How to configure highly available load balancer monitoring on Linux

How to configure high-availability load balancer monitoring on Linux

In modern Internet application architecture, the load balancer is a key component, which can distribute access requests to multiple servers to Improve overall performance and usability. However, the load balancer itself can become a single point of failure in the system. To solve this problem, we can use high availability technology to ensure the availability of the load balancer. This article will introduce how to configure highly available load balancer monitoring on Linux and provide relevant code examples.

1. Installing and configuring the load balancer

First, we need to choose a suitable load balancer software. Commonly used load balancer software on Linux include Nginx, HAProxy, and Keepalived. In this article, we will use Keepalived as an example to configure.

Install Keepalived on Linux using the following command:

$ sudo apt-get install keepalived

After the installation is complete, we need to configure Keepalived to enable high availability. Create a file named keepalived.conf in the /etc/keepalived/ directory, and add the following configuration content to the file:

# 只在主节点上运行
vrrp_script check_http {
        script "/usr/local/bin/check_http.sh"
        interval 2
}
vrrp_instance VI_1 {
        state MASTER
        virtual_router_id 51
        priority 100
        advert_int 1
        authentication {
                auth_type PASS
                auth_pass example
        }
        virtual_ipaddress {
                10.0.0.1/24
        }
        track_script {
                check_http
        }
}

Among them, check_http.sh is a customized script for checking Availability of the backend server where the load balancer resides. Scripts can be written according to actual needs.

2. Configuring load balancer monitoring

After completing the configuration of Keepalived, we can use other tools to monitor the running status of the load balancer. In this article, we will use a simple Python script to monitor load balancer availability.

First, we need to install Python’s requests module:

$ sudo pip install requests

Then, create a Python script named check_lb.py and add the following code to the file:

import requests

def check_lb():
    try:
        response = requests.get('http://10.0.0.1')
        if response.status_code == 200:
            print('负载均衡器正常运行')
        else:
            print('负载均衡器故障')
    except requests.exceptions.RequestException as e:
        print('负载均衡器故障')

if __name__ == '__main__':
    check_lb()

In the above code, we use the requests library to send HTTP requests and check the returned status code. If the status code is 200, it means that the load balancer is running normally; otherwise, it means that the load balancer is faulty.

3. Set up the automatic running monitoring script

In order to make the monitoring script run regularly, we can use cron tasks to run the script regularly. Open a terminal and enter the following command:

$ crontab -e

In the cron task editor that opens, add the following:

*/5 * * * * /usr/bin/python /path/to/check_lb.py

The above configuration will run the monitoring script every 5 minutes. This time interval can be modified according to actual needs.

4. Monitoring and alarming

In the monitoring script, we can modify the check_lb() function and add alarm logic. For example, sending an email when a load balancer fails or sending a message to a mobile application.

Here is a simple example, a code snippet for sending an email:

import smtplib
from email.mime.text import MIMEText

def send_email():
    sender = 'your_email@example.com'
    receiver = 'recipient@example.com'
    subject = '负载均衡器故障'
    message = '负载均衡器无法访问'

    msg = MIMEText(message)
    msg['Subject'] = subject
    msg['From'] = sender
    msg['To'] = receiver

    try:
        smtp_obj = smtplib.SMTP('localhost')
        smtp_obj.sendmail(sender, receiver, msg.as_string())
        smtp_obj.quit()
        print('邮件已发送')
    except smtplib.SMTPException:
        print('邮件发送失败')

In the above code, we are using the smtplib library to send an email. First, you need to set the email addresses of the sender and recipient, then create a MIMEText object, add the sent message and subject to the object, and use the SMTP server to send the email.

In the check_lb() function, when the load balancer fails, the send_email() function can be called to send an alarm email.

Summary:

In this article, we introduced how to configure highly available load balancer monitoring on Linux. We use Keepalived to provide high availability of the load balancer and use Python scripts and cron tasks to regularly monitor the running status of the load balancer. Additionally, we provide a simple example of how to send an email alert in the event of a load balancer failure. With these steps, you can easily set up a monitoring and alerting system for your load balancer and ensure high availability for your application.

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