Resource monitoring per container in Docker - Step-by-Step Execution

Process Flow - Resource monitoring per container

Start Docker Container

↓

Run 'docker stats'

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Collect CPU, Memory, Network, I/O

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Display live stats per container

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User observes resource usage

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Stop monitoring or container

This flow shows starting a container, running the docker stats command to collect live resource usage, and displaying it until stopped.

Execution Sample

Docker

docker run -d --name myapp nginx

docker stats myapp

Starts an nginx container named 'myapp' and then shows live resource usage stats for it.

Process Table

Step	Command	Action	Output/Result
1	docker run -d --name myapp nginx	Start container 'myapp' in background	Container ID returned, 'myapp' running
2	docker stats myapp	Start live resource monitoring for 'myapp'	Shows CPU %, Memory usage, Network I/O, Block I/O, PIDs
3	docker stats myapp (after 5 seconds)	Update resource stats	CPU 0.05%, Mem 10MiB / 500MiB, Net I/O 1kB / 0B, Block I/O 0B / 0B, PIDs 2
4	docker stats myapp (after 10 seconds)	Update resource stats	CPU 0.10%, Mem 12MiB / 500MiB, Net I/O 2kB / 0B, Block I/O 0B / 0B, PIDs 2
5	Ctrl+C	Stop monitoring	docker stats command exits
6	docker stop myapp	Stop container	'myapp' stopped
7	docker stats myapp	Try monitoring stopped container	Error: No such container: myapp

💡 Monitoring stops when user interrupts with Ctrl+C or container stops.

Status Tracker

Variable	Start	After Step 1	After Step 3	After Step 4	After Step 6	Final
Container State	Not running	Running	Running	Running	Stopped	Stopped
CPU %	0%	N/A	0.05%	0.10%	N/A	N/A
Memory Usage	0MiB	N/A	10MiB	12MiB	N/A	N/A
Network I/O	0B	N/A	1kB / 0B	2kB / 0B	N/A	N/A
Block I/O	0B	N/A	0B / 0B	0B / 0B	N/A	N/A
PIDs	0	N/A	2	2	N/A	N/A

Key Moments - 3 Insights

Why does 'docker stats' show an error after the container is stopped?

Because the container no longer exists or is not running, 'docker stats' cannot fetch resource data. See execution_table row 7.

Does 'docker stats' show a snapshot or live updates?

'docker stats' shows live updates of resource usage every second until stopped. See execution_table rows 2, 3, and 4.

What happens if you run 'docker stats' without specifying a container?

It shows stats for all running containers. Here we specified 'myapp' to focus on one container. This is implied in step 2.

Visual Quiz - 3 Questions

Look at the execution table, what is the CPU % of 'myapp' at step 4?

A 0.10%

B 0.05%

C 1%

D Not available

💡 Hint

Check the 'Output/Result' column at step 4 in the execution_table.

At which step does the container stop running?

A Step 3

B Step 6

C Step 7

D Step 2

💡 Hint

Look at the 'Container State' variable in variable_tracker after step 6.

If you do not press Ctrl+C, what will happen to the 'docker stats' command?

A It will exit immediately

B It will keep showing live stats continuously

C It will show stats once and stop

D It will stop after 10 seconds automatically

💡 Hint

Refer to execution_table steps 2 to 4 showing continuous updates.

Concept Snapshot

docker stats [container]
Shows live resource usage per container.
Includes CPU %, memory, network I/O, block I/O, and PIDs.
Runs continuously until stopped (Ctrl+C).
Only works on running containers.
Useful for monitoring container health in real time.

Full Transcript

This visual execution shows how to monitor resource usage per Docker container using the 'docker stats' command. First, a container named 'myapp' is started in detached mode. Then, 'docker stats myapp' is run to display live CPU, memory, network, and I/O usage. The stats update every second, showing changes in resource consumption. The monitoring continues until the user stops it with Ctrl+C. If the container is stopped, 'docker stats' cannot show data and returns an error. This helps users understand how to watch container resources live and what happens when containers stop.