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check-spelling run (pull_request) for Xe/actorify

Signed-off-by: check-spelling-bot <check-spelling-bot@users.noreply.github.com>
on-behalf-of: @check-spelling <check-spelling-bot@check-spelling.dev>

.github/actions/spelling/expect.txt

@@ -1,4 +1,7 @@
 acs
+Actorified
+actorifiedstore
+actorify
 Aibrew
 alibaba
 alrest
@@ -157,6 +160,7 @@ ifm
 Imagesift
 imgproxy
 impressum
+inbox
 inp
 internets
 IPTo

decaymap/decaymap.go

@@ -14,6 +14,12 @@ func Zilch[T any]() T {
 type Impl[K comparable, V any] struct {
 	data map[K]decayMapEntry[V]
 	lock sync.RWMutex
+
+	// deleteCh receives decay-deletion requests from readers.
+	deleteCh chan deleteReq[K]
+	// stopCh stops the background cleanup worker.
+	stopCh chan struct{}
+	wg     sync.WaitGroup
 }
 
 type decayMapEntry[V any] struct {
@@ -21,30 +27,38 @@ type decayMapEntry[V any] struct {
 	expiry time.Time
 }
 
+// deleteReq is a request to remove a key if its expiry timestamp still matches
+// the observed one. This prevents racing with concurrent Set updates.
+type deleteReq[K comparable] struct {
+	key    K
+	expiry time.Time
+}
+
 // New creates a new DecayMap of key type K and value type V.
 //
 // Key types must be comparable to work with maps.
 func New[K comparable, V any]() *Impl[K, V] {
-	return &Impl[K, V]{
+	m := &Impl[K, V]{
-		data: make(map[K]decayMapEntry[V]),
+		data:     make(map[K]decayMapEntry[V]),
+		deleteCh: make(chan deleteReq[K], 1024),
+		stopCh:   make(chan struct{}),
 	}
+	m.wg.Add(1)
+	go m.cleanupWorker()
+	return m
 }
 
 // expire forcibly expires a key by setting its time-to-live one second in the past.
 func (m *Impl[K, V]) expire(key K) bool {
-	m.lock.RLock()
+	// Use a single write lock to avoid RUnlock->Lock convoy.
+	m.lock.Lock()
+	defer m.lock.Unlock()
 	val, ok := m.data[key]
-	m.lock.RUnlock()
-
 	if !ok {
 		return false
 	}
-
-	m.lock.Lock()
 	val.expiry = time.Now().Add(-1 * time.Second)
 	m.data[key] = val
-	m.lock.Unlock()
-
 	return true
 }
 
@@ -53,19 +67,14 @@ func (m *Impl[K, V]) expire(key K) bool {
 // If the value does not exist, return false. Return true after
 // deletion.
 func (m *Impl[K, V]) Delete(key K) bool {
-	m.lock.RLock()
+	// Use a single write lock to avoid RUnlock->Lock convoy.
-	_, ok := m.data[key]
-	m.lock.RUnlock()
-
-	if !ok {
-		return false
-	}
-
 	m.lock.Lock()
-	delete(m.data, key)
+	defer m.lock.Unlock()
-	m.lock.Unlock()
+	_, ok := m.data[key]
-
+	if ok {
-	return true
+		delete(m.data, key)
+	}
+	return ok
 }
 
 // Get gets a value from the DecayMap by key.
@@ -81,13 +90,12 @@ func (m *Impl[K, V]) Get(key K) (V, bool) {
 	}
 
 	if time.Now().After(value.expiry) {
-		m.lock.Lock()
+		// Defer decay deletion to the background worker to avoid convoy.
-		// Since previously reading m.data[key], the value may have been updated.
+		select {
-		// Delete the entry only if the expiry time is still the same.
+		case m.deleteCh <- deleteReq[K]{key: key, expiry: value.expiry}:
-		if m.data[key].expiry.Equal(value.expiry) {
+		default:
-			delete(m.data, key)
+			// Channel full: drop request; a future Cleanup() or Get will retry.
 		}
-		m.lock.Unlock()
 
 		return Zilch[V](), false
 	}
@@ -125,3 +133,64 @@ func (m *Impl[K, V]) Len() int {
 	defer m.lock.RUnlock()
 	return len(m.data)
 }
+
+// Close stops the background cleanup worker. It's optional to call; maps live
+// for the process lifetime in many cases. Call in tests or when you know you no
+// longer need the map to avoid goroutine leaks.
+func (m *Impl[K, V]) Close() {
+	close(m.stopCh)
+	m.wg.Wait()
+}
+
+// cleanupWorker batches decay deletions to minimize lock contention.
+func (m *Impl[K, V]) cleanupWorker() {
+	defer m.wg.Done()
+	batch := make([]deleteReq[K], 0, 64)
+	ticker := time.NewTicker(10 * time.Millisecond)
+	defer ticker.Stop()
+
+	flush := func() {
+		if len(batch) == 0 {
+			return
+		}
+		m.applyDeletes(batch)
+		// reset batch without reallocating
+		batch = batch[:0]
+	}
+
+	for {
+		select {
+		case req := <-m.deleteCh:
+			batch = append(batch, req)
+		case <-ticker.C:
+			flush()
+		case <-m.stopCh:
+			// Drain any remaining requests then exit
+			for {
+				select {
+				case req := <-m.deleteCh:
+					batch = append(batch, req)
+				default:
+					flush()
+					return
+				}
+			}
+		}
+	}
+}
+
+func (m *Impl[K, V]) applyDeletes(batch []deleteReq[K]) {
+	now := time.Now()
+	m.lock.Lock()
+	for _, req := range batch {
+		entry, ok := m.data[req.key]
+		if !ok {
+			continue
+		}
+		// Only delete if the expiry is unchanged and already past.
+		if entry.expiry.Equal(req.expiry) && now.After(entry.expiry) {
+			delete(m.data, req.key)
+		}
+	}
+	m.lock.Unlock()
+}

decaymap/decaymap_test.go

@@ -7,6 +7,7 @@ import (
 
 func TestImpl(t *testing.T) {
 	dm := New[string, string]()
+	t.Cleanup(dm.Close)
 
 	dm.Set("test", "hi", 5*time.Minute)
 
@@ -28,10 +29,24 @@ func TestImpl(t *testing.T) {
 	if ok {
 		t.Error("got value even though it was supposed to be expired")
 	}
+
+	// Deletion of expired entries after Get is deferred to a background worker.
+	// Assert it eventually disappears from the map.
+	deadline := time.Now().Add(200 * time.Millisecond)
+	for time.Now().Before(deadline) {
+		if dm.Len() == 0 {
+			break
+		}
+		time.Sleep(5 * time.Millisecond)
+	}
+	if dm.Len() != 0 {
+		t.Fatalf("expected background cleanup to remove expired key; len=%d", dm.Len())
+	}
 }
 
 func TestCleanup(t *testing.T) {
 	dm := New[string, string]()
+	t.Cleanup(dm.Close)
 
 	dm.Set("test1", "hi1", 1*time.Second)
 	dm.Set("test2", "hi2", 2*time.Second)

docs/docs/CHANGELOG.md

@@ -13,12 +13,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 <!-- This changes the project to: -->
 
-- Document missing environment variables in installation guide: `SLOG_LEVEL`, `COOKIE_PREFIX`, `FORCED_LANGUAGE`, and `TARGET_DISABLE_KEEPALIVE` ([#1086](https://github.com/TecharoHQ/anubis/pull/1086))
+- Fix lock convoy problem in decaymap ([#1103](https://github.com/TecharoHQ/anubis/issues/1103)).
-- Add validation warning when persistent storage is used without setting signing keys
+- Fix lock convoy problem in bbolt by implementing the actor pattern ([#1103](https://github.com/TecharoHQ/anubis/issues/1103)).
-- Fixed `robots2policy` to properly group consecutive user agents into `any:` instead of only processing the last one ([#925](https://github.com/TecharoHQ/anubis/pull/925))
+- Document missing environment variables in installation guide: `SLOG_LEVEL`, `COOKIE_PREFIX`, `FORCED_LANGUAGE`, and `TARGET_DISABLE_KEEPALIVE` ([#1086](https://github.com/TecharoHQ/anubis/pull/1086)).
+- Add validation warning when persistent storage is used without setting signing keys.
+- Fixed `robots2policy` to properly group consecutive user agents into `any:` instead of only processing the last one ([#925](https://github.com/TecharoHQ/anubis/pull/925)).
 - Add the [`s3api` storage backend](./admin/policies.mdx#s3api) to allow Anubis to use S3 API compatible object storage as its storage backend.
 - Make `cmd/containerbuild` support commas for separating elements of the `--docker-tags` argument as well as newlines.
-- Add the `DIFFICULTY_IN_JWT` option, which allows one to add the `difficulty` field in the JWT claims which indicates the difficulty of the token ([#1063](https://github.com/TecharoHQ/anubis/pull/1063))
+- Add the `DIFFICULTY_IN_JWT` option, which allows one to add the `difficulty` field in the JWT claims which indicates the difficulty of the token ([#1063](https://github.com/TecharoHQ/anubis/pull/1063)).
 - Ported the client-side JS to TypeScript to avoid egregious errors in the future.
 - Fixes concurrency problems with very old browsers ([#1082](https://github.com/TecharoHQ/anubis/issues/1082)).
 

internal/actorify/actorify.go

@@ -0,0 +1,107 @@
+// Package actorify lets you transform a parallel operation into a serialized
+// operation via the Actor pattern[1].
+//
+// [1]: https://en.wikipedia.org/wiki/Actor_model
+package actorify
+
+import (
+	"context"
+	"errors"
+)
+
+func z[Z any]() Z {
+	var z Z
+	return z
+}
+
+var (
+	// ErrActorDied is returned when the actor inbox or reply channel was closed.
+	ErrActorDied = errors.New("actorify: the actor inbox or reply channel was closed")
+)
+
+// Handler is a function alias for the underlying logic the Actor should call.
+type Handler[Input, Output any] func(ctx context.Context, input Input) (Output, error)
+
+// Actor is a serializing wrapper that runs a function in a background goroutine.
+// Whenever the Call method is invoked, a message is sent to the actor's inbox and then
+// the callee waits for a response. Depending on how busy the actor is, this may take
+// a moment.
+type Actor[Input, Output any] struct {
+	handler Handler[Input, Output]
+	inbox   chan *message[Input, Output]
+}
+
+type message[Input, Output any] struct {
+	ctx   context.Context
+	arg   Input
+	reply chan reply[Output]
+}
+
+type reply[Output any] struct {
+	output Output
+	err    error
+}
+
+// New constructs a new Actor and starts its background thread. Cancel the context and you cancel
+// the Actor.
+func New[Input, Output any](ctx context.Context, handler Handler[Input, Output]) *Actor[Input, Output] {
+	result := &Actor[Input, Output]{
+		handler: handler,
+		inbox:   make(chan *message[Input, Output], 32),
+	}
+
+	go result.handle(ctx)
+
+	return result
+}
+
+func (a *Actor[Input, Output]) handle(ctx context.Context) {
+	for {
+		select {
+		case <-ctx.Done():
+			close(a.inbox)
+			return
+		case msg, ok := <-a.inbox:
+			if !ok {
+				if msg.reply != nil {
+					close(msg.reply)
+				}
+
+				return
+			}
+
+			result, err := a.handler(msg.ctx, msg.arg)
+
+			reply := reply[Output]{
+				output: result,
+				err:    err,
+			}
+
+			msg.reply <- reply
+		}
+	}
+}
+
+// Call calls the Actor with a given Input and returns the handler's Output.
+//
+// This only works with unary functions by design. If you need to have more inputs, define
+// a struct type to use as a container.
+func (a *Actor[Input, Output]) Call(ctx context.Context, input Input) (Output, error) {
+	replyCh := make(chan reply[Output])
+
+	a.inbox <- &message[Input, Output]{
+		arg:   input,
+		reply: replyCh,
+	}
+
+	select {
+	case reply, ok := <-replyCh:
+		if !ok {
+			return z[Output](), ErrActorDied
+		}
+
+		return reply.output, reply.err
+	case <-ctx.Done():
+		return z[Output](), context.Cause(ctx)
+	}
+}

lib/store/actorifiedstore.go

@@ -0,0 +1,82 @@
+package store
+
+import (
+	"context"
+	"time"
+
+	"github.com/TecharoHQ/anubis/internal/actorify"
+)
+
+type unit struct{}
+
+type ActorifiedStore struct {
+	Interface
+
+	deleteActor *actorify.Actor[string, unit]
+	getActor    *actorify.Actor[string, []byte]
+	setActor    *actorify.Actor[*actorSetReq, unit]
+	cancel      context.CancelFunc
+}
+
+type actorSetReq struct {
+	key    string
+	value  []byte
+	expiry time.Duration
+}
+
+func NewActorifiedStore(backend Interface) *ActorifiedStore {
+	ctx, cancel := context.WithCancel(context.Background())
+
+	result := &ActorifiedStore{
+		Interface: backend,
+		cancel:    cancel,
+	}
+
+	result.deleteActor = actorify.New(ctx, result.actorDelete)
+	result.getActor = actorify.New(ctx, backend.Get)
+	result.setActor = actorify.New(ctx, result.actorSet)
+
+	return result
+}
+
+func (a *ActorifiedStore) Close() { a.cancel() }
+
+func (a *ActorifiedStore) Delete(ctx context.Context, key string) error {
+	if _, err := a.deleteActor.Call(ctx, key); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (a *ActorifiedStore) Get(ctx context.Context, key string) ([]byte, error) {
+	return a.getActor.Call(ctx, key)
+}
+
+func (a *ActorifiedStore) Set(ctx context.Context, key string, value []byte, expiry time.Duration) error {
+	if _, err := a.setActor.Call(ctx, &actorSetReq{
+		key:    key,
+		value:  value,
+		expiry: expiry,
+	}); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (a *ActorifiedStore) actorDelete(ctx context.Context, key string) (unit, error) {
+	if err := a.Interface.Delete(ctx, key); err != nil {
+		return unit{}, err
+	}
+
+	return unit{}, nil
+}
+
+func (a *ActorifiedStore) actorSet(ctx context.Context, req *actorSetReq) (unit, error) {
+	if err := a.Interface.Set(ctx, req.key, req.value, req.expiry); err != nil {
+		return unit{}, err
+	}
+
+	return unit{}, nil
+}

lib/store/bbolt/factory.go

@@ -48,7 +48,7 @@ func (Factory) Build(ctx context.Context, data json.RawMessage) (store.Interface
 
 	go result.cleanupThread(ctx)
 
-	return result, nil
+	return store.NewActorifiedStore(result), nil
 }
 
 // Valid parses and validates the bbolt store Config or returns