Bad Request - There Was An Error Returned Querying The Prometheus Api - 400
Troubleshooting the Ghost: Decoding the “400 Bad Request” from the Prometheus API
4 minutes We have all been there. You have built a beautiful Grafana dashboard, or you are trying to fetch metrics via curl to debug a latency spike. You type the command, hit enter, and instead of a JSON payload of time series data, you are greeted with the digital equivalent of a slammed door: "400 Bad Request - There was an error returned querying the Prometheus API" It is vague. It is frustrating. And it usually happens at 2 AM during an incident. Prometheus throws a 400.
Prometheus expects a Content-Type header for POST queries ( application/x-www-form-urlencoded ). If the proxy manipulates this, Prometheus throws a 400. Prometheus throws a 400.