Support rounding big decimal metric values.

This temporarily fixes the API error: undefined method `new' for BigDecimal:Class.

main.go

@@ -18,12 +18,14 @@ import (
 )
 
 var (
-	prometheusURL    = flag.String("prom", "http://localhost:9090", "URL of Prometheus server")
-	statusPageAPIKey = flag.String("apikey", "", "Statuspage API key")
-	statusPageID     = flag.String("pageid", "", "Statuspage page ID")
-	queryConfigFile  = flag.String("config", "queries.yaml", "Query config file")
-	metricInterval   = flag.Duration("interval", 30*time.Second, "Metric push interval")
-	backfillDuration = flag.String("backfill", "", "Backfill the data points in, for example, 5d")
+	prometheusURL       = flag.String("prom", "http://localhost:9090", "URL of Prometheus server")
+	statusPageAPIKey    = flag.String("apikey", "", "Statuspage API key")
+	statusPageID        = flag.String("pageid", "", "Statuspage page ID")
+	queryConfigFile     = flag.String("config", "queries.yaml", "Query config file")
+	metricInterval      = flag.Duration("interval", 30*time.Second, "Metric push interval")
+	metricValueRounding = flag.Uint("rounding", 6, "Round metric values to specific decimal places")
+	backfillDuration    = flag.String("backfill", "", "Backfill the data points in, for example, 5d")
+	logLevel            = flag.String("log-level", "info", "Log level accepted by Logrus, for example, \"error\", \"warn\", \"info\", \"debug\", ...")
 
 	httpClient = &http.Client{
 		Timeout: 30 * time.Second,
@@ -34,6 +36,11 @@ var (
 
 func main() {
 	flag.Parse()
+	if lvl, err := log.ParseLevel(*logLevel); err != nil {
+		log.Fatal(err)
+	} else {
+		log.SetLevel(lvl)
+	}
 
 	qcd, err := ioutil.ReadFile(*queryConfigFile)
 	if err != nil {
@@ -66,7 +73,7 @@ func main() {
 func queryAndPush(backfill *time.Duration) {
 	log.Infof("Started to query and pushing metrics")
 
-	metrics := queryPrometheus(backfill)
+	metrics := queryPrometheus(backfill, *metricValueRounding)
 	chunkedMetrics := chunkMetrics(metrics)
 
 	for _, m := range chunkedMetrics {

metrics.go

@@ -1,8 +1,12 @@
 package main
 
+import (
+	"encoding/json"
+)
+
 type statuspageMetricPoint struct {
-	Timestamp int64   `json:"timestamp"`
-	Value     float64 `json:"value"`
+	Timestamp int64       `json:"timestamp"`
+	Value     json.Number `json:"value"`
 }
 
 type statuspageMetrics map[string][]statuspageMetricPoint

prometheus.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"math"
 	"time"
@@ -13,7 +14,7 @@ import (
 	"github.com/prometheus/common/model"
 )
 
-func queryPrometheus(backfill *time.Duration) statuspageMetrics {
+func queryPrometheus(backfill *time.Duration, decimal uint) statuspageMetrics {
 	client, err := api.NewClient(api.Config{Address: *prometheusURL})
 	if err != nil {
 		log.Fatalf("Couldn't create Prometheus client: %s", err)
@@ -34,9 +35,9 @@ func queryPrometheus(backfill *time.Duration) statuspageMetrics {
 		)
 
 		if backfill == nil {
-			metricPoints, warnings, err = queryInstant(api, query, ctxlog)
+			metricPoints, warnings, err = queryInstant(api, query, decimal, ctxlog)
 		} else {
-			metricPoints, warnings, err = queryRange(api, query, backfill, ctxlog)
+			metricPoints, warnings, err = queryRange(api, query, decimal, backfill, ctxlog)
 		}
 
 		for _, w := range warnings {
@@ -54,7 +55,7 @@ func queryPrometheus(backfill *time.Duration) statuspageMetrics {
 	return metrics
 }
 
-func queryInstant(api prometheus.API, query string, logger *log.Entry) ([]statuspageMetricPoint, prometheus.Warnings, error) {
+func queryInstant(api prometheus.API, query string, decimal uint, logger *log.Entry) ([]statuspageMetricPoint, prometheus.Warnings, error) {
 	now := time.Now()
 	response, warnings, err := api.Query(context.Background(), query, now)
 
@@ -81,12 +82,12 @@ func queryInstant(api prometheus.API, query string, logger *log.Entry) ([]status
 	return []statuspageMetricPoint{
 		{
 			Timestamp: int64(vec[0].Timestamp / 1000),
-			Value:     float64(value),
+			Value:     json.Number(fmt.Sprintf("%.*f", decimal, value)),
 		},
 	}, warnings, nil
 }
 
-func queryRange(api prometheus.API, query string, backfill *time.Duration, logger *log.Entry) ([]statuspageMetricPoint, prometheus.Warnings, error) {
+func queryRange(api prometheus.API, query string, decimal uint, backfill *time.Duration, logger *log.Entry) ([]statuspageMetricPoint, prometheus.Warnings, error) {
 	now := time.Now()
 	start := now.Add(-*backfill)
 	var (
@@ -132,7 +133,7 @@ func queryRange(api prometheus.API, query string, backfill *time.Duration, logge
 			}
 			metricPoints = append(metricPoints, statuspageMetricPoint{
 				Timestamp: int64(v.Timestamp / 1000),
-				Value:     float64(v.Value),
+				Value:     json.Number(fmt.Sprintf("%.*f", decimal, v.Value)),
 			})
 		}