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UI Etag support for embedded content (#7132)
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* UI etag embedded content

Scan embedded content on startup and serve etag header to FileServer.
FileServer will use the Etag and provide no content change if needed.

This will allow cache all static resources, which allow better
performance after the first load, in the web ui.

* apply code review changes
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nopcoder authored Dec 9, 2023
1 parent 17a5305 commit 315770a
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Showing 2 changed files with 81 additions and 4 deletions.
78 changes: 78 additions & 0 deletions pkg/api/etag_middleware.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,78 @@
package api

import (
"crypto/md5" //nolint:gosec
"encoding/hex"
"io"
"io/fs"
"net/http"
"path"
"strings"
)

// EtagMiddleware returns a new Etag middleware handler.
// It designs to work on embedded FS, where the content doesn't change.
// It calculates the Etag for each file on startup and serves it on each request.
func EtagMiddleware(root fs.FS, next http.Handler) http.Handler {
etags, err := scanFSEtags(root)
if err != nil {
panic(err)
}
return &etagHandler{
root: root,
next: next,
etags: etags,
}
}

type etagHandler struct {
root fs.FS
next http.Handler
etags map[string]string
}

func (e *etagHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
upath := r.URL.Path
if !strings.HasPrefix(upath, "/") {
upath = "/" + upath
}
upath = path.Clean(upath)
if strings.HasSuffix(upath, "/") {
upath += "index.html"
}
etag, ok := e.etags[upath]
if ok {
w.Header().Set("Etag", "\""+etag+"\"")
}
e.next.ServeHTTP(w, r)
}

func scanFSEtags(fSys fs.FS) (map[string]string, error) {
etags := make(map[string]string)
err := fs.WalkDir(fSys, ".", func(fpath string, d fs.DirEntry, err error) error {
if err != nil {
return err
}
if d.IsDir() {
return nil
}

f, err := fSys.Open(fpath)
if err != nil {
return err
}
defer func() { _ = f.Close() }()

h := md5.New() //nolint:gosec
if _, err := io.Copy(h, f); err != nil {
return err
}
hashValue := hex.EncodeToString(h.Sum(nil))
etags["/"+fpath] = hashValue
return nil
})
if err != nil {
return nil, err
}
return etags, nil
}
7 changes: 3 additions & 4 deletions pkg/api/ui_handler.go
Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,6 @@ import (
"strings"

gomime "github.com/cubewise-code/go-mime"
"github.com/go-chi/chi/v5/middleware"
"github.com/treeverse/lakefs/pkg/api/params"
gwerrors "github.com/treeverse/lakefs/pkg/gateway/errors"
"github.com/treeverse/lakefs/pkg/gateway/operations"
Expand All @@ -34,8 +33,8 @@ func NewUIHandler(gatewayDomains []string, snippets []params.CodeSnippet) http.H
panic(err)
}
fileSystem := http.FS(injectedContent)
nocacheContent := middleware.NoCache(http.StripPrefix("/", http.FileServer(fileSystem)))
return NewHandlerWithDefault(fileSystem, nocacheContent, gatewayDomains)
etagHandler := EtagMiddleware(injectedContent, http.StripPrefix("/", http.FileServer(fileSystem)))
return NewHandlerWithDefault(fileSystem, etagHandler, gatewayDomains)
}

func NewS3GatewayEndpointErrorHandler(gatewayDomains []string) http.Handler {
Expand All @@ -45,7 +44,7 @@ func NewS3GatewayEndpointErrorHandler(gatewayDomains []string) http.Handler {
return
}

// For other requests, return generic not found error
// For other requests, return generic "not found" error
w.WriteHeader(http.StatusNotFound)
})
}
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