implement suggestion

Signed-off-by: Harkishen-Singh <harkishensingh@hotmail.com>

pkg/rollup/decider.go

@@ -21,8 +21,8 @@ const (
 )
 
 type rollupInfo struct {
-	schemaName string
-	resolution time.Duration
+	schemaName      string
+	refreshInterval time.Duration
 }
 
 type Decider struct {
@@ -34,7 +34,7 @@ type Decider struct {
 	downsamplingEnabled bool
 
 	supportedMetrics map[string]struct{}
-	rollups          []rollupInfo // {schemaName, resolution} in ascending order of interval. Lesser the interval, more the granularity.
+	rollups          []rollupInfo // {schemaName, refreshInterval} in ascending order of interval. Lesser the interval, more the granularity.
 }
 
 func NewDecider(ctx context.Context, conn pgxconn.PgxConn, scrapeInterval time.Duration) (*Decider, error) {
@@ -50,8 +50,8 @@ func NewDecider(ctx context.Context, conn pgxconn.PgxConn, scrapeInterval time.D
 }
 
 // Decide returns the schema name of the rollups that should be used for querying.
-// The returned schema represents a downsampled resolution that should be an optimal
-// resolution for querying.
+// The returned schema represents a downsampled Prometheus data that should provide optimal
+// granularity for querying.
 //
 // If no rollups exists or if downsampling is disabled, DefaultSchema (i.e., "prom_data") is returned.
 func (h *Decider) Decide(minTs, maxTs int64) string {
@@ -61,8 +61,8 @@ func (h *Decider) Decide(minTs, maxTs int64) string {
 	if !h.downsamplingEnabled || len(h.rollups) == 0 {
 		return DefaultSchema
 	}
-	estimateSamples := func(resolution time.Duration) int64 {
-		return int64(float64(maxTs-minTs) / resolution.Seconds())
+	estimateSamples := func(interval time.Duration) int64 {
+		return int64(float64(maxTs-minTs) / interval.Seconds())
 	}
 
 	numRawSamples := estimateSamples(h.scrapeInterval)
@@ -71,7 +71,7 @@ func (h *Decider) Decide(minTs, maxTs int64) string {
 	}
 
 	for _, info := range h.rollups {
-		samples := estimateSamples(info.resolution)
+		samples := estimateSamples(info.refreshInterval) // Interval between 2 samples.
 		if samples < upperLimit {
 			// h.rollups is sorted by interval. So, the first rollup that is below upper limit is our answer.
 			// This is because it gives the maximum granularity while being in acceptable limits.
@@ -100,14 +100,14 @@ func (h *Decider) Refresh() error {
 		return fmt.Errorf("metric-type: %w", err)
 	}
 	if err := h.refreshRollup(); err != nil {
-		return fmt.Errorf("rollup resolutions: %w", err)
+		return fmt.Errorf("rollup: %w", err)
 	}
 	return nil
 }
 
 func (h *Decider) runRefreshRoutine(refreshInterval time.Duration) error {
 	if err := h.Refresh(); err != nil {
-		return fmt.Errorf("refreshing rollup resolution: %w", err)
+		return fmt.Errorf("refresh: %w", err)
 	}
 	go func() {
 		t := time.NewTicker(refreshInterval)
@@ -119,7 +119,7 @@ func (h *Decider) runRefreshRoutine(refreshInterval time.Duration) error {
 			case <-t.C:
 			}
 			if err := h.Refresh(); err != nil {
-				log.Error("msg", "error refreshing rollup resolution", "error", err.Error())
+				log.Error("msg", "error refreshing rollups", "error", err.Error())
 			}
 		}
 	}()
@@ -159,19 +159,19 @@ func (h *Decider) refreshSupportedMetrics() error {
 func (h *Decider) refreshRollup() error {
 	rows, err := h.conn.Query(h.ctx, "SELECT schema_name, resolution FROM _prom_catalog.rollup ORDER BY resolution ASC")
 	if err != nil {
-		return fmt.Errorf("fetching rollup resolutions: %w", err)
+		return fmt.Errorf("fetching rollup: %w", err)
 	}
 	defer rows.Close()
 	h.rollups = []rollupInfo{}
 	for rows.Next() {
 		var (
-			schemaName string
-			resolution time.Duration
+			schemaName      string
+			refreshInterval time.Duration
 		)
-		if err = rows.Scan(&schemaName, &resolution); err != nil {
+		if err = rows.Scan(&schemaName, &refreshInterval); err != nil {
 			return fmt.Errorf("error scanning rows: %w", err)
 		}
-		h.rollups = append(h.rollups, rollupInfo{schemaName: schemaName, resolution: resolution})
+		h.rollups = append(h.rollups, rollupInfo{schemaName: schemaName, refreshInterval: refreshInterval})
 	}
 	return nil
 }