X-Git-Url: https://git.giacomolli.uk/onechat/blobdiff_plain/522d7fd117285e4e4ce3ea5ec9b5a1722521b681..7b8d8e8f4b57bd51fd6d0f0d926b821f06b0e1f0:/subagent.go?ds=inline

diff --git a/subagent.go b/subagent.go
index 132ca47..4cb6381 100644
--- a/subagent.go
+++ b/subagent.go
@@ -28,10 +28,11 @@ const (
 // subagents.
 func newSubagents(dir string, clock func() time.Time, draw func() string) *Subagents {
 	return &Subagents{
-		dir:   dir,
-		clock: clock,
-		draw:  draw,
-		open:  make(map[string]*Subagent),
+		dir:      dir,
+		clock:    clock,
+		draw:     draw,
+		open:     make(map[string]*Subagent),
+		reserved: make(map[string]bool),
 	}
 }
 
@@ -44,8 +45,9 @@ type Subagents struct {
 	clock func() time.Time
 	draw  func() string
 
-	mutex sync.Mutex
-	open  map[string]*Subagent
+	mutex    sync.Mutex
+	open     map[string]*Subagent
+	reserved map[string]bool
 }
 
 // Create makes the directory and the log of a new subagent. It draws a name
@@ -58,6 +60,15 @@ func (s *Subagents) Create(ctx context.Context) (*Subagent, error) {
 
 	for range subagentNameDraws {
 		name := s.draw()
+		s.mutex.Lock()
+
+		reserved := s.reserved[name]
+		s.mutex.Unlock()
+
+		if reserved {
+			continue
+		}
+
 		err = os.Mkdir(filepath.Join(s.dir, name), 0o700)
 		if errors.Is(err, fs.ErrExist) {
 			continue
@@ -73,6 +84,39 @@ func (s *Subagents) Create(ctx context.Context) (*Subagent, error) {
 	return nil, fmt.Errorf("no free subagent name after %d draws", subagentNameDraws)
 }
 
+// Reserve keeps a child name out of future subagent draws. An existing subagent
+// directory or a reserved name is refused.
+func (s *Subagents) Reserve(name string) error {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+
+	if s.reserved[name] {
+		return fmt.Errorf("name %q is already used", name)
+	}
+
+	_, err := os.Lstat(filepath.Join(s.dir, name))
+	if err == nil {
+		return fmt.Errorf("name %q is already used by a subagent", name)
+	}
+
+	if !errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("check subagent name: %w", err)
+	}
+
+	s.reserved[name] = true
+
+	return nil
+}
+
+// Release frees a reservation after a child fails to publish. It does not
+// remove a subagent directory or change an open log.
+func (s *Subagents) Release(name string) {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+
+	delete(s.reserved, name)
+}
+
 // Get returns the subagent name with its log open. A name that is not valid or
 // that has no directory is an unknown agent.
 func (s *Subagents) Get(ctx context.Context, name string) (*Subagent, error) {
@@ -124,6 +168,30 @@ func (s *Subagents) Get(ctx context.Context, name string) (*Subagent, error) {
 	return subagent, nil
 }
 
+// Snapshot flushes and locks the open logs while snapshot reads the subagent
+// files. snapshot must not call Subagents or an open Subagent.
+func (s *Subagents) Snapshot(ctx context.Context, snapshot func() error) error {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+
+	for _, subagent := range s.open {
+		subagent.mutex.Lock()
+		defer subagent.mutex.Unlock()
+
+		err := subagent.Flush(ctx)
+		if err != nil {
+			return fmt.Errorf("flush subagent snapshot: %w", err)
+		}
+	}
+
+	err := snapshot()
+	if err != nil {
+		return fmt.Errorf("copy subagent snapshot: %w", err)
+	}
+
+	return nil
+}
+
 // Close makes the writes of each open log durable and closes it.
 func (s *Subagents) Close() error {
 	s.mutex.Lock()