Container metrics collection in Docker - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to list all running Docker containers.

Docker

docker [1]

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

Astart

Brun

Cps

Dstop

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'docker run' instead of 'docker ps' to list containers.

Using 'docker start' which starts a stopped container but does not list them.

The docker ps command lists all running containers.

2fill in blank

medium

Complete the command to show real-time stats of all running containers.

Docker

docker [1]

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

Astats

Blogs

Cinspect

Dtop

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'docker logs' which shows container logs, not metrics.

Using 'docker inspect' which shows detailed info but not live stats.

The docker stats command shows live metrics like CPU and memory usage for running containers.

3fill in blank

hard

Fix the error in the command to get stats for a specific container named 'webapp'.

Docker

docker stats [1]

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

Awebapp

B--name webapp

C-container webapp

Dcontainer webapp

Attempts:

3 left

💡 Hint

Common Mistakes

Adding unnecessary flags like '--name' which is not valid here.

Using incorrect flags like '-container' or 'container' which cause errors.

To get stats for a specific container, just provide its name or ID after docker stats.

4fill in blank

hard

Fill both blanks to create a command that outputs container stats in JSON format and limits output to 5 updates.

Docker

docker stats --format '[1]' --no-stream --[2] 5

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

A"{{.Name}}: CPU {{.CPUPerc}}, Mem {{.MemUsage}}"

Bstream

Climit

Djson

Attempts:

3 left

💡 Hint

Common Mistakes

Using '--json' which is not a valid flag for docker stats.

Using '--limit' which is not a recognized option.

The --format option customizes output, and --no-stream shows a single snapshot instead of continuous updates.

5fill in blank

hard

Fill all three blanks to create a command that filters stats for containers with names starting with 'db' and outputs only CPU percentage.

Docker

docker stats --format '{{{{.Name}}}}: {{{{.[1]' --filter name=[2] --no-stream | grep '^[3]'

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

ACPUPerc

Bdb

DMemUsage

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'MemUsage' instead of 'CPUPerc' for CPU stats.

Not using the correct filter syntax for container names.

The --filter name=db limits containers to those starting with 'db'. The format outputs CPU percentage. The grep filters lines starting with 'db'.

Practice

1. What does the docker stats command primarily show?

easy

A. Logs of a specific container

B. List of all Docker images on the system

C. Live resource usage metrics of running containers

D. Docker daemon configuration settings

Solution

1. Step 1: Understand the purpose of docker stats

   This command is designed to display live resource usage statistics such as CPU, memory, and network for running containers.

2. Step 2: Differentiate from other Docker commands

   Other commands like docker images list images, docker logs show logs, and docker info shows daemon info, so they do not match the description.

3. Final Answer:

   Live resource usage metrics of running containers -> Option C

4. Quick Check:

   docker stats = live container metrics [OK]

Hint: Remember: stats = live resource usage [OK]

Common Mistakes:

• Confusing stats with logs
• Thinking stats shows images
• Assuming stats shows config

2. Which of the following is the correct syntax to get a single snapshot of container metrics without continuous updates?

easy

A. docker stats --no-stream

B. docker stats --single

C. docker stats --once

D. docker stats --snapshot

Solution

1. Step 1: Identify the flag for single snapshot

   The --no-stream flag tells docker stats to show metrics once and exit instead of streaming live updates.

2. Step 2: Verify other options

   Flags like --single, --once, and --snapshot are not valid Docker flags for this command.

3. Final Answer:

   docker stats --no-stream -> Option A

4. Quick Check:

   Single snapshot flag = --no-stream [OK]

Hint: Use --no-stream for one-time metrics [OK]

Common Mistakes:

• Using invalid flags like --single
• Omitting the flag and expecting single output
• Confusing with other Docker commands

3. What will be the output of the command docker stats --no-stream my_container if my_container is running?

medium

A. A continuous live stream of resource usage for all containers

B. Logs of my_container

C. An error saying container not found

D. A single snapshot of resource usage metrics for my_container

Solution

1. Step 1: Understand the command components

   docker stats --no-stream requests a single snapshot, and specifying my_container limits output to that container only.

2. Step 2: Predict the output

   Since my_container is running, the command outputs one snapshot of its resource usage metrics, not a stream or logs.

3. Final Answer:

   A single snapshot of resource usage metrics for my_container -> Option D

4. Quick Check:

   --no-stream + container name = single snapshot for that container [OK]

Hint: Add container name for focused single snapshot [OK]

Common Mistakes:

• Expecting continuous stream despite --no-stream
• Confusing stats output with logs
• Assuming error if container is running

4. You run docker stats --no-stream my_container but get an error: Error: No such container: my_container. What is the most likely cause?

medium

A. You need to add --all flag to see stopped containers

B. The container my_container is not running or does not exist

C. Docker daemon is not running

D. The --no-stream flag is invalid

Solution

1. Step 1: Analyze the error message

   The error clearly states the container my_container cannot be found, meaning it is either stopped or never created.

2. Step 2: Check other options

   The --no-stream flag is valid, Docker daemon errors would be different, and docker stats does not support --all to show stopped containers.

3. Final Answer:

   The container my_container is not running or does not exist -> Option B

4. Quick Check:

   Error 'No such container' means container missing [OK]

Hint: Check container existence before stats command [OK]

Common Mistakes:

• Assuming flag is wrong
• Thinking Docker daemon is down
• Trying unsupported flags like --all

5. You want to monitor CPU and memory usage of two specific containers named webapp and db with a single snapshot. Which command should you run?

hard

A. docker stats --no-stream webapp db

B. docker stats webapp db --no-stream

C. docker stats --no-stream --filter webapp --filter db

D. docker stats --filter name=webapp,db --no-stream

Solution

1. Step 1: Understand how to specify multiple containers

   Docker stats accepts container names as arguments separated by spaces to monitor multiple containers.

2. Step 2: Use the correct flag placement

   The --no-stream flag should come before container names; docker stats --no-stream webapp db places it correctly.

3. Step 3: Evaluate other options

   docker stats webapp db --no-stream incorrectly places the flag after container names, causing Docker to interpret --no-stream as a container name and resulting in an error. Options C and D use invalid or unsupported --filter syntax for this command.

4. Final Answer:

   docker stats --no-stream webapp db -> Option A

5. Quick Check:

   Multiple containers + --no-stream = docker stats --no-stream webapp db [OK]

Hint: List containers after --no-stream for snapshot [OK]

Common Mistakes:

• Using invalid --filter syntax
• Placing flags after container names incorrectly
• Trying to monitor stopped containers