Class: Readthis::Cache

Inherits:
Object
  • Object
show all
Defined in:
lib/readthis/cache.rb

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(url, options = {}) ⇒ Cache

Creates a new Readthis::Cache object with the given redis URL. The URL is parsed by the redis client directly.

Examples:

Create a new cache instance

Readthis::Cache.new('redis://localhost:6379/0', namespace: 'cache')

Create a compressed cache instance

Readthis::Cache.new('redis://localhost:6379/0', compress: true, compression_threshold: 2048)

Parameters:

  • A (String) —

    redis compliant url with necessary connection details

  • [Boolean] (Hash) —

    a customizable set of options

  • [Number] (Hash) —

    a customizable set of options

  • [Module] (Hash) —

    a customizable set of options

  • [String] (Hash) —

    a customizable set of options



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# File 'lib/readthis/cache.rb', line 43

def initialize(url, options = {})
  @expires_in = options.fetch(:expires_in, nil)
  @namespace  = options.fetch(:namespace, nil)

  @entity = Readthis::Entity.new(
    marshal:   options.fetch(:marshal, Marshal),
    compress:  options.fetch(:compress, false),
    threshold: options.fetch(:compression_threshold, 1024)
  )

  @pool = ConnectionPool.new(pool_options(options)) do
    Redis.new(url: url, driver: :hiredis)
  end
end

Instance Attribute Details

#entity ⇒ Object (readonly)

Returns the value of attribute entity.



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# File 'lib/readthis/cache.rb', line 11

def entity
  @entity
end

#expires_in ⇒ Object (readonly)

Returns the value of attribute expires_in.



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# File 'lib/readthis/cache.rb', line 11

def expires_in
  @expires_in
end

#namespace ⇒ Object (readonly)

Returns the value of attribute namespace.



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# File 'lib/readthis/cache.rb', line 11

def namespace
  @namespace
end

#pool ⇒ Object (readonly)

Returns the value of attribute pool.



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# File 'lib/readthis/cache.rb', line 11

def pool
  @pool
end

Class Method Details

.notifications ⇒ Object

Provide a class level lookup of the proper notifications module. Instrumention is expected to occur within applications that have ActiveSupport::Notifications available, but needs to work even when it isn’t.



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# File 'lib/readthis/cache.rb', line 17

def self.notifications
  if Object.const_defined?('ActiveSupport::Notifications')
    ActiveSupport::Notifications
  else
    Readthis::Notifications
  end
end

Instance Method Details

#clear(options = {}) ⇒ Object

Clear the entire cache. This flushes the current database, no globbing is applied.

Examples:


cache.clear #=> 'OK'

Parameters:

  • Options, (Hash) —

    only present for compatibility.



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# File 'lib/readthis/cache.rb', line 316

def clear(options = {})
  invoke(:clear, '*', &:flushdb)
end

#decrement(key, amount = 1, options = {}) ⇒ Object

Decrement a key in the store.

If the key doesn’t exist it will be initialized at 0. If the key exists but it isn’t a Fixnum it will be initialized at 0.

Examples:


cache.write('counter', 20) # => 20
cache.decrement('counter') # => 19
cache.decrement('counter', 2) # => 17

Parameters:

  • Key (String) —

    for lookup

  • Value (Fixnum) —

    to decrement by

  • Optional (Hash) —

    overrides



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# File 'lib/readthis/cache.rb', line 195

def decrement(key, amount = 1, options = {})
  invoke(:decrement, key) do |store|
    alter(key, amount * -1, options)
  end
end

#delete(key, options = {}) ⇒ Object

Delete the value stored at the specified key. Returns ‘true` if anything was deleted, `false` otherwise.

Examples:


cache.delete('existing-key') # => true
cache.delete('random-key')   # => false



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# File 'lib/readthis/cache.rb', line 108

def delete(key, options = {})
  namespaced = namespaced_key(key, merged_options(options))

  invoke(:delete, key) do |store|
    store.del(namespaced) > 0
  end
end

#exist?(key, options = {}) ⇒ Boolean

Returns ‘true` if the cache contains an entry for the given key.

Examples:


cache.exist?('some-key') # => false
cache.exist?('some-key', namespace: 'cache') # => true

Parameters:

  • Key (String) —

    for lookup

  • Optional (Hash) —

    overrides

Returns:

  • (Boolean) 


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# File 'lib/readthis/cache.rb', line 302

def exist?(key, options = {})
  invoke(:exist?, key) do |store|
    store.exists(namespaced_key(key, merged_options(options)))
  end
end

#fetch(key, options = {}) ⇒ Object

Fetches data from the cache, using the given key. If there is data in the cache with the given key, then that data is returned.

If there is no such data in the cache (a cache miss), then ‘nil` will be returned. However, if a block has been passed, that block will be passed the key and executed in the event of a cache miss. The return value of the block will be written to the cache under the given cache key, and that return value will be returned.

Examples:

Typical


cache.write('today', 'Monday')
cache.fetch('today') # => "Monday"
cache.fetch('city')  # => nil

With a block


cache.fetch('city') do
  'Duckburgh'
end
cache.fetch('city')   # => "Duckburgh"

Cache Miss


cache.write('today', 'Monday')
cache.fetch('today', force: true) # => nil

Parameters:

  • Key (String) —

    for lookup

  • Optional (Block) —

    block for generating the value when missing

  • options (Hash) (defaults to: {}) —

    Optional overrides

Options Hash (options):

  • :force (Boolean) —

    Force a cache miss



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# File 'lib/readthis/cache.rb', line 148

def fetch(key, options = {})
  value = read(key, options) unless options[:force]

  if value.nil? && block_given?
    value = yield(key)
    write(key, value, options)
  end

  value
end

#fetch_multi(keys) ⇒ Object

Fetches multiple keys from the cache using a single call to the server and filling in any cache misses. All read and write operations are executed atomically.

Examples:


cache.fetch_multi('alpha', 'beta') do |key|
  "#{key}-was-missing"
end

cache.fetch_multi('a', 'b', expires_in: 60) do |key|
  key * 2
end

Return all values for the given keys, applying the block to the key when a value is missing.

Parameters:

  • One (String) —

    or more keys to fetch



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# File 'lib/readthis/cache.rb', line 272

def fetch_multi(*keys)
  results   = read_multi(*keys)
  extracted = extract_options!(keys)
  missing   = {}

  invoke(:fetch_multi, keys) do |store|
    results.each do |key, value|
      if value.nil?
        value = yield(key)
        missing[key] = value
        results[key] = value
      end
    end
  end

  write_multi(missing, extracted) if missing.any?

  results
end

#increment(key, amount = 1, options = {}) ⇒ Object

Increment a key in the store.

If the key doesn’t exist it will be initialized at 0. If the key exists but it isn’t a Fixnum it will be initialized at 0.

Examples:


cache.increment('counter') # => 0
cache.increment('counter') # => 1
cache.increment('counter', 2) # => 3

Parameters:

  • Key (String) —

    for lookup

  • Value (Fixnum) —

    to increment by

  • Optional (Hash) —

    overrides



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# File 'lib/readthis/cache.rb', line 174

def increment(key, amount = 1, options = {})
  invoke(:incremenet, key) do |store|
    alter(key, amount, options)
  end
end

#read(key, options = {}) ⇒ Object

Fetches data from the cache, using the given key. If there is data in the cache with the given key, then that data is returned. Otherwise, nil is returned.

Examples:


cache.read('missing') # => nil
cache.read('matched') # => 'some value'

Parameters:

  • Key (String) —

    for lookup

  • Optional (Hash) —

    overrides



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# File 'lib/readthis/cache.rb', line 70

def read(key, options = {})
  invoke(:read, key) do |store|
    value = store.get(namespaced_key(key, merged_options(options)))

    entity.load(value)
  end
end

#read_multi(keys) ⇒ Hash

Read multiple values at once from the cache. Options can be passed in the last argument.

Examples:


cache.write('a', 1)
cache.read_multi('a', 'b') # => { 'a' => 1, 'b' => nil }

Return all values for the given keys.

Parameters:

  • One (String) —

    or more keys to fetch

Returns:

  • (Hash) —

    A hash mapping keys to the values found.



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# File 'lib/readthis/cache.rb', line 215

def read_multi(*keys)
  options = merged_options(extract_options!(keys))
  mapping = keys.map { |key| namespaced_key(key, options) }

  return {} if keys.empty?

  invoke(:read_multi, keys) do |store|
    values = store.mget(mapping).map { |value| entity.load(value) }

    keys.zip(values).to_h
  end
end

#write(key, value, options = {}) ⇒ Object

Writes data to the cache using the given key. Will overwrite whatever value is already stored at that key.

Examples:


cache.write('some-key', 'a bunch of text')                     # => 'OK'
cache.write('some-key', 'short lived', expires_in: 60)         # => 'OK'
cache.write('some-key', 'lives elsehwere', namespace: 'cache') # => 'OK'

Parameters:

  • Key (String) —

    for lookup

  • Optional (Hash) —

    overrides



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# File 'lib/readthis/cache.rb', line 90

def write(key, value, options = {})
  options = merged_options(options)

  invoke(:write, key) do |store|
    write_entity(key, value, store, options)
  end
end

#write_multi(hash, options = {}) ⇒ Object

Write multiple key value pairs simultaneously. This is an atomic operation that will always succeed and will overwrite existing values.

This is a non-standard, but useful, cache method.

Examples:


cache.write_multi('a', 1, 'b', 2) # => true

Parameters:

  • Key (Hash) —

    value hash to write

  • Optional (Hash) —

    overrides



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# File 'lib/readthis/cache.rb', line 241

def write_multi(hash, options = {})
  options = merged_options(options)
  values  = hash.each_with_object([]) do |(key, value), memo|
    memo << namespaced_key(key, options)
    memo << entity.dump(value)
  end

  invoke(:write_multi, values) do |store|
    store.mset(values)
  end
end