Deploying chat web service using KakaoCloud MemStore

This document introduces how to deploy a chat application in the cloud based on a 3-tier architecture.

Basic information

• Estimated time: 60 minutes
• Recommended OS: MacOS, Ubuntu
• Region: kr-central-2
• Prerequisites: Access key

About this scenario

For use cases like chat or online gaming, where multiple users need to exchange messages simultaneously, persistent connections and real-time communication between the server and clients are essential. The HTTP protocol, commonly used for communication between browsers and servers, is stateless and allows the server to send data only upon a client request. To overcome this limitation, developers use Server-Sent Events (SSE) or WebSocket for direct communication from the server to the client. SSE is typically used for unidirectional messaging from the server to the client, whereas WebSocket is better suited for bidirectional communication. However, achieving real-time communication becomes challenging when clients are distributed across different servers.

To address this issue, the Pub/Sub pattern can be employed. Pub/Sub decouples message publishers from subscribers, enabling independent message delivery. By leveraging the Pub/Sub feature of KakaoCloud MemStore, multiple servers and clients can exchange messages in real time.

Scenario architecture

Operation scenario

1. User A composes a message and sends it to the server through the application.
2. The message is transmitted to the web server via the application load balancer.
3. The load balancer uses the sticky session feature to route requests from the same client to the same web server.
4. The web server forwards the message to the WebSocket server through the load balancer.
5. The load balancer uses the sticky session feature to route requests from the same client to the same WebSocket server.
6. The WebSocket server receives the message and publishes it to a specific channel in the MemStore Pub/Sub system.
7. MemStore distributes the published message to all WebSocket servers subscribed to the channel.
8. The WebSocket server that subscribed to the message sends it to User B, who receives the message in real time.

Before you start

In the prework stage, resources needed to configure the chat web service are created. First, a KakaoCloud network environment is set up to deploy the architecture. Next, we will configure the Web server instance and App server instance on the VM, along with a Bastion server instance—a middle server used to access servers located in a private network that cannot be accessed directly from outside for security reasons.

Set up network environment

Refer to the document Building network using NAT instances in multi-availability zones to build a network environment for the chat web service based on a 3-tier architecture. This document explains how to create a NAT instance to safely connect to the internet even in a private subnet.
Please follow the instructions in this document to configure the network environment required for practice.

1. Configure VPC and subnets

Before establishing a computing environment in KakaoCloud, it is necessary to configure the VPC and subnets. To do this, please refer to the document Building network using NAT instances in multi-availability zones to set up the network environment so that resources in the private subnet can communicate externally. The network settings required for the practice in this tutorial are based on the values specified in that document.

2. Configure security group

1. Go to KakaoCloud Console > VPC > Security Group.

2. Click the [Create security group] button on the right to create a new security group. Refer to the details below to create the security group.

   Security group: tutorial-bastion-sg

   1. Enter the security group name and description as follows.

      Name	Description (Optional)
      tutorial-bastion-sg	Security policy for Bastion host

   2. Click the [Add] button at the bottom, set the inbound rules as follows, and click the [Apply] button.
      

      Check my public IP

      Click the following button to check your current public IP.
      

      Inbound policy to add	Field	Configuration value
      Bastion inbound policy 1	Protocol	TCP
      	Source	{User Public IP}/32
      	Port number	10000-10010
      	Policy Description (Optional)	bastion inbound policy 1
      Bastion inbound policy 2	Protocol	TCP
      	Source	{User Public IP}/32
      	Port number	81
      	Policy Description (Optional)	bastion inbound policy 2
      Bastion inbound policy 3	Protocol	TCP
      	Source	{User Public IP}/32
      	Port number	22
      	Policy Description (Optional)	bastion inbound policy 3

   Security group: tutorial-web-sg

   1. Enter the security group name and description as follows.

      Name	Description (Optional)
      tutorial-web-sg	Security policy for web server

   2. Click the [Add] button at the bottom, set the inbound rules as follows, and click the [Apply] button.

      Inbound policy to add	Field	Configuration value
      web inbound policy	Protocol	TCP
      	Source	10.0.0.0/20
      	Port number	80
      	Policy Description (Optional)	web inbound

   Security group: tutorial-app-sg

   1. Enter the security group name and description as follows.

      Name	Description (Optional)
      tutorial-app-sg	Security policy for application server

   2. Click the [Add] button at the bottom, set the inbound rules as follows, and click the [Apply] button.

      Inbound policy to add	Field	Configuration value
      App inbound policy	Protocol	TCP
      	Source	10.0.32.0/20
      	Port number	8080
      	Policy description (Optional)	app inbound

   Security group: tutorial-redis-sg

   1. Enter the security group name and description as follows.

      Name	Description (Optional)
      tutorial-redis-sg	Security policy for Redis node

   2. Click the [Add] button at the bottom, set the inbound rules as follows, and click the [Apply] button.

      Inbound policy to add	Field	Configuration value
      Redis inbound policy	Protocol	TCP
      	Source	10.0.0.0/16
      	Port number	6379
      	Policy description (Optional)	Redis inbound

3. Create Bastion instance

A bastion host acts as a gateway to cloud instances, enhancing security by blocking direct access. This facilitates efficient remote access and management of cloud instances while enabling seamless coordination of inter-tier communication.

The following explains how to create a bastion instance in a VM.

1. Go to KakaoCloud Console > Beyond Compute Service > Virtual Machine.

2. In the Instance menu, click the [Create instance] button and create a VM instance as follows:

   Category	Field	Configuration/Value	Remarks
   Basic info	Name	tutorial-bastion
   	Number	1
   Image		Ubuntu 20.04
   Instance type		m2a.large
   Volume	Root Volume	20
   Key pair		{USER_KEYPAIR}	⚠️ The key pair must be securely stored during initial creation. Lost keys cannot be recovered and must be reissued.
   Network	VPC	tutorial
   	Subnet	main (10.0.0.0/20)
   	Security Group	tutorial-bastion-sg

4. Create Web instance

1. Go to the KakaoCloud Console > Beyond Compute Service > Virtual Machine menu.

2. In the Instance menu, click the [Create instance] button and create a VM instance as follows:

   caution

   • Key pair must be created once and stored safely. Lost keys cannot be recovered.
   • Security group should be created with the default settings and later modified according to detailed requirements.

   Category	Field	Configuration/Value	Remarks
   Basic information	Name	tutorial-web
   	Number	2
   Image		Ubuntu 20.04
   Instance type		m2a.large
   Volume	Root Volume	20
   Key pair		{USER_KEYPAIR}	Select the key pair created or used above
   Network	VPC	tutorial
   	Subnet	{VPC_ID}_sn_2 (10.0.16.0/20)
   	Security Group	tutorial-web-sg

5. Create App server instance

1. Go to the KakaoCloud Console > Beyond Compute Service > Virtual Machine menu.

2. In the Instance menu, click the [Create instance] button and create a VM server instance as follows:

   Category	Field	Configuration/Value	Remarks
   Basic information	Name	tutorial-app
   	Number	2
   Image		Ubuntu 20.04
   Instance type		m2a.large
   Volume	Root Volume	20
   Key pair		{USER_KEYPAIR}	Select the key pair created or used above
   Network	VPC	tutorial
   	Subnet	{VPC_ID}_sn_4 (10.0.48.0/20)
   	Security Group	tutorial-app-sg

Getting started

The detailed tasks for configuring the web service are as follows:

Step 1. Configure the Bastion host

The Bastion server acts as a gateway for accessing the Web and App servers, and it must be associated with a public IP for external access.

info

If a bad permissions error occurs due to key pair file permissions, you can resolve it by adding the sudo command.

1. In the Virtual Machine > Instance menu, select the previously created Bastion instance and click the [Associate public IP] button on the right.

   • The associated public IP can be confirmed in the Network tab.

2. Launch a terminal and use the cd command to Go to the folder where the key pair file was downloaded.

   • If you created and used the key file initially, it will typically be saved in the Downloads folder. (cd ~/Downloads)

3. Execute the following command to access the instance via SSH.

   chmod 400 ${PRIVATE_KEY}.pem # Grant read permissions
   ssh -i ${PRIVATE_KEY}.pem ubuntu@${BASTION_PUBLIC_IP}

   Environment Variable	Description
   PRIVATE_KEY🖌︎	key file name
   BASTION_PUBLIC_IP🖌︎	Virtual Machine > Instance menu > select the created `Bastion` instance > check Network tab

4. To run Nginx Proxy Manager, first configure the Bastion host. Perform provisioning with the following command.

   sudo curl -o /tmp/install-bastion.sh https://raw.githubusercontent.com/kakaoenterprise/kakaocloud-tutorials/bastion-host/install-bastion.sh
   bash /tmp/install-bastion.sh
   What is Nginx Proxy Manager (NPM)?

   Nginx Proxy Manager (NPM) is an open-source project that helps you easily set up and manage web servers based on Nginx. This tool allows users to effectively configure web servers and manage multiple domains.

5. Open a browser on your local environment and access the management page by entering the following address:

   • http://${BASTION_PUBLIC_IP}:81/login

   • Username: admin@example.com
   • Password: changeme

   Field	Description
   {BASTION_PUBLIC_IP}	Click the Bastion instance created in the Virtual Machine > Instance menu, then check the Network tab for the public IP

6. Go to Dashboard > Streams.

7. Enter the following information for each Web and App host:

   Name	Field	Value
   tutorial-web-1	Incoming Port	10000
   	Forward Host	The private IP of the tutorial-web-1 instance - In Virtual Machine > Instance > Network, select tutorial-web-1 to check the private IP.
   	Forward Port	22
   tutorial-web-2	Incoming Port	10001
   	Forward Host	The private IP of the tutorial-web-2 instance - In Virtual Machine > Instance > Network, select tutorial-web-2 to check the private IP.
   	Forward Port	22
   tutorial-app-1	Incoming Port	10002
   	Forward Host	The private IP of the tutorial-app-1 instance - In Virtual Machine > Instance > Network, select tutorial-app-1 to check the private IP.
   	Forward Port	22
   tutorial-app-2	Incoming Port	10003
   	Forward Host	The private IP of the tutorial-app-2 instance - In Virtual Machine > Instance > Network, select tutorial-app-2 to check the private IP.
   	Forward Port	22

8. Traffic to internal hosts is routed through the Bastion. To allow the Web and App hosts to receive traffic forwarded by the Bastion, configure the security groups as follows:

   Web instance

   1. Go to the Virtual Machine > Instance menu and click on the Web instance you created.

   2. In the Security tab, click on the hyperlink tutorial-web-sg↗️ and select Manage inbound policies.

   3. Click the [Add] button and configure the inbound policy as follows, then click the [Apply] button.

      caution

      Make sure to click the [Apply] button to save the changes.

      Category	Field	Value
      Web	Protocol	TCP
      	Source	{BASTION_PRIVATE_IP}/32 - Check the Network tab after selecting the Bastion instance in the Virtual Machine > Instance menu
      	Port Number	22
      	Policy Description (Optional)	Web inbound policy

   App instance

   1. Go to the Virtual Machine > Instance menu and click on the App instance you created.

   2. In the Security tab, click on the hyperlink tutorial-app-sg↗️ and select Manage inbound rule.

   3. Click the [Add] button and configure the inbound policy as follows, then click the [Apply] button.

      caution

      Make sure to click the [Apply] button; otherwise, the changes will not be saved.

      Category	Field	Value
      App	Protocol	TCP
      	Source	{BASTION_PRIVATE_IP}/32 - Check the Network tab after selecting the Bastion instance in the Virtual Machine > Instance menu
      	Port Number	22
      	Policy Description (Optional)	App inbound policy

9. To verify access to each host from your local environment, connect to each host using the appropriate port based on the previously configured forwarding information. Navigate to the folder containing the key pair file, and run the following command:

   # tutorial-web-1  
   ssh -i ${PRIVATE_KEY}.pem ubuntu@${BASTION_PUBLIC_IP} -p 10000
   
   # tutorial-web-2  
   ssh -i ${PRIVATE_KEY}.pem ubuntu@${BASTION_PUBLIC_IP} -p 10001
   
   # tutorial-app-1
   ssh -i ${PRIVATE_KEY}.pem ubuntu@${BASTION_PUBLIC_IP} -p 10002
   
   # tutorial-app-2  
   ssh -i ${PRIVATE_KEY}.pem ubuntu@${BASTION_PUBLIC_IP} -p 10003

   Environment Variable	Description
   PRIVATE_KEY🖌︎	key_file_name
   BASTION_PUBLIC_IP🖌︎	bastion_public_ip

Step 2. Create managed MySQL database

KakaoCloud's MySQL is a fully managed database service offered within a VPC environment. This service allows you to easily provision a MySQL instance through the console without a complex installation process and use it securely within a logically isolated network.

1. Go to KakaoCloud Console > Data Store > MySQL.

2. In the Instance Group menu, click the [Create instance group] button and create an instance group using the following settings as a reference:

   Category	Field	Configuration/Input
   Basic settings	Instance Group Name	tutorial-mysql
   	Description	Optional
   MySQL settings	Engine Version	Use the specified version
   	MySQL Username	(e.g.) admin
   	MySQL Password	(e.g.) root1234
   Instance availability/number		Single (Primary Instance)
   Instance type		m2a.large
   Storage type/size		100
   Log storage type/size		100
   Network settings	VPC	tutorial
   	Subnet	{VPC_ID}_sn_5 (10.0.64.0/20)
   Automatic backup	Backup Options	Disabled

Step 3. Create cluster

KakaoCloud's MemStore is an in-memory data store service offered within a VPC environment. This service automates all processes required for Redis node provisioning, such as creating operational servers or configuring networks, and is designed to allow easy management of the database through various management functions.

1. Go to KakaoCloud Console > Data Store > MemStore.

2. In the Cluster tab, click the [Create cluster] button and create a cluster using the following settings as a reference:

   Category	Field	Configuration/Input
   Configuration options		Create a new cluster
   Cluster mode settings		Disabled
   Basic settings	Cluster name	tutorial-redis
   	Description (Optional)	Tutorial Redis
   Redis compatibility settings	Engine Version	Redis 6.2.5
   	Port	6379
   Node count		2 (Check High Availability)
   Node type		m2a.large
   Network settings	VPC	tutorial
   	Subnet	{VPC_ID}_sn_5 (10.0.64.0/20)
   	Security Group	tutorial-redis-sg
   Node placement	Primary (Node)	{VPC_ID}_sn_5 (10.0.64.0/20)
   Node placement	Replica (Node)	{VPC_ID}_sn_5 (10.0.64.0/20)
   Automatic backup	Backup Options	Disabled

Step 4. Create Application server

The Web Application Server (WAS) connects to the database and can provide complex services such as user registration, login, and commenting.

1. Access the VM mapped to the ports configured in the nginx-proxy-manager.

   # tutorial-app-1
   ssh -i ${PRIVATE_KEY}.pem ubuntu@${BASTION_PUBLIC_IP} -p 10002
   
   # tutorial-app-2
   ssh -i ${PRIVATE_KEY}.pem ubuntu@${BASTION_PUBLIC_IP} -p 10003
   

   Environment Variable	Description
   PRIVATE_KEY🖌︎	Key file name
   BASTION_PUBLIC_IP🖌︎	Go to the Virtual Machine > Instance menu, click on the `Bastion` instance, and check the Network tab for details

2. Install the example project.

   git clone -b kakaocloud-library https://github.com/kakaoenterprise/kakaocloud-tutorials

3. Go to the folder where the example project is located.

   cd kakaocloud-tutorials

4. Install the packages required to build and run the example project.

   bash install-requirements.sh

5. Enter the environment variables and run the example application.

   sudo docker run -it \
   -e MYSQL_HOST=${MYSQL_HOST} \
   -e DB_USERNAME=${DB_USERNAME} \
   -e DB_PASSWORD=${DB_PASSWORD} \
   -e REDIS_HOST=${REDIS_HOST} \
   -p 8080:8080 \
   --name kakaocloud-library-server -d \
   $(sudo docker build -q -f ./server/deploy/Dockerfile ./server)

   Environment Variable	Value	Description
   MYSQL_HOST🖌︎	MYSQL_ENDPOINT	MySQL host address, can be found by selecting the `tutorial-mysql` instance group in the **MySQL > Instance Group** tab and checking the endpoint at the top
   DB_USERNAME🖌︎	ex. admin	Database username
   DB_PASSWORD🖌︎	ex. root1234	Database password
   REDIS_HOST🖌︎	REDIS_PRIMARY_ENDPOINT	Redis Primary endpoint

Step 5. Create load balancer for Application server

1. Go to KakaoCloud Console > Load Balancing, then click the [Create load balancer] button.

2. Enter the name and description for the load balancer, and set the VPC and subnet. Refer to the following information for the listener settings, then click the [Create] button.

   Category	Field	Configuration/Input
   Type	Application Load Balancer (L7)
   Basic information	Load balancer name	tutorial-app-lb
   Network	VPC	tutorial
   	Subnet	{VPC_ID}_sn_3 (10.0.32.0/20)
   Listener	Protocol	HTTP
   Port		8080

3. Wait for the Provisioning status of the created load balancer to become Active.

   • This may take 1-3 minutes.

4. Click Target Group in the left sidebar, then click the [Create target group] button.

5. Set the information as follows, then click the [Next] button.

   Category	Field	Configuration/Input
   Load Balancer	Available Zone	kr-central-2-a
   	Load balancer	tutorial-app-lb
   	Listener	HTTP:8080
   Basic info	Target group name	tutorial-app-target-group
   	Protocol	HTTP
   	Algorithm	Round Robin
   	Sticky Session	Enabled
   	Type	HTTP Cookie
   	Stickiness Duration	3600
   Health check		Enabled
   	Type	HTTP
   	HTTP method	GET
   	HTTP version	1.1
   	HTTP status code	200
   	Check path	/api/v1.0/status/chat
   	Check interval	10
   	Timeout	5
   	Transition criteria (success)	3
   	Transition criteria (failure)	3

6. From the list, select the App instances to be added to the target group.

7. Enter the port information as follows, click the [Add target] button, then click the [Next] button.

   Target instance	Port
   tutorial-app-1	8080
   tutorial-app-2	8080

8. Review the information, then click the [Create] button.

9. The load balancer and health checks must be able to access the target Application servers. To ensure this, add the following inbound policies to the security group tutorial-app-sg of the Application servers.

   1. Go to VPC > Security Group, and select tutorial-app-sg.

   2. Click the [Manage inbound rules] button and add the following policies. Two Health Check IPs need to be added.

      Inbound Policy	Description	Protocol	Source	Port
      App inbound policy 1	Access from Load Balancer	TCP	{app-lb-private-ip}/32 - Can be found in Load Balancer > Details after selecting the created App server load balancer from the Load Balancer list	8080
      App inbound policy 2	Access from Health Check Host 1	TCP	{healthcheck-ip1}/32 - Can be found in Load Balancer > Target Group menu > Target tab > Health Check IP by Subnet	8080
      App inbound policy 3	Access from Health Check Host 2	TCP	{healthcheck-ip2}/32 - Can be found in Load Balancer > Target Group menu > Target tab > Health Check IP by Subnet	8080

Step 6. Create Web server

A web server transmits static content such as HTML, CSS, and JavaScript to web browsers over the internet using the HTTP protocol. To serve static data, you'll install the Nginx web server application and configure it to serve a React example project as static content. Additionally, requests to paths under /api will be forwarded to the app server.

1. Access the VM mapped to the ports configured in the Nginx Proxy Manager. Go to the folder containing your key pair file and run the following commands.

   # tutorial-web-1
   ssh -i ${PRIVATE_KEY}.pem ubuntu@${BASTION_PUBLIC_IP} -p 10000
   
   # tutorial-web-2
   ssh -i ${PRIVATE_KEY}.pem ubuntu@${BASTION_PUBLIC_IP} -p 10001

   Environment Variable	Description
   PRIVATE_KEY🖌︎	Key file name
   BASTION_PUBLIC_IP🖌︎	Virtual Machine > Instance menu > select the created `Bastion` instance > check Network tab

2. Install the example project.

   git clone -b kakaocloud-library https://github.com/kakaoenterprise/kakaocloud-tutorials

3. Go to the folder where the example project is located.

    cd kakaocloud-tutorials

4. Install the packages required to build and run the example project.

   bash install-requirements.sh

5. Enter the environment variables and start the web server.

   sudo docker run -it \
   -e SERVER_ENDPOINT=http://${SERVER_ENDPOINT}:8080 \
   -p 80:80 -p 443:443 \
   --name kakaocloud-library-client -d \
   $(sudo docker build -q -f ./client/deploy/Dockerfile ./client)

   Environment Variable	Description
   SERVER_ENDPOINT🖌︎	Enter the private IP of the Application Load Balancer you created in `{APP_LB_PRIVATE_IP}`.

Step 7. Create load balancer for Web server

Set up a load balancer to distribute client requests to multiple servers on the web server.

1. Go to the KakaoCloud Console > Beyond Networking Service > Load Balancing, and click the [Create load balancer] button.

2. Refer to the following to enter the required information for creating the load balancer, and click the [Create] button.

   Category	Field	Configuration/Input
   Type		Application Load Balancer
   Basic information	Load Balancer Name	tutorial-web-lb
   Network	VPC	tutorial
   	Subnet	main
   Listener	Protocol	HTTP
   Port		80

3. Wait for the Provisioning status of the created load balancer to become Active.

   • This may take 1-3 minutes.

4. In the left sidebar, select Target Group and click the [Create target group] button.

5. Configure the settings as follows, then click the [Next] button.

   Category	Field	Configuration/Input
   Load Balancer	Available Zone	kr-central-2-a
   	Load Balancer	tutorial-web-lb
   	Listener	HTTP:80
   Basic info	Target Group Name	tutorial-web-target-group
   	Protocol	HTTP
   	Algorithm	Round Robin
   	Sticky Session	Enabled
   	Type	HTTP Cookie
   	Stickiness Duration	3600
   Health Check		Enabled
   	Type	HTTP
   	HTTP Method	GET
   	HTTP Version	1.1
   	HTTP Status Code	200
   	Check Path	/
   	Check Interval	10
   	Timeout	5
   	Healthy Threshold	3
   	Unhealthy Threshold	3

6. Select the instances to be added to the target group from the list.

7. Enter the following port information, click the [Add target] button, then click the [Next] button.

   Target Instance	Port
   tutorial-web-1	80
   tutorial-web-2	80

8. Review the information, then click the [Create] button.

9. The load balancer and health checks must be able to access the target Web servers. To ensure this, add the following inbound policies to the tutorial-web-sg security group of the Web servers.

   1. Go to VPC > Security Groups and select tutorial-web-sg.

   2. Click the [Manage inbound policies] button and add the following policies. You need to add two Health Check IPs.

      Inbound policy	Description	Protocol	Source	Port
      web inbound policy 1	Access from Load Balancer	TCP	{web-lb-private-ip}/32 - Found in Load Balancer > Details after selecting the created Web server load balancer from the Load Balancer list	80
      web inbound policy 2	Access from Health Check Host 1	TCP	{healthcheck-ip1}/32 - Found in Load Balancer > Target Group menu > Target tab > Health check IP by subnet	80
      web inbound policy 3	Access from Health Check Host 2	TCP	{healthcheck-ip2}/32 - Found in Load Balancer > Target Group menu > Target tab > Health check IP by subnet	80

Step 8. Associate public IP with Web server load balancer

1. Go to the Load Balancing > Load Balancer tab and select the Web load balancer you created.
2. Click [Associate public IP].
3. In the Details tab, confirm the public IP address.

Step 9. Verify chat functionality

Access the service by entering the registered public IP address in your browser. If everything is connected correctly, you should be able to verify the chat functionality by clicking the chat button at the bottom right of the 'KakaoCloud Library' service interface.