Merge pull request #22 from prometheus/feature/accept-header-discrimination

WIP — Protocol Buffer negotiation support in handler.

Makefile.TRAVIS

@@ -20,7 +20,10 @@ preparation:
 	ln -sf "$(PWD)" $(PROMETHEUS_TARGET)
 
 dependencies:
+	go get code.google.com/p/goprotobuf/proto
 	go get github.com/matttproud/gocheck
+	go get github.com/matttproud/golang_protobuf_extensions/ext
+	go get github.com/prometheus/client_model/go
 
 test: dependencies preparation
 	$(MAKE) test

extraction/discriminator.go

@@ -33,11 +33,10 @@ func ProcessorForRequestHeader(header http.Header) (Processor, error) {
 	}
 	switch mediatype {
 	case "application/vnd.google.protobuf":
-		// BUG(matt): Version?
 		if params["proto"] != "io.prometheus.client.MetricFamily" {
 			return nil, fmt.Errorf("Unrecognized Protocol Message %s", params["proto"])
 		}
-		if params["encoding"] != "varint record length-delimited" {
+		if params["encoding"] != "delimited" {
 			return nil, fmt.Errorf("Unsupported Encoding %s", params["encoding"])
 		}
 		return MetricFamilyProcessor, nil

extraction/discriminator_test.go

@@ -57,12 +57,12 @@ func testDiscriminatorHttpHeader(t test.Tester) {
 			err:    nil,
 		},
 		{
-			input:  map[string]string{"Content-Type": `application/vnd.google.protobuf; proto="io.prometheus.client.MetricFamily"; encoding="varint record length-delimited"`},
+			input:  map[string]string{"Content-Type": `application/vnd.google.protobuf; proto="io.prometheus.client.MetricFamily"; encoding="delimited"`},
 			output: MetricFamilyProcessor,
 			err:    nil,
 		},
 		{
-			input:  map[string]string{"Content-Type": `application/vnd.google.protobuf; proto="illegal"; encoding="varint record length-delimited"`},
+			input:  map[string]string{"Content-Type": `application/vnd.google.protobuf; proto="illegal"; encoding="delimited"`},
 			output: nil,
 			err:    fmt.Errorf("Unrecognized Protocol Message illegal"),
 		},

prometheus/constants.go

@@ -28,9 +28,11 @@ const (
 
 	// The content type and schema information set on telemetry data responses.
 	TelemetryContentType = `application/json; schema="prometheus/telemetry"; version=` + APIVersion
+	// The content type and schema information set on telemetry data responses.
+	DelimitedTelemetryContentType = `application/vnd.google.protobuf; proto="io.prometheus.client.MetricFamily"; encoding="delimited"`
 
 	// The customary web services endpoint on which telemetric data is exposed.
-	ExpositionResource = "/metrics.json"
+	ExpositionResource = "/metrics"
 
 	baseLabelsKey = "baseLabels"
 	docstringKey  = "docstring"

prometheus/counter.go

@@ -10,6 +10,10 @@ import (
 	"encoding/json"
 	"fmt"
 	"sync"
+
+	dto "github.com/prometheus/client_model/go"
+
+	"code.google.com/p/goprotobuf/proto"
 )
 
 // TODO(matt): Refactor to de-duplicate behaviors.
@@ -31,13 +35,13 @@ type counterVector struct {
 
 func NewCounter() Counter {
 	return &counter{
-		values: map[string]*counterVector{},
+		values: map[uint64]*counterVector{},
 	}
 }
 
 type counter struct {
 	mutex  sync.RWMutex
-	values map[string]*counterVector
+	values map[uint64]*counterVector
 }
 
 func (metric *counter) Set(labels map[string]string, value float64) float64 {
@@ -147,3 +151,31 @@ func (metric *counter) MarshalJSON() ([]byte, error) {
 		typeKey:  counterTypeValue,
 	})
 }
+
+func (metric *counter) dumpChildren(f *dto.MetricFamily) {
+	metric.mutex.RLock()
+	defer metric.mutex.RUnlock()
+
+	f.Type = dto.MetricType_COUNTER.Enum()
+
+	for _, child := range metric.values {
+		c := &dto.Counter{
+			Value: proto.Float64(child.Value),
+		}
+
+		m := &dto.Metric{
+			Counter: c,
+		}
+
+		for name, value := range child.Labels {
+			p := &dto.LabelPair{
+				Name:  proto.String(name),
+				Value: proto.String(value),
+			}
+
+			m.Label = append(m.Label, p)
+		}
+
+		f.Metric = append(f.Metric, m)
+	}
+}

prometheus/gauge.go

@@ -10,6 +10,10 @@ import (
 	"encoding/json"
 	"fmt"
 	"sync"
+
+	"code.google.com/p/goprotobuf/proto"
+
+	dto "github.com/prometheus/client_model/go"
 )
 
 // A gauge metric merely provides an instantaneous representation of a scalar
@@ -28,13 +32,13 @@ type gaugeVector struct {
 
 func NewGauge() Gauge {
 	return &gauge{
-		values: map[string]*gaugeVector{},
+		values: map[uint64]*gaugeVector{},
 	}
 }
 
 type gauge struct {
 	mutex  sync.RWMutex
-	values map[string]*gaugeVector
+	values map[uint64]*gaugeVector
 }
 
 func (metric *gauge) String() string {
@@ -94,3 +98,31 @@ func (metric *gauge) MarshalJSON() ([]byte, error) {
 		valueKey: values,
 	})
 }
+
+func (metric *gauge) dumpChildren(f *dto.MetricFamily) {
+	metric.mutex.RLock()
+	defer metric.mutex.RUnlock()
+
+	f.Type = dto.MetricType_GAUGE.Enum()
+
+	for _, child := range metric.values {
+		c := &dto.Gauge{
+			Value: proto.Float64(child.Value),
+		}
+
+		m := &dto.Metric{
+			Gauge: c,
+		}
+
+		for name, value := range child.Labels {
+			p := &dto.LabelPair{
+				Name:  proto.String(name),
+				Value: proto.String(value),
+			}
+
+			m.Label = append(m.Label, p)
+		}
+
+		f.Metric = append(f.Metric, m)
+	}
+}

prometheus/histogram.go

@@ -13,6 +13,10 @@ import (
 	"math"
 	"strconv"
 	"sync"
+
+	dto "github.com/prometheus/client_model/go"
+
+	"code.google.com/p/goprotobuf/proto"
 )
 
 // This generates count-buckets of equal size distributed along the open
@@ -75,7 +79,7 @@ type histogram struct {
 	// These are the buckets that capture samples as they are emitted to the
 	// histogram.  Please consult the reference interface and its implements for
 	// further details about behavior expectations.
-	values map[string]*histogramVector
+	values map[uint64]*histogramVector
 	// These are the percentile values that will be reported on marshalling.
 	reportablePercentiles []float64
 }
@@ -157,7 +161,7 @@ func prospectiveIndexForPercentile(percentile float64, totalObservations int) in
 }
 
 // Determine the next bucket element when interim bucket intervals may be empty.
-func (h histogram) nextNonEmptyBucketElement(signature string, currentIndex, bucketCount int, observationsByBucket []int) (*Bucket, int) {
+func (h histogram) nextNonEmptyBucketElement(signature uint64, currentIndex, bucketCount int, observationsByBucket []int) (*Bucket, int) {
 	for i := currentIndex; i < bucketCount; i++ {
 		if observationsByBucket[i] == 0 {
 			continue
@@ -176,7 +180,7 @@ func (h histogram) nextNonEmptyBucketElement(signature string, currentIndex, buc
 // longer contained by the bucket, the index of the last item is returned.  This
 // may occur if the underlying bucket catalogs values and employs an eviction
 // strategy.
-func (h histogram) bucketForPercentile(signature string, percentile float64) (*Bucket, int) {
+func (h histogram) bucketForPercentile(signature uint64, percentile float64) (*Bucket, int) {
 	bucketCount := len(h.bucketStarts)
 
 	// This captures the quantity of samples in a given bucket's range.
@@ -229,7 +233,7 @@ func (h histogram) bucketForPercentile(signature string, percentile float64) (*B
 // Return the histogram's estimate of the value for a given percentile of
 // collected samples.  The requested percentile is expected to be a real
 // value within (0, 1.0].
-func (h histogram) percentile(signature string, percentile float64) float64 {
+func (h histogram) percentile(signature uint64, percentile float64) float64 {
 	bucket, index := h.bucketForPercentile(signature, percentile)
 
 	return (*bucket).ValueForIndex(index)
@@ -284,7 +288,7 @@ func NewHistogram(specification *HistogramSpecification) Histogram {
 		bucketMaker:           specification.BucketBuilder,
 		bucketStarts:          specification.Starts,
 		reportablePercentiles: specification.ReportablePercentiles,
-		values:                map[string]*histogramVector{},
+		values:                map[uint64]*histogramVector{},
 	}
 
 	return metric
@@ -301,3 +305,38 @@ func NewDefaultHistogram() Histogram {
 		},
 	)
 }
+
+func (metric *histogram) dumpChildren(f *dto.MetricFamily) {
+	metric.mutex.RLock()
+	defer metric.mutex.RUnlock()
+
+	f.Type = dto.MetricType_SUMMARY.Enum()
+
+	for signature, child := range metric.values {
+		c := &dto.Summary{}
+
+		m := &dto.Metric{
+			Summary: c,
+		}
+
+		for name, value := range child.labels {
+			p := &dto.LabelPair{
+				Name:  proto.String(name),
+				Value: proto.String(value),
+			}
+
+			m.Label = append(m.Label, p)
+		}
+
+		for _, percentile := range metric.reportablePercentiles {
+			q := &dto.Quantile{
+				Quantile: proto.Float64(percentile),
+				Value:    proto.Float64(metric.percentile(signature, percentile)),
+			}
+
+			c.Quantile = append(c.Quantile, q)
+		}
+
+		f.Metric = append(f.Metric, m)
+	}
+}

prometheus/metric.go

@@ -6,7 +6,11 @@
 
 package prometheus
 
-import "encoding/json"
+import (
+	"encoding/json"
+
+	dto "github.com/prometheus/client_model/go"
+)
 
 // A Metric is something that can be exposed via the registry framework.
 type Metric interface {
@@ -16,4 +20,6 @@ type Metric interface {
 	ResetAll()
 	// Produce a human-consumable representation of the metric.
 	String() string
+	// dumpChildren populates the child metrics of the given family.
+	dumpChildren(*dto.MetricFamily)
 }

prometheus/registry.go

@@ -19,25 +19,26 @@ import (
 	"strings"
 	"sync"
 	"time"
+
+	dto "github.com/prometheus/client_model/go"
+
+	"code.google.com/p/goprotobuf/proto"
+	"github.com/matttproud/golang_protobuf_extensions/ext"
+
+	"github.com/prometheus/client_golang/vendor/goautoneg"
 )
 
 const (
-	acceptEncodingHeader     = "Accept-Encoding"
 	authorization            = "Authorization"
 	authorizationHeader      = "WWW-Authenticate"
 	authorizationHeaderValue = "Basic"
+
+	acceptEncodingHeader     = "Accept-Encoding"
 	contentEncodingHeader    = "Content-Encoding"
 	contentTypeHeader        = "Content-Type"
 	gzipAcceptEncodingValue  = "gzip"
 	gzipContentEncodingValue = "gzip"
 	jsonContentType          = "application/json"
-	jsonSuffix               = ".json"
-)
-
-var (
-	abortOnMisuse             bool
-	debugRegistration         bool
-	useAggressiveSanityChecks bool
 )
 
 // container represents a top-level registered metric that encompasses its
@@ -49,9 +50,23 @@ type container struct {
 	name       string
 }
 
+type containers []*container
+
+func (c containers) Len() int {
+	return len(c)
+}
+
+func (c containers) Swap(i, j int) {
+	c[i], c[j] = c[j], c[i]
+}
+
+func (c containers) Less(i, j int) bool {
+	return c[i].name < c[j].name
+}
+
 type registry struct {
 	mutex               sync.RWMutex
-	signatureContainers map[string]container
+	signatureContainers map[uint64]*container
 }
 
 // Registry is a registrar where metrics are listed.
@@ -72,8 +87,8 @@ type Registry interface {
 // This builds a new metric registry.  It is not needed in the majority of
 // cases.
 func NewRegistry() Registry {
-	return registry{
+	return &registry{
-		signatureContainers: make(map[string]container),
+		signatureContainers: make(map[uint64]*container),
 	}
 }
 
@@ -83,33 +98,28 @@ func Register(name, docstring string, baseLabels map[string]string, metric Metri
 }
 
 // Implements json.Marshaler
-func (r registry) MarshalJSON() (_ []byte, err error) {
+func (r *registry) MarshalJSON() ([]byte, error) {
-	metrics := make([]interface{}, 0, len(r.signatureContainers))
+	containers := make(containers, 0, len(r.signatureContainers))
 
-	keys := make([]string, 0, len(metrics))
+	for _, container := range r.signatureContainers {
-	for key := range r.signatureContainers {
+		containers = append(containers, container)
-		keys = append(keys, key)
 	}
 
-	sort.Strings(keys)
+	sort.Sort(containers)
 
-	for _, key := range keys {
+	return json.Marshal(containers)
-		metrics = append(metrics, r.signatureContainers[key])
-	}
-
-	return json.Marshal(metrics)
 }
 
 // isValidCandidate returns true if the candidate is acceptable for use.  In the
 // event of any apparent incorrect use it will report the problem, invalidate
 // the candidate, or outright abort.
-func (r registry) isValidCandidate(name string, baseLabels map[string]string) (signature string, err error) {
+func (r *registry) isValidCandidate(name string, baseLabels map[string]string) (signature uint64, err error) {
 	if len(name) == 0 {
 		err = fmt.Errorf("unnamed metric named with baseLabels %s is invalid", baseLabels)
 
-		if abortOnMisuse {
+		if *abortOnMisuse {
 			panic(err)
-		} else if debugRegistration {
+		} else if *debugRegistration {
 			log.Println(err)
 		}
 	}
@@ -117,13 +127,13 @@ func (r registry) isValidCandidate(name string, baseLabels map[string]string) (s
 	if _, contains := baseLabels[nameLabel]; contains {
 		err = fmt.Errorf("metric named %s with baseLabels %s contains reserved label name %s in baseLabels", name, baseLabels, nameLabel)
 
-		if abortOnMisuse {
+		if *abortOnMisuse {
 			panic(err)
-		} else if debugRegistration {
+		} else if *debugRegistration {
 			log.Println(err)
 		}
 
-		return
+		return signature, err
 	}
 
 	baseLabels[nameLabel] = name
@@ -131,34 +141,34 @@ func (r registry) isValidCandidate(name string, baseLabels map[string]string) (s
 
 	if _, contains := r.signatureContainers[signature]; contains {
 		err = fmt.Errorf("metric named %s with baseLabels %s is already registered", name, baseLabels)
-		if abortOnMisuse {
+		if *abortOnMisuse {
 			panic(err)
-		} else if debugRegistration {
+		} else if *debugRegistration {
 			log.Println(err)
 		}
 
-		return
+		return signature, err
 	}
 
-	if useAggressiveSanityChecks {
+	if *useAggressiveSanityChecks {
 		for _, container := range r.signatureContainers {
 			if container.name == name {
 				err = fmt.Errorf("metric named %s with baseLabels %s is already registered as %s and risks causing confusion", name, baseLabels, container.BaseLabels)
-				if abortOnMisuse {
+				if *abortOnMisuse {
 					panic(err)
-				} else if debugRegistration {
+				} else if *debugRegistration {
 					log.Println(err)
 				}
 
-				return
+				return signature, err
 			}
 		}
 	}
 
-	return
+	return signature, err
 }
 
-func (r registry) Register(name, docstring string, baseLabels map[string]string, metric Metric) (err error) {
+func (r *registry) Register(name, docstring string, baseLabels map[string]string, metric Metric) error {
 	r.mutex.Lock()
 	defer r.mutex.Unlock()
 
@@ -168,25 +178,26 @@ func (r registry) Register(name, docstring string, baseLabels map[string]string,
 
 	signature, err := r.isValidCandidate(name, baseLabels)
 	if err != nil {
-		return
+		return err
 	}
 
-	r.signatureContainers[signature] = container{
+	r.signatureContainers[signature] = &container{
 		BaseLabels: baseLabels,
 		Docstring:  docstring,
 		Metric:     metric,
 		name:       name,
 	}
 
-	return
+	return nil
 }
 
 // YieldBasicAuthExporter creates a http.HandlerFunc that is protected by HTTP's
 // basic authentication.
-func (register registry) YieldBasicAuthExporter(username, password string) http.HandlerFunc {
+func (register *registry) YieldBasicAuthExporter(username, password string) http.HandlerFunc {
 	// XXX: Work with Daniel to get this removed from the library, as it is really
 	//      superfluous and can be much more elegantly accomplished via
 	//      delegation.
+	log.Println("Registry.YieldBasicAuthExporter is deprecated.")
 	exporter := register.YieldExporter()
 
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@@ -225,38 +236,81 @@ func decorateWriter(request *http.Request, writer http.ResponseWriter) io.Writer
 	return gziper
 }
 
-func (registry registry) YieldExporter() http.HandlerFunc {
+func (registry *registry) YieldExporter() http.HandlerFunc {
 	log.Println("Registry.YieldExporter is deprecated in favor of Registry.Handler.")
 
 	return registry.Handler()
 }
 
-func (registry registry) Handler() http.HandlerFunc {
+func (r *registry) dumpDelimitedPB(w io.Writer) {
+	r.mutex.RLock()
+	defer r.mutex.RUnlock()
+
+	f := new(dto.MetricFamily)
+	for _, container := range r.signatureContainers {
+		f.Reset()
+
+		f.Name = proto.String(container.name)
+		f.Help = proto.String(container.Docstring)
+
+		container.Metric.dumpChildren(f)
+
+		for name, value := range container.BaseLabels {
+			p := &dto.LabelPair{
+				Name:  proto.String(name),
+				Value: proto.String(value),
+			}
+
+			for _, child := range f.Metric {
+				child.Label = append(child.Label, p)
+			}
+		}
+
+		ext.WriteDelimited(w, f)
+	}
+}
+
+func (registry *registry) Handler() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		defer requestLatencyAccumulator(time.Now())
 
 		requestCount.Increment(nil)
-		url := r.URL
+		header := w.Header()
 
-		if strings.HasSuffix(url.Path, jsonSuffix) {
+		writer := decorateWriter(r, w)
-			header := w.Header()
-			header.Set(contentTypeHeader, TelemetryContentType)
 
-			writer := decorateWriter(r, w)
+		if closer, ok := writer.(io.Closer); ok {
+			defer closer.Close()
+		}
 
-			if closer, ok := writer.(io.Closer); ok {
+		accepts := goautoneg.ParseAccept(r.Header.Get("Accept"))
-				defer closer.Close()
+		for _, accept := range accepts {
+			if accept.Type != "application" {
+				continue
 			}
 
-			json.NewEncoder(writer).Encode(registry)
+			if accept.SubType == "vnd.google.protobuf" {
-		} else {
+				if accept.Params["proto"] != "io.prometheus.client.MetricFamily" {
-			w.WriteHeader(http.StatusNotFound)
+					continue
+				}
+				if accept.Params["encoding"] != "delimited" {
+					continue
+				}
+
+				header.Set(contentTypeHeader, DelimitedTelemetryContentType)
+				registry.dumpDelimitedPB(writer)
+
+				return
+			}
 		}
+
+		header.Set(contentTypeHeader, TelemetryContentType)
+		json.NewEncoder(writer).Encode(registry)
 	}
 }
 
-func init() {
+var (
-	flag.BoolVar(&abortOnMisuse, FlagNamespace+"abortonmisuse", false, "abort if a semantic misuse is encountered (bool).")
+	abortOnMisuse             = flag.Bool(FlagNamespace+"abortonmisuse", false, "abort if a semantic misuse is encountered (bool).")
-	flag.BoolVar(&debugRegistration, FlagNamespace+"debugregistration", false, "display information about the metric registration process (bool).")
+	debugRegistration         = flag.Bool(FlagNamespace+"debugregistration", false, "display information about the metric registration process (bool).")
-	flag.BoolVar(&useAggressiveSanityChecks, FlagNamespace+"useaggressivesanitychecks", false, "perform expensive validation of metrics (bool).")
+	useAggressiveSanityChecks = flag.Bool(FlagNamespace+"useaggressivesanitychecks", false, "perform expensive validation of metrics (bool).")
-}
+)

prometheus/registry_test.go

@@ -13,6 +13,8 @@ import (
 	"io"
 	"net/http"
 	"testing"
+
+	"code.google.com/p/goprotobuf/proto"
 )
 
 func testRegister(t tester) {
@@ -21,14 +23,14 @@ func testRegister(t tester) {
 		debugRegistration         bool
 		useAggressiveSanityChecks bool
 	}{
-		abortOnMisuse:             abortOnMisuse,
+		abortOnMisuse:             *abortOnMisuse,
-		debugRegistration:         debugRegistration,
+		debugRegistration:         *debugRegistration,
-		useAggressiveSanityChecks: useAggressiveSanityChecks,
+		useAggressiveSanityChecks: *useAggressiveSanityChecks,
 	}
 	defer func() {
-		abortOnMisuse = oldState.abortOnMisuse
+		abortOnMisuse = &(oldState.abortOnMisuse)
-		debugRegistration = oldState.debugRegistration
+		debugRegistration = &(oldState.debugRegistration)
-		useAggressiveSanityChecks = oldState.useAggressiveSanityChecks
+		useAggressiveSanityChecks = &(oldState.useAggressiveSanityChecks)
 	}()
 
 	type input struct {
@@ -139,9 +141,9 @@ func testRegister(t tester) {
 			t.Fatalf("%d. expected scenario output length %d, got %d", i, len(scenario.inputs), len(scenario.outputs))
 		}
 
-		abortOnMisuse = false
+		abortOnMisuse = proto.Bool(false)
-		debugRegistration = false
+		debugRegistration = proto.Bool(false)
-		useAggressiveSanityChecks = true
+		useAggressiveSanityChecks = proto.Bool(true)
 
 		registry := NewRegistry()
 
@@ -297,7 +299,7 @@ func testDumpToWriter(t tester) {
 	}
 
 	for i, scenario := range scenarios {
-		registry := NewRegistry().(registry)
+		registry := NewRegistry().(*registry)
 
 		for name, metric := range scenario.in.metrics {
 			err := registry.Register(name, fmt.Sprintf("metric %s", name), map[string]string{fmt.Sprintf("label_%s", name): name}, metric)

prometheus/signature.go

@@ -7,35 +7,28 @@
 package prometheus
 
 import (
-	"bytes"
+	"fmt"
+	"hash/fnv"
 	"sort"
-)
 
-const (
+	"github.com/prometheus/client_golang/model"
-	delimiter = "|"
 )
 
 // LabelsToSignature provides a way of building a unique signature
 // (i.e., fingerprint) for a given label set sequence.
-func labelsToSignature(labels map[string]string) string {
+func labelsToSignature(labels map[string]string) uint64 {
-	// TODO(matt): This is a wart, and we'll want to validate that collisions
+	names := make(model.LabelNames, 0, len(labels))
-	//             do not occur in less-than-diligent environments.
+	for name := range labels {
-	cardinality := len(labels)
+		names = append(names, model.LabelName(name))
-	keys := make([]string, 0, cardinality)
-
-	for label := range labels {
-		keys = append(keys, label)
 	}
 
-	sort.Strings(keys)
+	sort.Sort(names)
 
-	buffer := bytes.Buffer{}
+	hasher := fnv.New64a()
 
-	for _, label := range keys {
+	for _, name := range names {
-		buffer.WriteString(label)
+		fmt.Fprintf(hasher, string(name), labels[string(name)])
-		buffer.WriteString(delimiter)
-		buffer.WriteString(labels[label])
 	}
 
-	return buffer.String()
+	return hasher.Sum64()
 }

prometheus/signature_test.go

@@ -13,13 +13,16 @@ import (
 func testLabelsToSignature(t tester) {
 	var scenarios = []struct {
 		in  map[string]string
-		out string
+		out uint64
 	}{
 		{
 			in:  map[string]string{},
-			out: "",
+			out: 14695981039346656037,
+		},
+		{
+			in:  map[string]string{"name": "garland, briggs", "fear": "love is not enough"},
+			out: 15753083015552662396,
 		},
-		{},
 	}
 
 	for i, scenario := range scenarios {

vendor/goautoneg/MANIFEST

@@ -0,0 +1 @@
+Imported at 75cd24fc2f2c from https://bitbucket.org/ww/goautoneg.

vendor/goautoneg/Makefile

@@ -0,0 +1,13 @@
+include $(GOROOT)/src/Make.inc
+
+TARG=bitbucket.org/ww/goautoneg
+GOFILES=autoneg.go
+
+include $(GOROOT)/src/Make.pkg
+
+format:
+	gofmt -w *.go
+
+docs:
+	gomake clean
+	godoc ${TARG} > README.txt

vendor/goautoneg/README.txt

@@ -0,0 +1,67 @@
+PACKAGE
+
+package goautoneg
+import "bitbucket.org/ww/goautoneg"
+
+HTTP Content-Type Autonegotiation.
+
+The functions in this package implement the behaviour specified in
+http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
+
+Copyright (c) 2011, Open Knowledge Foundation Ltd.
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+    Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+
+    Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in
+    the documentation and/or other materials provided with the
+    distribution.
+
+    Neither the name of the Open Knowledge Foundation Ltd. nor the
+    names of its contributors may be used to endorse or promote
+    products derived from this software without specific prior written
+    permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+FUNCTIONS
+
+func Negotiate(header string, alternatives []string) (content_type string)
+Negotiate the most appropriate content_type given the accept header
+and a list of alternatives.
+
+func ParseAccept(header string) (accept []Accept)
+Parse an Accept Header string returning a sorted list
+of clauses
+
+
+TYPES
+
+type Accept struct {
+    Type, SubType string
+    Q             float32
+    Params        map[string]string
+}
+Structure to represent a clause in an HTTP Accept Header
+
+
+SUBDIRECTORIES
+
+	.hg

vendor/goautoneg/autoneg.go

@@ -0,0 +1,162 @@
+/*
+HTTP Content-Type Autonegotiation.
+
+The functions in this package implement the behaviour specified in
+http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
+
+Copyright (c) 2011, Open Knowledge Foundation Ltd.
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+    Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+
+    Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in
+    the documentation and/or other materials provided with the
+    distribution.
+
+    Neither the name of the Open Knowledge Foundation Ltd. nor the
+    names of its contributors may be used to endorse or promote
+    products derived from this software without specific prior written
+    permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+*/
+package goautoneg
+
+import (
+	"sort"
+	"strconv"
+	"strings"
+)
+
+// Structure to represent a clause in an HTTP Accept Header
+type Accept struct {
+	Type, SubType string
+	Q             float64
+	Params        map[string]string
+}
+
+// For internal use, so that we can use the sort interface
+type accept_slice []Accept
+
+func (accept accept_slice) Len() int {
+	slice := []Accept(accept)
+	return len(slice)
+}
+
+func (accept accept_slice) Less(i, j int) bool {
+	slice := []Accept(accept)
+	ai, aj := slice[i], slice[j]
+	if ai.Q > aj.Q {
+		return true
+	}
+	if ai.Type != "*" && aj.Type == "*" {
+		return true
+	}
+	if ai.SubType != "*" && aj.SubType == "*" {
+		return true
+	}
+	return false
+}
+
+func (accept accept_slice) Swap(i, j int) {
+	slice := []Accept(accept)
+	slice[i], slice[j] = slice[j], slice[i]
+}
+
+// Parse an Accept Header string returning a sorted list
+// of clauses
+func ParseAccept(header string) (accept []Accept) {
+	parts := strings.Split(header, ",")
+	accept = make([]Accept, 0, len(parts))
+	for _, part := range parts {
+		part := strings.Trim(part, " ")
+
+		a := Accept{}
+		a.Params = make(map[string]string)
+		a.Q = 1.0
+
+		mrp := strings.Split(part, ";")
+
+		media_range := mrp[0]
+		sp := strings.Split(media_range, "/")
+		a.Type = strings.Trim(sp[0], " ")
+
+		switch {
+		case len(sp) == 1 && a.Type == "*":
+			a.SubType = "*"
+		case len(sp) == 2:
+			a.SubType = strings.Trim(sp[1], " ")
+		default:
+			continue
+		}
+
+		if len(mrp) == 1 {
+			accept = append(accept, a)
+			continue
+		}
+
+		for _, param := range mrp[1:] {
+			sp := strings.SplitN(param, "=", 2)
+			if len(sp) != 2 {
+				continue
+			}
+			token := strings.Trim(sp[0], " ")
+			if token == "q" {
+				a.Q, _ = strconv.ParseFloat(sp[1], 32)
+			} else {
+				a.Params[token] = strings.Trim(sp[1], " ")
+			}
+		}
+
+		accept = append(accept, a)
+	}
+
+	slice := accept_slice(accept)
+	sort.Sort(slice)
+
+	return
+}
+
+// Negotiate the most appropriate content_type given the accept header
+// and a list of alternatives.
+func Negotiate(header string, alternatives []string) (content_type string) {
+	asp := make([][]string, 0, len(alternatives))
+	for _, ctype := range alternatives {
+		asp = append(asp, strings.SplitN(ctype, "/", 2))
+	}
+	for _, clause := range ParseAccept(header) {
+		for i, ctsp := range asp {
+			if clause.Type == ctsp[0] && clause.SubType == ctsp[1] {
+				content_type = alternatives[i]
+				return
+			}
+			if clause.Type == ctsp[0] && clause.SubType == "*" {
+				content_type = alternatives[i]
+				return
+			}
+			if clause.Type == "*" && clause.SubType == "*" {
+				content_type = alternatives[i]
+				return
+			}
+		}
+	}
+	return
+}

vendor/goautoneg/autoneg_test.go

@@ -0,0 +1,33 @@
+package goautoneg
+
+import (
+	"testing"
+)
+
+var chrome = "application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5"
+
+func TestParseAccept(t *testing.T) {
+	alternatives := []string{"text/html", "image/png"}
+	content_type := Negotiate(chrome, alternatives)
+	if content_type != "image/png" {
+		t.Errorf("got %s expected image/png", content_type)
+	}
+
+	alternatives = []string{"text/html", "text/plain", "text/n3"}
+	content_type = Negotiate(chrome, alternatives)
+	if content_type != "text/html" {
+		t.Errorf("got %s expected text/html", content_type)
+	}
+
+	alternatives = []string{"text/n3", "text/plain"}
+	content_type = Negotiate(chrome, alternatives)
+	if content_type != "text/plain" {
+		t.Errorf("got %s expected text/plain", content_type)
+	}
+
+	alternatives = []string{"text/n3", "application/rdf+xml"}
+	content_type = Negotiate(chrome, alternatives)
+	if content_type != "text/n3" {
+		t.Errorf("got %s expected text/n3", content_type)
+	}
+}