Class: Sprockets::Cache

Inherits:
Object
  • Object
show all
Defined in:
lib/sprockets/cache.rb,
lib/sprockets/cache/file_store.rb,
lib/sprockets/cache/null_store.rb,
lib/sprockets/cache/memory_store.rb

Overview

Public: Wrapper interface to backend cache stores. Ensures a consistent API even when the backend uses get/set or read/write.

Public cache interface

Always assign the backend store instance to Environment#cache=.

environment.cache = Sprockets::Cache::MemoryStore.new(1000)

Environment#cache will always return a wrapped Cache interface. See the methods marked public on this class.

Backend cache interface

The Backend cache store must implement two methods.

get(key)

key - An opaque String with a length less than 250 characters.

Returns an JSON serializable object.

set(key, value)

Will only be called once per key. Setting a key "foo" with value "bar",
then later key "foo" with value "baz" is an undefined behavior.

key   - An opaque String with a length less than 250 characters.
value - A JSON serializable object.

Returns argument value.

clear(options)

Clear the entire cache. Be careful with this method since it could
affect other processes if shared cache is being used.

The options hash is passed to the underlying cache implementation.

Defined Under Namespace

Classes: FileStore, GetWrapper, HashWrapper, MemoryStore, NullStore, ReadWriteWrapper, Wrapper

Constant Summary collapse

VERSION =

Internal: Cache key version for this class. Rarely should have to change unless the cache format radically changes. Will be bump on major version releases though.

'4.0'

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(cache = nil, logger = self.class.default_logger) ⇒ Cache

Internal: Wrap a backend cache store.

Always assign a backend cache store instance to Environment#cache= and use Environment#cache to retreive a wrapped interface.

cache - A compatible backend cache store instance.


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# File 'lib/sprockets/cache.rb', line 68

def initialize(cache = nil, logger = self.class.default_logger)
  @cache_wrapper = get_cache_wrapper(cache)
  @fetch_cache   = Cache::MemoryStore.new(1024)
  @logger        = logger
end

Class Method Details

.default_loggerObject


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# File 'lib/sprockets/cache.rb', line 56

def self.default_logger
  logger = Logger.new($stderr)
  logger.level = Logger::FATAL
  logger
end

Instance Method Details

#clear(options = nil) ⇒ Object

Public: Clear cache

Returns truthy on success, potentially raises exception on failure


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# File 'lib/sprockets/cache.rb', line 156

def clear(options=nil)
  @cache_wrapper.clear
  @fetch_cache.clear
end

#fetch(key) ⇒ Object

Public: Prefer API to retrieve and set values in the cache store.

key - JSON serializable key block -

Must return a consistent JSON serializable object for the given key.

Examples

cache.fetch("foo") { "bar" }

Returns a JSON serializable object.


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# File 'lib/sprockets/cache.rb', line 85

def fetch(key)
  start = Time.now.to_f
  expanded_key = expand_key(key)
  value = @fetch_cache.get(expanded_key)
  if value.nil?
    value = @cache_wrapper.get(expanded_key)
    if value.nil?
      value = yield
      @cache_wrapper.set(expanded_key, value)
      @logger.debug do
        ms = "(#{((Time.now.to_f - start) * 1000).to_i}ms)"
        "Sprockets Cache miss #{peek_key(key)}  #{ms}"
      end
    end
    @fetch_cache.set(expanded_key, value)
  end
  value
end

#get(key, local = false) ⇒ Object

Public: Low level API to retrieve item directly from the backend cache store.

This API may be used publicly, but may have undefined behavior depending on the backend store being used. Prefer the Cache#fetch API over using this.

key - JSON serializable key local - Check local cache first (default: false)

Returns a JSON serializable object or nil if there was a cache miss.


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# File 'lib/sprockets/cache.rb', line 115

def get(key, local = false)
  expanded_key = expand_key(key)

  if local && value = @fetch_cache.get(expanded_key)
    return value
  end

  value = @cache_wrapper.get(expanded_key)
  @fetch_cache.set(expanded_key, value) if local

  value
end

#inspectObject

Public: Pretty inspect

Returns String.


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# File 'lib/sprockets/cache.rb', line 149

def inspect
  "#<#{self.class} local=#{@fetch_cache.inspect} store=#{@cache_wrapper.cache.inspect}>"
end

#set(key, value, local = false) ⇒ Object

Public: Low level API to set item directly to the backend cache store.

This API may be used publicly, but may have undefined behavior depending on the backend store being used. Prefer the Cache#fetch API over using this.

key - JSON serializable key value - A consistent JSON serializable object for the given key. Setting

a different value for the given key has undefined behavior.

local - Set on local cache (default: false)

Returns the value argument.


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# File 'lib/sprockets/cache.rb', line 140

def set(key, value, local = false)
  expanded_key = expand_key(key)
  @fetch_cache.set(expanded_key, value) if local
  @cache_wrapper.set(expanded_key, value)
end