Docker 101: How to Monitor and Auto-Restart Docker Containers

How to Monitor and Auto-Restart Docker Containers

To create a process that monitors your running Docker containers and automatically restarts them if they stop, you can use one of the following methods:

Method 1: Docker’s Built-In Restart Policies

English:

• Docker has built-in restart policies that you can use to automatically restart containers when they stop or fail. This is the simplest and most efficient way to ensure that your containers are always running.

Chinese:

• Docker 提供了内置的重启策略，您可以使用这些策略在容器停止或失败时自动重启容器。这是确保您的容器始终运行的最简单且最有效的方法。

1. Use --restart Option

English:

• When you start a container, you can use the --restart option to specify a restart policy. Common options include:
  • no: Do not automatically restart the container (default).
  • on-failure: Restart the container if it exits with a non-zero exit code (you can also specify the maximum number of restart attempts).
  • always: Always restart the container if it stops, regardless of the exit code.
  • unless-stopped: Always restart the container unless it is explicitly stopped by the user.

Chinese:

• 启动容器时，可以使用 --restart 选项指定重启策略。常见选项包括：
  • no: 不自动重启容器（默认）。
  • on-failure: 如果容器以非零退出代码退出，则重启容器（您还可以指定最大重启尝试次数）。
  • always: 如果容器停止，则始终重启容器，而不管退出代码如何。
  • unless-stopped: 除非用户明确停止容器，否则始终重启容器。

Example Command:

English:

docker run --restart unless-stopped my-docker-image

Chinese:

docker run --restart unless-stopped my-docker-image

Explanation:

• English: This command runs a container with a policy that ensures it is always restarted unless you explicitly stop it.
• Chinese: 该命令运行一个具有策略的容器，确保除非您明确停止它，否则它将始终重启。

Method 2: Using Docker Compose

English:

• If you are managing multiple containers, using Docker Compose is an efficient way to manage restart policies across multiple services.

Chinese:

• 如果您管理多个容器，使用 Docker Compose 是在多个服务之间管理重启策略的有效方法。

1. Create a docker-compose.yml File

English:

• Define your services in a docker-compose.yml file, specifying the restart policy for each service.

Chinese:

• 在 docker-compose.yml 文件中定义您的服务，并为每个服务指定 restart 策略。

version: '3'
services:
  web:
    image: my-web-image
    restart: unless-stopped

  database:
    image: my-db-image
    restart: always

2. Start the Services

English:

• Start the services using Docker Compose. The specified restart policies will automatically handle restarting the containers if they stop.

Chinese:

• 使用 Docker Compose 启动服务。如果容器停止，指定的重启策略将自动处理重启容器。

docker-compose up -d

Method 3: Custom Monitoring Script

English:

• If you need more control or custom behavior, you can create a script to monitor your containers and restart them if necessary.

Chinese:

• 如果您需要更多控制或自定义行为，您可以创建一个脚本来监控您的容器并在必要时重启它们。

1. Bash Script Example

English:

• The following is a simple Bash script that monitors running containers and restarts any that have stopped.

Chinese:

• 以下是一个简单的 Bash 脚本，用于监控运行中的容器并重启任何已停止的容器。

#!/bin/bash

# Interval to check the containers (in seconds)
CHECK_INTERVAL=60

while true; do
  # Get the list of all stopped containers
  stopped_containers=$(docker ps -a --filter "status=exited" --format "{{.ID}}")

  for container in $stopped_containers; do
    echo "Restarting stopped container: $container"
    docker start $container
  done

  # Wait for the next check
  sleep $CHECK_INTERVAL
done

2. Run the Script

English:

• Make the script executable and run it in the background. This will continuously monitor and restart any stopped containers.

Chinese:

• 使脚本可执行并在后台运行。这样将持续监控并重启任何已停止的容器。

chmod +x monitor_containers.sh
./monitor_containers.sh &

Explanation:

• English: This script checks for stopped containers every 60 seconds and restarts them. You can adjust the interval and other parameters as needed.
• Chinese: 该脚本每 60 秒检查一次已停止的容器并重新启动它们。您可以根据需要调整间隔和其他参数。

Method 4: Using a Monitoring Tool

English:

• For more complex setups, you can use monitoring tools like Prometheus with Alertmanager, which can monitor Docker containers and trigger alerts or actions (like restarting) based on specific conditions.

Chinese:

• 对于更复杂的设置，您可以使用 Prometheus 和 Alertmanager 等监控工具，这些工具可以监控 Docker 容器并根据特定条件触发警报或操作（如重启）。

1. Tips

• English: Use Docker’s built-in restart policies for most use cases. For more complex needs, consider custom scripts or external monitoring tools.
• Chinese: 对于大多数用例，使用 Docker 的内置重启策略。对于更复杂的需求，考虑使用自定义脚本或外部监控工具。

2. Warning

• English: Ensure that the cause of container stoppage is addressed. Constantly restarting a failing container without understanding the root cause can lead to more significant issues.
• Chinese: 确保解决容器停止的原因。在不了解根本原因的情况下，不断重启失败的容器可能会导致更严重的问题。

These methods provide different approaches to monitor and ensure that your Docker containers remain running, depending on your specific requirements and environment.