[#369] Request reproducer

Signed-off-by: Nikita Zinkevich <n.zinkevich@yadro.com>

api/layer/object.go

@@ -12,6 +12,7 @@ import (
 	"fmt"
 	"io"
 	"mime"
+	"net/http"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -21,6 +22,7 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/data"
 	apiErrors "git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/errors"
 	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/internal/logs"
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/pkg/detector"
 	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client"
 	cid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id"
 	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
@@ -245,11 +247,11 @@ func (n *Layer) PutObject(ctx context.Context, p *PutObjectParams) (*data.Extend
 	if r != nil {
 		if len(p.Header[api.ContentType]) == 0 {
 			if contentType := MimeByFilePath(p.Object); len(contentType) == 0 {
-				d := newDetector(r)
+				d := detector.NewDetector(r, http.DetectContentType)
 				if contentType, err := d.Detect(); err == nil {
 					p.Header[api.ContentType] = contentType
 				}
-				r = d.MultiReader()
+				r = d.RestoredReader()
 			} else {
 				p.Header[api.ContentType] = contentType
 			}

api/middleware/log_http.go

@@ -32,10 +32,6 @@ type (
 		*zap.Logger
 		logRoller *lumberjack.Logger
 	}
-	// Implementation of zap.Sink for using lumberjack.
-	lumberjackSink struct {
-		*lumberjack.Logger
-	}
 	// responseReadWriter helps read http response body.
 	responseReadWriter struct {
 		http.ResponseWriter
@@ -49,10 +45,6 @@ const (
 	responseLabel = "response"
 )
 
-func (lumberjackSink) Sync() error {
-	return nil
-}
-
 func (lc *LogHTTPConfig) InitHTTPLogger(log *zap.Logger) {
 	if err := lc.initHTTPLogger(); err != nil {
 		log.Error(logs.FailedToInitializeHTTPLogger, zap.Error(err))

cmd/s3-playback/internal/playback/multipart.go

@@ -0,0 +1,50 @@
+package playback
+
+import (
+	"encoding/xml"
+	"fmt"
+	"net/http"
+)
+
+type MultipartUpload struct {
+	XMLName  xml.Name `xml:"http://s3.amazonaws.com/doc/2006-03-01/ InitiateMultipartUploadResult" json:"-"`
+	Bucket   string   `json:"bucket" xml:"Bucket"`
+	Key      string   `json:"key" xml:"Key"`
+	UploadID string   `json:"uploadId" xml:"UploadId"`
+}
+
+func HandleResponse(r *http.Request, mparts map[string]MultipartUpload, resp []byte, logResponse []byte) error {
+	var mpart, mpartOld MultipartUpload
+	if r.Method != "POST" || !r.URL.Query().Has("uploads") {
+		return nil
+	}
+	// get new uploadId from response
+	err := xml.Unmarshal(resp, &mpart)
+	if err != nil {
+		return fmt.Errorf("xml unmarshal error: %w", err)
+	}
+	// get old uploadId from logs
+	err = xml.Unmarshal(logResponse, &mpartOld)
+	if err != nil {
+		return fmt.Errorf("xml unmarshal error: %w", err)
+	}
+	if mpartOld.UploadID != "" {
+		mparts[mpartOld.UploadID] = mpart
+	}
+
+	return nil
+}
+
+func SwapUploadID(r *http.Request, settings *Settings) error {
+	var uploadID string
+	query := r.URL.Query()
+	uploadID = query.Get("uploadId")
+	mpart, ok := settings.Multiparts[uploadID]
+	if !ok {
+		return fmt.Errorf("no multipart upload with specified uploadId")
+	}
+	query.Set("uploadId", mpart.UploadID)
+	r.URL.RawQuery = query.Encode()
+
+	return nil
+}

cmd/s3-playback/internal/playback/request.go

@@ -0,0 +1,97 @@
+package playback
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api"
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/auth"
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/pkg/detector"
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/pkg/xmlutils"
+	v4 "github.com/aws/aws-sdk-go-v2/aws/signer/v4"
+	"github.com/aws/aws-sdk-go-v2/credentials"
+)
+
+type (
+	httpBody      []byte
+	LoggedRequest struct {
+		From     string      `json:"from"`
+		URI      string      `json:"URI"`
+		Method   string      `json:"method"`
+		Payload  httpBody    `json:"payload,omitempty"`
+		Response httpBody    `json:"response,omitempty"`
+		Query    url.Values  `json:"query"`
+		Header   http.Header `json:"headers"`
+	}
+	Credentials struct {
+		AccessKey string
+		SecretKey string
+	}
+	Settings struct {
+		Endpoint   string
+		Creds      Credentials
+		Multiparts map[string]MultipartUpload
+		Client     *http.Client
+	}
+)
+
+func (h *httpBody) UnmarshalJSON(data []byte) error {
+	unquoted, err := strconv.Unquote(string(data))
+	if err != nil {
+		return fmt.Errorf("failed to unquote data: %w", err)
+	}
+	detect := detector.NewDetector(strings.NewReader(unquoted), xmlutils.DetectXML)
+	dataType, err := detect.Detect()
+	if err != nil {
+		return fmt.Errorf("failed to detect data: %w", err)
+	}
+	reader := xmlutils.ChooseReader(dataType, detect.RestoredReader())
+	*h, err = io.ReadAll(reader)
+	if err != nil {
+		return fmt.Errorf("failed to unmarshal httpbody: %w", err)
+	}
+
+	return nil
+}
+
+// Sign replace Authorization header with new Access key id and Signature values.
+func Sign(ctx context.Context, r *http.Request, creds Credentials) error {
+	credProvider := credentials.NewStaticCredentialsProvider(creds.AccessKey, creds.SecretKey, "")
+	awsCred, err := credProvider.Retrieve(ctx)
+	if err != nil {
+		return err
+	}
+
+	authHdr := r.Header.Get(auth.AuthorizationHdr)
+	authInfo, err := parseAuthHeader(authHdr)
+	if err != nil {
+		return err
+	}
+	newHeader := strings.Replace(authHdr, authInfo["access_key_id"], creds.AccessKey, 1)
+	r.Header.Set(auth.AuthorizationHdr, newHeader)
+
+	signer := v4.NewSigner()
+	signatureDateTimeStr := r.Header.Get(api.AmzDate)
+	signatureDateTime, err := time.Parse("20060102T150405Z", signatureDateTimeStr)
+	if err != nil {
+		return err
+	}
+
+	return signer.SignHTTP(ctx, awsCred, r, r.Header.Get(api.AmzContentSha256), authInfo["service"], authInfo["region"], signatureDateTime)
+}
+
+func parseAuthHeader(authHeader string) (map[string]string, error) {
+	authInfo := auth.NewRegexpMatcher(auth.AuthorizationFieldRegexp).GetSubmatches(authHeader)
+	if len(authInfo) == 0 {
+		return nil, errors.New("no matches found")
+	}
+
+	return authInfo, nil
+}

cmd/s3-playback/internal/playback/request_test.go

@@ -0,0 +1,98 @@
+package playback
+
+import (
+	"errors"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+var errNoMatches = errors.New("no matches found")
+
+func withoutValue(data map[string]string, field string) map[string]string {
+	result := make(map[string]string)
+	for k, v := range data {
+		result[k] = v
+	}
+	result[field] = ""
+
+	return result
+}
+
+func TestParseAuthHeader(t *testing.T) {
+	defaultHeader := "AWS4-HMAC-SHA256 Credential=oid0cid/20210809/us-east-1/s3/aws4_request, SignedHeaders=host;x-amz-content-sha256;x-amz-date, Signature=2811ccb9e242f41426738fb1f"
+
+	defaultAuthInfo := map[string]string{
+		"access_key_id":        "oid0cid",
+		"service":              "s3",
+		"region":               "us-east-1",
+		"v4_signature":         "2811ccb9e242f41426738fb1f",
+		"signed_header_fields": "host;x-amz-content-sha256;x-amz-date",
+		"date":                 "20210809",
+	}
+	for _, tc := range []struct {
+		title    string
+		header   string
+		err      error
+		expected map[string]string
+	}{
+		{
+			title:    "correct full header",
+			header:   defaultHeader,
+			err:      nil,
+			expected: defaultAuthInfo,
+		},
+		{
+			title:    "correct with empty region",
+			header:   strings.Replace(defaultHeader, "/us-east-1/", "//", 1),
+			err:      nil,
+			expected: withoutValue(defaultAuthInfo, "region"),
+		},
+		{
+			title:    "empty access key",
+			header:   strings.Replace(defaultHeader, "oid0cid", "", 1),
+			err:      errNoMatches,
+			expected: nil,
+		},
+		{
+			title:    "empty service",
+			header:   strings.Replace(defaultHeader, "/s3/", "//", 1),
+			err:      errNoMatches,
+			expected: nil,
+		},
+		{
+			title:    "empty date",
+			header:   strings.Replace(defaultHeader, "/20210809/", "//", 1),
+			err:      errNoMatches,
+			expected: nil,
+		},
+		{
+			title: "empty v4_signature",
+			header: strings.Replace(defaultHeader, "Signature=2811ccb9e242f41426738fb1f",
+				"Signature=", 1),
+			err:      errNoMatches,
+			expected: nil,
+		},
+		{
+			title: "empty signed_fields",
+			header: strings.Replace(defaultHeader, "SignedHeaders=host;x-amz-content-sha256;x-amz-date",
+				"SignedHeaders=", 1),
+			err:      errNoMatches,
+			expected: nil,
+		},
+		{
+			title: "empty signed_fields",
+			header: strings.Replace(defaultHeader, "SignedHeaders=host;x-amz-content-sha256;x-amz-date",
+				"SignedHeaders=", 1),
+			err:      errNoMatches,
+			expected: nil,
+		},
+	} {
+		t.Run(tc.title, func(t *testing.T) {
+			authInfo, err := parseAuthHeader(tc.header)
+			require.Equal(t, err, tc.err, tc.header)
+			require.Equal(t, tc.expected, authInfo, tc.header)
+		})
+	}
+}

cmd/s3-playback/main.go

@@ -0,0 +1,20 @@
+package main
+
+import (
+	"context"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/cmd/s3-playback/modules"
+)
+
+func main() {
+	ctx, _ := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM, syscall.SIGHUP)
+
+	if cmd, err := modules.Execute(ctx); err != nil {
+		cmd.PrintErrln("Error:", err.Error())
+		cmd.PrintErrf("Run '%v --help' for usage.\n", cmd.CommandPath())
+		os.Exit(1)
+	}
+}

cmd/s3-playback/modules/root.go

@@ -0,0 +1,67 @@
+package modules
+
+import (
+	"context"
+	"os"
+	"strings"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/internal/version"
+	"github.com/spf13/cobra"
+	"github.com/spf13/pflag"
+	"github.com/spf13/viper"
+)
+
+const (
+	defaultPrintResponseLimit = 1024
+	cfgConfigPath             = "config"
+	cfgHTTPTimeoutFlag        = "http-timeout"
+	cfgSkipVerifyTLS          = "skip-verify-tls"
+)
+
+var (
+	cfgFile string
+	rootCmd = &cobra.Command{
+		Use:     "frostfs-s3-playback",
+		Version: version.Version,
+		Short:   "FrostFS S3 Traffic Playback",
+		Long:    "Helps to reproduce s3 commands from log files",
+		Example: "frostfs-s3-playback [--skip-verify-tls] [--http-timeout <timeout>] " +
+			"[--version] --config <config_path> <command>",
+		SilenceUsage:  true,
+		SilenceErrors: true,
+		PersistentPreRunE: func(cmd *cobra.Command, _ []string) error {
+			return viper.BindPFlags(cmd.Flags())
+		},
+		RunE: func(cmd *cobra.Command, _ []string) error {
+			return cmd.Help()
+		},
+	}
+)
+
+func Execute(ctx context.Context) (*cobra.Command, error) {
+	return rootCmd.ExecuteContextC(ctx)
+}
+
+func initConfig() {
+	viper.SetConfigFile(cfgFile)
+	_ = viper.ReadInConfig()
+}
+
+func init() {
+	cobra.OnInitialize(initConfig)
+	cobra.EnableTraverseRunHooks = true
+	rootCmd.SetGlobalNormalizationFunc(func(_ *pflag.FlagSet, name string) pflag.NormalizedName {
+		return pflag.NormalizedName(strings.ReplaceAll(name, "_", "-"))
+	})
+
+	rootCmd.PersistentFlags().StringVar(&cfgFile, cfgConfigPath, "", "configuration filepath")
+	_ = rootCmd.MarkPersistentFlagRequired(cfgConfigPath)
+	_ = rootCmd.MarkPersistentFlagFilename(cfgConfigPath)
+	rootCmd.PersistentFlags().Duration(cfgHTTPTimeoutFlag, time.Minute, "http request timeout")
+	rootCmd.PersistentFlags().Bool(cfgSkipVerifyTLS, false, "skip TLS certificate verification")
+	rootCmd.SetOut(os.Stdout)
+
+	initRunCmd()
+	rootCmd.AddCommand(runCmd)
+}

cmd/s3-playback/modules/run.go

@@ -45,7 +45,7 @@ var runCmd = &cobra.Command{
 	RunE: run,
 }
 
-func init() {
+func initRunCmd() {
 	runCmd.Flags().String(cfgLogPath, "./request.log", "log file path")
 	runCmd.Flags().String(cfgEndpoint, "", "endpoint URL")
 	runCmd.Flags().Int(cfgPrintResponseLimit, defaultPrintResponseLimit, "print limit for http response body")

config/config.env

@@ -57,7 +57,7 @@ S3_GW_HTTP_LOGGING_ENABLED=false
 # max body size to log
 S3_GW_HTTP_LOGGING_MAX_BODY=1024
 # max log size in Mb
-S3_GW_HTTP_LOGGING_MAX_LOG_SIZE: 20
+S3_GW_HTTP_LOGGING_MAX_LOG_SIZE=20
 # use log compression
 S3_GW_HTTP_LOGGING_GZIP=true
 # possible destination output values: filesystem path, url, "stdout", "stderr"

config/playback/playback.yaml

@@ -0,0 +1,8 @@
+endpoint: http://localhost:8084
+log: ./log/request.log
+credentials:
+  access_key: CAtUxDSSFtuVyVCjHTMhwx3eP3YSPo5ffwbPcnKfcdrD06WwUSn72T5EBNe3jcgjL54rmxFM6u3nUAoNBps8qJ1PD
+  secret_key: 560027d81c277de7378f71cbf12a32e4f7f541de724be59bcfdbfdc925425f30
+http_timeout: 60s
+skip_verify_tls: false
+print_response_limit: 1024

docs/configuration.md

@@ -380,6 +380,11 @@ logger:
 
 ### `http_logging` section
 
+Could be enabled only in builds with `loghttp` build tag. To build with `loghttp` tag, pass `GOFLAGS` var to `make`:
+```bash
+make GOFLAGS="-tags=loghttp" [target]
+```
+
 ```yaml
 http_logging:
   enabled: false
@@ -387,7 +392,6 @@ http_logging:
   max_log_size: 20
   gzip: true
   destination: stdout
-  log_response: true
 ```
 
 | Parameter      | Type     | SIGHUP reload | Default value | Description                                                                                                                                                                                 |
@@ -397,7 +401,6 @@ http_logging:
 | `max_log_size` | `int`    | yes           | `50`          | Log file size threshold (in megabytes) to be moved in backup file. After reaching  threshold, initial filename is appended with timestamp. And new empty file with initial name is created. |
 | `gzip`         | `bool`   | yes           | `false`       | Whether to enable Gzip compression to backup log files.                                                                                                                                     |
 | `destination`  | `string` | yes           | `stdout`      | Specify path for log output. Accepts log file path, or "stdout" and "stderr" reserved words to print in output streams. File and folders are created if necessary.                          |
-| `log_response` | bool   | yes           | true          | Whether to attach response body to the log.                                                                                                                                                 |
 
 
 ### `cache` section

docs/playback.md

@@ -0,0 +1,48 @@
+# FrostFS S3 Playback
+
+Playback is a tool to reproduce queries to `frostfs-s3-gw` in dev environment. Network logs could be
+gathered from `s3-gw` via HTTP Logger which could be enabled on build with `loghttp` build tag
+and `http_logging.enabled` option set to `true` in `s3-gw` configuration.
+
+## Commands
+
+`run` - reads log file and reproduces send requests from it to specified endpoint
+
+#### Example
+```bash
+frostfs-s3-playback --config <config_path> run [--endpoint=<endpoint>] [--log=<log_path>]
+```
+
+## Configuration
+
+Playback accepts configuration file path in yaml with corresponding options:
+```yaml
+endpoint: http://localhost:8084
+log: ./request.log
+env: .env
+credentials:
+  access_key: CAtUxDSSFtuVyVCjHTMhwx3eP3YSPo5ffwbPcnKfcdrD06WwUSn72T5EBNe3jcgjL54rmxFM6u3nUAoNBps8qJ1PD
+  secret_key: 560027d81c277de7378f71cbf12a32e4f7f541de724be59bcfdbfdc925425f30
+http_timeout: 60s
+skip_verify_tls: true
+```
+Configuration path is passed via required `--config` flag.
+If corresponding flag is set, it overrides parameter from config.
+
+### Configuration parameters
+
+#### Global parameters
+| Config parameter name   | Flag name         | Type       | Default value | Description                                                                   |
+|-------------------------|-------------------|------------|---------------|-------------------------------------------------------------------------------|
+| -                       | `config`          | `string`   | -             | config file path (e.g. `./config/playback.yaml`)                              |
+| `http_timeout`          | `http-timeout`    | `duration` | `60s`         | http request timeout                                                          |
+| `skip_verify_tls`       | `skip-verify-tls` | `bool`     | `false`       | skips tls certificate verification for https endpoints                        |
+| `credentials.accessKey` | -                 | `string`   | -             | AWS access key id                                                             |
+| `credentials.secretKey` | -                 | `string`   | -             | AWS secret key                                                                |
+| `print_response_limit`  | -                 | `int`      | `1024`        | max response length to be printed in stdout, the rest of body will be omitted |
+
+#### `run` command parameters
+| Config parameter name | Flag name | Type   | Default value | Description                                            |
+|-----------------------|-----------|--------|---------------|--------------------------------------------------------|
+| `endpoint`            | endpoint  | string | -             | s3-gw endpoint URL                                     |
+| `log`                 | log       | string | ./request.log | path to log file, could be either absolute or relative |

go.mod

@@ -10,7 +10,8 @@ require (
 	git.frostfs.info/TrueCloudLab/policy-engine v0.0.0-20240822104152-a3bc3099bd5b
 	git.frostfs.info/TrueCloudLab/zapjournald v0.0.0-20240124114243-cb2e66427d02
 	github.com/aws/aws-sdk-go v1.44.6
-	github.com/aws/aws-sdk-go-v2 v1.18.1
+	github.com/aws/aws-sdk-go-v2 v1.30.3
+	github.com/aws/aws-sdk-go-v2/credentials v1.17.27
 	github.com/bluele/gcache v0.0.2
 	github.com/go-chi/chi/v5 v5.0.8
 	github.com/google/uuid v1.6.0
@@ -46,7 +47,7 @@ require (
 	git.frostfs.info/TrueCloudLab/tzhash v1.8.0 // indirect
 	github.com/VictoriaMetrics/easyproto v0.1.4 // indirect
 	github.com/antlr4-go/antlr/v4 v4.13.0 // indirect
-	github.com/aws/smithy-go v1.13.5 // indirect
+	github.com/aws/smithy-go v1.20.3 // indirect
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cenkalti/backoff/v4 v4.2.1 // indirect
 	github.com/cespare/xxhash/v2 v2.2.0 // indirect

go.sum

@@ -66,10 +66,12 @@ github.com/antlr4-go/antlr/v4 v4.13.0 h1:lxCg3LAv+EUK6t1i0y1V6/SLeUi0eKEKdhQAlS8
 github.com/antlr4-go/antlr/v4 v4.13.0/go.mod h1:pfChB/xh/Unjila75QW7+VU4TSnWnnk9UTnmpPaOR2g=
 github.com/aws/aws-sdk-go v1.44.6 h1:Y+uHxmZfhRTLX2X3khkdxCoTZAyGEX21aOUHe1U6geg=
 github.com/aws/aws-sdk-go v1.44.6/go.mod h1:y4AeaBuwd2Lk+GepC1E9v0qOiTws0MIWAX4oIKwKHZo=
-github.com/aws/aws-sdk-go-v2 v1.18.1 h1:+tefE750oAb7ZQGzla6bLkOwfcQCEtC5y2RqoqCeqKo=
-github.com/aws/aws-sdk-go-v2 v1.18.1/go.mod h1:uzbQtefpm44goOPmdKyAlXSNcwlRgF3ePWVW6EtJvvw=
-github.com/aws/smithy-go v1.13.5 h1:hgz0X/DX0dGqTYpGALqXJoRKRj5oQ7150i5FdTePzO8=
-github.com/aws/smithy-go v1.13.5/go.mod h1:Tg+OJXh4MB2R/uN61Ko2f6hTZwB/ZYGOtib8J3gBHzA=
+github.com/aws/aws-sdk-go-v2 v1.30.3 h1:jUeBtG0Ih+ZIFH0F4UkmL9w3cSpaMv9tYYDbzILP8dY=
+github.com/aws/aws-sdk-go-v2 v1.30.3/go.mod h1:nIQjQVp5sfpQcTc9mPSr1B0PaWK5ByX9MOoDadSN4lc=
+github.com/aws/aws-sdk-go-v2/credentials v1.17.27 h1:2raNba6gr2IfA0eqqiP2XiQ0UVOpGPgDSi0I9iAP+UI=
+github.com/aws/aws-sdk-go-v2/credentials v1.17.27/go.mod h1:gniiwbGahQByxan6YjQUMcW4Aov6bLC3m+evgcoN4r4=
+github.com/aws/smithy-go v1.20.3 h1:ryHwveWzPV5BIof6fyDvor6V3iUL7nTfiTKXHiW05nE=
+github.com/aws/smithy-go v1.20.3/go.mod h1:krry+ya/rV9RDcV/Q16kpu6ypI4K2czasz0NC3qS14E=
 github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
 github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
 github.com/bits-and-blooms/bitset v1.8.0 h1:FD+XqgOZDUxxZ8hzoBFuV9+cGWY9CslN6d5MS5JVb4c=
@@ -177,7 +179,6 @@ github.com/google/go-cmp v0.5.2/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/
 github.com/google/go-cmp v0.5.4/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.6/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
-github.com/google/go-cmp v0.5.8/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/martian v2.1.0+incompatible/go.mod h1:9I4somxYTbIHy5NJKHRl3wXiIaQGbYVAs8BPL6v8lEs=

pkg/detector/detector.go

@@ -1,15 +1,15 @@
-package layer
+package detector
 
 import (
 	"io"
-	"net/http"
 )
 
 type (
-	detector struct {
+	Detector struct {
 		io.Reader
 		err        error
 		data       []byte
+		detectFunc func([]byte) string
 	}
 	errReader struct {
 		data   []byte
@@ -36,23 +36,24 @@ func (r *errReader) Read(b []byte) (int, error) {
 	return n, nil
 }
 
-func newDetector(reader io.Reader) *detector {
-	return &detector{
+func NewDetector(reader io.Reader, detectFunc func([]byte) string) *Detector {
+	return &Detector{
 		data:       make([]byte, contentTypeDetectSize),
 		Reader:     reader,
+		detectFunc: detectFunc,
 	}
 }
 
-func (d *detector) Detect() (string, error) {
+func (d *Detector) Detect() (string, error) {
 	n, err := d.Reader.Read(d.data)
 	if err != nil && err != io.EOF {
 		d.err = err
 		return "", err
 	}
 	d.data = d.data[:n]
-	return http.DetectContentType(d.data), nil
+	return d.detectFunc(d.data), nil
 }
 
-func (d *detector) MultiReader() io.Reader {
+func (d *Detector) RestoredReader() io.Reader {
 	return io.MultiReader(newReader(d.data, d.err), d.Reader)
 }