New Relic Agent (Docker Compose) not showing container metrics

The Problem

I recently set up the New Relic Agent using Docker Compose. I could see my containers in the New Relic UI, but all of the container metrics were reporting zero values.

The Cause

The guided install process and New Relic’s Docker Compose guide do not grant the agent access to the host’s cgroup namespace.

On systems using cgroup v2, the agent reads container metrics from /sys/fs/cgroup. When the container runs in its default (private) cgroup namespace, it can only see its own cgroup — even with privileged: true — and not the rest of the host’s container hierarchy. Therefore, the agent cannot read metrics from other containers on the host.

Interestingly, the docker run examples in the documentation do include the required flag: --cgroupns=host.

However, the Docker Compose examples omit the equivalent setting.

The Solution

Therefore, the fix is to set the cgroup namespace to host for the service. The equivalent of --cgroupns=host in Docker Compose parlance is cgroup: host:

version: "3"
services:
  agent:
    container_name: newrelic-infra
    image: newrelic/infrastructure:latest
    cap_add:
      - SYS_PTRACE
    network_mode: host
    pid: host
    privileged: true
    cgroup: host
    volumes:
      - "/:/host:ro"
      - "/var/run/docker.sock:/var/run/docker.sock"
    environment:
      NRIA_LICENSE_KEY: "YOUR_LICENSE_KEY"
    restart: unless-stopped

You can find more details in the Compose reference.

If you’re using a recent version of Docker Compose, you should also remove the version key as it is no longer required.

With that change and a quick docker compose up -d, your container metrics should start trickling through to the New Relic UI.