Skip to content

Latest commit

 

History

History
85 lines (45 loc) · 5.17 KB

Docker Advanced Concepts.md

File metadata and controls

85 lines (45 loc) · 5.17 KB

Advanced Docker Concepts

Docker Swarm: native clustering and orchestration

Docker Swarm is a native clustering and orchestration solution built into Docker. It allows you to create and manage a swarm, which is a group of Docker nodes (machines) that work together to run and scale your containerized applications.

Key concepts:

  1. Nodes: Nodes are Docker instances that participate in the swarm. Nodes can be either manager nodes, which manage the swarm state and make decisions, or worker nodes, which execute tasks.

  2. Services: A service is a higher-level abstraction of a containerized application. It defines the desired state of the application, including the image, number of replicas, and configuration.

  3. Tasks: Tasks are individual units of work that run on nodes. Each task corresponds to a container running on a node.

  4. Networking: Docker Swarm provides built-in networking support for service discovery, load balancing, and encrypted communication between nodes.

To create and manage a swarm:

  1. Initialize a swarm: On the manager node, run docker swarm init to create a new swarm.

  2. Join worker nodes: On the worker nodes, run the docker swarm join command provided by the manager node to join the swarm.

  3. Create a service: Run docker service create with the desired image, replicas, and configuration options to create a new service.

    Example: docker service create --name my-service --replicas 3 --publish 80:80 my-image

  4. Manage services: Use docker service ls, docker service inspect, docker service update, and docker service rm to list, inspect, update, and remove services, respectively.

  5. Scale services: Use docker service scale to scale the number of replicas for a service.

    Example: docker service scale my-service=5

Building Docker plugins

Docker plugins are extensions that provide additional functionality to the Docker engine, such as custom storage drivers, network drivers, or authorization mechanisms.

To create a Docker plugin:

  1. Choose a plugin type: Determine the type of plugin you want to create (e.g., storage, network, or authorization).

  2. Implement the plugin API: Implement the required API for the chosen plugin type, using the Docker plugin SDK (usually in Go).

  3. Package the plugin: Package the plugin as a container image, including a config.json file that defines the plugin metadata and settings.

  4. Install and enable the plugin: Use docker plugin install to install the plugin on the Docker host, and docker plugin enable to enable it.

  5. Use the plugin: Once installed and enabled, the plugin can be used with Docker commands, such as docker volume create for storage plugins, or docker network create for network plugins.

Troubleshooting and debugging Docker containers

  1. Inspect containers: Use docker inspect to view detailed information about a container, including its configuration, state, network settings, and more.

  2. View logs: Use docker logs to view the stdout and stderr logs of a container. This can help you diagnose issues with your application or the container itself.

    Example: docker logs my-container

  3. Monitor container performance: Use docker stats to view real-time performance metrics for your containers, such as CPU, memory, network, and I/O usage.

  4. Attach to a running container: Use docker attach to attach your terminal to a running container, allowing you to interact with the container's process directly.

    Example: docker attach my-container

  5. Exec commands inside a container: Use docker exec to run commands inside a running container. This can help you diagnose issues or perform maintenance tasks.

    Example: docker exec -it my-container /bin/bash or docker exec -it my-container sh

  6. Use docker top: The docker top command allows you to view the processes running inside a container. This can help you identify any unexpected or resource-consuming processes.

    Example: docker top my-container

  7. Debugging container crashes: If a container is crashing or restarting frequently, you can use docker events to monitor container events and identify potential causes. Additionally, you can use docker inspect to view the container's exit code and other information that may help diagnose the issue.

  8. Health checks: Implement health checks in your Dockerfile or service definition to ensure that your containers are functioning correctly. Health checks allow Docker to monitor the health of your application and take appropriate actions, such as restarting the container if it becomes unresponsive.

    Example:

    FROM nginx:1.21
HEALTHCHECK --interval=5m --timeout=3s \
  CMD curl -f http://localhost/ || exit 1

  9. Network troubleshooting: Use docker network commands to inspect and manage container networks. You can also use common network diagnostic tools, such as ping, traceroute, or nslookup, inside containers or on the host system to troubleshoot network issues.

  10. Use Docker's built-in debugging tools: Docker includes a docker debug command, which allows you to collect debugging information and diagnostic data from the Docker daemon, containers, and images. This information can be helpful when troubleshooting complex issues.