Add Money::Distributed::Storage

Author: DarthSim

.gitignore

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+/.bundle/
+/.yardoc
+/Gemfile.lock
+/_yardoc/
+/coverage/
+/doc/
+/pkg/
+/spec/reports/
+/tmp/

.rspec

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+--color

Gemfile

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+source 'https://rubygems.org'
+
+# Specify your gem's dependencies in money-distributed.gemspec
+gemspec

lib/money-distributed.rb

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+require 'money/distributed/storage'

lib/money/distributed/redis.rb

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+require 'redis'
+require 'connection_pool'
+
+class Money
+  module Distributed
+    # Wrapper over different parameters that can be provided for redis
+    class Redis
+      def initialize(redis)
+        @redis_proc = build_redis_proc(redis)
+      end
+
+      def exec(&block)
+        @redis_proc.call(&block)
+      end
+
+      private
+
+      # rubocop: disable Metrics/MethodLength
+      def build_redis_proc(redis)
+        case redis
+        when ::Redis
+          proc { |&b| b.call(redis) }
+        when ConnectionPool
+          proc { |&b| redis.with { |r| b.call(r) } }
+        when Hash
+          build_redis_proc(::Redis.new(redis))
+        when Proc
+          redis
+        else
+          raise ArgumentError, 'Redis, ConnectionPool, Hash or Proc is required'
+        end
+      end
+      # rubocop: enable Metrics/MethodLength
+    end
+  end
+end

lib/money/distributed/storage.rb

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+require 'bigdecimal'
+require 'money/distributed/redis'
+
+class Money
+  module Distributed
+    # Storage for `Money::Bank::VariableExchange` that stores rates in Redis
+    class Storage
+      INDEX_KEY_SEPARATOR = '_TO_'.freeze
+      REDIS_KEY = 'money_rates'.freeze
+
+      def initialize(redis, cache_ttl = nil)
+        @redis = Money::Distributed::Redis.new(redis)
+
+        @cache = {}
+        @cache_ttl = cache_ttl
+        @cache_updated_at = nil
+
+        @mutex = Mutex.new
+      end
+
+      def add_rate(iso_from, iso_to, rate)
+        @redis.exec do |r|
+          r.hset(REDIS_KEY, key_for(iso_from, iso_to), rate)
+        end
+        clear_cache
+      end
+
+      def get_rate(iso_from, iso_to)
+        cached_rates[key_for(iso_from, iso_to)]
+      end
+
+      def each_rate
+        enum = Enumerator.new do |yielder|
+          cached_rates.each do |key, rate|
+            iso_from, iso_to = key.split(INDEX_KEY_SEPARATOR)
+            yielder.yield iso_from, iso_to, rate
+          end
+        end
+
+        block_given? ? enum.each(&block) : enum
+      end
+
+      def transaction
+        # We don't need transactions, we all thread safe here
+        yield
+      end
+
+      def marshal_dump
+        [self.class, @cache_ttl]
+      end
+
+      private
+
+      def key_for(iso_from, iso_to)
+        [iso_from, iso_to].join(INDEX_KEY_SEPARATOR).upcase
+      end
+
+      def cached_rates
+        @mutex.synchronize do
+          retrieve_rates if @cache.empty? || cache_outdated?
+          @cache
+        end
+      end
+
+      def cache_outdated?
+        return false unless @cache_ttl
+        @cache_updated_at.nil? ||
+          @cache_updated_at < Time.now - @cache_ttl
+      end
+
+      def clear_cache
+        @mutex.synchronize do
+          @cache.clear
+        end
+      end
+
+      def retrieve_rates
+        @redis.exec do |r|
+          r.hgetall(REDIS_KEY).each_with_object(@cache) do |(key, val), h|
+            h[key] = BigDecimal.new(val)
+          end
+        end
+        @cache_updated_at = Time.now
+      end
+    end
+  end
+end

lib/money/distributed/version.rb

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+class Money
+  module Distributed
+    VERSION = '0.0.1'.freeze
+  end
+end

money-distributed.gemspec

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+# coding: utf-8
+lib = File.expand_path('../lib', __FILE__)
+$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
+require 'money/distributed/version'
+
+Gem::Specification.new do |spec|
+  spec.name          = 'money-distributed'
+  spec.version       = Money::Distributed::VERSION
+  spec.authors       = ['DarthSim']
+  spec.email         = ['[email protected]']
+
+  spec.summary       = 'Money gem extension for distributed systems'
+  spec.homepage      = 'https://github.com/DarthSim/money-distributed'
+  spec.license       = 'MIT'
+
+  spec.files = `git ls-files -z`.split("\x0").reject do |f|
+    f.match(%r{^(test|spec|features)/})
+  end
+
+  spec.bindir        = 'exe'
+  spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
+  spec.require_paths = ['lib']
+
+  spec.add_development_dependency 'bundler', '~> 1.10'
+  spec.add_development_dependency 'rake', '~> 10.0'
+  spec.add_development_dependency 'rspec'
+  spec.add_development_dependency 'timecop'
+  spec.add_development_dependency 'pry'
+  spec.add_development_dependency 'rubocop'
+
+  spec.add_dependency 'money'
+  spec.add_dependency 'redis'
+  spec.add_dependency 'connection_pool'
+end

spec/redis_spec.rb

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+require 'spec_helper'
+
+describe Money::Distributed::Redis do
+  it 'accepts Redis' do
+    redis = Redis.new
+    expect(described_class.new(redis).exec(&:ping)).to eq 'PONG'
+  end
+
+  it 'accepts ConnectionPool' do
+    pool = ConnectionPool.new { Redis.new }
+    expect(described_class.new(pool).exec(&:ping)).to eq 'PONG'
+  end
+
+  it 'accepts Proc' do
+    redis = Redis.new
+    redis_proc = proc { |&b| b.call(redis) }
+    expect(described_class.new(redis_proc).exec(&:ping)).to eq 'PONG'
+  end
+
+  it 'accepts Hash' do
+    options = { host: '127.0.0.1', db: 0 }
+    expect(described_class.new(options).exec(&:ping)).to eq 'PONG'
+  end
+
+  it "doesn't accept other classes" do
+    redis = double(ping: true)
+    expect { described_class.new(redis).exec(&:ping) }.to \
+      raise_error(ArgumentError)
+  end
+end

spec/spec_helper.rb

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+require 'rspec'
+require 'timecop'
+require 'money-distributed'
+
+RSpec.configure do |c|
+  c.order = :random
+  c.filter_run :focus
+  c.run_all_when_everything_filtered = true
+
+  c.after do
+    Timecop.return
+  end
+end

spec/storage_spec.rb

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+require 'spec_helper'
+
+describe Money::Distributed::Storage do
+  let(:redis) { Redis.new }
+  let(:ttl) { 3600 }
+
+  subject { described_class.new(redis, ttl) }
+
+  it 'stores rates in redis' do
+    subject.add_rate 'USD', 'RUB', 60.123
+    expect(redis.hget(described_class::REDIS_KEY, 'USD_TO_RUB')).to eq '60.123'
+  end
+
+  it 'gets rates from redis' do
+    redis.hset(described_class::REDIS_KEY, 'USD_TO_RUB', 60.123)
+    expect(subject.get_rate('USD', 'RUB')).to eq 60.123
+  end
+
+  it 'caches rates in memory' do
+    redis.hset(described_class::REDIS_KEY, 'USD_TO_RUB', 60.123)
+    subject.get_rate('USD', 'RUB')
+    redis.hset(described_class::REDIS_KEY, 'USD_TO_RUB', 70.456)
+
+    expect(subject.get_rate('USD', 'RUB')).to eq 60.123
+  end
+
+  it 'clears rates cache after ttl' do
+    redis.hset(described_class::REDIS_KEY, 'USD_TO_RUB', 60.123)
+    subject.get_rate('USD', 'RUB')
+    redis.hset(described_class::REDIS_KEY, 'USD_TO_RUB', 70.456)
+
+    Timecop.freeze(Time.now + ttl + 1)
+    expect(subject.get_rate('USD', 'RUB')).to eq 70.456
+  end
+end