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prometheus.go
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prometheus.go
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//
// Copyright (C) 2019-2021 vdaas.org vald team <vald@vdaas.org>
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// Package prometheus provides a prometheus exporter.
package prometheus
import (
"context"
"net/http"
"sync"
"contrib.go.opencensus.io/exporter/prometheus"
"github.com/vdaas/vald/internal/observability/exporter"
)
var (
instance *exp
once sync.Once
)
type prometheusOptions struct {
endpoint string
options *prometheus.Options
}
type Prometheus interface {
exporter.Exporter
NewHTTPHandler() http.Handler
}
type exp struct {
exporter *prometheus.Exporter
options prometheusOptions
}
func New(opts ...PrometheusOption) (Prometheus, error) {
po := new(prometheusOptions)
po.options = new(prometheus.Options)
for _, opt := range append(prometheusDefaultOpts, opts...) {
err := opt(po)
if err != nil {
return nil, err
}
}
ex, err := prometheus.NewExporter(*po.options)
if err != nil {
return nil, err
}
e := exp{
exporter: ex,
options: *po,
}
once.Do(func() {
instance = &e
})
return &e, nil
}
func (e *exp) Start(ctx context.Context) error {
return nil
}
func (e *exp) Stop(ctx context.Context) {
}
func (e *exp) NewHTTPHandler() http.Handler {
mux := http.NewServeMux()
mux.Handle(e.options.endpoint, e.exporter)
return mux
}
func Exporter() (Prometheus, error) {
if instance != nil {
return instance, nil
}
return New()
}