Docker stats

Docker Stats

Docker provides several commands to monitor the status and performance of containers. The docker stats command is used to display real-time statistics about running containers.

Here are some key statistics provided by docker stats:

• CPU usage: The percentage of CPU time spent by the container.
• Memory usage: The amount of memory allocated to the container in bytes, along with a percentage of total available memory.
• Network I/O: The number of network packets sent and received by the container.
• Block I/O: The number of block operations (e.g., disk reads/writes) performed by the container.

Example:

bash
docker run -d --name my-container ubuntu:latest /bin/bash -c "while true; do echo Hello World! >> /dev/null; done"
# Run docker stats to view container statistics
docker stats my-container
CONTAINER ID        NAME                CPU %      MEM USAGE/LIMIT     MEM %      NET I/O           BLOCK I/O     
f0d65...    my-container    0.00%       15.4M of 500M   3.05%       23.1kB / 21.9kB   10.2kB / 5.33kB

In this example, the docker stats command displays real-time statistics about the container named my-container. The output shows that the container is using approximately 15.4MB of memory out of a total available 500MB (3.05% utilization), and has performed some network I/O.

Logging

Docker provides several ways to log events and errors from containers, including:

• Docker logs: The docker logs command can be used to view the output of container processes, including standard output, standard error, and any other output generated by the container.
• Log drivers: Docker supports various log drivers that allow you to route container logs to external logging systems, such as syslog, JSON file, or a third-party logging service like ELK (Elasticsearch, Logstash, Kibana).
• Container events: Docker emits events for various container lifecycle events, such as start, stop, and delete. These events can be captured by log drivers and sent to external logging systems.

Example:

bash
docker run -d --name my-container ubuntu:latest /bin/bash -c "while true; do echo Hello World! >> /dev/null; done"
# Run docker logs to view container output
docker logs my-container
Hello World!
# View container events using the docker events command
docker events --since 1m

In this example, the docker logs command is used to view the output of the container named my-container. The output shows that the container has executed a while loop that outputs "Hello World!" repeatedly. The docker events command is then used to capture and display container lifecycle events over the past minute.

Note: Docker also provides other features such as Container isolation, Resource Management, Networking, etc., which are not covered in this summary.