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Implement fully-featured content negotiation for API requests, and allow overriding the default API codec. 

Signed-off-by: Charles Korn <charles.korn@grafana.com>
This commit is contained in:
Charles Korn 2023-02-27 13:27:09 +11:00
parent eaad7c0fc8
commit 46a28899a0
No known key found for this signature in database
6 changed files with 175 additions and 47 deletions
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2
go.mod
View File

@ -160,7 +160,7 @@ require (
github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
github.com/modern-go/reflect2 v1.0.2 // indirect
github.com/morikuni/aec v1.0.0 // indirect
github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822
github.com/opencontainers/go-digest v1.0.0 // indirect
github.com/opencontainers/image-spec v1.0.2 // indirect
github.com/pmezard/go-difflib v1.0.0 // indirect

78
web/api/v1/api.go
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@ -32,6 +32,7 @@ import (
"github.com/go-kit/log/level"
"github.com/grafana/regexp"
jsoniter "github.com/json-iterator/go"
"github.com/munnerz/goautoneg"
"github.com/pkg/errors"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/common/model"
@ -68,20 +69,19 @@ const (
type errorType string
const (
errorNone errorType = ""
errorTimeout errorType = "timeout"
errorCanceled errorType = "canceled"
errorExec errorType = "execution"
errorBadData errorType = "bad_data"
errorInternal errorType = "internal"
errorUnavailable errorType = "unavailable"
errorNotFound errorType = "not_found"
errorNone errorType = ""
errorTimeout errorType = "timeout"
errorCanceled errorType = "canceled"
errorExec errorType = "execution"
errorBadData errorType = "bad_data"
errorInternal errorType = "internal"
errorUnavailable errorType = "unavailable"
errorNotFound errorType = "not_found"
errorNotAcceptable errorType = "not_acceptable"
)
var LocalhostRepresentations = []string{"127.0.0.1", "localhost", "::1"}
var defaultCodec = JSONCodec{}
type apiError struct {
typ errorType
err error
@ -212,7 +212,7 @@ type API struct {
remoteWriteHandler http.Handler
remoteReadHandler http.Handler
codecs map[string]Codec
codecs []Codec
}
// NewAPI returns an initialized API type.
@ -271,11 +271,9 @@ func NewAPI(
statsRenderer: defaultStatsRenderer,
remoteReadHandler: remote.NewReadHandler(logger, registerer, q, configFunc, remoteReadSampleLimit, remoteReadConcurrencyLimit, remoteReadMaxBytesInFrame),
codecs: map[string]Codec{},
}
a.InstallCodec(defaultCodec)
a.InstallCodec(JSONCodec{})
if statsRenderer != nil {
a.statsRenderer = statsRenderer
@ -289,13 +287,15 @@ func NewAPI(
}
// InstallCodec adds codec to this API's available codecs.
// If codec handles a content type handled by a codec already installed in this API, codec replaces the previous codec.
// Codecs installed first take precedence over codecs installed later when evaluating wildcards in Accept headers.
// The first installed codec is used as a fallback when the Accept header cannot be satisfied or if there is no Accept header.
func (api *API) InstallCodec(codec Codec) {
if api.codecs == nil {
api.codecs = map[string]Codec{}
}
api.codecs = append(api.codecs, codec)
}
api.codecs[codec.ContentType()] = codec
// ClearCodecs removes all available codecs from this API, including the default codec installed by NewAPI.
func (api *API) ClearCodecs() {
api.codecs = nil
}
func setUnavailStatusOnTSDBNotReady(r apiFuncResult) apiFuncResult {
@ -1583,7 +1583,12 @@ func (api *API) respond(w http.ResponseWriter, req *http.Request, data interface
Warnings: warningStrings,
}
codec := api.negotiateCodec(req, resp)
codec, err := api.negotiateCodec(req, resp)
if err != nil {
api.respondError(w, &apiError{errorNotAcceptable, err}, nil)
return
}
b, err := codec.Encode(resp)
if err != nil {
level.Error(api.logger).Log("msg", "error marshaling response", "err", err)
@ -1591,33 +1596,28 @@ func (api *API) respond(w http.ResponseWriter, req *http.Request, data interface
return
}
w.Header().Set("Content-Type", codec.ContentType())
w.Header().Set("Content-Type", codec.ContentType().String())
w.WriteHeader(http.StatusOK)
if n, err := w.Write(b); err != nil {
level.Error(api.logger).Log("msg", "error writing response", "bytesWritten", n, "err", err)
}
}
// HTTP content negotiation is hard (see https://developer.mozilla.org/en-US/docs/Web/HTTP/Content_negotiation).
// Ideally, we shouldn't be implementing this ourselves - https://github.com/golang/go/issues/19307 is an open proposal to add
// this to the Go stdlib and has links to a number of other implementations.
//
// This is an MVP, and doesn't support features like wildcards or weighting.
func (api *API) negotiateCodec(req *http.Request, resp *Response) Codec {
acceptHeader := req.Header.Get("Accept")
if acceptHeader == "" {
return defaultCodec
}
for _, contentType := range strings.Split(acceptHeader, ",") {
codec, ok := api.codecs[strings.TrimSpace(contentType)]
if ok && codec.CanEncode(resp) {
return codec
func (api *API) negotiateCodec(req *http.Request, resp *Response) (Codec, error) {
for _, clause := range goautoneg.ParseAccept(req.Header.Get("Accept")) {
for _, codec := range api.codecs {
if codec.ContentType().Satisfies(clause) && codec.CanEncode(resp) {
return codec, nil
}
}
}
level.Debug(api.logger).Log("msg", "could not find suitable codec for response, falling back to default codec", "accept_header", acceptHeader)
return defaultCodec
defaultCodec := api.codecs[0]
if !defaultCodec.CanEncode(resp) {
return nil, fmt.Errorf("cannot encode response as %s", defaultCodec.ContentType())
}
return defaultCodec, nil
}
func (api *API) respondError(w http.ResponseWriter, apiErr *apiError, data interface{}) {
@ -1648,6 +1648,8 @@ func (api *API) respondError(w http.ResponseWriter, apiErr *apiError, data inter
code = http.StatusInternalServerError
case errorNotFound:
code = http.StatusNotFound
case errorNotAcceptable:
code = http.StatusNotAcceptable
default:
code = http.StatusInternalServerError
}

41
web/api/v1/api_test.go
View File

@ -2769,9 +2769,11 @@ func TestRespondSuccess(t *testing.T) {
logger: log.NewNopLogger(),
}
api.InstallCodec(&testCodec{contentType: "test/cannot-encode", canEncode: false})
api.InstallCodec(&testCodec{contentType: "test/can-encode", canEncode: true})
api.InstallCodec(&testCodec{contentType: "test/can-encode-2", canEncode: true})
api.ClearCodecs()
api.InstallCodec(JSONCodec{})
api.InstallCodec(&testCodec{contentType: MIMEType{"test", "cannot-encode"}, canEncode: false})
api.InstallCodec(&testCodec{contentType: MIMEType{"test", "can-encode"}, canEncode: true})
api.InstallCodec(&testCodec{contentType: MIMEType{"test", "can-encode-2"}, canEncode: true})
s := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
api.respond(w, r, "test", nil)
@ -2854,6 +2856,34 @@ func TestRespondSuccess(t *testing.T) {
}
}
func TestRespondSuccess_DefaultCodecCannotEncodeResponse(t *testing.T) {
api := API{
logger: log.NewNopLogger(),
}
api.ClearCodecs()
api.InstallCodec(&testCodec{contentType: MIMEType{"application", "default-format"}, canEncode: false})
s := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
api.respond(w, r, "test", nil)
}))
defer s.Close()
req, err := http.NewRequest(http.MethodGet, s.URL, nil)
require.NoError(t, err)
resp, err := http.DefaultClient.Do(req)
require.NoError(t, err)
body, err := io.ReadAll(resp.Body)
defer resp.Body.Close()
require.NoError(t, err)
require.Equal(t, http.StatusNotAcceptable, resp.StatusCode)
require.Equal(t, "application/json", resp.Header.Get("Content-Type"))
require.Equal(t, `{"status":"error","errorType":"not_acceptable","error":"cannot encode response as application/default-format"}`, string(body))
}
func TestRespondError(t *testing.T) {
s := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
api := API{}
@ -3193,6 +3223,7 @@ func BenchmarkRespond(b *testing.B) {
}
b.ResetTimer()
api := API{}
api.InstallCodec(JSONCodec{})
for n := 0; n < b.N; n++ {
api.respond(&testResponseWriter, request, response, nil)
}
@ -3307,11 +3338,11 @@ func TestGetGlobalURL(t *testing.T) {
}
type testCodec struct {
contentType string
contentType MIMEType
canEncode bool
}
func (t *testCodec) ContentType() string {
func (t *testCodec) ContentType() MIMEType {
return t.contentType
}

29
web/api/v1/codec.go
View File

@ -13,10 +13,12 @@
package v1
import "github.com/munnerz/goautoneg"
// A Codec performs encoding of API responses.
type Codec interface {
// ContentType returns the MIME time that this Codec emits.
ContentType() string
ContentType() MIMEType
// CanEncode determines if this Codec can encode resp.
CanEncode(resp *Response) bool
@ -24,3 +26,28 @@ type Codec interface {
// Encode encodes resp, ready for transmission to an API consumer.
Encode(resp *Response) ([]byte, error)
}
type MIMEType struct {
Type string
SubType string
}
func (m MIMEType) String() string {
return m.Type + "/" + m.SubType
}
func (m MIMEType) Satisfies(accept goautoneg.Accept) bool {
if accept.Type == "*" && accept.SubType == "*" {
return true
}
if accept.Type == m.Type && accept.SubType == "*" {
return true
}
if accept.Type == m.Type && accept.SubType == m.SubType {
return true
}
return false
}

68
web/api/v1/codec_test.go Normal file
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@ -0,0 +1,68 @@
// Copyright 2016 The Prometheus Authors
// 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
//
// http://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 v1
import (
"testing"
"github.com/munnerz/goautoneg"
"github.com/stretchr/testify/require"
)
func TestMIMEType_String(t *testing.T) {
m := MIMEType{Type: "application", SubType: "json"}
require.Equal(t, "application/json", m.String())
}
func TestMIMEType_Satisfies(t *testing.T) {
m := MIMEType{Type: "application", SubType: "json"}
scenarios := map[string]struct {
accept goautoneg.Accept
expected bool
}{
"exact match": {
accept: goautoneg.Accept{Type: "application", SubType: "json"},
expected: true,
},
"sub-type wildcard match": {
accept: goautoneg.Accept{Type: "application", SubType: "*"},
expected: true,
},
"full wildcard match": {
accept: goautoneg.Accept{Type: "*", SubType: "*"},
expected: true,
},
"inverted": {
accept: goautoneg.Accept{Type: "json", SubType: "application"},
expected: false,
},
"inverted sub-type wildcard": {
accept: goautoneg.Accept{Type: "json", SubType: "*"},
expected: false,
},
"complete mismatch": {
accept: goautoneg.Accept{Type: "text", SubType: "plain"},
expected: false,
},
}
for name, scenario := range scenarios {
t.Run(name, func(t *testing.T) {
actual := m.Satisfies(scenario.accept)
require.Equal(t, scenario.expected, actual)
})
}
}

4
web/api/v1/json_codec.go
View File

@ -34,8 +34,8 @@ func init() {
// JSONCodec is a Codec that encodes API responses as JSON.
type JSONCodec struct{}
func (j JSONCodec) ContentType() string {
return "application/json"
func (j JSONCodec) ContentType() MIMEType {
return MIMEType{Type: "application", SubType: "json"}
}
func (j JSONCodec) CanEncode(_ *Response) bool {