X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/165993fac96251ec0ec2e881fab40a5db113a282..991d7d7967cef46bf5aebf95f946e3072aa1e933:/services/keep-web/webdav.go

diff --git a/services/keep-web/webdav.go b/services/keep-web/webdav.go
index 0a7b7822b2..57f3f53a99 100644
--- a/services/keep-web/webdav.go
+++ b/services/keep-web/webdav.go
@@ -11,9 +11,12 @@ import (
 	prand "math/rand"
 	"net/http"
 	"os"
+	"sync"
 	"sync/atomic"
 	"time"
 
+	"git.curoverse.com/arvados.git/sdk/go/arvados"
+
 	"golang.org/x/net/context"
 	"golang.org/x/net/webdav"
 )
@@ -24,10 +27,10 @@ var (
 	errReadOnly           = errors.New("read-only filesystem")
 )
 
-// webdavFS implements a read-only webdav.FileSystem by wrapping
-// http.Filesystem.
+// webdavFS implements a read-only webdav.FileSystem by wrapping an
+// arvados.CollectionFilesystem.
 type webdavFS struct {
-	httpfs http.FileSystem
+	collfs arvados.CollectionFileSystem
 }
 
 var _ webdav.FileSystem = &webdavFS{}
@@ -37,11 +40,11 @@ func (fs *webdavFS) Mkdir(ctx context.Context, name string, perm os.FileMode) er
 }
 
 func (fs *webdavFS) OpenFile(ctx context.Context, name string, flag int, perm os.FileMode) (webdav.File, error) {
-	f, err := fs.httpfs.Open(name)
+	fi, err := fs.collfs.Stat(name)
 	if err != nil {
 		return nil, err
 	}
-	return &webdavFile{File: f}, nil
+	return &webdavFile{collfs: fs.collfs, fileInfo: fi, name: name}, nil
 }
 
 func (fs *webdavFS) RemoveAll(ctx context.Context, name string) error {
@@ -53,23 +56,76 @@ func (fs *webdavFS) Rename(ctx context.Context, oldName, newName string) error {
 }
 
 func (fs *webdavFS) Stat(ctx context.Context, name string) (os.FileInfo, error) {
-	if f, err := fs.httpfs.Open(name); err != nil {
-		return nil, err
-	} else {
-		return f.Stat()
-	}
+	return fs.collfs.Stat(name)
 }
 
 // webdavFile implements a read-only webdav.File by wrapping
-// http.File. Writes fail.
+// http.File.
+//
+// The http.File is opened from an arvados.CollectionFileSystem, but
+// not until Seek, Read, or Readdir is called. This deferred-open
+// strategy makes webdav's OpenFile-Stat-Close cycle fast even though
+// the collfs's Open method is slow. This is relevant because webdav
+// does OpenFile-Stat-Close on each file when preparing directory
+// listings.
+//
+// Writes to a webdavFile always fail.
 type webdavFile struct {
-	http.File
+	// fields populated by (*webdavFS).OpenFile()
+	collfs   http.FileSystem
+	fileInfo os.FileInfo
+	name     string
+
+	// internal fields
+	file     http.File
+	loadOnce sync.Once
+	err      error
+}
+
+func (f *webdavFile) load() {
+	f.file, f.err = f.collfs.Open(f.name)
 }
 
 func (f *webdavFile) Write([]byte) (int, error) {
 	return 0, errReadOnly
 }
 
+func (f *webdavFile) Seek(offset int64, whence int) (int64, error) {
+	f.loadOnce.Do(f.load)
+	if f.err != nil {
+		return 0, f.err
+	}
+	return f.file.Seek(offset, whence)
+}
+
+func (f *webdavFile) Read(buf []byte) (int, error) {
+	f.loadOnce.Do(f.load)
+	if f.err != nil {
+		return 0, f.err
+	}
+	return f.file.Read(buf)
+}
+
+func (f *webdavFile) Close() error {
+	if f.file == nil {
+		// We never called load(), or load() failed
+		return f.err
+	}
+	return f.file.Close()
+}
+
+func (f *webdavFile) Readdir(n int) ([]os.FileInfo, error) {
+	f.loadOnce.Do(f.load)
+	if f.err != nil {
+		return nil, f.err
+	}
+	return f.file.Readdir(n)
+}
+
+func (f *webdavFile) Stat() (os.FileInfo, error) {
+	return f.fileInfo, nil
+}
+
 // noLockSystem implements webdav.LockSystem by returning success for
 // every possible locking operation, even though it has no side
 // effects such as actually locking anything. This works for a