Limit the default time window for label name and label value APIs

Signed-off-by: Kemal Akkoyun <kakkoyun@gmail.com>

pkg/api/query/v1.go

@@ -421,11 +421,13 @@ func (qapi *QueryAPI) labelValues(r *http.Request) (interface{}, []error, *api.A
 		return nil, nil, &api.ApiError{Typ: api.ErrorBadData, Err: errors.Errorf("invalid label name: %q", name)}
 	}
 
-	start, err := parseTimeParam(r, "start", minTime)
+	// If start and end time not specified, we get the last 2h window.
+	now := time.Now()
+	start, err := parseTimeParam(r, "start", now.Add(-2*time.Hour))
 	if err != nil {
 		return nil, nil, &api.ApiError{Typ: api.ErrorBadData, Err: err}
 	}
-	end, err := parseTimeParam(r, "end", maxTime)
+	end, err := parseTimeParam(r, "end", now)
 	if err != nil {
 		return nil, nil, &api.ApiError{Typ: api.ErrorBadData, Err: err}
 	}
@@ -582,11 +584,13 @@ func parseDuration(s string) (time.Duration, error) {
 func (qapi *QueryAPI) labelNames(r *http.Request) (interface{}, []error, *api.ApiError) {
 	ctx := r.Context()
 
-	start, err := parseTimeParam(r, "start", minTime)
+	// If start and end time not specified, we get the last 2h window.
+	now := time.Now()
+	start, err := parseTimeParam(r, "start", now.Add(-2*time.Hour))
 	if err != nil {
 		return nil, nil, &api.ApiError{Typ: api.ErrorBadData, Err: err}
 	}
-	end, err := parseTimeParam(r, "end", maxTime)
+	end, err := parseTimeParam(r, "end", now)
 	if err != nil {
 		return nil, nil, &api.ApiError{Typ: api.ErrorBadData, Err: err}
 	}