Changed the configuration allowing content-type and encoding preferences for both sending and receiving.

Signed-off-by: bwplotka <bwplotka@gmail.com>

cmd/prometheus/main.go

@@ -158,10 +158,8 @@ type flagConfig struct {
 	enableNewSDManager         bool
 	enablePerStepStats         bool
 	enableAutoGOMAXPROCS       bool
-	// todo: how to use the enable feature flag properly + use the remote format enum type
-	rwFormat                 int
-	enableAutoGOMEMLIMIT     bool
-	enableConcurrentRuleEval bool
+	enableAutoGOMEMLIMIT       bool
+	enableConcurrentRuleEval   bool
 
 	prometheusURL   string
 	corsRegexString string
@@ -314,6 +312,12 @@ func main() {
 	a.Flag("web.enable-remote-write-receiver", "Enable API endpoint accepting remote write requests.").
 		Default("false").BoolVar(&cfg.web.EnableRemoteWriteReceiver)
 
+	a.Flag("web.remote-write-receiver.protobuf-types", fmt.Sprintf("List of accepted remote write 2.0 content types to advertise to senders, ordered by the preference. Note that the final decision is on the sender. Supported list values: %v", config.DefaultRemoteWriteProtoTypes.String())).
+		Default(config.DefaultRemoteWriteProtoTypes.Strings()...).SetValue(rwProtoTypeFlagValue(&cfg.web.RemoteWriteReceiverProtoTypes))
+
+	a.Flag("web.remote-write-receiver.compressions", fmt.Sprintf("List of accepted remote write 2.0 content encodings (compressions) to advertise to senders, ordered by the preference. Note that the final decision is on the sender. Supported list values: %v", config.DefaultRemoteWriteCompressions.String())).
+		Default(config.DefaultRemoteWriteCompressions.Strings()...).SetValue(rwCompressionFlagValue(&cfg.web.RemoteWriteReceiverCompressions))
+
 	a.Flag("web.console.templates", "Path to the console template directory, available at /consoles.").
 		Default("consoles").StringVar(&cfg.web.ConsoleTemplatesPath)
 
@@ -455,9 +459,6 @@ func main() {
 	a.Flag("enable-feature", "Comma separated feature names to enable. Valid options: agent, auto-gomemlimit, exemplar-storage, expand-external-labels, memory-snapshot-on-shutdown, promql-per-step-stats, promql-experimental-functions, remote-write-receiver (DEPRECATED), extra-scrape-metrics, new-service-discovery-manager, auto-gomaxprocs, no-default-scrape-port, native-histograms, otlp-write-receiver, created-timestamp-zero-ingestion, concurrent-rule-eval. See https://prometheus.io/docs/prometheus/latest/feature_flags/ for more details.").
 		Default("").StringsVar(&cfg.featureList)
 
-	a.Flag("remote-write-format", "remote write proto format to use, valid options: 0 (1.0), 1 (reduced format), 3 (min64 format)").
-		Default("0").IntVar(&cfg.rwFormat)
-
 	promlogflag.AddFlags(a, &cfg.promlogConfig)
 
 	a.Flag("write-documentation", "Generate command line documentation. Internal use.").Hidden().Action(func(ctx *kingpin.ParseContext) error {
@@ -820,7 +821,6 @@ func main() {
 		cfg.web.Flags[f.Name] = f.Value.String()
 	}
 
-	cfg.web.RemoteWriteFormat = config.RemoteWriteFormat(cfg.rwFormat)
 	// Depends on cfg.web.ScrapeManager so needs to be after cfg.web.ScrapeManager = scrapeManager.
 	webHandler := web.New(log.With(logger, "component", "web"), &cfg.web)
 
@@ -1737,3 +1737,63 @@ type discoveryManager interface {
 	Run() error
 	SyncCh() <-chan map[string][]*targetgroup.Group
 }
+
+// TODO(bwplotka): Add unit test.
+type rwProtoTypeFlagParser struct {
+	types *[]config.RemoteWriteProtoType
+}
+
+func rwProtoTypeFlagValue(types *[]config.RemoteWriteProtoType) kingpin.Value {
+	return &rwProtoTypeFlagParser{types: types}
+}
+
+func (p *rwProtoTypeFlagParser) IsCumulative() bool {
+	return true
+}
+
+func (p *rwProtoTypeFlagParser) String() string {
+	ss := make([]string, 0, len(*p.types))
+	for _, t := range *p.types {
+		ss = append(ss, string(t))
+	}
+	return strings.Join(ss, ",")
+}
+
+func (p *rwProtoTypeFlagParser) Set(opt string) error {
+	t := config.RemoteWriteProtoType(opt)
+	if err := t.Validate(); err != nil {
+		return err
+	}
+	*p.types = append(*p.types, t)
+	return nil
+}
+
+// TODO(bwplotka): Add unit test.
+type rwCompressionFlagParser struct {
+	types *[]config.RemoteWriteCompression
+}
+
+func rwCompressionFlagValue(types *[]config.RemoteWriteCompression) kingpin.Value {
+	return &rwCompressionFlagParser{types: types}
+}
+
+func (p *rwCompressionFlagParser) IsCumulative() bool {
+	return true
+}
+
+func (p *rwCompressionFlagParser) String() string {
+	ss := make([]string, 0, len(*p.types))
+	for _, t := range *p.types {
+		ss = append(ss, string(t))
+	}
+	return strings.Join(ss, ",")
+}
+
+func (p *rwCompressionFlagParser) Set(opt string) error {
+	t := config.RemoteWriteCompression(opt)
+	if err := t.Validate(); err != nil {
+		return err
+	}
+	*p.types = append(*p.types, t)
+	return nil
+}

config/config.go

@@ -172,7 +172,10 @@ var (
 
 	// DefaultRemoteWriteConfig is the default remote write configuration.
 	DefaultRemoteWriteConfig = RemoteWriteConfig{
-		RemoteTimeout:    model.Duration(30 * time.Second),
+		RemoteTimeout: model.Duration(30 * time.Second),
+		ProtobufTypes: DefaultRemoteWriteProtoTypes,
+		Compressions:  DefaultRemoteWriteCompressions,
+
 		QueueConfig:      DefaultQueueConfig,
 		MetadataConfig:   DefaultMetadataConfig,
 		HTTPClientConfig: config.DefaultHTTPClientConfig,
@@ -1025,22 +1028,18 @@ func CheckTargetAddress(address model.LabelValue) error {
 	return nil
 }
 
-// This needs to live here rather than in the remote package to avoid an import cycle.
-type RemoteWriteFormat int64
-
 // RemoteWriteConfig is the configuration for writing to remote storage.
 type RemoteWriteConfig struct {
-	URL                  *config.URL       `yaml:"url"`
-	RemoteTimeout        model.Duration    `yaml:"remote_timeout,omitempty"`
-	Headers              map[string]string `yaml:"headers,omitempty"`
-	WriteRelabelConfigs  []*relabel.Config `yaml:"write_relabel_configs,omitempty"`
-	Name                 string            `yaml:"name,omitempty"`
-	SendExemplars        bool              `yaml:"send_exemplars,omitempty"`
-	SendNativeHistograms bool              `yaml:"send_native_histograms,omitempty"`
-	ProtocolVersion      RemoteWriteFormat `yaml:"remote_write_version,omitempty"`
+	URL                  *config.URL              `yaml:"url"`
+	RemoteTimeout        model.Duration           `yaml:"remote_timeout,omitempty"`
+	Headers              map[string]string        `yaml:"headers,omitempty"`
+	WriteRelabelConfigs  []*relabel.Config        `yaml:"write_relabel_configs,omitempty"`
+	Name                 string                   `yaml:"name,omitempty"`
+	SendExemplars        bool                     `yaml:"send_exemplars,omitempty"`
+	SendNativeHistograms bool                     `yaml:"send_native_histograms,omitempty"`
+	ProtobufTypes        []RemoteWriteProtoType   `yaml:"proto_types,omitempty"`
+	Compressions         []RemoteWriteCompression `yaml:"compressions,omitempty"`
 
-	// We cannot do proper Go type embedding below as the parser will then parse
-	// values arbitrarily into the overflow maps of further-down types.
 	HTTPClientConfig config.HTTPClientConfig `yaml:",inline"`
 	QueueConfig      QueueConfig             `yaml:"queue_config,omitempty"`
 	MetadataConfig   MetadataConfig          `yaml:"metadata_config,omitempty"`
@@ -1072,6 +1071,20 @@ func (c *RemoteWriteConfig) UnmarshalYAML(unmarshal func(interface{}) error) err
 		return err
 	}
 
+	if c.ProtobufTypes == nil {
+		c.ProtobufTypes = DefaultRemoteWriteProtoTypes
+	}
+	if err := validateRemoteWriteProtoTypes(c.ProtobufTypes); err != nil {
+		return fmt.Errorf("invalid protobuf_types value: %w", err)
+	}
+
+	if c.Compressions == nil {
+		c.Compressions = DefaultRemoteWriteCompressions
+	}
+	if err := validateRemoteWriteCompressions(c.Compressions); err != nil {
+		return fmt.Errorf("invalid compressions value: %w", err)
+	}
+
 	// The UnmarshalYAML method of HTTPClientConfig is not being called because it's not a pointer.
 	// We cannot make it a pointer as the parser panics for inlined pointer structs.
 	// Thus we just do its validation here.

config/config_remote_write.go

@@ -0,0 +1,162 @@
+package config
+
+import (
+	"errors"
+	"fmt"
+	"sort"
+	"strings"
+)
+
+// TODO(bwplotka): Consider an util for "preference enums" as it's similar code for rw compression, proto type and scrape protocol.
+
+// RemoteWriteProtoType represents the supported protobuf types for the remote write.
+type RemoteWriteProtoType string
+
+// Validate returns error if the given protobuf type is not supported.
+func (s RemoteWriteProtoType) Validate() error {
+	if _, ok := RemoteWriteContentTypeHeaders[s]; !ok {
+		return fmt.Errorf("unknown remote write protobuf type %v, supported: %v",
+			s, func() (ret []string) {
+				for k := range RemoteWriteContentTypeHeaders {
+					ret = append(ret, string(k))
+				}
+				sort.Strings(ret)
+				return ret
+			}())
+	}
+	return nil
+}
+
+type RemoteWriteProtoTypes []RemoteWriteProtoType
+
+func (t RemoteWriteProtoTypes) Strings() []string {
+	ret := make([]string, 0, len(t))
+	for _, typ := range t {
+		ret = append(ret, string(typ))
+	}
+	return ret
+}
+
+func (t RemoteWriteProtoTypes) String() string {
+	return strings.Join(t.Strings(), ",")
+}
+
+// ServerAcceptHeaderValue returns server Accept header value for
+// given list of proto types as per RFC 9110 https://www.rfc-editor.org/rfc/rfc9110.html#section-12.5.1-14
+func (t RemoteWriteProtoTypes) ServerAcceptHeaderValue() string {
+	// TODO(bwplotka): Consider implementing an optional quality factor.
+	ret := make([]string, 0, len(t))
+	for _, typ := range t {
+		ret = append(ret, RemoteWriteContentTypeHeaders[typ])
+	}
+	return strings.Join(ret, ",")
+}
+
+var (
+	RemoteWriteProtoTypeV1        RemoteWriteProtoType = "v1.WriteRequest"
+	RemoteWriteProtoTypeV2        RemoteWriteProtoType = "v2.WriteRequest"
+	RemoteWriteContentTypeHeaders                      = map[RemoteWriteProtoType]string{
+		RemoteWriteProtoTypeV1: "application/x-protobuf", // Also application/x-protobuf; proto=prometheus.WriteRequest but simplified for compatibility with 1.x spec.
+		RemoteWriteProtoTypeV2: "application/x-protobuf;proto=io.prometheus.remote.write.v2.WriteRequest",
+	}
+
+	// DefaultRemoteWriteProtoTypes is the set of remote write protobuf types that will be
+	// preferred by the remote write client.
+	DefaultRemoteWriteProtoTypes = RemoteWriteProtoTypes{
+		RemoteWriteProtoTypeV1,
+		RemoteWriteProtoTypeV2,
+	}
+)
+
+// validateRemoteWriteProtoTypes return errors if we see problems with rw protobuf types in
+// the Prometheus configuration.
+func validateRemoteWriteProtoTypes(ts []RemoteWriteProtoType) error {
+	if len(ts) == 0 {
+		return errors.New("protobuf_types cannot be empty")
+	}
+	dups := map[string]struct{}{}
+	for _, t := range ts {
+		if _, ok := dups[strings.ToLower(string(t))]; ok {
+			return fmt.Errorf("duplicated protobuf types in protobuf_types, got %v", ts)
+		}
+		if err := t.Validate(); err != nil {
+			return fmt.Errorf("protobuf_types: %w", err)
+		}
+		dups[strings.ToLower(string(t))] = struct{}{}
+	}
+	return nil
+}
+
+// RemoteWriteCompression represents the supported compressions for the remote write.
+type RemoteWriteCompression string
+
+// Validate returns error if the given protobuf type is not supported.
+func (s RemoteWriteCompression) Validate() error {
+	if _, ok := RemoteWriteContentEncodingHeaders[s]; !ok {
+		return fmt.Errorf("unknown remote write protobuf type %v, supported: %v",
+			s, func() (ret []string) {
+				for k := range RemoteWriteContentEncodingHeaders {
+					ret = append(ret, string(k))
+				}
+				sort.Strings(ret)
+				return ret
+			}())
+	}
+	return nil
+}
+
+type RemoteWriteCompressions []RemoteWriteCompression
+
+func (cs RemoteWriteCompressions) Strings() []string {
+	ret := make([]string, 0, len(cs))
+	for _, c := range cs {
+		ret = append(ret, string(c))
+	}
+	return ret
+}
+
+func (cs RemoteWriteCompressions) String() string {
+	return strings.Join(cs.Strings(), ",")
+}
+
+// ServerAcceptEncodingHeaderValue returns server Accept-Encoding header value for
+// given list of compressions as per RFC 9110 https://www.rfc-editor.org/rfc/rfc9110.html#name-accept-encoding
+func (cs RemoteWriteCompressions) ServerAcceptEncodingHeaderValue() string {
+	// TODO(bwplotka): Consider implementing an optional quality factor.
+	ret := make([]string, 0, len(cs))
+	for _, typ := range cs {
+		ret = append(ret, RemoteWriteContentEncodingHeaders[typ])
+	}
+	return strings.Join(ret, ",")
+}
+
+// validateRemoteWriteCompressions return errors if we see problems with rw compressions in
+// the Prometheus configuration.
+func validateRemoteWriteCompressions(cs []RemoteWriteCompression) error {
+	if len(cs) == 0 {
+		return errors.New("compressions cannot be empty")
+	}
+	dups := map[string]struct{}{}
+	for _, c := range cs {
+		if _, ok := dups[strings.ToLower(string(c))]; ok {
+			return fmt.Errorf("duplicated compression in compressions, got %v", cs)
+		}
+		if err := c.Validate(); err != nil {
+			return fmt.Errorf("compressions: %w", err)
+		}
+		dups[strings.ToLower(string(c))] = struct{}{}
+	}
+	return nil
+}
+
+var (
+	RemoteWriteCompressionSnappy RemoteWriteCompression = "snappy"
+
+	RemoteWriteContentEncodingHeaders = map[RemoteWriteCompression]string{
+		RemoteWriteCompressionSnappy: "snappy",
+	}
+
+	DefaultRemoteWriteCompressions = RemoteWriteCompressions{
+		RemoteWriteCompressionSnappy,
+	}
+)

storage/remote/write_handler.go

@@ -19,7 +19,6 @@ import (
 	"fmt"
 	"io"
 	"net/http"
-	"strings"
 
 	"github.com/go-kit/log"
 	"github.com/go-kit/log/level"
@@ -38,89 +37,31 @@ import (
 	otlptranslator "github.com/prometheus/prometheus/storage/remote/otlptranslator/prometheusremotewrite"
 )
 
-const (
-	RemoteWriteVersionHeader        = "X-Prometheus-Remote-Write-Version"
-	RemoteWriteVersion1HeaderValue  = "0.1.0"
-	RemoteWriteVersion20HeaderValue = "2.0"
-)
-
-func rwHeaderNameValues(rwFormat config.RemoteWriteFormat) map[string]string {
-	// Return the correct remote write header name/values based on provided rwFormat.
-	ret := make(map[string]string, 1)
-
-	switch rwFormat {
-	case Version1:
-		ret[RemoteWriteVersionHeader] = RemoteWriteVersion1HeaderValue
-	case Version2:
-		// We need to add the supported protocol definitions in order:
-		tuples := make([]string, 0, 2)
-		// Add "2.0;snappy".
-		tuples = append(tuples, RemoteWriteVersion20HeaderValue+";snappy")
-		// Add default "0.1.0".
-		tuples = append(tuples, RemoteWriteVersion1HeaderValue)
-		ret[RemoteWriteVersionHeader] = strings.Join(tuples, ",")
-	}
-	return ret
-}
-
-type writeHeadHandler struct {
-	logger log.Logger
-
-	remoteWriteHeadRequests prometheus.Counter
-
-	// Experimental feature, new remote write proto format.
-	// The handler will accept the new format, but it can still accept the old one.
-	rwFormat config.RemoteWriteFormat
-}
-
-func NewWriteHeadHandler(logger log.Logger, reg prometheus.Registerer, rwFormat config.RemoteWriteFormat) http.Handler {
-	h := &writeHeadHandler{
-		logger:   logger,
-		rwFormat: rwFormat,
-		remoteWriteHeadRequests: prometheus.NewCounter(prometheus.CounterOpts{
-			Namespace: "prometheus",
-			Subsystem: "api",
-			Name:      "remote_write_head_requests",
-			Help:      "The number of remote write HEAD requests.",
-		}),
-	}
-	if reg != nil {
-		reg.MustRegister(h.remoteWriteHeadRequests)
-	}
-	return h
-}
-
-// Send a response to the HEAD request based on the format supported.
-func (h *writeHeadHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
-	// Add appropriate header values for the specific rwFormat.
-	for hName, hValue := range rwHeaderNameValues(h.rwFormat) {
-		w.Header().Set(hName, hValue)
-	}
-
-	// Increment counter
-	h.remoteWriteHeadRequests.Inc()
-
-	w.WriteHeader(http.StatusOK)
-}
-
 type writeHandler struct {
 	logger     log.Logger
 	appendable storage.Appendable
 
 	samplesWithInvalidLabelsTotal prometheus.Counter
 
-	// Experimental feature, new remote write proto format.
-	// The handler will accept the new format, but it can still accept the old one.
-	rwFormat config.RemoteWriteFormat
+	// PRW 2.0 definies backward compatible content negotiation across prototypes
+	// and compressions.
+	protoTypes                []config.RemoteWriteProtoType
+	acceptHeaderValue         string
+	compressions              []config.RemoteWriteCompression
+	acceptEncodingHeaderValue string
 }
 
 // NewWriteHandler creates a http.Handler that accepts remote write requests and
 // writes them to the provided appendable.
-func NewWriteHandler(logger log.Logger, reg prometheus.Registerer, appendable storage.Appendable, rwFormat config.RemoteWriteFormat) http.Handler {
+// Compatible with both 1.x and 2.0 spec.
+func NewWriteHandler(logger log.Logger, reg prometheus.Registerer, appendable storage.Appendable, protoTypes []config.RemoteWriteProtoType, compressions []config.RemoteWriteCompression) http.Handler {
 	h := &writeHandler{
-		logger:     logger,
-		appendable: appendable,
-		rwFormat:   rwFormat,
+		logger:                    logger,
+		appendable:                appendable,
+		protoTypes:                protoTypes,
+		acceptHeaderValue:         config.RemoteWriteProtoTypes(protoTypes).ServerAcceptHeaderValue(),
+		compressions:              compressions,
+		acceptEncodingHeaderValue: config.RemoteWriteCompressions(compressions).ServerAcceptEncodingHeaderValue(),
 		samplesWithInvalidLabelsTotal: prometheus.NewCounter(prometheus.CounterOpts{
 			Namespace: "prometheus",
 			Subsystem: "api",
@@ -134,35 +75,59 @@ func NewWriteHandler(logger log.Logger, reg prometheus.Registerer, appendable st
 	return h
 }
 
-func (h *writeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
-	var err error
-
-	// Set the header(s) in the response based on the rwFormat the server supports.
-	for hName, hValue := range rwHeaderNameValues(h.rwFormat) {
-		w.Header().Set(hName, hValue)
+func (h *writeHandler) parseEncoding(contentEncoding string) (config.RemoteWriteCompression, error) {
+	// TODO(bwplotka): TBD
+	got := config.RemoteWriteCompression(contentEncoding)
+	if err := got.Validate(); err != nil {
+		return "", err // TODO(bwplotka): Wrap properly
 	}
 
-	// Parse the headers to work out how to handle this.
-	contentEncoding := r.Header.Get("Content-Encoding")
-	protoVer := r.Header.Get(RemoteWriteVersionHeader)
+	// TODO(bwplotka): Build utils for this.
+	for _, c := range h.compressions {
+		if c == got {
+			return got, nil
+		}
+	}
+	return "", fmt.Errorf("unsupported compression, got %v, supported %v", got, h.acceptEncodingHeaderValue)
+}
 
-	switch protoVer {
-	case "":
-		// No header provided, assume 0.1.0 as everything that relies on later.
-		protoVer = RemoteWriteVersion1HeaderValue
-	case RemoteWriteVersion1HeaderValue, RemoteWriteVersion20HeaderValue:
-		// We know this header, woo.
-	default:
-		// We have a version in the header but it is not one we recognise.
-		level.Error(h.logger).Log("msg", "Error decoding remote write request", "err", "Unknown remote write version in headers", "ver", protoVer)
-		// Return a 406 so that the client can choose a more appropriate protocol to use.
-		http.Error(w, "Unknown remote write version in headers", http.StatusNotAcceptable)
+func (h *writeHandler) parseType(contentType string) (config.RemoteWriteProtoType, error) {
+	// TODO(bwplotka): TBD
+	got := config.RemoteWriteProtoType(contentType)
+	if err := got.Validate(); err != nil {
+		return "", err // TODO(bwplotka): Wrap properly
+	}
+
+	// TODO(bwplotka): Build utils for this.
+	for _, c := range h.protoTypes {
+		if c == got {
+			return got, nil
+		}
+	}
+	return "", fmt.Errorf("unsupported proto type, got %v, supported %v", got, h.acceptHeaderValue)
+}
+
+func (h *writeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	// Start with ensuring receiver response headers indicate PRW 2.0 and accepted
+	// content type and compressions.
+	w.Header().Set("Accept", h.acceptHeaderValue)
+	w.Header().Set("Accept-Encoding", h.acceptEncodingHeaderValue)
+
+	// Initial content type and encoding negotiation.
+	// NOTE: PRW 2.0 deprecated X-Prometheus-Remote-Write-Version, ignore it, we
+	// rely on content-type header only.
+	enc, err := h.parseEncoding(r.Header.Get("Content-Encoding"))
+	if err != nil {
+
+		w.WriteHeader(http.StatusUnsupportedMediaType)
+		w.Write([]byte(err.Error())) // TODO(bwplotka) Format? Log?
 		return
 	}
-
-	// Deal with 0.1.0 clients that forget to send Content-Encoding.
-	if protoVer == RemoteWriteVersion1HeaderValue && contentEncoding == "" {
-		contentEncoding = "snappy"
+	typ, err := h.parseType(r.Header.Get("Content-Type"))
+	if err != nil {
+		w.WriteHeader(http.StatusUnsupportedMediaType)
+		w.Write([]byte(err.Error())) // TODO(bwplotka) Format? Log? use http.Error
+		return
 	}
 
 	// Read the request body.
@@ -173,11 +138,9 @@ func (h *writeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	// Deal with contentEncoding first.
 	var decompressed []byte
-
-	switch contentEncoding {
-	case "snappy":
+	switch enc {
+	case config.RemoteWriteCompressionSnappy:
 		decompressed, err = snappy.Decode(nil, body)
 		if err != nil {
 			level.Error(h.logger).Log("msg", "Error decoding remote write request", "err", err.Error())
@@ -185,16 +148,11 @@ func (h *writeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 			return
 		}
 	default:
-		level.Error(h.logger).Log("msg", "Error decoding remote write request", "err", "Unsupported Content-Encoding", "contentEncoding", contentEncoding)
-		// Return a 406 so that the client can choose a more appropriate protocol to use.
-		http.Error(w, "Unsupported Content-Encoding", http.StatusNotAcceptable)
-		return
+		panic("should not happen")
 	}
 
-	// Now we have a decompressed buffer we can unmarshal it.
-	// At this point we are happy with the version but need to check the encoding.
-	switch protoVer {
-	case RemoteWriteVersion1HeaderValue:
+	switch typ {
+	case config.RemoteWriteProtoTypeV1:
 		var req prompb.WriteRequest
 		if err := proto.Unmarshal(decompressed, &req); err != nil {
 			level.Error(h.logger).Log("msg", "Error decoding remote write request", "err", err.Error())
@@ -202,7 +160,7 @@ func (h *writeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 			return
 		}
 		err = h.write(r.Context(), &req)
-	case RemoteWriteVersion20HeaderValue:
+	case config.RemoteWriteProtoTypeV2:
 		// 2.0 request.
 		var reqMinStr writev2.WriteRequest
 		if err := proto.Unmarshal(decompressed, &reqMinStr); err != nil {
@@ -211,6 +169,8 @@ func (h *writeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 			return
 		}
 		err = h.writeMinStr(r.Context(), &reqMinStr)
+	default:
+		panic("should not happen")
 	}
 
 	switch {

web/api/v1/api.go

@@ -210,10 +210,9 @@ type API struct {
 	isAgent       bool
 	statsRenderer StatsRenderer
 
-	remoteWriteHeadHandler http.Handler
-	remoteWriteHandler     http.Handler
-	remoteReadHandler      http.Handler
-	otlpWriteHandler       http.Handler
+	remoteWriteHandler http.Handler
+	remoteReadHandler  http.Handler
+	otlpWriteHandler   http.Handler
 
 	codecs []Codec
 }
@@ -247,7 +246,8 @@ func NewAPI(
 	registerer prometheus.Registerer,
 	statsRenderer StatsRenderer,
 	rwEnabled bool,
-	rwFormat config.RemoteWriteFormat,
+	rwProtoTypes []config.RemoteWriteProtoType,
+	rwCompressions []config.RemoteWriteCompression,
 	otlpEnabled bool,
 ) *API {
 	a := &API{
@@ -290,20 +290,7 @@ func NewAPI(
 	}
 
 	if rwEnabled {
-		// TODO(alexg) - Two phase rwFormat rollout needs to create handlers with flag for advertising.
-		// For rollout we do two phases:
-		// 0. (Before) no flags set
-		// 1. (During) support new protocols but don't advertise
-		// <wait until all servers have rolled out and now support RW2.0>
-		// 2. (After) support new protocols and advertise
-		//
-		// For rollback the two phases are:
-		// 0. (Before) support new protocols and advertise
-		// 1. (During) support new protocols but don't advertise
-		// <wait a suitable period for all sending clients to be aware that receiving servers no longer support 2.0>
-		// 2. (After) no flags set
-		a.remoteWriteHandler = remote.NewWriteHandler(logger, registerer, ap, rwFormat)
-		a.remoteWriteHeadHandler = remote.NewWriteHeadHandler(logger, registerer, rwFormat)
+		a.remoteWriteHandler = remote.NewWriteHandler(logger, registerer, ap, rwProtoTypes, rwCompressions)
 	}
 	if otlpEnabled {
 		a.otlpWriteHandler = remote.NewOTLPWriteHandler(logger, ap)
@@ -400,7 +387,6 @@ func (api *API) Register(r *route.Router) {
 	r.Get("/status/walreplay", api.serveWALReplayStatus)
 	r.Post("/read", api.ready(api.remoteRead))
 	r.Post("/write", api.ready(api.remoteWrite))
-	r.Head("/write", api.remoteWriteHead)
 	r.Post("/otlp/v1/metrics", api.ready(api.otlpWrite))
 
 	r.Get("/alerts", wrapAgent(api.alerts))
@@ -1661,14 +1647,6 @@ func (api *API) remoteRead(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
-func (api *API) remoteWriteHead(w http.ResponseWriter, r *http.Request) {
-	if api.remoteWriteHeadHandler != nil {
-		api.remoteWriteHeadHandler.ServeHTTP(w, r)
-	} else {
-		http.Error(w, "remote write receiver needs to be enabled with --web.enable-remote-write-receiver", http.StatusNotFound)
-	}
-}
-
 func (api *API) remoteWrite(w http.ResponseWriter, r *http.Request) {
 	if api.remoteWriteHandler != nil {
 		api.remoteWriteHandler.ServeHTTP(w, r)

web/web.go

@@ -244,28 +244,28 @@ type Options struct {
 	Version               *PrometheusVersion
 	Flags                 map[string]string
 
-	ListenAddress              string
-	CORSOrigin                 *regexp.Regexp
-	ReadTimeout                time.Duration
-	MaxConnections             int
-	ExternalURL                *url.URL
-	RoutePrefix                string
-	UseLocalAssets             bool
-	UserAssetsPath             string
-	ConsoleTemplatesPath       string
-	ConsoleLibrariesPath       string
-	EnableLifecycle            bool
-	EnableAdminAPI             bool
-	PageTitle                  string
-	RemoteReadSampleLimit      int
-	RemoteReadConcurrencyLimit int
-	RemoteReadBytesInFrame     int
-	EnableRemoteWriteReceiver  bool
-	EnableOTLPWriteReceiver    bool
-	IsAgent                    bool
-	AppName                    string
-	// TODO(cstyan): should this change to a list of tuples, maybe via the content negotiation PR?
-	RemoteWriteFormat config.RemoteWriteFormat
+	ListenAddress                   string
+	CORSOrigin                      *regexp.Regexp
+	ReadTimeout                     time.Duration
+	MaxConnections                  int
+	ExternalURL                     *url.URL
+	RoutePrefix                     string
+	UseLocalAssets                  bool
+	UserAssetsPath                  string
+	ConsoleTemplatesPath            string
+	ConsoleLibrariesPath            string
+	EnableLifecycle                 bool
+	EnableAdminAPI                  bool
+	PageTitle                       string
+	RemoteReadSampleLimit           int
+	RemoteReadConcurrencyLimit      int
+	RemoteReadBytesInFrame          int
+	EnableRemoteWriteReceiver       bool
+	RemoteWriteReceiverProtoTypes   []config.RemoteWriteProtoType
+	RemoteWriteReceiverCompressions []config.RemoteWriteCompression
+	EnableOTLPWriteReceiver         bool
+	IsAgent                         bool
+	AppName                         string
 
 	Gatherer   prometheus.Gatherer
 	Registerer prometheus.Registerer
@@ -355,7 +355,8 @@ func New(logger log.Logger, o *Options) *Handler {
 		o.Registerer,
 		nil,
 		o.EnableRemoteWriteReceiver,
-		o.RemoteWriteFormat,
+		o.RemoteWriteReceiverProtoTypes,
+		o.RemoteWriteReceiverCompressions,
 		o.EnableOTLPWriteReceiver,
 	)