Docker container cannot be killed

Docker containers have become the standard way to deploy modern applications, especially for enterprises using microservices architecture. However, in actual use, we may encounter some problems, such as the container cannot be killed, etc. This article will introduce some reasons why containers cannot be killed and how to solve these problems.

1. Excessive use of container resources

Within the Docker container, each container has its own CPU, memory and other resources. When resources are overused, the system may not be able to timely Respond to the kill command. At this time, you need to manually kill the container process, or use the kill command with the -f parameter to force stop.

However, if you don’t want to manually kill the container’s process while the container is running, there are some tools that can help you stop the container automatically. For example using AWS EC2 Container Service or Kubernetes, these tools can automatically monitor container resource usage and stop containers when resources are overused.

2. Problems caused by the mount point between the container and the host

When files are shared between the container and the host, the container mounts the files on the host When clamped, the container may not be killed. This is because when the container exits, the operating system may need to wait for file system I/O operations to complete before terminating the application, otherwise file system corruption may result.

To solve this problem, we need to ensure that the container does not have any files open for writing in the mounted shared folder. You can use the lsof command to view the open files within the container, and then manually close these files. In addition, when the container exits, we can let the host unmount the mounted folder so that the operating system does not wait for I/O operations.

3. Use docker stop command instead of docker kill command

Sometimes we may use docker stop command to stop the container process. However, when the container cannot be stopped normally, the docker stop command may cause problems. At this time, we need to use the docker kill command to force stop the container. Because the docker kill command can forcefully stop the container process and does not wait for the process to be cleaned up.

Before using the docker kill command, we need to ensure that there are no running applications in the container, otherwise it may cause data loss or memory leaks.

4. Subprocesses within the container

The application within the Docker container may create its own subprocesses, and these subprocesses may prevent the container process from being killed. Because when the parent process exits, the child process may become an "orphan process", and the operating system may transfer the orphan process to the init process and continue running. In this case, the container cannot be killed.

There are two ways to solve this problem: one is to set up a signal processing mechanism when running the application in the container. When the container process receives the kill signal, it sends a signal to the child process and lets the child process exit. In this way This allows the container process to exit smoothly; the second is to use the docker kill command to forcefully kill the container process, so that the child process will also be terminated.

5. Threads in the container

Applications in the container may use multiple threads, and these threads may prevent the container from being killed. Because when the container process ends, the thread may continue to run, causing the container process to be unable to exit.

To solve this problem, we need to check all threads in the container to ensure that the thread has exited. You can use the strace command or the lsmod command to list all threads in the container and then stop these threads manually.

Summary

When using Docker containers, being unable to kill the container is a common problem. This article describes some possible reasons why a container cannot be killed and how to resolve these issues. I hope these solutions can help and prevent you from encountering similar problems when using Docker containers.

The above is the detailed content of Docker container cannot be killed. For more information, please follow other related articles on the PHP Chinese website!