1 files changed, 156 insertions, 0 deletions
diff --git a/service/metrics/rpc.go b/service/metrics/rpc.go
new file mode 100644
index 00000000..30ad6c62
--- /dev/null
+++ b/service/metrics/rpc.go
@@ -0,0 +1,156 @@
+package metrics
+
+import (
+	"fmt"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+type rpcServer struct{ svc *Service }
+
+// Metric represent single metric produced by the application.
+type Metric struct {
+	// Collector name.
+	Name string
+
+	// Collector value.
+	Value float64
+
+	// Labels associated with metric. Only for vector metrics.
+	Labels []string
+}
+
+// Add new metric to the designated collector.
+func (rpc *rpcServer) Add(m *Metric, ok *bool) error {
+	c := rpc.svc.Collector(m.Name)
+	if c == nil {
+		return fmt.Errorf("undefined collector `%s`", m.Name)
+	}
+
+	switch c.(type) {
+	case prometheus.Gauge:
+		c.(prometheus.Gauge).Add(m.Value)
+
+	case *prometheus.GaugeVec:
+		if len(m.Labels) == 0 {
+			return fmt.Errorf("required labels for collector `%s`", m.Name)
+		}
+
+		c.(*prometheus.GaugeVec).WithLabelValues(m.Labels...).Add(m.Value)
+
+	case prometheus.Counter:
+		c.(prometheus.Counter).Add(m.Value)
+
+	case *prometheus.CounterVec:
+		if len(m.Labels) == 0 {
+			return fmt.Errorf("required labels for collector `%s`", m.Name)
+		}
+
+		c.(*prometheus.CounterVec).WithLabelValues(m.Labels...).Add(m.Value)
+
+	case prometheus.Summary:
+		c.(prometheus.Counter).Add(m.Value)
+
+	case *prometheus.SummaryVec:
+		if len(m.Labels) == 0 {
+			return fmt.Errorf("required labels for collector `%s`", m.Name)
+		}
+
+		c.(*prometheus.SummaryVec).WithLabelValues(m.Labels...).Observe(m.Value)
+
+	case prometheus.Histogram:
+		c.(prometheus.Histogram).Observe(m.Value)
+
+	case *prometheus.HistogramVec:
+		if len(m.Labels) == 0 {
+			return fmt.Errorf("required labels for collector `%s`", m.Name)
+		}
+
+		c.(*prometheus.HistogramVec).WithLabelValues(m.Labels...).Observe(m.Value)
+	}
+
+	*ok = true
+	return nil
+}
+
+// Sub subtract the value from the specific metric (gauge only).
+func (rpc *rpcServer) Sub(m *Metric, ok *bool) error {
+	c := rpc.svc.Collector(m.Name)
+	if c == nil {
+		return fmt.Errorf("undefined collector `%s`", m.Name)
+	}
+
+	switch c.(type) {
+	case prometheus.Gauge:
+		c.(prometheus.Gauge).Sub(m.Value)
+
+	case *prometheus.GaugeVec:
+		if len(m.Labels) == 0 {
+			return fmt.Errorf("required labels for collector `%s`", m.Name)
+		}
+
+		c.(*prometheus.GaugeVec).WithLabelValues(m.Labels...).Sub(m.Value)
+	default:
+		return fmt.Errorf("collector `%s` does not support method `Sub`", m.Name)
+	}
+
+	*ok = true
+	return nil
+}
+
+// Observe the value (histogram and summary only).
+func (rpc *rpcServer) Observe(m *Metric, ok *bool) error {
+	c := rpc.svc.Collector(m.Name)
+	if c == nil {
+		return fmt.Errorf("undefined collector `%s`", m.Name)
+	}
+
+	switch c.(type) {
+	case *prometheus.SummaryVec:
+		if len(m.Labels) == 0 {
+			return fmt.Errorf("required labels for collector `%s`", m.Name)
+		}
+
+		c.(*prometheus.SummaryVec).WithLabelValues(m.Labels...).Observe(m.Value)
+
+	case prometheus.Histogram:
+		c.(prometheus.Histogram).Observe(m.Value)
+
+	case *prometheus.HistogramVec:
+		if len(m.Labels) == 0 {
+			return fmt.Errorf("required labels for collector `%s`", m.Name)
+		}
+
+		c.(*prometheus.HistogramVec).WithLabelValues(m.Labels...).Observe(m.Value)
+	default:
+		return fmt.Errorf("collector `%s` does not support method `Observe`", m.Name)
+	}
+
+	*ok = true
+	return nil
+}
+
+// Set the metric value (only for gaude).
+func (rpc *rpcServer) Set(m *Metric, ok *bool) error {
+	c := rpc.svc.Collector(m.Name)
+	if c == nil {
+		return fmt.Errorf("undefined collector `%s`", m.Name)
+	}
+
+	switch c.(type) {
+	case prometheus.Gauge:
+		c.(prometheus.Gauge).Set(m.Value)
+
+	case *prometheus.GaugeVec:
+		if len(m.Labels) == 0 {
+			return fmt.Errorf("required labels for collector `%s`", m.Name)
+		}
+
+		c.(*prometheus.GaugeVec).WithLabelValues(m.Labels...).Set(m.Value)
+
+	default:
+		return fmt.Errorf("collector `%s` does not support method `Set`", m.Name)
+	}
+
+	*ok = true
+	return nil
+}