1  // Copyright 2015 The Prometheus Authors
 2  // Licensed under the Apache License, Version 2.0 (the "License");
 3  // you may not use this file except in compliance with the License.
 4  // You may obtain a copy of the License at
 5  //
 6  // http://www.apache.org/licenses/LICENSE-2.0
 7  //
 8  // Unless required by applicable law or agreed to in writing, software
 9  // distributed under the License is distributed on an "AS IS" BASIS,
10  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
11  // See the License for the specific language governing permissions and
12  // limitations under the License.
13  
14  package expfmt
15  
16  import (
17  	"fmt"
18  	"io"
19  	"net/http"
20  
21  	"github.com/golang/protobuf/proto"
22  	"github.com/matttproud/golang_protobuf_extensions/pbutil"
23  	"github.com/prometheus/common/internal/bitbucket.org/ww/goautoneg"
24  
25  	dto "github.com/prometheus/client_model/go"
26  )
27  
28  // Encoder types encode metric families into an underlying wire protocol.
29  type Encoder interface {
30  	Encode(*dto.MetricFamily) error
31  }
32  
33  type encoder func(*dto.MetricFamily) error
34  
35  func (e encoder) Encode(v *dto.MetricFamily) error {
36  	return e(v)
37  }
38  
39  // Negotiate returns the Content-Type based on the given Accept header.
40  // If no appropriate accepted type is found, FmtText is returned.
41  func Negotiate(h http.Header) Format {
42  	for _, ac := range goautoneg.ParseAccept(h.Get(hdrAccept)) {
43  		// Check for protocol buffer
44  		if ac.Type+"/"+ac.SubType == ProtoType && ac.Params["proto"] == ProtoProtocol {
45  			switch ac.Params["encoding"] {
46  			case "delimited":
47  				return FmtProtoDelim
48  			case "text":
49  				return FmtProtoText
50  			case "compact-text":
51  				return FmtProtoCompact
52  			}
53  		}
54  		// Check for text format.
55  		ver := ac.Params["version"]
56  		if ac.Type == "text" && ac.SubType == "plain" && (ver == TextVersion || ver == "") {
57  			return FmtText
58  		}
59  	}
60  	return FmtText
61  }
62  
63  // NewEncoder returns a new encoder based on content type negotiation.
64  func NewEncoder(w io.Writer, format Format) Encoder {
65  	switch format {
66  	case FmtProtoDelim:
67  		return encoder(func(v *dto.MetricFamily) error {
68  			_, err := pbutil.WriteDelimited(w, v)
69  			return err
70  		})
71  	case FmtProtoCompact:
72  		return encoder(func(v *dto.MetricFamily) error {
73  			_, err := fmt.Fprintln(w, v.String())
74  			return err
75  		})
76  	case FmtProtoText:
77  		return encoder(func(v *dto.MetricFamily) error {
78  			_, err := fmt.Fprintln(w, proto.MarshalTextString(v))
79  			return err
80  		})
81  	case FmtText:
82  		return encoder(func(v *dto.MetricFamily) error {
83  			_, err := MetricFamilyToText(w, v)
84  			return err
85  		})
86  	}
87  	panic("expfmt.NewEncoder: unknown format")
88  }