Class: Startback::Caching::EntityCache

Inherits:
Object
  • Object
show all
Includes:
Support::Robustness
Defined in:
lib/startback/caching/entity_cache.rb

Overview

A overriable caching abstraction aiming at making Entity-based caching easy.

This class MUST be overriden:

  • the ‘load_entity` protected method MUST be implemented to load data from a primary & context unaware key.

  • the ‘primary_key` protected method MAY be implemented to convert candidate keys (received from ultimate callers) to primary keys. The method is also a good place to check and/or log the keys actually used by callers.

  • the ‘context_free_key` protected method MAY be overriden to provide domain unrelated caching keys from primary keys, e.g. by encoding the context into the caching key itself, if needed.

  • the ‘valid?` protected method MAY be overriden to check validity of data extracted from the cache and force a refresh even if found.

An EntityCache takes an actual store at construction. The object must meet the specification writtern in Store. The ‘cache’ ruby gem can be used in practice.

Cache hits, outdated and miss are logged in debug, info, and info severity. The ‘cache_hit`, `cache_outdated`, `cache_miss` protected methods MAY be overriden to change that behavior.

Class Attribute Summary collapse

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Support::Robustness

#log, #monitor, #stop_errors, #try_max_times

Constructor Details

#initialize(store, context = nil) ⇒ EntityCache

class DSL



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# File 'lib/startback/caching/entity_cache.rb', line 43

def initialize(store, context = nil)
  @store = store
  @context = context
end

Class Attribute Details

.default_ttl ⇒ Object 



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# File 'lib/startback/caching/entity_cache.rb', line 37

def default_ttl
  @default_ttl || (superclass.respond_to?(:default_ttl, true) && superclass.default_ttl) || 3600
end

Instance Attribute Details

#context ⇒ Object (readonly)

Returns the value of attribute context.



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# File 'lib/startback/caching/entity_cache.rb', line 47

def context
  @context
end

#store ⇒ Object (readonly)

Returns the value of attribute store.



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# File 'lib/startback/caching/entity_cache.rb', line 47

def store
  @store
end

Instance Method Details

#get(candidate_key, caching_options = default_caching_options) ⇒ Object

Returns the entity corresponding to a given key.

If the entity is not in cache, loads it and puts it in cache using the caching options passed as second parameter.



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# File 'lib/startback/caching/entity_cache.rb', line 53

def get(candidate_key, caching_options = default_caching_options)
  pkey = primary_key(candidate_key)
  cache_key = encode_key(context_free_key(pkey))
  if store.exist?(cache_key)
    cached = store.get(cache_key)
    if valid?(pkey, cached)
      cache_hit(pkey, cached)
      return cached
    else
      cache_outdated(pkey, cached)
    end
  end
  cache_miss(pkey)
  load_entity(pkey).tap{|to_cache|
    store.set(cache_key, to_cache, caching_options)
  }
end

#invalidate(candidate_key) ⇒ Object

Invalidates the cache under a given key.



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# File 'lib/startback/caching/entity_cache.rb', line 72

def invalidate(candidate_key)
  pkey = primary_key(candidate_key)
  cache_key = encode_key(context_free_key(pkey))
  store.delete(cache_key)
end