Car Parking Management System - Step-by-Step Guide

Introduction

This guide will walk you through setting up a Car Parking Management System using AWS services. The system leverages Amazon SNS (Simple Notification Service), Amazon SQS (Simple Queue Service), and AWS Lambda to manage and process parking events, such as car entries, exits, and parking space updates. The guide will also cover testing the setup, monitoring logs in CloudWatch, and cleaning up resources afterward.

Use Case

Scenario

Imagine a smart parking lot in a busy city. The parking lot is equipped with sensors and cameras to detect when cars enter or exit and to update the status of parking spaces. These events need to be processed in real-time to update parking availability, calculate parking fees, and notify parking lot managers.

Workflow

1. Car Entry: When a car enters the parking lot, the system logs the car number and entry time.
2. Car Exit: When a car exits, the system logs the car number and exit time, calculates the parking fee, and updates the parking space status.
3. Parking Space Update: As soon as a car enters a parking space, the system updates the status of the space (e.g., occupied, under maintenance, reserved, or free) based on the car number and parking space ID.

Prerequisites

Before you begin, make sure you have the following:

• An AWS account with necessary permissions to create and manage SNS, SQS, Lambda, and CloudWatch.
• Basic knowledge of AWS services, IAM roles, and Lambda functions.

Step 1: Create an SNS Topic

1. Navigate to the Amazon SNS Console.
2. Click on Create topic.
3. Select Standard as the topic type.
4. Enter a Topic name (e.g., ParkingEvents).
5. Click Create topic.

Step 2: Create SQS Queues

2.1 Car Entry Queue

1. Navigate to the Amazon SQS Console.
2. Click on Create Queue.
3. Choose Standard Queue.
4. Enter a Queue Name (e.g., CarEntryQueue).
5. Configure other settings as needed and click Create Queue.

2.2 Car Exit Queue

1. Repeat the steps to create another queue, but name it CarExitQueue.

2.3 Parking Space Update Queue

1. Repeat the steps to create another queue, but name it ParkingSpaceUpdateQueue.

Step 3: Subscribe SQS Queues to the SNS Topic

1. Go back to the Amazon SNS Console.

2. Under the Subscriptions tab, click Create subscription.

3. For Topic ARN, choose ParkingEvent.

4. For Protocol, choose SQS.

5. For Endpoint, select the ARN of CarEntryQueue.

6. Checked checkbox Enable raw message delivery

7. In the Subscription filter policy section, add the following JSON to filter messages based on the EventType:

   {
     "EventType": ["CarEntry"]
   }

8. Click Create subscription to complete the setup.

9. Repeat these steps to create a subscription for ParkingSpaceUpdateQueue, with the following filter policy:

   {
     "EventType": ["ParkingSpaceUpdate"]
   }

10. Repeat these steps to create a subscription for CarExitQueue, with the following filter policy:

{
  "EventType": ["CarExit"]
}

Step 4: Configure Access Policy for Each Queue

To allow the ParkingEvent SNS topic to send messages to your SQS queues, you need to configure the access policy for each queue.

1. Navigate to the SQS Console:

   • Go to the Amazon SQS Console.
   • Ensure the Region is set to Asia Pacific (Mumbai) ap-south-1.

2. Select CarExitQueue:

   • Choose the CarExitQueue from the list of SQS queues.
   • Go to the Permissions tab.
   • Click on Edit policy.

3. Add the Access Policy:

   • In the policy editor, add the following JSON policy:

     {
       "Sid": "Stmt1724523688641",
       "Effect": "Allow",
       "Principal": {
         "Service": "sns.amazonaws.com"
       },
       "Action": "sqs:SendMessage",
       "Resource": "<arn of queue>",
       "Condition": {
         "ArnEquals": {
           "aws:SourceArn": "<arn of sns>"
         }
       }
     }

   • Replace <arn of queue> with the ARN of the CarExitQueue.

   • Replace <arn of sns> with the ARN of the ParkingEvent SNS Topic.

4. Save Changes:

   • After replacing the placeholders with the actual ARNs, save the policy.

5. Repeat for Other Queues:

   • Repeat the above steps for CarEntryQueue and ParkingSpaceUpdateQueue:
     • Replace <arn of queue> with the ARN of CarEntryQueue or ParkingSpaceUpdateQueue.
     • Use the same <arn of sns> for the ParkingEvent SNS Topic.

6. Verify the Policy:

   • Ensure that each SQS queue (CarEntryQueue, CarExitQueue, ParkingSpaceUpdateQueue) has the correct policy allowing the ParkingEvent SNS topic to send messages.

Example of the Final Policy for CarExitQueue:

{
  "Sid": "Stmt1724523688641",
  "Effect": "Allow",
  "Principal": {
    "Service": "sns.amazonaws.com"
  },
  "Action": "sqs:SendMessage",
  "Resource": "arn:aws:sqs:ap-south-1:123456789012:CarExitQueue",
  "Condition": {
    "ArnEquals": {
      "aws:SourceArn": "arn:aws:sns:ap-south-1:123456789012:ParkingEvents"
    }
  }
}

Step 5: Create IAM Role for Lambda Functions

1. Navigate to the IAM Console.
2. Click on Roles and then Create role.
3. Select Trusted entity type as AWS Service and Use case as Lambda.
4. Attach the following policies:
   • AmazonSQSFullAccess
   • AWSLambdaBasicExecutionRole
   • AmazonSNSFullAccess
5. Name the role CarParkingLambdaRole and click Create role.

Step 6: Create Lambda Functions

6.1 Car Entry Lambda Function

1. Navigate to the AWS Lambda Console.
2. Click on Create function.
3. Choose Author from scratch.
4. Enter a Function name (e.g., CarEntryLambda).
5. Select .NET Core 8 as the runtime.
6. Under Permissions, choose the IAM role created earlier (CarParkingLambdaRole).
7. Click Create function.

6.2 Car Exit Lambda Function

1. Repeat the steps to create another function, but name it CarExitLambda.

6.3 Parking Space Update Lambda Function

1. Repeat the steps to create another function, but name it ParkingSpaceUpdateLambda.

6.4 Write the Lambda Function Code

Refer src folder

6.5 Create a ZIP File for the Lambda Deployment

1. Install Amazon.Lambda.Tools Global Tools if not already installed.

    dotnet tool install -g Amazon.Lambda.Tools

If already installed check if new version is available.

    dotnet tool update -g Amazon.Lambda.Tools

2. Run following command where your csproj file is stored in command prompt

dotnet lambda package *.csproj -o bin/package.zip

6.6 Upload the ZIP File to Lambda

1. Go back to the Lambda Console.
2. In the Code tab, click on Upload from and select .zip file.
3. Choose the ZIP file you created.
4. Click Save to deploy the function.

Edit Runtime Settings

5. After the upload, navigate to the Runtime settings section under the Code tab.
6. Set the Handler:
   • Enter the handler as "ParkingEventProcessorLambda::ParkingEventProcessorLambda.Function::FunctionHandler".
7. Save Changes:
   • Click Save to apply the new handler settings.

Step 7: Configure Triggers for Lambda Functions

7.1 Car Entry Queue Trigger

1. In the CarEntryLambda Lambda function, go to the Configuration tab.
2. Click on Add Trigger.
3. Select SQS and choose the CarEntryQueue.
4. Click Add.

7.2 Car Exit Queue Trigger

1. Repeat the steps to add a trigger to the CarExitLambda for the CarExitQueue.

7.3 Parking Space Update Queue Trigger

1. Repeat the steps to add a trigger to the ParkingSpaceUpdateLambda for the ParkingSpaceUpdateQueue.

Step 8: Test the Setup

1. Publish a Test Message to the ParkingEvents SNS Topic

1. Navigate to the SNS Dashboard:

2. Select the Topic:

   • In the SNS dashboard, click on Topics in the left-hand navigation pane.
   • Find and select the ParkingEvents topic from the list.

3. Publish a Message:

   • Click the Publish message button.
   • In the Publish message form:
     • Message body: Enter a JSON payload for testing, e.g.:

       {
         "EventType": "CarEntry",
         "CarId": "MH05SR7",
         "EntryTime": "2024-08-11T08:30:00Z"
       }

Step 9: Monitor CloudWatch Logs

1. Navigate to CloudWatch in the AWS Console.
2. Go to Logs and select the log group for your Lambda function (e.g., /aws/lambda/CarEntryLambda).
3. Review the logs to verify that events are processed correctly and that no errors occurred.

Step 10: Clean Up Resources

After testing, clean up the resources to avoid unnecessary charges:

1. Delete the Lambda Functions: Go to the Lambda Console and delete CarEntryLambda, CarExitLambda, and ParkingSpaceUpdateLambda.
2. Delete the SQS Queues: Go to the SQS Console and delete CarEntryQueue, CarExitQueue, and ParkingSpaceUpdateQueue.
3. Delete the SNS Topic: Go to the SNS Console and delete the ParkingEvents topic.
4. Delete the IAM Role: Go to the IAM Console and delete the CarParkingLambdaRole role.
5. Delete CloudWatch Log Groups: Go to CloudWatch Logs and delete the log groups associated with your Lambda functions.

Example JSON Payloads

1. Car Entry Event (CarEntry)

{
  "EventType": "CarEntry",
  "CarId": "ABC1234",
  "EntryTime": "2024-08-11T08:30:00Z"
}

2. Car Exit Event (CarExit)

{
  "EventType": "CarExit",
  "CarId": "ABC1234",
  "ExitTime": "2024-08-11T10:45:00Z"
}

3. Parking Space Update Event (ParkingSpaceUpdate)

{
  "EventType": "ParkingSpaceUpdate",
  "CarId": "ABC1234",
  "ParkingSpaceId": "PS45",
  "Status": "Occupied",
  "UpdateTime": "2024-08-11T08:30:00Z"
}