage ret = this.usageCostProcessorFunction.run(req, context);
+
+        // Verify
+        assertEquals(ret.getStatus(), HttpStatus.OK);
+    }
+
+    @Test
+    public void shouldTriggerHttpAzureFunctionJavaWithUsageDetailEventType() throws Exception {
+        // Setup
+        @SuppressWarnings("unchecked")
+        final HttpRequestMessage<Optional<String>> req = mock(HttpRequestMessage.class);
+        String fileAbsolutePath = getClass().getResource("/usageDetailEvent.json").getPath().replaceAll("%20", " "),
+                jsonBody = Files.readString(Paths.get(fileAbsolutePath)).replaceAll("\n", " ");
+        doReturn(Optional.of(jsonBody)).when(req).getBody();
+        doReturn(Logger.getGlobal()).when(context).getLogger();
+
+        when(this.mockMessageHandlerUtilityForUsageADetail.readFromPersistantStorage(any(MessageReference.class),
+                eq(Logger.getGlobal()))).thenReturn(messageToRead);
+        doAnswer(new Answer<HttpResponseMessage.Builder>() {
+            @Override
+            public HttpResponseMessage.Builder answer(InvocationOnMock invocation) {
+                HttpStatus status = (HttpStatus) invocation.getArguments()[0];
+                return new HttpResponseMessageMock.HttpResponseMessageBuilderMock().status(status);
+            }
+        }).when(req).createResponseBuilder(any(HttpStatus.class));
+
+        assertNotNull(this.mockMessageHandlerUtilityForUsageADetail);
+        assertEquals(this.messageToRead, this.mockMessageHandlerUtilityForUsageADetail
+                .readFromPersistantStorage(this.messageReference, Logger.getGlobal()));
+
+        // Invoke
+        final HttpResponseMessage ret = this.usageCostProcessorFunction.run(req, context);
+
+        // Verify
+        assertEquals(HttpStatus.OK, ret.getStatus());
+        assertEquals("Message is dropped successfully", ret.getBody());
+    }
+
+}
--- a/cloud-claim-check-pattern/call-usage-app/src/test/java/com/iluwatar/claimcheckpattern/producer/calldetails/functions/UsageDetailPublisherFunctionTest.java
+++ b/cloud-claim-check-pattern/call-usage-app/src/test/java/com/iluwatar/claimcheckpattern/producer/calldetails/functions/UsageDetailPublisherFunctionTest.java
@ -0,0 +1,119 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 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.claimcheckpattern.producer.calldetails.functions;
+
+import com.iluwatar.claimcheckpattern.HttpResponseMessageMock;
+import com.iluwatar.claimcheckpattern.domain.MessageHeader;
+import com.iluwatar.claimcheckpattern.domain.UsageDetail;
+import com.iluwatar.claimcheckpattern.utility.EventHandlerUtility;
+import com.iluwatar.claimcheckpattern.utility.MessageHandlerUtility;
+import com.microsoft.azure.functions.ExecutionContext;
+import com.microsoft.azure.functions.HttpRequestMessage;
+import com.microsoft.azure.functions.HttpResponseMessage;
+import com.microsoft.azure.functions.HttpStatus;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.invocation.InvocationOnMock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.mockito.stubbing.Answer;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.*;
+import java.util.logging.Logger;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.*;
+
+/**
+ * Unit test for Function class.
+ */
+@ExtendWith(MockitoExtension.class)
+public class UsageDetailPublisherFunctionTest {
+    @Mock
+    MessageHandlerUtility<UsageDetail> mockMessageHandlerUtility;
+    @Mock
+    EventHandlerUtility<MessageHeader> mockEventHandlerUtility;
+
+    @InjectMocks
+    UsageDetailPublisherFunction usageDetailPublisherFunction;
+
+    /**
+     * Unit test for HttpTriggerJava method.
+     */
+    @Test
+    public void shouldTriggerHttpAzureFunctionJavaWithSubscriptionValidationEventType() throws Exception {
+
+        // Setup
+        @SuppressWarnings("unchecked")
+        final HttpRequestMessage<Optional<String>> req = mock(HttpRequestMessage.class);
+        String fileAbsolutePath = getClass().getResource("/subscriptionValidationEvent.json").getPath()
+                .replaceAll("%20", " "), jsonBody = Files.readString(Paths.get(fileAbsolutePath)).replaceAll("\n", " ");
+        doReturn(Optional.of(jsonBody)).when(req).getBody();
+        doAnswer(new Answer<HttpResponseMessage.Builder>() {
+            @Override
+            public HttpResponseMessage.Builder answer(InvocationOnMock invocation) {
+                HttpStatus status = (HttpStatus) invocation.getArguments()[0];
+                return new HttpResponseMessageMock.HttpResponseMessageBuilderMock().status(status);
+            }
+        }).when(req).createResponseBuilder(any(HttpStatus.class));
+
+        final ExecutionContext context = mock(ExecutionContext.class);
+
+        // Invoke
+        final HttpResponseMessage ret = this.usageDetailPublisherFunction.run(req, context);
+
+        // Verify
+        assertEquals(ret.getStatus(), HttpStatus.OK);
+    }
+
+    @Test
+    public void shouldTriggerHttpAzureFunctionJavaWithUsageDetailEventType() throws Exception {
+
+        // Setup
+        @SuppressWarnings("unchecked")
+        final HttpRequestMessage<Optional<String>> req = mock(HttpRequestMessage.class);
+        String fileAbsolutePath = getClass().getResource("/usageDetailEvent.json").getPath().replaceAll("%20", " "),
+                jsonBody = Files.readString(Paths.get(fileAbsolutePath)).replaceAll("\n", " ");
+        doReturn(Optional.of(jsonBody)).when(req).getBody();
+        doAnswer(new Answer<HttpResponseMessage.Builder>() {
+            @Override
+            public HttpResponseMessage.Builder answer(InvocationOnMock invocation) {
+                HttpStatus status = (HttpStatus) invocation.getArguments()[0];
+                return new HttpResponseMessageMock.HttpResponseMessageBuilderMock().status(status);
+            }
+        }).when(req).createResponseBuilder(any(HttpStatus.class));
+
+        final ExecutionContext context = mock(ExecutionContext.class);
+        doReturn(Logger.getGlobal()).when(context).getLogger();
+
+        // Invoke
+        final HttpResponseMessage ret = this.usageDetailPublisherFunction.run(req, context);
+
+        // Verify
+        assertEquals(ret.getStatus(), HttpStatus.OK);
+    }
+
+}
--- a/cloud-claim-check-pattern/call-usage-app/src/test/java/com/iluwatar/claimcheckpattern/utility/EventHandlerUtilityTest.java
+++ b/cloud-claim-check-pattern/call-usage-app/src/test/java/com/iluwatar/claimcheckpattern/utility/EventHandlerUtilityTest.java
@ -0,0 +1,70 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 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.claimcheckpattern.utility;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.*;
+
+import com.azure.core.util.BinaryData;
+import com.azure.messaging.eventgrid.EventGridPublisherClient;
+import com.iluwatar.claimcheckpattern.domain.Message;
+import com.iluwatar.claimcheckpattern.domain.UsageDetail;
+import java.util.logging.Logger;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+@ExtendWith(MockitoExtension.class)
+public class EventHandlerUtilityTest {
+
+    @Mock
+    EventGridPublisherClient<BinaryData> mockCustomEventClient;
+
+    @InjectMocks
+    EventHandlerUtility<Message<UsageDetail>> eventHandlerUtility;
+
+    @BeforeEach
+    public void setUp() {
+
+        System.setProperty("EventGridURL", "https://www.dummyEndpoint.com/api/events");
+        System.setProperty("EventGridKey", "EventGridURL");
+    }
+
+    @Test
+    void shouldPublishEvent() {
+        doNothing().when(mockCustomEventClient).sendEvent(any(BinaryData.class));
+        eventHandlerUtility.publishEvent(null, Logger.getLogger("logger"));
+        verify(mockCustomEventClient, times(1)).sendEvent(any(BinaryData.class));
+
+    }
+
+    @Test
+    void shouldPublishEventWithNullLogger() {
+        eventHandlerUtility.publishEvent(null, null);
+        verify(mockCustomEventClient, times(1)).sendEvent(any(BinaryData.class));
+    }
+}
--- a/cloud-claim-check-pattern/call-usage-app/src/test/java/com/iluwatar/claimcheckpattern/utility/MessageHandlerUtilityTest.java
+++ b/cloud-claim-check-pattern/call-usage-app/src/test/java/com/iluwatar/claimcheckpattern/utility/MessageHandlerUtilityTest.java
@ -0,0 +1,114 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 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.claimcheckpattern.utility;
+
+import com.azure.storage.blob.BlobClient;
+import com.azure.storage.blob.BlobContainerClient;
+import com.azure.storage.blob.BlobServiceClient;
+import com.iluwatar.claimcheckpattern.domain.*;
+import com.iluwatar.claimcheckpattern.utility.MessageHandlerUtility;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import java.time.OffsetDateTime;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import java.util.UUID;
+import java.util.logging.Logger;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.*;
+
+@ExtendWith(MockitoExtension.class)
+public class MessageHandlerUtilityTest {
+    @Mock
+    private BlobClient mockBlobClient;
+
+    @Mock
+    private BlobContainerClient mockContainerClient;
+
+    @Mock
+    private BlobServiceClient mockBlobServiceClient;
+
+    @InjectMocks
+    private MessageHandlerUtility<UsageDetail> messageHandlerUtility;
+
+    private Message<UsageDetail> messageToPublish;
+    private MessageReference messageReference;
+
+    @BeforeEach
+    public void setUp() {
+        System.setProperty("BlobStorageConnectionString", "https://www.dummyEndpoint.com/api/blobs");
+
+        var messageBody = new MessageBody<UsageDetail>();
+        var usageDetailsList = new ArrayList<UsageDetail>();
+        var random = new Random();
+        for (int i = 0; i < 51; i++) {
+            var usageDetail = new UsageDetail();
+            usageDetail.setUserId("userId" + i);
+            usageDetail.setData(random.nextInt(500));
+            usageDetail.setDuration(random.nextInt(500));
+
+            usageDetailsList.add(usageDetail);
+        }
+        messageBody.setData(usageDetailsList);
+
+        // Create message header
+        var messageHeader = new MessageHeader();
+        messageHeader.setId(UUID.randomUUID().toString());
+        messageHeader.setSubject("UsageDetailPublisher");
+        messageHeader.setTopic("usagecostprocessorfunction-topic");
+        messageHeader.setEventType("UsageDetail");
+        messageHeader.setEventTime(OffsetDateTime.now().toString());
+        this.messageReference = new MessageReference("callusageapp", messageHeader.getId() + "/input.json");
+        messageHeader.setData(messageReference);
+        messageHeader.setDataVersion("v1.0");
+
+        // Create entire message
+        this.messageToPublish = new Message<>();
+        this.messageToPublish.setMessageHeader(messageHeader);
+        this.messageToPublish.setMessageBody(messageBody);
+
+        when(mockContainerClient.getBlobClient(anyString())).thenReturn(mockBlobClient);
+        when(mockBlobServiceClient.getBlobContainerClient(anyString())).thenReturn(mockContainerClient);
+    }
+
+    @Test
+    void shouldDropMessageToPersistantStorage() {
+        messageHandlerUtility.dropToPersistantStorage(messageToPublish, Logger.getLogger("logger"));
+        verify(mockBlobServiceClient, times(1)).getBlobContainerClient(anyString());
+        // verify(mockContainerClient, times(0)).exists();
+    }
+
+    @Test
+    void shouldReadMessageFromPersistantStorage() {
+
+        messageHandlerUtility.readFromPersistantStorage(messageReference, Logger.getLogger("logger"));
+        verify(mockBlobServiceClient, times(1)).getBlobContainerClient(anyString());
+    }
+}
--- a/cloud-claim-check-pattern/call-usage-app/src/test/resources/mockito-extensions/org.mockito.plugins.MockMaker
+++ b/cloud-claim-check-pattern/call-usage-app/src/test/resources/mockito-extensions/org.mockito.plugins.MockMaker
@ -0,0 +1 @@
+mock-maker-inline
--- a/cloud-claim-check-pattern/call-usage-app/src/test/resources/subscriptionValidationEvent.json
+++ b/cloud-claim-check-pattern/call-usage-app/src/test/resources/subscriptionValidationEvent.json
@ -0,0 +1,15 @@
+[
+  {
+    "data": {
+      "validationCode": "C12F266E-79D9-4C0A-9922-5EF6201A34C2",
+      "validationUrl": "https://rp-centralindia.eventgrid.azure.net:553/eventsubscriptions/usagedetailpublisherfunction-subscription/validate?idu003dC12F266E-79D9-4C0A-9922-5EF6201A34C2u0026tu003d2021-10-26T08:10:52.4999377Zu0026apiVersionu003d2020-10-15-previewu0026tokenu003d30kEVoL8rAOWzQv0buurhrKnbP%2bGMtHObbA%2bax6wb4Y%3d"
+    },
+    "dataVersion": "2",
+    "eventTime": "2021-10-26T08:10:52.4999377Z",
+    "eventType": "Microsoft.EventGrid.SubscriptionValidationEvent",
+    "id": "e2a8466b-3dc0-46b7-bb7d-b999e51a2848",
+    "metadataVersion": "1",
+    "subject": "",
+    "topic": "/subscriptions/0fef643d-a6b1-48f9-a256-53fbd0d22f48/resourceGroups/resource-group-ccp/providers/Microsoft.EventGrid/domains/event-grid-domains-ccp/topics/usagedetailpublisherfunction-topic"
+  }
+]
--- a/cloud-claim-check-pattern/call-usage-app/src/test/resources/usageDetailEvent.json
+++ b/cloud-claim-check-pattern/call-usage-app/src/test/resources/usageDetailEvent.json
@ -0,0 +1,15 @@
+[
+  {
+    "data": {
+      "dataFileName": "d8284456-dfff-4bd4-9cef-ea99f70f4835/input.json",
+      "dataLocation": "callusageapp"
+    },
+    "dataVersion": "v1.0",
+    "eventTime": "2021-10-25T19:17:15.7468501Z",
+    "eventType": "UsageDetail",
+    "id": "d8284456-dfff-4bd4-9cef-ea99f70f4835",
+    "metadataVersion": "1",
+    "subject": "UsageDetailPublisher",
+    "topic": "/subscriptions/0fef643d-a6b1-48f9-a256-ea99f70f4835/resourceGroups/resource-group-ccp/providers/Microsoft.EventGrid/domains/event-grid-domains-ccp/topics/usagecostprocessorfunction-topic"
+  }
+]