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MODEL_SETUP.md

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Model Setup

Include the GlobalLMTCacheConcern.

class Foo < ActiveRecord::Base
  include AtomicCache::GlobalLMTCacheConcern
end

force_cache_class

By default the cache identifier for a class is set to the name of a class (ie. self.to_s). In some cases it makes sense to set a custom value for the cache identifier. In cases where a custom cache identifier is set, it's important that the identifier remain unique across the project.

class SuperDescriptiveDomainModelAbstractFactoryImplManager < ActiveRecord::Base
  include AtomicCache::GlobalLMTCacheConcern
  force_cache_class('sddmafim')
end

★ Best Practice ★

Generally it should only be necessary to explicitly set a cache_class in cases where the class name is extremely long and causing the max key length to be hit. In such a case the cache_class can be set to an abbreviation of the class name.

cache_version

In cases where a code change that is incompatible with cached values already written needs to be deployed, a cache version can be set which further sub-divides the cache namespace, preventing old values from being read. When the version is nil (the default), no version is added to the cache key.

class Foo < ActiveRecord::Base
  include AtomicCache::GlobalLMTCacheConcern
  cache_version(5)
end

Inheritance

When either force_cache_class or cache_version are used, those values will always be preferred by classes which inherit from the class on which those macros exist. When macros are used on descendant classes, the "closet" value wins.

Example #1

The keys used by Bar will be prefixed with custom:v5, as it prefers both the 'custom' class name and version 5 from the parent.

class Foo < ActiveRecord::Base
  include AtomicCache::GlobalLMTCacheConcern
  force_cache_class('custom')
  cache_version(5)
end

class Bar < Foo
end

Example #2

The keys used by Bar will be prefixed with bar:v5, as the version 5 is taken from the parent, but the use of forcing on the child class result in the cache class of 'bar'.

class Foo < ActiveRecord::Base
  include AtomicCache::GlobalLMTCacheConcern
  cache_version(5)
end

class Bar < Foo
  force_cache_class('bar')
end

Example #3

The keys used by Bar will be still be prefixed with bar:v5 for the same reasons as above.

class Foo < ActiveRecord::Base
  include AtomicCache::GlobalLMTCacheConcern
  force_cache_class('custom')
  cache_version(5)
end

class Bar < Foo
  force_cache_class('bar')
end

Rails Model Inheritance

It's not uncommon in rails to end up with model inhertiance. For example:

class Content < ActiveRecord::Base
  include AtomicCache::GlobalLMTCacheConcern
  force_cache_class('content')
end

class BlogPost < Content
end

If these models will be cached together into a single key, it's preferable to force the cache class on the parent, causing all the descendant types to use the same keyspace. Not doing this will cause each subtype to use it's own last modified time.

If the models will be treated as separate collections and cached separately, this is not recommended. Alternately, if only some subtypes will be cached together, those should share a forced cache class and version.