.

go/zodb/storage/fs1/filestorage.go

@@ -87,7 +87,7 @@ import (
 type FileStorage struct {
 	file  *os.File
 
-	// protects updates to index and to everything below - in other words
+	// protects updates to index and to txnh{Min,Max} - in other words
 	// to everything that depends on what current last transaction is.
 	mu sync.RWMutex
 
@@ -97,6 +97,8 @@ type FileStorage struct {
 	// (both with .Len=0 & .Tid=0 if database is empty)
 	txnhMin TxnHeader
 	txnhMax TxnHeader
+
+	watchq chan XXX
 }
 
 // IStorageDriver
@@ -449,6 +451,8 @@ func (fs *FileStorage) watch() (err error) {
 	f := fs.file
 	defer xerr.Contextf(&err, "%s: watch", f.Name())
 
+	// XXX race -> start watching before FileStorage is returned to user
+
 	// setup watcher to changes on f
 	w, err := fsnotify.NewWatcher()
 	if err != nil {
@@ -461,19 +465,114 @@ func (fs *FileStorage) watch() (err error) {
 		return err
 	}
 
+	// loop checking f.size vs topPos vs posLastChecked (XXX)
+	//
+	// besides relying on notify we also check file periodically to avoid
+	// stalls due to e.g. OS notification errors.
 	toppos := fs.index.TopPos
+	var it *Iter
+	resetit := func() { // reset it to start from toppos with empty buffer
+		it = Iterate(seqReadAt(f), toppos, IterForward)
+	}
+	resetit()
+	tick := time.NewTicker(1*time.Second)
+	defer tick.Stop()
+	var tpartWrite time.Time
 
-	// loop checking f.size vs topPos vs posLastChecked (XXX)
 	for {
+		// XXX select here
+
 		fi, err := f.Stat()
 		if err != nil {
 			return err
 		}
 		fsize := fi.Size()
-		if fsize > toppos {
-			// XXX
+		switch {
+		case fsize == toppos:
+			continue // same as before
+		case fsize < toppos:
+			// XXX add pack support
+			return fmt.Errorf("file truncated (%d -> %d)", toppos, fsize)
 		}
 
+		// there is some data after toppos - try to read it. always create buffer
+		// anew, since there could be written and then aborted transactions.
+		err = it.NextTxn(LoadNoStrings)
+		if err != nil {
+			// transaction header could not be fully read.
+			//
+			// Even though FileStorage code always calls write with full txn
+			// header, the kernel could do the write in parts, e.g. if written
+			// region overlaps page boundary.
+			//
+			// we check for some time to distinguish in-progress write from just
+			// garbage.
+			if errors.Cause(err) == io.ErrUnexpectedEOF {
+				now := time.Now()
+				if tpartWrite.IsZero() {
+					tpartWrite = now
+				} else if now.Sub(tpartialStart) > 3*time.Second {
+					return err
+				}
+			} else {
+				// not ok - e.g. IO error
+				// EOF is ok - it is e.g. when transaction was aborted
+				if err != io.EOF {
+					return err
+				}
+
+				// EOF - reset t(partial)
+				tpartWrite = time.Time{}
+
+			}
+
+			// after an error (EOF, partial read) we have to retry with
+			// reset bufferring.
+			resetit()
+			continue
+		}
+
+		tpartWrite = time.Time{} // reset
+
+		// XXX dup wrt Index.Update
+
+		// we could successfully read the transaction header. Try to see now,
+		// whether it is finished transaction or not.
+		if it.Txnh.Status == zodb.TxnInprogress {
+			// not yet. we have to reset because transaction finish writes
+			// what we have already buffered.
+			resetit()
+			continue
+		}
+
+		// it is fully-committed transaction. scan its data records to update
+		// our index & notify watchers. There is no expected errors here.
+		var oidv []zodb.Oid
+		update := map[zodb.Oid]int64{}
+		for {
+			err = it.NextData()
+			if err != nil {
+				err = okEOF(err)
+				if err != nil {
+					return err
+				}
+				break
+			}
+
+			update[it.Datah.Oid] = it.Datah.Pos
+			oidv = append(oidv, it.Datah.Oid)
+		}
+
+		// update index
+		fs.mu.Lock()
+		index.TopPos = it.Txnh.Pos + it.Txnh.Len
+		for oid, pos := range update {
+			index.Set(oid, pos)
+		}
+		fs.mu.Unlock()
+
+		// XXX -> watchq
+
 		select {
 		// XXX handle quit
 
@@ -491,11 +590,16 @@ func (fs *FileStorage) watch() (err error) {
 			// write, truncate, chown ...) -> it is time to check the file again.
 			continue
 
-		// TODO + time.After(30s) to avoid stalls due to e.g. OS notification errors
+		case <-tick.C:
+			// recheck the file periodically.
+			continue
 		}
 	}
 }
 
+//func (fs *FileStorage) readUpdates() {
+//}
+
 func (fs *FileStorage) Watch(ctx context.Context) (zodb.Tid, []zodb.Oid, error) {
 	panic("TODO")
 }

go/zodb/storage/fs1/filestorage_test.go

@@ -435,6 +435,8 @@ func TestWatch(t *testing.T) {
 		if objvWant := []zodb.Oid{0, i}; !(tid == at && reflect.DeepEqual(objv, objvWant)) {
 			t.Fatalf("watch:\nhave: %s %s\nwant: %s %s", tid, objv, at, objvWant)
 		}
+
+		checkLastTid(at)
 	}
 
 	err := fs.Close()
@@ -443,5 +445,5 @@ func TestWatch(t *testing.T) {
 	}
 
 	_, _, err = fs.Watch(ctx)
-	// assert err = "closed"
+	// XXX assert err = "closed"
 }

go/zodb/storage/fs1/index.go

@@ -469,7 +469,7 @@ func (index *Index) Update(ctx context.Context, r io.ReaderAt, topPos int64, pro
 		// do not update the index immediately so that in case of error
 		// in the middle of txn's data, index stays consistent and
 		// correct for topPos pointing to previous transaction.
-		update := map[zodb.Oid]int64{} // XXX malloc every time -> better reuse
+		update := map[zodb.Oid]int64{}
 		for {
 			err = it.NextData()
 			if err != nil {
@@ -492,7 +492,7 @@ func (index *Index) Update(ctx context.Context, r io.ReaderAt, topPos int64, pro
 		// notify progress
 		if progress != nil {
 			pd.TxnIndexed++
-			progress(pd)
+			progress(pd)	// XXX + update
 		}
 	}
 

go/zodb/storage/fs1/index_test.go

@@ -293,7 +293,7 @@ var haveZODBPy = false
 var workRoot string
 
 func TestMain(m *testing.M) {
-	// check whether we have zodb/py
+	// check whether we have zodb/py	XXX + zodbtools
 	cmd := exec.Command("python2", "-c", "import ZODB")
 	err := cmd.Run()
 	if err == nil {