Managing Swarm Services

This post will cover topic related to ‘Managing Swarm Services’ with multiple docker command examples and different scenerios. So this will help you to understand the command docker and options available in it. Also this post will explain you how to use docker command.

The docker service command is an essential tool for managing services in Docker Swarm mode. Swarm mode allows you to manage a cluster of Docker engines, and services are the units of deployment in this cluster. Using the docker service command, you can create, update, scale, and inspect these services to ensure that your applications are running as expected. Below are some examples illustrating different uses of the docker service command, each tailored to managing Swarm services.

1. Create a New Service

docker service create --name my_service --replicas 3 nginx

This command creates a new service named my_service running the nginx image with 3 replicas. Each replica is an instance of the service, ensuring high availability.

Output:

The command will output a service ID, which can be used to refer to this service in future commands.

2. List All Services

docker service ls

This command lists all the services running in the current Docker Swarm. It shows details such as service ID, name, and the number of replicas.

Output:

Service ID | Name | Replicas | Image

abcdefgh1234 | my_service | 3/3 | nginx

3. Inspect a Service

docker service inspect my_service

This command provides detailed information about the service my_service, including its configuration and status.

Output:

The output will be a JSON object with details about the service, including its image, replicas, and networks.

4. Update a Service

docker service update --image nginx:latest my_service

This command updates the my_service service to use the latest version of the nginx image.

Output:

The command provides an ID for the update operation and a status indicating that the update is in progress.

5. Scale a Service

docker service scale my_service=5

This command scales the my_service service to 5 replicas, adjusting the number of running instances of the service.

Output:

The command confirms that the service has been scaled to 5 replicas.

6. Remove a Service

docker service rm my_service

This command removes the my_service service from the Docker Swarm. Be cautious as this will stop all running instances of the service.

Output:

The command will confirm the removal of the service.

7. View Service Logs

docker service logs my_service

This command displays the logs for the my_service service, which can help in troubleshooting and monitoring the service’s behavior.

Output:

The output consists of log entries from all the containers in the service.

8. Pause a Service

docker service update --pause my_service

This command pauses the my_service service, preventing new tasks from starting and stopping ongoing tasks.

Output:

The command confirms that the service has been paused.

9. Resume a Paused Service

docker service update --resume my_service

This command resumes a previously paused service, allowing it to start new tasks and continue operation.

Output:

The command confirms that the service has been resumed.

10. Show Service Overview

docker service ps my_service

This command shows the tasks associated with the my_service service, including their status and where they are running.

Output:

The output lists tasks with details such as task ID, service, desired state, and current state.

Verification Steps:

To verify that a command has executed successfully, you can:

• Check the output of the command for confirmation messages or statuses.
• Use docker service ls to ensure that the service appears in the list with the expected configurations.
• For updates and scaling, verify the changes by inspecting the service with docker service inspect and checking the number of replicas.
• For logs, use docker service logs to view recent logs and confirm that the service is functioning as expected.
• For removal, use docker service ls again to confirm that the service is no longer listed.

Also check similar articles.

Managing Docker Volumes
Managing Docker Networks
Managing Swarm Secrets
Managing Swarm Nodes
Managing Swarm Configurations