How to manage Docker services using 'docker service' (with examples)

The Docker service command is an essential tool for managing services on a Docker daemon. It allows users to create, list, inspect, scale, and remove services, enabling efficient orchestration of containerized applications in a swarm environment. These functionalities are crucial for deploying and maintaining applications at scale. The command is particularly useful for developers and system administrators who need to manage distributed applications efficiently.

Use case 1: List the services on a Docker daemon

Code:

docker service ls

Motivation:

Listing services is a fundamental task in Docker’s management toolset. It allows administrators and developers to get an overview of the currently running services in their Docker Swarm. This is particularly useful for troubleshooting, ensuring all required services are running, and gaining insight into the state of your deployments.

Explanation:

• docker: This is the Docker command-line interface.
• service: It specifies that the operation pertains to Docker services.
• ls: This argument lists all the services currently running on the Docker daemon.

Example Output:

ID                  NAME                MODE                REPLICAS            IMAGE               PORTS
x2z9z4z5t1fw        web                 replicated          3/3                 nginx:latest        *:80->80/tcp
y7p5z9z5t5yz        api                 replicated          2/2                 api-service:latest  *:8080->80/tcp

Use case 2: Create a new service

Code:

docker service create --name web_service nginx:latest

Motivation:

Creating a new service is a critical action in deploying containerized applications. This command allows you to set up a new instance of a containerized application, specifying its name, the image to use, and additional parameters if desired. It’s the starting point for running an application within a Docker Swarm.

Explanation:

• docker: Invokes the Docker command-line tool.
• service: Indicates that a service-related task is being performed.
• create: Initiates the creation of a new service.
• --name web_service: Assigns the human-readable name web_service to the new service.
• nginx:latest: Specifies the Docker image and tag to use, in this case, the latest version of the Nginx image.

Example Output:

udxyvynvfete1ra7eqwf65tzu

Use case 3: Display detailed information about one or more services

Code:

docker service inspect web_service

Motivation:

Understanding the details of a service is imperative for debugging and effective management. The inspect command provides comprehensive details about a service, including settings, assigned tasks, and current status. It’s helpful for gaining in-depth insights and verifying configurations.

Explanation:

• docker: Calls the Docker command utility.
• service: Specifies that the service commands are being invoked.
• inspect: Indicates you want to view detailed information.
• web_service: The name or ID of the service you want to inspect.

Example Output:

[
    {
        "ID": "udxyvynvfete1ra7eqwf65tzu",
        "Version": {
            "Index": 51
        },
        "CreatedAt": "2023-08-01T23:36:28.270896182Z",
        "UpdatedAt": "2023-08-01T23:36:30.326888945Z",
        "Spec": {
            "Name": "web_service",
            ...
        }
    }
]

Use case 4: List the tasks of one or more services

Code:

docker service ps web_service

Motivation:

Monitoring tasks provides insights into how work progresses across the swarm. It helps in assessing task distribution, rebalancing, or determining if scaling actions were successful. This information aids in performance tuning and resource allocation.

Explanation:

• docker: The command to access Docker’s command-line interface.
• service: These commands specifically target services.
• ps: Lists the tasks of the specified service.
• web_service: The service name for which you want to list tasks.

Example Output:

ID                  NAME                IMAGE               NODE                DESIRED STATE       CURRENT STATE           ERROR               PORTS
tx1cabcwi9c9        web_service.1       nginx:latest        node-1              Running             Running 9 minutes ago                               
tanfovansnw7        web_service.2       nginx:latest        node-2              Running             Running 9 minutes ago

Use case 5: Scale to a specific number of replicas for a service

Code:

docker service scale web_service=5

Motivation:

Scaling services according to demand is essential for meeting user requirements while optimizing resource utilization. Adjusting replicas helps handle varying workloads and ensures high availability, making sure services remain reliable even under heavy traffic.

Explanation:

• docker: Initiates the Docker interface.
• service: Directs the commands to service-level actions.
• scale: Specifies the desire to adjust the number of replicas.
• web_service=5: Targets the specified service (web_service) and sets the number of replicas to 5.

Example Output:

web_service scaled to 5
overall progress: 5 out of 5 tasks 

Use case 6: Remove one or more services

Code:

docker service rm web_service

Motivation:

Effectively removing services when they are no longer needed or when cleaning up unused resources is critical for maintaining an efficient Docker environment. This helps free system resources and keeps the swarm environment uncluttered.

Explanation:

• docker: Accesses the Docker command-line interface.
• service: Pertains to services within Docker.
• rm: Removes the specified service(s).
• web_service: The service name you intend to remove.

Example Output:

web_service

Conclusion

The docker service command embodies a set of powerful tools that simplify and enhance the management of Docker services within a swarm. From creating new services to scaling existing ones and removing services that are no longer needed, each use case demonstrates essential tasks for orchestrating distributed applications. By mastering these commands, developers and system administrators can effectively manage their containerized applications and maintain robust, scalable infrastructures.