> For the complete documentation index, see [llms.txt](https://azutopia.gitbook.io/azu/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://azutopia.gitbook.io/azu/api-reference/cache.md). # Cache The cache module provides flexible caching with multiple backend support. ## Cache Stores ### MemoryStore In-process memory cache. ```crystal Azu.configure do |config| config.cache = Azu::Cache::MemoryStore.new end ``` **Options:** * `max_size : Int32` - Maximum entries (default: 10000) * `default_ttl : Time::Span` - Default expiration (default: 1.hour) ### RedisStore Redis-backed distributed cache. ```crystal Azu.configure do |config| config.cache = Azu::Cache::RedisStore.new( url: ENV["REDIS_URL"] ) end ``` **Options:** * `url : String` - Redis connection URL * `pool_size : Int32` - Connection pool size * `namespace : String?` - Key prefix * `default_ttl : Time::Span` - Default expiration ## Cache Methods ### set Store a value. ```crystal Azu.cache.set("key", "value") Azu.cache.set("key", "value", expires_in: 1.hour) ``` **Parameters:** * `key : String` - Cache key * `value : String` - Value to store * `expires_in : Time::Span?` - Optional TTL ### get Retrieve a value. ```crystal value = Azu.cache.get("key") # => String? ``` **Parameters:** * `key : String` - Cache key **Returns:** `String?` - Cached value or nil ### fetch Get or compute a value. ```crystal value = Azu.cache.fetch("key", expires_in: 1.hour) do expensive_computation end ``` **Parameters:** * `key : String` - Cache key * `expires_in : Time::Span?` - Optional TTL * `&block` - Block to compute value if missing **Returns:** `String` - Cached or computed value ### delete Remove a value. ```crystal Azu.cache.delete("key") ``` **Parameters:** * `key : String` - Cache key ### exists? Check if key exists. ```crystal if Azu.cache.exists?("key") # Key is cached end ``` **Parameters:** * `key : String` - Cache key **Returns:** `Bool` ### clear Remove all cached values. ```crystal Azu.cache.clear ``` ### increment Increment a numeric value. ```crystal Azu.cache.increment("counter") # => 1 Azu.cache.increment("counter") # => 2 Azu.cache.increment("counter", by: 5) # => 7 ``` **Parameters:** * `key : String` - Cache key * `by : Int32` - Increment amount (default: 1) **Returns:** `Int32` - New value ### decrement Decrement a numeric value. ```crystal Azu.cache.decrement("counter") Azu.cache.decrement("counter", by: 5) ``` **Parameters:** * `key : String` - Cache key * `by : Int32` - Decrement amount (default: 1) **Returns:** `Int32` - New value ### expire Set expiration on existing key. ```crystal Azu.cache.expire("key", 30.minutes) ``` **Parameters:** * `key : String` - Cache key * `ttl : Time::Span` - Time to live ## RedisStore-Specific Methods ### delete\_matched Delete keys matching a pattern. ```crystal Azu.cache.delete_matched("user:*") ``` **Parameters:** * `pattern : String` - Glob pattern ### ttl Get remaining time to live. ```crystal remaining = Azu.cache.ttl("key") # => Time::Span? ``` **Parameters:** * `key : String` - Cache key **Returns:** `Time::Span?` - Remaining TTL or nil ## Cache Patterns ### Cache-Aside ```crystal def get_user(id : Int64) : User? cache_key = "user:#{id}" cached = Azu.cache.get(cache_key) return User.from_json(cached) if cached user = User.find?(id) if user Azu.cache.set(cache_key, user.to_json, expires_in: 15.minutes) end user end ``` ### Write-Through ```crystal class User after_save :update_cache after_destroy :remove_from_cache private def update_cache Azu.cache.set("user:#{id}", to_json, expires_in: 1.hour) end private def remove_from_cache Azu.cache.delete("user:#{id}") end end ``` ### Cache Stampede Prevention ```crystal def fetch_with_lock(key : String, expires_in : Time::Span, &) # Try cache first cached = Azu.cache.get(key) return cached if cached # Try to acquire lock lock_key = "lock:#{key}" if Azu.cache.set(lock_key, "1", expires_in: 10.seconds, nx: true) begin value = yield Azu.cache.set(key, value, expires_in: expires_in) value ensure Azu.cache.delete(lock_key) end else # Wait and retry sleep 100.milliseconds Azu.cache.get(key) || yield end end ``` ## Configuration Example ```crystal Azu.configure do |config| if ENV["AZU_ENV"] == "production" config.cache = Azu::Cache::RedisStore.new( url: ENV["REDIS_URL"], pool_size: 10, namespace: "myapp:production", default_ttl: 1.hour ) else config.cache = Azu::Cache::MemoryStore.new( max_size: 1000, default_ttl: 15.minutes ) end end ``` ## See Also * [How to Set Up Memory Cache](/azu/caching/setup-memory-cache.md) * [How to Set Up Redis Cache](/azu/caching/setup-redis-cache.md) --- # Agent Instructions This documentation is published with GitBook. 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