Improve resolution of gcp metrics, enable $__interval $__rate_interval

Author: BSick7

gcp/cloudmonitoring/time_series_fetcher.go

@@ -2,27 +2,35 @@ package cloudmonitoring
 
 import (
 	"context"
-	"github.com/nullstone-io/deployment-sdk/prometheus"
-	"github.com/nullstone-io/deployment-sdk/workspace"
 	"sync"
 	"time"
+
+	"github.com/nullstone-io/deployment-sdk/prometheus"
+	"github.com/nullstone-io/deployment-sdk/workspace"
 )
 
 // TimeSeriesFetcherFromMapping creates an interface for fetching the metrics in a background goroutine
-// This fetcher utilizes the QueryClient to fetch metrics using MQL
+// This fetcher uses the QueryClient to fetch metrics using MQL
 func TimeSeriesFetcherFromMapping(mapping MetricMapping, options workspace.MetricsGetterOptions, series *workspace.MetricSeries) *TimeSeriesFetcher {
-	interval := CalcPeriod(options.StartTime, options.EndTime)
-	steps := int(interval / time.Second)
-	qo := prometheus.QueryOptions{
-		Start: options.StartTime,
-		End:   options.EndTime,
-		Step:  steps,
+	end := time.Now()
+	start := end.Add(-time.Hour)
+	if options.StartTime != nil {
+		start = *options.StartTime
 	}
-	if qo.Start == nil {
-		start := time.Now().Add(-time.Hour)
-		qo.Start = &start
+	if options.EndTime != nil {
+		end = *options.EndTime
 	}
 
+	qo := prometheus.QueryOptions{
+		Start: start,
+		End:   end,
+		IntervalCalculator: prometheus.NewIntervalCalculator(prometheus.IntervalOptions{
+			Start:          start,
+			End:            end,
+			PanelWidth:     options.PanelWidth,
+			ScrapeInterval: options.ScrapeInterval,
+		}),
+	}
 	return &TimeSeriesFetcher{
 		Query:   mapping.Query,
 		Options: qo,

prometheus/interval_calculator.go

@@ -0,0 +1,159 @@
+package prometheus
+
+import (
+	"fmt"
+	"math"
+	"regexp"
+	"time"
+)
+
+const (
+	DefaultPanelWidth     = 1200
+	DefaultScrapeInterval = 60
+)
+
+type IntervalOptions struct {
+	Start time.Time
+	End   time.Time
+	// PanelWidth refers to the width of the panel, measured in pixels
+	// This is used to
+	PanelWidth int
+	// ScrapeInterval refers to the interval at which the metric is scraped, measured in number of seconds
+	ScrapeInterval int
+	// MaxDataPoints refers to the maximum number of data points to plot (if 0, use PanelWidth)
+	MaxDataPoints int
+	// MinInterval refers to the minimum interval to use (if 0, use ScrapeInterval)
+	MinInterval int
+}
+
+// IntervalCalculator handles interval calculations and query substitution
+type IntervalCalculator struct {
+	interval     int // calculated $__interval in seconds
+	rateInterval int // calculated $__rate_interval in seconds
+}
+
+// NewIntervalCalculator creates a new calculator with the given parameters
+func NewIntervalCalculator(opts IntervalOptions) *IntervalCalculator {
+	calc := &IntervalCalculator{}
+	calc.calculate(opts)
+	return calc
+}
+
+// calculate computes $__interval and $__rate_interval
+func (c *IntervalCalculator) calculate(opts IntervalOptions) {
+	// Set defaults
+	width := opts.PanelWidth
+	if width == 0 {
+		width = DefaultPanelWidth
+	}
+
+	scrapeInterval := opts.ScrapeInterval
+	if scrapeInterval == 0 {
+		scrapeInterval = DefaultScrapeInterval
+	}
+
+	maxDataPoints := opts.MaxDataPoints
+	if maxDataPoints == 0 {
+		maxDataPoints = width
+	}
+
+	minInterval := opts.MinInterval
+	if minInterval == 0 {
+		minInterval = scrapeInterval
+	}
+
+	// Calculate range in seconds
+	rangeSeconds := int(opts.End.Sub(opts.Start).Seconds())
+
+	// Calculate $__interval (basic interval)
+	// interval = range / desired_points
+	interval := rangeSeconds / maxDataPoints
+
+	// Ensure minimum interval
+	if interval < minInterval {
+		interval = minInterval
+	}
+
+	c.interval = interval
+
+	// Calculate $__rate_interval
+	// rate_interval = max(interval + scrape_interval, 4 * scrape_interval)
+	optionA := interval + scrapeInterval
+	optionB := 4 * scrapeInterval
+
+	c.rateInterval = int(math.Max(float64(optionA), float64(optionB)))
+}
+
+// GetInterval returns the calculated $__interval in seconds
+func (c *IntervalCalculator) GetInterval() int {
+	return c.interval
+}
+
+// GetRateInterval returns the calculated $__rate_interval in seconds
+func (c *IntervalCalculator) GetRateInterval() int {
+	return c.rateInterval
+}
+
+// GetIntervalString returns $__interval as a duration string (e.g., "60s")
+func (c *IntervalCalculator) GetIntervalString() string {
+	return formatDuration(c.interval)
+}
+
+// GetRateIntervalString returns $__rate_interval as a duration string
+func (c *IntervalCalculator) GetRateIntervalString() string {
+	return formatDuration(c.rateInterval)
+}
+
+// SubstituteVariables replaces ${__interval} and ${__rate_interval} in the query
+func (c *IntervalCalculator) SubstituteVariables(query string) string {
+	// Replace ${__interval} and $__interval
+	query = replaceVariable(query, "__interval", c.GetIntervalString())
+
+	// Replace ${__rate_interval} and $__rate_interval
+	query = replaceVariable(query, "__rate_interval", c.GetRateIntervalString())
+
+	return query
+}
+
+// replaceVariable replaces both ${var} and $var patterns
+func replaceVariable(query, varName, value string) string {
+	// Pattern 1: ${__variable}
+	pattern1 := regexp.MustCompile(`\$\{` + varName + `\}`)
+	query = pattern1.ReplaceAllString(query, value)
+
+	// Pattern 2: $__variable (without braces)
+	pattern2 := regexp.MustCompile(`\$` + varName + `\b`)
+	query = pattern2.ReplaceAllString(query, value)
+
+	return query
+}
+
+// formatDuration converts seconds to Prometheus duration string
+func formatDuration(seconds int) string {
+	if seconds < 60 {
+		return fmt.Sprintf("%ds", seconds)
+	} else if seconds < 3600 {
+		minutes := seconds / 60
+		remainder := seconds % 60
+		if remainder == 0 {
+			return fmt.Sprintf("%dm", minutes)
+		}
+		return fmt.Sprintf("%dm%ds", minutes, remainder)
+	} else if seconds < 86400 {
+		hours := seconds / 3600
+		remainder := seconds % 3600
+		if remainder == 0 {
+			return fmt.Sprintf("%dh", hours)
+		}
+		minutes := remainder / 60
+		return fmt.Sprintf("%dh%dm", hours, minutes)
+	} else {
+		days := seconds / 86400
+		remainder := seconds % 86400
+		if remainder == 0 {
+			return fmt.Sprintf("%dd", days)
+		}
+		hours := remainder / 3600
+		return fmt.Sprintf("%dd%dh", days, hours)
+	}
+}

prometheus/query_client.go

@@ -21,24 +21,21 @@ type QueryClient struct {
 }
 
 type QueryOptions struct {
-	Start *time.Time
-	End   *time.Time
-	// Step refers to the resolution of datapoints, measured in number of seconds
-	Step int
+	Start              time.Time
+	End                time.Time
+	IntervalCalculator *IntervalCalculator
 }
 
 func (c *QueryClient) Query(ctx context.Context, query string, options QueryOptions) (*QueryResponse, error) {
+	finalQuery := options.IntervalCalculator.SubstituteVariables(query)
+
 	u := *c.BaseUrl
 	u.Path = path.Join(c.BaseUrl.Path, "api/v1/query_range")
 	params := url.Values{}
-	params.Add("query", query)
-	if options.Start != nil {
-		params.Add("start", options.Start.Format(time.RFC3339))
-	}
-	if options.End != nil {
-		params.Add("end", options.End.Format(time.RFC3339))
-	}
-	params.Add("step", fmt.Sprint(options.Step))
+	params.Add("query", finalQuery)
+	params.Add("start", options.Start.Format(time.RFC3339))
+	params.Add("end", options.End.Format(time.RFC3339))
+	params.Add("step", fmt.Sprint(options.IntervalCalculator.GetInterval()))
 	u.RawQuery = params.Encode()
 
 	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u.String(), nil)

workspace/metrics_getter.go

@@ -15,6 +15,13 @@ type MetricsGetterOptions struct {
 	StartTime *time.Time
 	EndTime   *time.Time
 
+	// PanelWidth refers to the width of the panel, measured in pixels
+	// This is used to calculate the number of data points to plot
+	PanelWidth int
+	// ScrapeInterval is how often metrics are collected from targets, in seconds.
+	// Determines the minimum window size for rate() to have enough data points (default: 60).
+	ScrapeInterval int
+
 	Metrics []string
 }