Move ExchangeRates to Redis

Gemfile

@@ -5,6 +5,7 @@ gem 'puma', '~> 3.7'
 
 gem 'pg', '~> 0.18'
 gem 'rails', '~> 5.1.1'
+gem 'redis', '~>3.2'
 
 gem 'bugsnag'
 gem 'countries'

Gemfile.lock

@@ -139,6 +139,7 @@ GEM
     rb-fsevent (0.9.8)
     rb-inotify (0.9.8)
       ffi (>= 0.5.0)
+    redis (3.3.3)
     ruby_dep (1.5.0)
     sixarm_ruby_unaccent (1.1.1)
     slop (3.6.0)
@@ -178,6 +179,7 @@ DEPENDENCIES
   pg (~> 0.18)
   puma (~> 3.7)
   rails (~> 5.1.1)
+  redis (~> 3.2)
   spring
   spring-watcher-listen (~> 2.0.0)
 

app/models/exchange_rate.rb

@@ -1,12 +1,19 @@
-class ExchangeRate < ApplicationRecord
-  def self.get_rate(from_iso_code, to_iso_code)
-    rate = find_by(from: from_iso_code, to: to_iso_code)
-    rate.present? ? rate.rate : 0
+class ExchangeRate
+  def initialize(opts)
+    @client = Redis.new(opts)
   end
 
-  def self.add_rate(from_iso_code, to_iso_code, rate)
-    exrate = find_or_initialize_by(from: from_iso_code, to: to_iso_code)
-    exrate.rate = rate
-    exrate.save!
+  def add_rate(iso_from, iso_to, rate)
+    @client.set key(iso_from, iso_to), rate
+  end
+
+  def get_rate(iso_from, iso_to)
+    @client.get key(iso_from, iso_to)
+  end
+
+  private
+
+  def key(a, b)
+    "#{a}_TO_#{b}"
   end
 end

config/initializers/money.rb

@@ -1,3 +1,4 @@
 MoneyRails.configure do |config|
-  config.default_bank = Money::Bank::VariableExchange.new(ExchangeRate)
+  REDIS_URL = ENV.fetch('REDIS_URL', 'redis://localhost:6379')
+  config.default_bank = Money::Bank::VariableExchange.new(ExchangeRate.new(url: REDIS_URL))
 end

db/migrate/20170515170820_drop_exchange_rates.rb

@@ -0,0 +1,5 @@
+class DropExchangeRates < ActiveRecord::Migration[5.1]
+  def change
+    drop_table :exchange_rates
+  end
+end

db/schema.rb

@@ -10,19 +10,11 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20170514215902) do
+ActiveRecord::Schema.define(version: 20170515170820) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
 
-  create_table "exchange_rates", force: :cascade do |t|
-    t.string "from", limit: 3
-    t.string "to", limit: 3
-    t.float "rate"
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
-  end
-
   create_table "games", force: :cascade do |t|
     t.string "game_code"
     t.string "parsed_game_code"

lib/tasks/currencies.rake

@@ -5,13 +5,14 @@ API_URL = 'http://rate-exchange-1.appspot.com/currency'.freeze
 namespace :currencies do
   desc 'Get all currencies exchange rates'
   task retrieve_all: :environment do
-    currencies = Price.pluck(:currency).uniq
+    currencies = Price.pluck(:currency).uniq.sort
 
     currencies.each do |from|
-      (currencies - [from]).each do |to|
+      puts "Retieving #{currencies.count} rates for #{from} currency..."
+      currencies.each do |to|
         response = HTTParty.get(API_URL, query: { from: from, to: to})
         rate = JSON.parse(response.body, symbolize_names: true)[:rate]
-        ExchangeRate.find_or_create_by(from: from, to: to).update_attribute(:rate, rate)
+        Money.add_rate(from, to, rate)
       end
     end
   end