Service scaling in Docker - Cheat Sheet & Quick Revision

Recall & Review

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What is service scaling in Docker?

Service scaling means increasing or decreasing the number of containers running a service to handle more or less work.

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Which Docker command is used to scale a service?

The command docker service scale SERVICE=NUMBER changes the number of containers for a service.

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What happens if you scale a service down in Docker?

Docker stops some containers of the service to reduce the total number running, saving resources.

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How can you check the current number of containers running for a service?

Use docker service ls to see services and docker service ps SERVICE to see containers running for that service.

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Why is service scaling useful in real life?

It helps handle more users or traffic by adding containers, or save money by reducing containers when less work is needed.

Which command scales a Docker service to 5 containers?

A docker container scale myservice 5

B docker service scale myservice=5

C docker scale service myservice 5

D docker service update --scale 5 myservice

The correct syntax to scale a service is docker service scale SERVICE=NUMBER.

What does scaling a service up mean?

A Adding more containers

B Stopping containers

C Updating container images

D Removing the service

Scaling up means increasing the number of containers running the service.

How do you see the current number of containers for a service?

A docker service inspect SERVICE

B docker container ls

C docker service ps SERVICE

D docker ps -a

The command docker service ps SERVICE lists containers running for that service.

If you scale a service down, what happens?

A Containers stop to reduce count

B Nothing changes

C Service is deleted

D More containers start

Scaling down stops some containers to reduce the total number running.

Why might you want to scale a service automatically?

A To backup data

B To save disk space

C To update software versions

D To handle changing user demand

Automatic scaling helps match the number of containers to user demand or traffic.

Explain how you would scale a Docker service named 'webapp' to 3 containers and check the result.

Think about the command to change container count and how to verify it.

Describe why service scaling is important in managing applications with changing traffic.

Consider what happens when many or few users visit your app.