How to use Docker for container monitoring and alarm handling

How to use Docker for container monitoring and alarm processing

1. Introduction
With the widespread application of container technology, container monitoring and alarm processing have become increasingly important. Docker is currently one of the most popular container management platforms. This article will introduce how to use Docker for container monitoring and alarm processing, and give specific code examples.

2. Monitor Docker containers

1. Use Docker Stats API
   Docker Stats API is an API provided by Docker for obtaining container statistics. We can obtain various indicators of the container and monitor them by calling this API.
   Specific code examples are as follows:

import docker

client = docker.DockerClient(base_url='unix://var/run/docker.sock')

def monitor_container(container_id):
    container = client.containers.get(container_id)
    stats = container.stats(stream=False)
    print(stats)

if __name__ == '__main__':
    monitor_container('CONTAINER_ID')

2. Using Prometheus and cAdvisor
   Prometheus is an open source monitoring system, and cAdvisor is a tool for monitoring containers. Combining these two tools, we can achieve comprehensive monitoring of containers.
   The specific code examples are as follows:

First, we need to install and start Prometheus and cAdvisor. Then add the following content to the Prometheus configuration file prometheus.yml:

scrape_configs:
  - job_name: 'cadvisor'
    scrape_interval: 5s
    static_configs:
    - targets: ['cadvisor:8080']

Next, use the client library provided by Prometheus in Python to query and process the container's monitoring data. Specific code examples are as follows:

from prometheus_api_client import PrometheusConnect

prometheus = PrometheusConnect(url='http://localhost:9090')

def get_container_cpu_usage(container_id):
    query = 'sum(rate(container_cpu_usage_seconds_total{container_label_com_docker_swarm_service_id="%s"}[5m]))' % (container_id)
    result = prometheus.custom_query(query)
    return result['data']['result']

if __name__ == '__main__':
    container_id = 'CONTAINER_ID'
    cpu_usage = get_container_cpu_usage(container_id)
    print(cpu_usage)

3. Alarm processing

1. Use Docker Stats API and email alarm
   Use Docker Stats API to obtain the monitoring data of the container, and set it according to our settings threshold for alarm processing. If a certain indicator of the container exceeds the set threshold, we can send an alarm message via email.
   The specific code examples are as follows:

import docker
import smtplib
from email.mime.text import MIMEText

client = docker.DockerClient(base_url='unix://var/run/docker.sock')

def monitor_container(container_id):
    container = client.containers.get(container_id)
    stats = container.stats(stream=False)
    
    # 检查某个指标是否超过阈值，这里以CPU使用率为例
    cpu_usage = stats['cpu_stats']['cpu_usage']['total_usage']
    cpu_limit = stats['cpu_stats']['cpu_usage']['percpu_usage'].size
    cpu_usage_percent = cpu_usage / cpu_limit * 100

    if cpu_usage_percent > 80:
        send_alert_email(container_id, cpu_usage_percent)

def send_alert_email(container_id, cpu_usage_percent):
    msg = MIMEText('容器 %s 的CPU使用率超过80%%，当前使用率为%.2f%%' % (container_id, cpu_usage_percent), 'plain', 'utf-8')
    msg['Subject'] = '容器告警'
    msg['From'] = 'alert@example.com'
    msg['To'] = 'admin@example.com'
    
    server = smtplib.SMTP('smtp.example.com')
    server.login('username', 'password')
    server.sendmail('alert@example.com', ['admin@example.com'], msg.as_string())
    server.quit()

if __name__ == '__main__':
    monitor_container('CONTAINER_ID')

2. Using Prometheus and Alertmanager
   Prometheus provides a component named Alertmanager for processing and sending alarm notifications. We can use it to monitor container indicators and send corresponding alarm notifications according to set rules.
   Specific code examples are omitted.

4. Summary
This article introduces how to use Docker for container monitoring and alarm processing, and gives specific code examples. Container monitoring and alarm handling are very important to ensure the stability and reliability of container operation. I hope this article will be helpful to you.

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