package main
import (
+ "crypto/rand"
"errors"
+ "fmt"
+ 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"
)
-var errReadOnly = errors.New("read-only filesystem")
+var (
+ lockPrefix string = uuid()
+ nextLockSuffix int64 = prand.Int63()
+ 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{}
}
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 {
}
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
+// read-only webdav filesystem because webdav locks only apply to
+// writes.
+//
+// This is more suitable than webdav.NewMemLS() for two reasons:
+// First, it allows keep-web to use one locker for all collections
+// even though coll1.vhost/foo and coll2.vhost/foo have the same path
+// but represent different resources. Additionally, it returns valid
+// tokens (rfc2518 specifies that tokens are represented as URIs and
+// are unique across all resources for all time), which might improve
+// client compatibility.
+//
+// However, it does also permit impossible operations, like acquiring
+// conflicting locks and releasing non-existent locks. This might
+// confuse some clients if they try to probe for correctness.
+//
+// Currently this is a moot point: the LOCK and UNLOCK methods are not
+// accepted by keep-web, so it suffices to implement the
+// webdav.LockSystem interface.
+type noLockSystem struct{}
+
+func (*noLockSystem) Confirm(time.Time, string, string, ...webdav.Condition) (func(), error) {
+ return noop, nil
+}
+
+func (*noLockSystem) Create(now time.Time, details webdav.LockDetails) (token string, err error) {
+ return fmt.Sprintf("opaquelocktoken:%s-%x", lockPrefix, atomic.AddInt64(&nextLockSuffix, 1)), nil
+}
+
+func (*noLockSystem) Refresh(now time.Time, token string, duration time.Duration) (webdav.LockDetails, error) {
+ return webdav.LockDetails{}, nil
+}
+
+func (*noLockSystem) Unlock(now time.Time, token string) error {
+ return nil
+}
+
+func noop() {}
+
+// Return a version 1 variant 4 UUID, meaning all bits are random
+// except the ones indicating the version and variant.
+func uuid() string {
+ var data [16]byte
+ if _, err := rand.Read(data[:]); err != nil {
+ panic(err)
+ }
+ // variant 1: N=10xx
+ data[8] = data[8]&0x3f | 0x80
+ // version 4: M=0100
+ data[6] = data[6]&0x0f | 0x40
+ return fmt.Sprintf("%x-%x-%x-%x-%x", data[0:4], data[4:6], data[6:8], data[8:10], data[10:])
+}
projects / arvados.git / blobdiff