Class: Rotary::Storage::Redis

Inherits:
Object
  • Object
show all
Defined in:
lib/rotary/storage/redis.rb

Defined Under Namespace

Classes: Retry

Constant Summary collapse

DEFAULT_PREFIX = 
'rotary'.freeze

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(connection:, ttl:, serializer:, prefix: DEFAULT_PREFIX) ⇒ Redis

Returns a new instance of Redis.



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# File 'lib/rotary/storage/redis.rb', line 16

def initialize(connection:, ttl:, serializer:, prefix: DEFAULT_PREFIX)
  @redis = connection
  @ttl = ttl # in seconds
  @prefix = "#{prefix}::"
  @serializer = serializer
  @pool_list = "#{@prefix}pool"
end

Class Method Details

.default_connection ⇒ Object 



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# File 'lib/rotary/storage/redis.rb', line 12

def self.default_connection
  ::Redis.new
end

Instance Method Details

#clean_older_than(n) ⇒ Object

Removes sessions, where ttl is bigger than threshold n.



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# File 'lib/rotary/storage/redis.rb', line 62

def clean_older_than(n)
  # It doesn't have to happen atomically.
  # New session will be lpush'ed, we can easily check only
  # N sessions from the right.
  size.times do
    serialized_session = @redis.rpop(@pool_list)

    # We have no sessions left. It can happen.
    break unless serialized_session

    key = ttl_key(serialized_session)
    ttl_marker = @redis.ttl(key)

    # When key doesn't exist
    #   redis <= 2.6 returns -1
    #   redis >= 2.8 returns -2
    no_key = [-1, -2].include?(ttl_marker)
    next if no_key

    old = @ttl ? ttl_marker < (@ttl - n) : false
    if old
      # delete ttl key
      @redis.del(key)
      # and execute the block with session as arg
      session = @serializer.load(serialized_session)
      yield(session) if block_given?
    else
      # push back from the left side
      @redis.lpush(@pool_list, serialized_session)
    end
  end
end

#clear ⇒ Object 



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# File 'lib/rotary/storage/redis.rb', line 57

def clear
  @redis.del(@pool_list)
end

#pop ⇒ Object 



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# File 'lib/rotary/storage/redis.rb', line 38

def pop
  serialized = @redis.rpop(@pool_list)
  obj = serialized ? @serializer.load(serialized) : nil
  return obj unless @ttl
  if obj
    # TTL-only logic below
    key = ttl_key(serialized)
    raise Retry unless @redis.get(key)
    @redis.del(key)
  end
  obj
rescue Retry
  retry
end

#push(obj) ⇒ Object 



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# File 'lib/rotary/storage/redis.rb', line 24

def push(obj)
  serialized = @serializer.dump(obj)
  # TODO: make lpush + set/expire transactional somehow
  @redis.lpush(@pool_list, serialized)
  if @ttl
    key = ttl_key(serialized)
    @redis.multi do
      @redis.set(key, 1)
      @redis.expire(key, @ttl)
    end
  end
  self
end

#size ⇒ Object 



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# File 'lib/rotary/storage/redis.rb', line 53

def size
  @redis.llen(@pool_list)
end