Contents

require 'dalli-elasticache'
require 'alephant/logger'

module Alephant
  module Sequencer
    class SequenceCache
      include Logger

      attr_reader :config

      DEFAULT_TTL = 2

      def initialize(config = {})
        @config = config

        if config_endpoint.nil?
          logger.debug 'Alephant::SequenceCache::#initialize: No config endpoint, NullClient used'
          logger.metric 'NoConfigEndpoint'
          @client = NullClient.new
        else
          @elasticache ||= ::Dalli::ElastiCache.new(config_endpoint, expires_in: ttl)
          @client ||= @elasticache.client
        end
      end

      def get(key)
        versioned_key = versioned key
        result = @client.get versioned_key
        logger.info "Alephant::SequenceCache#get key: #{versioned_key} - #{result ? 'hit' : 'miss'}"
        logger.metric 'GetKeyMiss' unless result
        result ? result : set(key, yield)
      rescue StandardError => e
        yield
      end

      def set(key, value, ttl = nil)
        value.tap { |o| @client.set(versioned(key), o, ttl) }
      end

      private

      def config_endpoint
        config[:elasticache_config_endpoint] || config['elasticache_config_endpoint']
      end

      def ttl
        config[:sequencer_elasticache_ttl] || config['sequencer_elasticache_ttl'] || DEFAULT_TTL
      end

      def versioned(key)
        [key, cache_version].compact.join('_')
      end

      def cache_version
        config[:elasticache_cache_version] || config['elasticache_cache_version']
      end
    end

    class NullClient
      def get(key); end

      def set(_key, value, _ttl = nil)
        value
      end
    end
  end
end

Version data entries

3 entries across 3 versions & 1 rubygems

Version	Path
alephant-sequencer-3.1.1	lib/alephant/sequencer/sequence_cache.rb
alephant-sequencer-3.1.0	lib/alephant/sequencer/sequence_cache.rb
alephant-sequencer-3.0.3	lib/alephant/sequencer/sequence_cache.rb