Notmuch: use adhoc write connection.

Notmuch only allows a single write connection, all other clients trying to
modify the db block. Hence we should only open one when we actually need it.

Apparently we also need to refresh the RO DB connection upon modification,
else we get stale message tag results

worker/notmuch/message.go

@@ -20,10 +20,12 @@ type Message struct {
 	uid     uint32
 	key     string
 	msg     *notmuch.Message
+	rwDB    func() (*notmuch.DB, error) // used to open a db for writing
+	refresh func(*Message) error        // called after msg modification
 }
 
 // NewReader reads a message into memory and returns an io.Reader for it.
-func (m Message) NewReader() (io.Reader, error) {
+func (m *Message) NewReader() (io.Reader, error) {
 	f, err := os.Open(m.msg.Filename())
 	if err != nil {
 		return nil, err
@@ -37,13 +39,13 @@ func (m Message) NewReader() (io.Reader, error) {
 }
 
 // MessageInfo populates a models.MessageInfo struct for the message.
-func (m Message) MessageInfo() (*models.MessageInfo, error) {
+func (m *Message) MessageInfo() (*models.MessageInfo, error) {
 	return lib.MessageInfo(m)
 }
 
 // NewBodyPartReader creates a new io.Reader for the requested body part(s) of
 // the message.
-func (m Message) NewBodyPartReader(requestedParts []int) (io.Reader, error) {
+func (m *Message) NewBodyPartReader(requestedParts []int) (io.Reader, error) {
 	f, err := os.Open(m.msg.Filename())
 	if err != nil {
 		return nil, err
@@ -57,7 +59,7 @@ func (m Message) NewBodyPartReader(requestedParts []int) (io.Reader, error) {
 }
 
 // MarkRead either adds or removes the maildir.FlagSeen flag from the message.
-func (m Message) MarkRead(seen bool) error {
+func (m *Message) MarkRead(seen bool) error {
 	haveUnread := false
 	for _, t := range m.tags() {
 		if t == "unread" {
@@ -71,14 +73,14 @@ func (m Message) MarkRead(seen bool) error {
 	}
 
 	if haveUnread {
-		err := m.msg.RemoveTag("unread")
+		err := m.RemoveTag("unread")
 		if err != nil {
 			return err
 		}
 		return nil
 	}
 
-	err := m.msg.AddTag("unread")
+	err := m.AddTag("unread")
 	if err != nil {
 		return err
 	}
@@ -86,7 +88,7 @@ func (m Message) MarkRead(seen bool) error {
 }
 
 // tags returns the notmuch tags of a message
-func (m Message) tags() []string {
+func (m *Message) tags() []string {
 	ts := m.msg.Tags()
 	var tags []string
 	var tag *notmuch.Tag
@@ -96,7 +98,72 @@ func (m Message) tags() []string {
 	return tags
 }
 
-func (m Message) ModelFlags() ([]models.Flag, error) {
+func (m *Message) modify(cb func(*notmuch.Message) error) error {
+	db, err := m.rwDB()
+	if err != nil {
+		return err
+	}
+	defer db.Close()
+	msg, err := db.FindMessage(m.key)
+	if err != nil {
+		return err
+	}
+	err = cb(msg)
+	if err != nil {
+		return err
+	}
+	// we need to explicitly close here, else we don't commit
+	dcerr := db.Close()
+	if dcerr != nil && err == nil {
+		err = dcerr
+	}
+	// next we need to refresh the notmuch msg, else we serve stale tags
+	rerr := m.refresh(m)
+	if rerr != nil && err == nil {
+		err = rerr
+	}
+	return err
+}
+
+func (m *Message) AddTag(tag string) error {
+	err := m.modify(func(msg *notmuch.Message) error {
+		return msg.AddTag(tag)
+	})
+	return err
+}
+
+func (m *Message) AddTags(tags []string) error {
+	err := m.modify(func(msg *notmuch.Message) error {
+		ierr := msg.Atomic(func(msg *notmuch.Message) {
+			for _, t := range tags {
+				msg.AddTag(t)
+			}
+		})
+		return ierr
+	})
+	return err
+}
+
+func (m *Message) RemoveTag(tag string) error {
+	err := m.modify(func(msg *notmuch.Message) error {
+		return msg.RemoveTag(tag)
+	})
+	return err
+}
+
+func (m *Message) RemoveTags(tags []string) error {
+	err := m.modify(func(msg *notmuch.Message) error {
+		ierr := msg.Atomic(func(msg *notmuch.Message) {
+			for _, t := range tags {
+				msg.RemoveTag(t)
+			}
+		})
+		return ierr
+	})
+	return err
+}
+
+func (m *Message) ModelFlags() ([]models.Flag, error) {
 	var flags []models.Flag
 	seen := true
 
@@ -118,6 +185,6 @@ func (m Message) ModelFlags() ([]models.Flag, error) {
 	return flags, nil
 }
 
-func (m Message) UID() uint32 {
+func (m *Message) UID() uint32 {
 	return m.uid
 }

worker/notmuch/worker.go

@@ -29,7 +29,7 @@ type worker struct {
 	w            *types.Worker
 	pathToDB     string
 	db           *notmuch.DB
-	selected     *notmuch.Query
+	query        string
 	uidStore     *uidstore.Store
 	excludedTags []string
 	nameQueryMap map[string]string
@@ -129,12 +129,36 @@ func (w *worker) handleConfigure(msg *types.Configure) error {
 	return nil
 }
 
-func (w *worker) handleConnect(msg *types.Connect) error {
+// connectRW returns a writable notmuch DB, which needs to be closed to commit
+// the changes and to release the DB lock
+func (w *worker) connectRW() (*notmuch.DB, error) {
+	db, err := notmuch.Open(w.pathToDB, notmuch.DBReadWrite)
+	if err != nil {
+		return nil, fmt.Errorf("could not connect to notmuch db: %v", err)
+	}
+	return db, err
+}
+
+// connectRO connects a RO db to the worker
+func (w *worker) connectRO() error {
+	if w.db != nil {
+		if err := w.db.Close(); err != nil {
+			w.w.Logger.Printf("connectRO: could not close the old db: %v", err)
+		}
+	}
 	var err error
-	w.db, err = notmuch.Open(w.pathToDB, notmuch.DBReadWrite)
+	w.db, err = notmuch.Open(w.pathToDB, notmuch.DBReadOnly)
 	if err != nil {
 		return fmt.Errorf("could not connect to notmuch db: %v", err)
 	}
+	return nil
+}
+
+func (w *worker) handleConnect(msg *types.Connect) error {
+	err := w.connectRO()
+	if err != nil {
+		return err
+	}
 	w.done(msg)
 	return nil
 }
@@ -153,22 +177,33 @@ func (w *worker) handleListDirectories(msg *types.ListDirectories) error {
 	return nil
 }
 
+//query returns a query based on the query string on w.query.
+//it also configures the query as specified on the worker
+func (w *worker) getQuery() (*notmuch.Query, error) {
+	q := w.db.NewQuery(w.query)
+	q.SetExcludeScheme(notmuch.EXCLUDE_TRUE)
+	q.SetSortScheme(notmuch.SORT_OLDEST_FIRST)
+	for _, t := range w.excludedTags {
+		err := q.AddTagExclude(t)
+		if err != nil && err != notmuch.ErrIgnored {
+			return nil, err
+		}
+	}
+	return q, nil
+}
+
 func (w *worker) handleOpenDirectory(msg *types.OpenDirectory) error {
 	w.w.Logger.Printf("opening %s", msg.Directory)
 	// try the friendly name first, if that fails assume it's a query
-	query, ok := w.nameQueryMap[msg.Directory]
+	q, ok := w.nameQueryMap[msg.Directory]
 	if !ok {
-		query = msg.Directory
+		q = msg.Directory
 	}
-	w.selected = w.db.NewQuery(query)
+	w.query = q
-	w.selected.SetExcludeScheme(notmuch.EXCLUDE_TRUE)
+	query, err := w.getQuery()
-	w.selected.SetSortScheme(notmuch.SORT_OLDEST_FIRST)
+	if err != nil {
-	for _, t := range w.excludedTags {
-		err := w.selected.AddTagExclude(t)
-		if err != nil && err != notmuch.ErrIgnored {
 		return err
 	}
-	}
 	//TODO: why does this need to be sent twice??
 	info := &types.DirectoryInfo{
 		Info: &models.DirectoryInfo{
@@ -176,7 +211,7 @@ func (w *worker) handleOpenDirectory(msg *types.OpenDirectory) error {
 			Flags:    []string{},
 			ReadOnly: false,
 			// total messages
-			Exists: w.selected.CountMessages(),
+			Exists: query.CountMessages(),
 			// new messages since mailbox was last opened
 			Recent: 0,
 			// total unread
@@ -191,7 +226,11 @@ func (w *worker) handleOpenDirectory(msg *types.OpenDirectory) error {
 
 func (w *worker) handleFetchDirectoryContents(
 	msg *types.FetchDirectoryContents) error {
-	uids, err := w.uidsFromQuery(w.selected)
+	q, err := w.getQuery()
+	if err != nil {
+		return err
+	}
+	uids, err := w.uidsFromQuery(q)
 	if err != nil {
 		w.w.Logger.Printf("error scanning uids: %v", err)
 		return err
@@ -256,6 +295,17 @@ func (w *worker) msgFromUid(uid uint32) (*Message, error) {
 		key:  key,
 		uid:  uid,
 		msg:  nm,
+		rwDB: w.connectRW,
+		refresh: func(m *Message) error {
+			//close the old message manually, else we segfault during gc
+			m.msg.Close()
+			err := w.connectRO()
+			if err != nil {
+				return err
+			}
+			m.msg, err = w.db.FindMessage(m.key)
+			return err
+		},
 	}
 	return msg, nil
 }