dcos-3dt.service is the diagnostics utility for DC/OS systemd components. This service runs on every host, tracking the internal state of the systemd unit. The service runs in two modes, with or without the
-pull argument. If running on a master host, it executes
/opt/mesosphere/bin/3dt -pull which queries Mesos-DNS for a list of known masters in the cluster, then queries a master (usually itself)
:5050/statesummary and gets a list of agents.
From this complete list of cluster hosts, it queries all 3DT health endpoints
:1050/system/health/v1/health. This endpoint returns health state for the DC/OS systemd units on that host. The master 3DT processes, along with doing this aggregation also expose
/system/health/v1/ endpoints to feed this data by
node IP to the DC/OS user interface.
To create a DC/OS diagnostic bundle run these commands from the DC/OS CLI (DC/OS 1.8+),