Add prometheus exporter

go.mod

@@ -9,6 +9,8 @@ require (
 	github.com/gorilla/websocket v1.4.1
 	github.com/pelletier/go-toml v1.6.0 // indirect
 	github.com/sdslabs/kiwi v1.0.0
+	github.com/prometheus/client_golang v0.9.3
+	github.com/prometheus/common v0.4.0
 	github.com/sirupsen/logrus v1.4.2
 	github.com/spf13/afero v1.2.2 // indirect
 	github.com/spf13/cast v1.3.1 // indirect

go.sum

@@ -213,6 +213,7 @@ github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZN
 github.com/prometheus/client_golang v0.9.1/go.mod h1:7SWBe2y4D6OKWSNQJUaRYU/AaXPKyh/dDVn+NZz0KFw=
 github.com/prometheus/client_golang v0.9.3 h1:9iH4JKXLzFbOAdtqv/a+j8aewx2Y8lAjAydhbaScPF8=
 github.com/prometheus/client_golang v0.9.3/go.mod h1:/TN21ttK/J9q6uSwhBd54HahCDft0ttaMvbicHlPoso=
+github.com/prometheus/client_golang v1.8.0 h1:zvJNkoCFAnYFNC24FV8nW4JdRJ3GIFcLbg65lL/JDcw=
 github.com/prometheus/client_model v0.0.0-20180712105110-5c3871d89910/go.mod h1:MbSGuTsp3dbXC40dX6PRTWyKYBIrTGTE9sqQNg2J8bo=
 github.com/prometheus/client_model v0.0.0-20190129233127-fd36f4220a90/go.mod h1:xMI15A0UPsDsEKsMN9yxemIoYk6Tm2C1GtYGdfGttqA=
 github.com/prometheus/client_model v0.0.0-20190812154241-14fe0d1b01d4 h1:gQz4mCbXsO+nc9n1hCxHcGA3Zx3Eo+UHZoInFGUIXNM=

pkg/exporter/prometheus/doc.go

@@ -0,0 +1,6 @@
+// Copyright (c) 2020 SDSLabs
+// Use of this source code is governed by an MIT license
+// details of which can be found in the LICENSE file.
+
+// Package prometheus implements the prometheus metrics exporter.
+package prometheus

pkg/exporter/prometheus/exporter.go

@@ -0,0 +1,157 @@
+// Copyright (c) 2020 SDSLabs
+// Use of this source code is governed by an MIT license
+// details of which can be found in the LICENSE file.
+
+package prometheus
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"github.com/prometheus/common/log"
+
+	"github.com/sdslabs/pinger/pkg/appcontext"
+	"github.com/sdslabs/pinger/pkg/checker"
+	"github.com/sdslabs/pinger/pkg/exporter"
+)
+
+const (
+	probeLatencyLabel = "probe_latency"
+	probeStatusLabel  = "probe_status"
+	exporterName      = "prometheus"
+)
+
+func init() {
+	exporter.Register(exporterName, func() exporter.Exporter { return new(Exporter) })
+}
+
+// Exporter for exporting metrics to prometheus db.
+type Exporter struct {
+	Metrics map[string]*prometheus.Desc
+	checks  []checker.Metric
+}
+
+// NewExporter creates an empty but not-nil `*Exporter`.
+func NewExporter() *Exporter {
+	metrics := make(map[string]*prometheus.Desc)
+
+	// Probe latency metrics descriptor.
+	metrics[probeLatencyLabel] = prometheus.NewDesc(
+		// Name of the metrics defined by the descriptor
+		probeLatencyLabel,
+		// Help message for the metrics
+		"Time in micro seconds which measures the latency of the probe defined by the controller",
+		// Metrics variable level dimensions
+		[]string{"check_name"},
+		// Metrics constant label dimensions.
+		nil,
+	)
+
+	// Status metrics descriptor.
+	//
+	// Value is 0.0 if the probe failed,
+	// -1.0 if it failed due to timeout and +1.0 if it succeeded.
+	metrics[probeStatusLabel] = prometheus.NewDesc(
+		probeStatusLabel,
+		"Status of the probe, value is 0.0 on probe failure, -1.0 on failure due to timeout and +1.0 on success",
+		[]string{"check_name"},
+		nil,
+	)
+
+	return &Exporter{
+		Metrics: metrics,
+		checks:  nil,
+	}
+}
+
+// Describe implements prometheus.Collector.
+func (e *Exporter) Describe(ch chan<- *prometheus.Desc) {
+	for _, desc := range e.Metrics {
+		ch <- desc
+	}
+}
+
+// Collect implements prometheus.Collector.
+func (e *Exporter) Collect(ch chan<- prometheus.Metric) {
+	log.Info("Starting to collect prometheus metrics.")
+
+	// Iterate over each check and send them to prometheus.
+	for _, check := range e.checks {
+		latencyMetric := prometheus.MustNewConstMetric(
+			e.Metrics[probeLatencyLabel],
+			prometheus.GaugeValue,
+			float64(check.GetDuration()/1e3),
+
+			// variable labels for the metric.
+			check.GetCheckName(),
+		)
+		ch <- prometheus.NewMetricWithTimestamp(check.GetStartTime(), latencyMetric)
+
+		var statusVal float64 = 1.0
+		if check.IsTimeout() {
+			statusVal = -1.0
+		} else if !check.IsSuccessful() {
+			statusVal = 0.0
+		}
+		statusMetric := prometheus.MustNewConstMetric(
+			e.Metrics[probeStatusLabel],
+			prometheus.GaugeValue,
+			statusVal,
+
+			check.GetCheckName(),
+		)
+		ch <- prometheus.NewMetricWithTimestamp(check.GetStartTime(), statusMetric)
+	}
+}
+
+// Provision sets e's configuration.
+func (e *Exporter) Provision(ctx *appcontext.Context, provider exporter.Provider) error {
+	exporter := NewExporter()
+	prometheus.MustRegister(exporter)
+
+	httpServer := http.Server{
+		Addr: fmt.Sprintf(":%d", provider.GetPort()),
+	}
+	defer httpServer.Close() //nolint:errcheck
+
+	http.Handle("/metrics", promhttp.Handler())
+	log.Infoln("Beginning to serve prometheus metrics on port", provider.GetPort())
+
+	if err := httpServer.ListenAndServe(); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Export exports the metrics to the exporter.
+func (e *Exporter) Export(_ context.Context, metrics []checker.Metric) error {
+	ch1 := make(chan<- *prometheus.Desc)
+	e.Describe(ch1)
+
+	e.checks = metrics
+	ch2 := make(chan<- prometheus.Metric)
+	e.Collect(ch2)
+
+	return nil
+}
+
+// GetMetrics get the metrics of the given checks.
+func (e *Exporter) GetMetrics(
+	ctx context.Context,
+	time time.Duration,
+	checkIDs ...string,
+) (map[string][]checker.Metric, error) {
+	if len(checkIDs) == 0 {
+		return nil, nil
+	}
+
+	return nil, nil
+}
+
+// Interface guard.
+var _ exporter.Exporter = (*Exporter)(nil)