https://your.cds.instance/mon/status returns the status of CDS Engine.
If status != OK, something is wrong on your CDS Instance.
Example:
{
"now": "2018-01-09T20:24:20.481193492Z",
"lines": [
{ "status": "OK", "component": "Version", "value": "0.25.1-snapshot+1455.cds" },
...
{ "status": "OK", "component": "Database", "value": "20 conns" },
{ "status": "OK", "component": "LastUpdate Connected", "value": "14" },
{ "status": "OK", "component": "Worker Model Errors", "value": "0" }
...
}
# display the current job's queue
./cdsctl queue
# display the status of all service, except the status OK
./cdsctl -c prod health status --filter STATUS="[^O].*"