Monitoring Docker container metrics using cAdvisor
- create a local multi-container Docker Compose installation that includes containers running Prometheus, cAdvisor, and a server, respectively
- examine some container metrics produced by the Redis container, collected by cAdvisor, and scraped by Prometheus
First, you’ll need to configure Prometheus to scrape metrics from cAdvisor. Create a file and populate it with this configuration:
Docker Compose configuration
Now we’ll need to create a Docker Compose configuration that specifies which containers are part of our installation as well as which ports are exposed by each container, which volumes are used, and so on.
In the same folder where you created the file, create a docker-compose.yml
file and populate it with this Docker Compose configuration:
version: '3.2'
services:
prometheus:
image: prom/prometheus:latest
container_name: prometheus
ports:
- 9090:9090
- --config.file=/etc/prometheus/prometheus.yml
volumes:
- ./prometheus.yml:/etc/prometheus/prometheus.yml:ro
depends_on:
- cadvisor
cadvisor:
image: gcr.io/google-containers/cadvisor:latest
container_name: cadvisor
ports:
- 8080:8080
- /:/rootfs:ro
- /var/run:/var/run:rw
- /sys:/sys:ro
- /var/lib/docker/:/var/lib/docker:ro
- redis
redis:
image: redis:latest
container_name: redis
ports:
- 6379:6379
This configuration instructs Docker Compose to run three services, each of which corresponds to a Docker container:
- The
prometheus
service uses the localprometheus.yml
configuration file (imported into the container by thevolumes
parameter). - The
cadvisor
service exposes port 8080 (the default port for cAdvisor metrics) and relies on a variety of local volumes (/
,/var/run
, etc.). - The
redis
service is a standard Redis server. cAdvisor will gather container metrics from this container automatically, i.e. without any further configuration.
If Docker Compose successfully starts up all three containers, you should see output like this:
prometheus | level=info ts=2018-07-12T22:02:40.5195272Z caller=main.go:500 msg="Server is ready to receive web requests."
You can verify that all three containers are running using the command:
Your output will look something like this:
----------------------------------------------------------------------------
cadvisor /usr/bin/cadvisor -logtostderr Up 8080/tcp
prometheus /bin/prometheus --config.f ... Up 0.0.0.0:9090->9090/tcp
redis docker-entrypoint.sh redis ... Up 0.0.0.0:6379->6379/tcp
You can access the cAdvisor web UI at http://localhost:8080
. You can explore stats and graphs for specific Docker containers in our installation at http://localhost:8080/docker/<container>
. Metrics for the Redis container, for example, can be accessed at http://localhost:8080/docker/redis
, Prometheus at http://localhost:8080/docker/prometheus
, and so on.
Exploring metrics in the expression browser
Let’s start by exploring the container_start_time_seconds
metric, which records the start time of containers (in seconds). You can select for specific containers by name using the name="<container_name>"
expression. The container name corresponds to the container_name
parameter in the Docker Compose configuration. The container_start_time_seconds{name="redis"}
expression, for example, shows the start time for the redis
container.
The table below lists some other example expressions
Summary
In this guide, we ran three separate containers in a single installation using Docker Compose: a Prometheus container scraped metrics from a cAdvisor container which, in turns, gathered metrics produced by a Redis container. We then explored a handful of cAdvisor container metrics using the Prometheus expression browser.