docker never exits container

To keep the Docker container running and not exiting, there are many ways to do it. In this article, we'll cover some commonly used methods and their pros and cons.

Method 1: Use the --restart option

Docker provides an option --restart, which can automatically restart the container when the container exits abnormally. There are three optional values, namely no, on-failure and always, which respectively correspond to no restart, restart on abnormal exit and always restart. Specific example:

docker run --restart=always IMAGE_NAME

The advantage of using the --restart option is that it is simple and easy to use. You only need to add an option to the command line. But if an error occurs in the container, it will continue to restart until the container is manually stopped. This can lead to code instability and data loss.

Method 2: Use Docker Compose

Docker Compose is a tool that can define and run multiple Docker containers. It can describe the relationship between containers and startup parameters through a yml file. Add the following configuration in the docker-compose.yml file:

version: '3'

services:
  app:
    build: .
    restart: always

Then you can use the docker-compose command to start the container:

docker-compose up -d

# The ##restart: always option tells Docker to automatically restart the container when the container exits abnormally. The advantage of this method is that it can manage multiple containers, which is convenient and fast, but there is still the problem of containers restarting all the time.

Method 3: Use a daemon process

Using a daemon process is a reliable way to keep the Docker container from exiting. Start a daemon in the container and let the Docker container run under the supervision of the daemon. If there is a problem with the container, the daemon will restart the container.

The following is an example, using the

supervisor daemon to start a Node.js service:

Install supervisor:

npm install -g supervisor

Create the
2. supervisord.conf file and add the following content:

[supervisord]
nodaemon=true

[program:app]
command=supervisor app.js
directory=/app
autostart=true
autorestart=true
user=root

Add the following configuration in the Dockerfile:

RUN apt-get update && apt-get install -y supervisor

COPY supervisord.conf /etc/supervisor/conf.d/supervisord.conf

Generate Mirror and start the container:

docker build -t IMAGE_NAME .
docker run -d IMAGE_NAME

The advantage of using a daemon is that you can flexibly control the behavior of the container, but it requires some additional configuration work, and you need to start a daemon, which takes up some system resources.

Method 4: Use external monitoring

Using an external monitoring system to monitor the Docker container and restart the container when an exception occurs, you can control the behavior of the container more flexibly. When a container is abnormal, the monitoring system can take some actions, such as issuing an alarm, recording logs, restarting the container, etc.

For example, you can use

systemd to monitor Docker containers:

Create a systemd unit file, such as
1. mydocker.service, the file content is as follows :

[Unit]
Description=My Docker Container

[Service]
ExecStart=/usr/bin/docker start -a myapp
Restart=always
RestartSec=10s
ExecStop=/usr/bin/docker stop -t 2 myapp

[Install]
WantedBy=default.target

This file defines a container named

myapp. When a problem occurs with the container, systemd will automatically restart the container. Use the systemctl command to enable this service:

sudo systemctl daemon-reload
sudo systemctl enable mydocker.service
sudo systemctl start mydocker.service

The advantage of using external monitoring is that it is more flexible and can use various third-party monitoring systems, but it requires additional configuration and maintenance work.

In general, there are many ways to keep Docker containers running for a long time, each with its own advantages and disadvantages. The specific choice should be based on actual needs. When starting a container, you should also consider the stability and security of the container's operation, and use appropriate automation tools to reduce manual operations.

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