metrics.go

package corednslmetric
import (
	"fmt"
	"log"
	"net"
	"net/http"
	"bitbucket.org/levenlabs/llib/lmetric"
	"github.com/coredns/coredns/plugin/metrics"
	"github.com/gogo/protobuf/proto"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promhttp"
	dto "github.com/prometheus/client_model/go"
)
// Metrics wraps a prometheus.Metrics to expose lmetric metrics as well
type Metrics struct {
	*metrics.Metrics
	ln net.Listener
}
// Name implements the Handler interface.
func (m *Metrics) Name() string { return "lmetric" }
// Listen sets up a listener
func (m *Metrics) Listen() error {
	ln, err := net.Listen("tcp", m.Metrics.Addr)
	if err != nil {
		log.Printf("[ERROR] Failed to start lmetric listener: %s", err)
		return err
	}
	m.ln = ln
	gatherers := prometheus.Gatherers{
		lmetric.NewPrometheus(lmetric.TagMetrics()),
		lmetric.NewPrometheus(lmetric.DefaultMetrics),
		// since coredns has a vendor folder, the registery has different path and
		// so none of the imports match up so we have to do this hacky thing
		prometheus.GathererFunc(func() ([]*dto.MetricFamily, error) {
			fs, err := m.Metrics.Reg.Gather()
			if err != nil {
				return nil, err
			}
			nfs := make([]*dto.MetricFamily, len(fs))
			for i := range fs {
				b, err := proto.Marshal(fs[i])
				if err != nil {
					return nil, fmt.Errorf("error marshalling coredns-style MetricFamily: %v", err)
				}
				nfs[i] = new(dto.MetricFamily)
				if err = proto.Unmarshal(b, nfs[i]); err != nil {
					return nil, fmt.Errorf("error unmarshalling coredns-style MetricFamily: %v", err)
				}
			}
			return nfs, nil
		}),
	}
	mux := http.NewServeMux()
	mux.Handle("/metrics", promhttp.HandlerFor(gatherers, promhttp.HandlerOpts{
		// we do this ourselves, and all gzip libraries are too stupid to
		// realize when something is being double compressed
		DisableCompression: true,
	}))
	go func() {
		http.Serve(ln, mux)
	}()
	return nil
}
// Close closes the listener.
func (m *Metrics) Close() error {
	if m.ln != nil {
		return m.ln.Close()
	}
	return nil
}