Using Dedicated Load Balancers (Entry Level)

Scenarios

You have a web application, which often needs to handle heavy traffic and is deployed on two ECSs for load balancing.

You can create a load balancer to distribute traffic across multiple backend servers based on the forwarding policy you have configured, which eliminates SPOFs and makes your application more available.

Prerequisites

  • You have added security group rules to allow traffic from the ports used by the two ECSs. (Alternatively, you can enable all ports first and then disable the ports that are no longer used after service deployment.)

  • You have verified that the security group containing the ECSs allows access traffic from the VPC where the load balancer works and that the health check function is normal.

    Note

    If IP as a Backend is not enabled for a dedicated load balancer that has a TCP or UDP listener, there is no need to configure security group rules to allow traffic from the VPC where the load balancer backend subnet works to the backend servers.

Creating ECSs

ECSs are used as backend servers.

Each ECS needs an EIP for accessing the Internet, and the EIP is used for configuring the application on the ECS. You can determine whether to bind an EIP to each ECS based on your requirements.

  1. Log in to the management console.

  2. In the upper left corner of the page, click image1 and select the desired region and project.

  3. Hover on image2 in the upper left corner to display Service List and choose Computing > Elastic Cloud Server.

  4. Click Create ECS, configure the parameters, and click Create Now.

    The following table lists the specifications of the two ECSs.

    Table 1 ECS specifications

    Item

    Example Value

    Name

    ECS01 and ECS02

    OS

    CentOS 7.2 64bit

    vCPUs

    2

    Memory

    4 GB

    System disk

    40 GB

    Data disk

    100 GB

    Bandwidth

    5 Mbit/s

  5. Submit your request.

Deploying the Application

Deploy Nginx on the two ECSs and edit two HTML pages so that a page with message "Welcome to ELB test page one!" is returned when ECS01 is accessed, and the other page with message "Welcome to ELB test page two!" is returned when ECS02 is accessed.

  1. Log in to the ECSs.

  2. Install and start Nginx.

    1. Run the wget command to download the Nginx installation package for your operating system in use. CentOS 7.6 is used as an example here.

      wget http://nginx.org/packages/centos/7/noarch/RPMS/nginx-release-centos-7-0.el7.ngx.noarch.rpm

    2. Run the following command to create the Nginx yum repository:

      rpm -ivh nginx-release-centos-7-0.el7.ngx.noarch.rpm

    3. Run the following command to install Nginx:

      yum -y install nginx

    4. Run the following commands to start Nginx and configure automatic Nginx enabling upon ECS startup:

      systemctl start nginx
systemctl enable nginx

    5. Enter http://EIP bound to the ECS in the address box of your browser. If the following page is displayed, Nginx has been installed.

      **Figure 1** Nginx installed successfully

      Figure 1 Nginx installed successfully

  3. Modify the HTML page of ECS01.

    Modify the index.html file in the default root directory of Nginx /usr/share/nginx/html to identify access to ECS01.

    1. Open the index.html file.

      vim /usr/share/nginx/html/index.html

    2. Press i to enter editing mode.

    3. Modify the index.html file to be as follows:

      ...
   <body>
       <h1>Welcome to <strong>ELB</strong> test page one!</h1>

       <div class="content">
           <p>This page is used to test the <strong>ELB</strong>!</p>

           <div class="alert">
               <h2>ELB01</h2>
               <div class="content">
                   <p><strong>ELB test (page one)!</strong></p>
                   <p><strong>ELB test (page one)!</strong></p>
                   <p><strong>ELB test (page one)!</strong></p>
               </div>
           </div>
       </div>
   </body>

    4. Press Esc to exit editing mode. Then, enter :wq to save the settings and exit the file.

  4. Modify the HTML page of ECS02.

    Modify the index.html file in the default root directory of Nginx /usr/share/nginx/html to identify access to ECS02.

    1. Open the index.html file.

      vim /usr/share/nginx/html/index.html

    2. Press i to enter editing mode.

    3. Modify the index.html file to be as follows:

      ...
    <body>
        <h1>Welcome to <strong>ELB</strong> test page two!</h1>

        <div class="content">
            <p>This page is used to test the <strong>ELB</strong>!</p>

            <div class="alert">
                <h2>ELB02</h2>
                <div class="content">
                    <p><strong>ELB test (page two)!</strong></p>
                    <p><strong>ELB test (page two)!</strong></p>
                    <p><strong>ELB test (page two)!</strong></p>
                </div>
             </div>
        </div>
    </body>

    4. Press Esc to exit editing mode. Then, enter :wq to save the settings and exit the file.

  5. Use your browser to access http://ECS01 EIP and http://ECS02 EIP to verify that Nginx has been deployed.

    If the modified HTML pages are displayed, Nginx has been deployed.

    • HTML page of ECS01

      **Figure 2** Nginx successfully deployed on ECS01

      Figure 2 Nginx successfully deployed on ECS01

    • HTML page of ECS02

      **Figure 3** Nginx successfully deployed on ECS02

      Figure 3 Nginx successfully deployed on ECS02

Creating a Load Balancer

The load balancer needs an EIP to access the application deployed on the ECSs over the Internet. You can determine whether to bind an EIP to the load balancer based on your requirements. For details, see Load Balancing on a Public or Private Network.

  1. In the upper left corner of the page, click image3 and select the desired region and project.

  2. Hover on image4 in the upper left corner to display Service List and choose Network > Elastic Load Balancing.

  3. Click Create Elastic Load Balancer and then configure the parameters.

  4. Click Create Now.

  5. Confirm the configuration and submit your request.

  6. View the newly created load balancer in the load balancer list.

Note

After you create a dedicated load balancer, configure the security group that contains the ECSs to allow traffic from the VPC where the load balancer works.

Procedure

  1. Log in to the management console.

  2. In the upper left corner of the page, click image5 and select the desired region and project.

  3. Hover on image6 in the upper left corner to display Service List and choose Computing > Elastic Cloud Server.

  4. In the ECS list, locate the ECS and click its name.

    The ECS details page is displayed.

  5. Click Security Groups, locate the security group, and view security group rules.

  6. Click the security group rule ID or Modify Security Group Rule. The security group details page is displayed.

  7. On the Inbound Rules tab page, click Add Rule. Configure an inbound rule based on Table 2.

    Table 2 Security group rules

    Backend Protocol

    Policy

    Protocol & Port

    Source IP Address

    HTTP or HTTPS

    Allow

    Protocol: TCP

    Port: the port used by the backend server and health check port

    Backend subnet of the load balancer

    TCP

    Allow

    Protocol: TCP

    Port: health check port

    UDP

    Allow

    Protocol: UDP and ICMP

    Port: health check port

    Note

    • After a load balancer is created, do not change the subnet. If the subnet is changed, the IP addresses occupied by the load balancer will not be released, and traffic from the previous backend subnet is still need to be allowed to backend servers.

    • Traffic from the new backend subnet is also need to be allowed to backend servers.

  8. Click OK.

Firewall Rules

To control traffic in and out of a subnet, you can associate a firewall with the subnet. Firewall rules control access to subnets and add an additional layer of defense to your subnets. Default firewall rules reject all inbound and outbound traffic. If the subnet of a load balancer or associated backend servers has a firewall associated, the load balancer cannot receive traffic from the Internet or route traffic to backend servers, and backend servers cannot receive traffic from and respond to the load balancer.

Configure an inbound firewall rule to allow traffic from the VPC where the load balancer works to backend servers.

  1. Log in to the management console.

  2. In the upper left corner of the page, click image7 and select the desired region and project.

  3. Click image8 in the upper left corner of the page and choose Network > Virtual Private Cloud.

  4. In the navigation pane on the left, choose Access Control > Firewall.

  5. In the firewall list, click the name of the firewall to switch to the page showing its details.

  6. On the Inbound Rules or Outbound Rules tab page, click Add Rule to add a rule.

    • Action: Select Allow.

    • Protocol: The protocol must be the same as the one you selected for the listener.

    • Source: Set it to the VPC CIDR block.

    • Source Port Range: Select a port range.

    • Destination: If you keep the default value, 0.0.0.0/0, traffic will be allowed for all destination IP addresses.

    • Destination Port Range: Select a port range.

    • (Optional) Description: Describe the firewall rule.

  7. Click OK.

Adding a Listener

Add a listener to the created load balancer. When you add the listener, create a backend server group, configure a health check, and add the two ECSs to the created backend server group.

**Figure 4** Traffic forwarding

Figure 4 Traffic forwarding

  1. Hover on image9 in the upper left corner to display Service List and choose Network > Elastic Load Balancing.

  2. Locate the created load balancer (elb-01) and click its name.

  3. Under Listeners, click Add Listener.

  4. Configure the listener and click Next.

    • Name: Enter a name, for example, listener-HTTP.

    • Frontend Protocol/Port: Select a protocol and enter a port for the load balancer to receive requests. For example, set it to HTTP and 80.

      **Figure 5** Adding a listener

      Figure 5 Adding a listener

  5. Create a backend server group and configure a health check.

    • Backend server group

      • Name: Enter a name, for example, server_group-ELB.

      • Load Balancing Algorithm: Select an algorithm that the load balancer will use to route requests, for example, Weighted round robin.

    • Health check

      • Protocol: Select a protocol for the load balancer to perform health checks on backend servers. If the load balancer uses TCP, HTTP, or HTTPS to receive requests, the health check protocol can be TCP or HTTP. Here we use HTTP as an example.

      • Domain Name: Enter a domain name that will be used for health checks, for example, www.example.com.

      • Port: Enter a port for the load balancer to perform health checks on backend servers, for example, 80.

  6. Click the name of the newly added listener. On the Backend Server Groups tab page on the right, click Add.

  7. Select the servers you want to add, set the backend port, and click Finish.

    • Backend servers: Select ECS01 and ECS02.

    • Backend port: Set it to 80. Backend servers will use this port to communicate with the load balancer.

Verifying Load Balancing

After the load balancer is configured, you can access the domain name to check whether the two ECSs are accessible.

  1. Modify the C:\Windows\System32\drivers\etc\hosts file on your PC to map the domain name to the load balancer EIP.

    View the load balancer EIP on the Summary page of the load balancer.

    **Figure 6** **hosts** file on your PC

    Figure 6 hosts file on your PC

  2. On the CLI of your PC, run the following command to check whether the domain name is mapped to the load balancer EIP:

    ping www.example.com

    If data packets are returned, the domain name has been mapped to the load balancer EIP.

  3. Use your browser to access http://www.example.com. If the following page is displayed, the load balancer has routed the request to ECS01.

    **Figure 7** Accessing ECS01

    Figure 7 Accessing ECS01

  4. Use your browser to access http://www.example.com. If the following page is displayed, the load balancer has routed the request to ECS02.

    **Figure 8** Accessing ECS02

    Figure 8 Accessing ECS02

last updated: 2024-05-03 00:42