DockerCadvisorDown: what to do when it fires

Alert rule

alert: DockerCadvisorDown
expr: up{job=~"cadvisor.*"} == 0
for: 3m
severity: critical

Alert message: cAdvisor is down ({{ $labels.instance }})

What it means

Container metrics are not being collected from the host: up == 0 for the cAdvisor job for 3 minutes. While this alert is active, the other Docker alerts for this host do not work.

Common causes

The cAdvisor container is stopped, port 8080 is unreachable, the host is down, the wrong address in scrape_configs.

Diagnostics

docker ps -a --filter name=cadvisor
docker logs --tail 50 cadvisor
curl -sS -m 5 http://<host>:8080/metrics | head
ss -ltnp | grep 8080

How to fix

Start the container (docker start cadvisor / docker compose up -d), check the permissions of the mounts (/, /var/run, /sys, /var/lib/docker), fix the address or the firewall.

When it is OK to silence

During host maintenance or a cAdvisor upgrade.

Related alerts

• DockerContainerGone
• DockerContainerRestartLoop
• DockerContainerCpuThrottled
• DockerContainerMemoryNearLimit

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