snapshot of https://github.com/grpc/grpc-go.git (master, 2026-09-15; blobs > 131072B omitted)

internal/cache/timeoutCache.go

@@ -0,0 +1,151 @@
+/*
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Package cache implements caches to be used in gRPC.
+package cache
+
+import (
+	"sync"
+	"time"
+)
+
+type cacheEntry struct {
+	item any
+	// Note that to avoid deadlocks (potentially caused by lock ordering),
+	// callback can only be called without holding cache's mutex.
+	callback func()
+	timer    *time.Timer
+	// deleted is set to true in Remove() when the call to timer.Stop() fails.
+	// This can happen when the timer in the cache entry fires around the same
+	// time that timer.stop() is called in Remove().
+	deleted bool
+}
+
+// TimeoutCache is a cache with items to be deleted after a timeout.
+type TimeoutCache struct {
+	mu      sync.Mutex
+	timeout time.Duration
+	cache   map[any]*cacheEntry
+}
+
+// NewTimeoutCache creates a TimeoutCache with the given timeout.
+func NewTimeoutCache(timeout time.Duration) *TimeoutCache {
+	return &TimeoutCache{
+		timeout: timeout,
+		cache:   make(map[any]*cacheEntry),
+	}
+}
+
+// Add adds an item to the cache, with the specified callback to be called when
+// the item is removed from the cache upon timeout. If the item is removed from
+// the cache using a call to Remove before the timeout expires, the callback
+// will not be called.
+//
+// If the Add was successful, it returns (newly added item, true). If there is
+// an existing entry for the specified key, the cache entry is not be updated
+// with the specified item and it returns (existing item, false).
+func (c *TimeoutCache) Add(key, item any, callback func()) (any, bool) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if e, ok := c.cache[key]; ok {
+		return e.item, false
+	}
+
+	entry := &cacheEntry{
+		item:     item,
+		callback: callback,
+	}
+	entry.timer = time.AfterFunc(c.timeout, func() {
+		c.mu.Lock()
+		if entry.deleted {
+			c.mu.Unlock()
+			// Abort the delete since this has been taken care of in Remove().
+			return
+		}
+		delete(c.cache, key)
+		c.mu.Unlock()
+		entry.callback()
+	})
+	c.cache[key] = entry
+	return item, true
+}
+
+// Remove the item with the key from the cache.
+//
+// If the specified key exists in the cache, it returns (item associated with
+// key, true) and the callback associated with the item is guaranteed to be not
+// called. If the given key is not found in the cache, it returns (nil, false)
+func (c *TimeoutCache) Remove(key any) (item any, ok bool) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	entry, ok := c.removeInternal(key)
+	if !ok {
+		return nil, false
+	}
+	return entry.item, true
+}
+
+// removeInternal removes and returns the item with key.
+//
+// caller must hold c.mu.
+func (c *TimeoutCache) removeInternal(key any) (*cacheEntry, bool) {
+	entry, ok := c.cache[key]
+	if !ok {
+		return nil, false
+	}
+	delete(c.cache, key)
+	if !entry.timer.Stop() {
+		// If stop was not successful, the timer has fired (this can only happen
+		// in a race). But the deleting function is blocked on c.mu because the
+		// mutex was held by the caller of this function.
+		//
+		// Set deleted to true to abort the deleting function. When the lock is
+		// released, the delete function will acquire the lock, check the value
+		// of deleted and return.
+		entry.deleted = true
+	}
+	return entry, true
+}
+
+// Clear removes all entries, and runs the callbacks if runCallback is true.
+func (c *TimeoutCache) Clear(runCallback bool) {
+	var entries []*cacheEntry
+	c.mu.Lock()
+	for key := range c.cache {
+		if e, ok := c.removeInternal(key); ok {
+			entries = append(entries, e)
+		}
+	}
+	c.mu.Unlock()
+
+	if !runCallback {
+		return
+	}
+
+	// removeInternal removes entries from cache, and also stops the timer, so
+	// the callback is guaranteed to be not called. If runCallback is true,
+	// manual execute all callbacks.
+	for _, entry := range entries {
+		entry.callback()
+	}
+}
+
+// Len returns the number of entries in the cache.
+func (c *TimeoutCache) Len() int {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return len(c.cache)
+}