Add Datadob support

Author: rs

README.md

@@ -97,4 +97,11 @@ jplot --url http://:8080/debug/vars \
 
 ![](doc/memstats.png)
 
+### Datadog
+
+To graph metrics from Datadob, you have to pass a Datadog API and Application key to jplot as follow:
+
+```
+jplot --url datadog://<api_key>/<app_key> metrics…
+```
 

data/datadog.go

@@ -0,0 +1,97 @@
+package data
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/elgs/gojq"
+	"gopkg.in/zorkian/go-datadog-api.v2"
+)
+
+type datadogSource struct {
+	client *datadog.Client
+	specs  []Spec
+	c      chan res
+	done   chan struct{}
+
+	// state
+	lastQueryTime int64
+}
+
+// FromDatadog fetches data from Datadog service (http://datadog.com).
+func FromDatadog(apiKey, appKey string, specs []Spec, interval time.Duration, size int) *Points {
+	client := datadog.NewClient(apiKey, appKey)
+	s := &datadogSource{
+		client:        client,
+		specs:         specs,
+		c:             make(chan res),
+		done:          make(chan struct{}),
+		lastQueryTime: time.Now().Unix(),
+	}
+	go s.run(interval)
+	return &Points{
+		Size:   size,
+		Source: s,
+	}
+}
+
+func (s *datadogSource) run(interval time.Duration) {
+	t := time.NewTicker(interval)
+	defer t.Stop()
+	for {
+		select {
+		case <-t.C:
+			s.fetch()
+		case <-s.done:
+			close(s.c)
+			return
+		}
+	}
+}
+
+func (s *datadogSource) fetch() {
+	maxUpdateTimestamp := int64(s.lastQueryTime)
+	dataPoints := make(map[string]datadog.DataPoint, len(s.specs))
+	var err error
+	for _, spec := range s.specs {
+		for _, field := range spec.Fields {
+			query := s.formatQuery(field)
+			series, err := s.client.QueryMetrics(s.lastQueryTime, time.Now().Unix(), query)
+			if err != nil {
+				s.c <- res{err: err}
+				return
+			}
+			if len(series) == 0 {
+				s.c <- res{err: fmt.Errorf("no data for %s", field.Name)}
+				return
+			}
+			endTs := int64(series[0].GetEnd() / 1000)
+			if endTs > maxUpdateTimestamp {
+				maxUpdateTimestamp = endTs
+			}
+			// assume the last data point is the latest
+			dataPoints[field.ID] = series[0].Points[len(series[0].Points)-1]
+		}
+	}
+
+	jq := gojq.NewQuery(dataPoints)
+	s.c <- res{jq: jq, err: err}
+}
+
+func (s *datadogSource) formatQuery(field Field) string {
+	querySuffix := ""
+	if field.IsCounter {
+		querySuffix = ".as_count()"
+	}
+	return fmt.Sprintf("%s%s", field.Name, querySuffix)
+}
+
+func (s *datadogSource) Get() (*gojq.JQ, error) {
+	res := <-s.c
+	return res.jq, res.err
+}
+
+func (s *datadogSource) Close() error {
+	close(s.done)
+	return nil
+}

data/http.go

@@ -18,7 +18,7 @@ type res struct {
 	err error
 }
 
-// FromHTTP fetch data points from url every interval and keep size points.
+// FromHTTP fetches data points from url every interval and keep size points.
 func FromHTTP(url string, interval time.Duration, size int) *Points {
 	h := httpSource{
 		c:    make(chan res),

main.go

@@ -36,7 +36,15 @@ func main() {
 	}
 	var dp *data.Points
 	if *url != "" {
-		dp = data.FromHTTP(*url, *interval, *steps)
+		if strings.HasPrefix(*url, "datadog://") {
+			keys := strings.Split((*url)[10:], "/")
+			if len(keys) != 2 {
+				fatal("invalid datadog url, format is datadog://apiKey/appKey")
+			}
+			dp = data.FromDatadog(keys[0], keys[1], specs, *interval, *steps)
+		} else {
+			dp = data.FromHTTP(*url, *interval, *steps)
+		}
 	} else {
 		dp = data.FromStdin(*steps)
 	}