MCP Toolbox for Databases

// Copyright 2025 Google LLC // // 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 bigquery import ( "sync" "time" ) // Item holds the cached value and its expiration timestamp type Item struct { Value any ExpiresAt int64 // Unix nano timestamp } // IsExpired checks if the item is expired func (item Item) IsExpired() bool { return time.Now().UnixNano() > item.ExpiresAt } // OnEvictFunc is the signature for the callback type OnEvictFunc func(key string, value any) // Cache is a thread-safe, expiring key-value store type Cache struct { mu sync.RWMutex items map[string]Item onEvict OnEvictFunc } // NewCache creates a new cache and cleans up every 55 min func NewCache(onEvict OnEvictFunc) *Cache { const cleanupInterval = 55 * time.Minute c := &Cache{ items: make(map[string]Item), onEvict: onEvict, } go c.startCleanup(cleanupInterval) return c } // startCleanup runs a ticker to periodically delete expired items func (c *Cache) startCleanup(interval time.Duration) { ticker := time.NewTicker(interval) defer ticker.Stop() for range ticker.C { c.DeleteExpired() } } // delete is an internal helper that assumes the write lock is held func (c *Cache) delete(key string, item Item) { if c.onEvict != nil { c.onEvict(key, item.Value) } delete(c.items, key) } // Set adds an item to the cache func (c *Cache) Set(key string, value any) { const ttl = 55 * time.Minute expires := time.Now().Add(ttl).UnixNano() c.mu.Lock() defer c.mu.Unlock() // If item already exists, evict the old one before replacing if oldItem, found := c.items[key]; found { c.delete(key, oldItem) } c.items[key] = Item{ Value: value, ExpiresAt: expires, } } // Get retrieves an item from the cache func (c *Cache) Get(key string) (any, bool) { c.mu.RLock() item, found := c.items[key] if !found || item.IsExpired() { c.mu.RUnlock() return nil, false } c.mu.RUnlock() return item.Value, true } // Delete manually evicts an item func (c *Cache) Delete(key string) { c.mu.Lock() defer c.mu.Unlock() if item, found := c.items[key]; found { c.delete(key, item) } } // DeleteExpired removes all expired items func (c *Cache) DeleteExpired() { c.mu.Lock() defer c.mu.Unlock() for key, item := range c.items { if item.IsExpired() { c.delete(key, item) } } }