Canary deployment pattern in Docker - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the Docker command to run a container with a specific image tag for canary deployment.

Docker

docker run -d --name canary_app [1] myapp:canary

Drag options to blanks, or click blank then click option'

A-p 8080:80

B--rm

C-it

D--network host

Attempts:

3 left

💡 Hint

Common Mistakes

Using --rm removes the container after it stops, which is not suitable for a running canary.

Using -it is for interactive mode, not needed here.

Using --network host bypasses port mapping, which is less flexible.

The -p 8080:80 option maps port 8080 on the host to port 80 in the container, allowing access to the canary deployment.

2fill in blank

medium

Complete the Docker Compose service definition to deploy a canary version of the app with limited replicas.

Docker

services:
  app_canary:
    image: myapp:canary
    deploy:
      replicas: [1]

Drag options to blanks, or click blank then click option'

A10

B0

C2

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Setting replicas to 0 means no containers run.

Setting replicas to 10 or 5 is too large for a canary.

Setting replicas to 2 allows a small portion of traffic to be served by the canary version, which is typical for canary deployments.

3fill in blank

hard

Fix the error in the Docker command to update the canary container with a new image version.

Docker

docker container [1] canary_app myapp:canary_v2

Drag options to blanks, or click blank then click option'

Aupdate

Bexec

Crun

Drestart

Attempts:

3 left

💡 Hint

Common Mistakes

docker container update does not update the image used by the container.

docker container run creates a new container, not update existing.

docker container exec runs a command inside a running container.

The docker container restart command restarts the container, which is needed after updating the image locally to apply changes.

4fill in blank

hard

Fill both blanks to create a Docker Compose snippet that routes 10% of traffic to the canary service using labels.

Docker

services:
  app_canary:
    image: myapp:canary
    deploy:
      replicas: 2
      labels:
        - "traefik.weight=[1]"
  app_stable:
    image: myapp:stable
    deploy:
      replicas: 8
      labels:
        - "traefik.weight=[2]"

Drag options to blanks, or click blank then click option'

A1

B9

C10

D90

Attempts:

3 left

💡 Hint

Common Mistakes

Using weights that do not add up proportionally to 100.

Assigning higher weight to canary than stable.

Setting traefik.weight=1 for canary and traefik.weight=90 for stable routes roughly 10% traffic to canary and 90% to stable.

5fill in blank

hard

Fill all three blanks to define a Docker Compose healthcheck that retries 3 times with 5 seconds interval for the canary service.

Docker

services:
  app_canary:
    image: myapp:canary
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost/[1]"]
      interval: [2]s
      retries: [3]

Drag options to blanks, or click blank then click option'

Ahealth

B10

C3

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong endpoint path in test command.

Setting interval or retries to zero or too high values.

The healthcheck tests the /health endpoint, retries 3 times, and waits 5 seconds between attempts to ensure the canary is healthy before routing traffic.