Send tracing spans to Prometheus

api/server/prom_zip_collector.go

@@ -0,0 +1,80 @@
+package server
+
+import (
+	"github.com/fnproject/fn/api/agent"
+	"github.com/openzipkin/zipkin-go-opentracing"
+	"github.com/openzipkin/zipkin-go-opentracing/thrift/gen-go/zipkincore"
+	"github.com/prometheus/client_golang/prometheus"
+	"strings"
+)
+
+// Each span name is published as a separate Histogram metric
+// Using metric names of the form fn_span_<span-name>_duration_seconds
+var histogramVecMap = make(map[string]*prometheus.HistogramVec)
+
+// Return the HistogramVec corresponding to the specified spanName.
+// If a HistogramVec does not already exist for specified spanName then one is created and configured with the specified labels
+// otherwise the labels parameter is ignored.
+func getHistogramVecForSpanName(spanName string, labels []string) *prometheus.HistogramVec {
+	thisHistogramVec, found := histogramVecMap[spanName]
+	if !found {
+		thisHistogramVec = prometheus.NewHistogramVec(
+			prometheus.HistogramOpts{
+				Name: "fn_span_" + spanName + "_duration_seconds",
+				Help: "Span " + spanName + " duration, by span name",
+			},
+			labels,
+		)
+		histogramVecMap[spanName] = thisHistogramVec
+		prometheus.MustRegister(thisHistogramVec)
+	}
+	return thisHistogramVec
+}
+
+// PrometheusCollector is a custom Collector
+// which sends ZipKin traces to Prometheus
+type PrometheusCollector struct {
+	a agent.Agent
+}
+
+// NewPrometheusCollector returns a new PrometheusCollector
+func NewPrometheusCollector(agent agent.Agent) (zipkintracer.Collector, error) {
+	pc := &PrometheusCollector{}
+	pc.a = agent
+	return pc, nil
+}
+
+// PrometheusCollector implements Collector.
+func (pc PrometheusCollector) Collect(span *zipkincore.Span) error {
+
+	// extract any label values from the span
+	labelKeys, labelValueMap := getLabels(span)
+
+	getHistogramVecForSpanName(span.GetName(), labelKeys).With(labelValueMap).Observe(float64(span.GetDuration()) / 1000000)
+
+	return nil
+}
+
+// extract from the specified span the key/value pairs that we want to add as labels to the Prometheus metric for this span
+// returns an array of keys, and a map of key-value pairs
+func getLabels(span *zipkincore.Span) ([]string, map[string]string) {
+
+	var keys []string
+	labelMap := make(map[string]string)
+
+	// extract any tags whose key starts with "fn" from the span
+	binaryAnnotations := span.GetBinaryAnnotations()
+	for _, thisBinaryAnnotation := range binaryAnnotations {
+		key := thisBinaryAnnotation.GetKey()
+		if thisBinaryAnnotation.GetAnnotationType() == zipkincore.AnnotationType_STRING && strings.HasPrefix(key, "fn") {
+			keys = append(keys, key)
+			value := string(thisBinaryAnnotation.GetValue()[:])
+			labelMap[key] = value
+		}
+	}
+
+	return keys, labelMap
+}
+
+// PrometheusCollector implements Collector.
+func (PrometheusCollector) Close() error { return nil }