feature: Send the CPU count and the Docker state in the status #44

Blocker: no. This can wait until the agent stack is merged. It goes on top of the disk activity in the same stack.

Part of contract v0.5.0, section "2026-09-24 — Sites and Docker": "status: the CPU count and Docker".

Defect

• The status of the agent has no CPU count and no Docker state.
• Thus the control plane reads these values over SSH on each view of the Status page.

Cost

• The Status page waits for an SSH command.
• The control plane cannot stop its SSH reads while the agent does not send the values.

Benefit of the fix

• The agent sends the CPU count, the Docker state and the Docker version with its status.
• The control plane can show the CPU load as a percent, and the Docker line, from its database.

Fix

1. Add the optional status field cpu_count: the number of cpuN lines in /proc/stat.
2. Send GET /version to /var/run/docker.sock, with a limit of 5 seconds. Use only the Go standard library. Do not use the docker command.
3. Set docker_status:
   • running when the request answers
   • not_running when there is no socket, or the connection is refused, and /usr/bin/dockerd exists
   • not_installed in the same case without /usr/bin/dockerd
   • null for each other result, for example "permission denied" or no answer in 5 seconds
4. Set docker_version from the answer, only when docker_status is running.

Caution

• Send only GET /version and GET /containers/json to the socket. Access to the socket is root access.

Completion checks

• cpu_count equals nproc.
• Each rule of docker_status has a test.
• A socket that does not answer gives null after 5 seconds, and the report still goes.
• The agent sends no other request to the socket.