Merge pull request zendesk#23 from zendesk/cache

etag-cache responses by default

Author: steved

lib/zendesk_api/client.rb

@@ -5,6 +5,8 @@
 require 'zendesk_api/rescue'
 require 'zendesk_api/configuration'
 require 'zendesk_api/collection'
+require 'zendesk_api/lru_cache'
+require 'zendesk_api/middleware/request/etag_cache'
 require 'zendesk_api/middleware/request/retry'
 require 'zendesk_api/middleware/request/upload'
 require 'zendesk_api/middleware/response/callback'
@@ -135,6 +137,7 @@ def build_connection
  builder.use ZendeskAPI::Middleware::Response::Deflate
 
  # request
+ builder.use ZendeskAPI::Middleware::Request::EtagCache, :cache => config.cache
  builder.use ZendeskAPI::Middleware::Request::Upload
  builder.request :multipart
  builder.request :json

lib/zendesk_api/configuration.rb

@@ -2,23 +2,37 @@ module ZendeskAPI
  class Configuration
  # @return [String] The basic auth username.
  attr_accessor :username
+
  # @return [String] The basic auth password.
  attr_accessor :password
+
  # @return [String] The API url. Must be https unless {#allow_http} is set.
  attr_accessor :url
+
  # @return [Boolean] Whether to attempt to retry when rate-limited (http status: 429).
  attr_accessor :retry
+
  # @return [Logger] Logger to use when logging requests.
  attr_accessor :logger
+
  # @return [Hash] Client configurations (eg ssh config) to pass to Faraday
  attr_accessor :client_options
+
  # @return [Symbol] Faraday adapter
  attr_accessor :adapter
+
  # @return [Boolean] Whether to allow non-HTTPS connections for development purposes.
  attr_accessor :allow_http
 
+ # Use this cache instead of default ZendeskAPI::LRUCache.new
+ # - must respond to read/write/fetch e.g. ActiveSupport::Cache::MemoryStore.new)
+ # - pass false to disable caching
+ # @return [ZendeskAPI::LRUCache]
+ attr_accessor :cache
+
  def initialize
  @client_options = {}
+ self.cache = ZendeskAPI::LRUCache.new(1000)
  end
 
  # Sets accept and user_agent headers, and url.

lib/zendesk_api/lru_cache.rb

@@ -0,0 +1,38 @@
+module ZendeskAPI
+ # http://codesnippets.joyent.com/posts/show/12329
+ class ZendeskAPI::LRUCache
+ attr_accessor :size
+
+ def initialize(size = 10)
+ @size = size
+ @store = {}
+ @lru = []
+ end
+
+ def write(key, value)
+ @store[key] = value
+ set_lru(key)
+ @store.delete(@lru.pop) if @lru.size > @size
+ value
+ end
+
+ def read(key)
+ set_lru(key)
+ @store[key]
+ end
+
+ def fetch(key)
+ if @store.has_key? key
+ read key
+ else
+ write key, yield
+ end
+ end
+
+ private
+
+ def set_lru(key)
+ @lru.unshift(@lru.delete(key) || key)
+ end
+ end
+end

lib/zendesk_api/middleware/request/etag_cache.rb

@@ -0,0 +1,38 @@
+require "faraday/middleware"
+
+module ZendeskAPI
+ module Middleware
+ module Request
+ # Request middleware that caches responses based on etags
+ # can be removed once this is merged: https://github.com/pengwynn/faraday_middleware/pull/42
+ class EtagCache < Faraday::Middleware
+ def initialize(app, options = {})
+ @app = app
+ @cache = options[:cache] ||
+ raise("need :cache option e.g. ActiveSupport::Cache::MemoryStore.new")
+ @cache_key_prefix = options.fetch(:cache_key_prefix, :faraday_etags)
+ end
+
+ def call(env)
+ return @app.call(env) unless [:get, :head].include?(env[:method])
+ cache_key = [@cache_key_prefix, env[:url].to_s]
+
+ # send known etag
+ if cached = @cache.read(cache_key)
+ env[:request_headers]["If-None-Match"] ||= cached[:response_headers]["Etag"]
+ end
+
+ @app.call(env).on_complete do
+ if cached && env[:status] == 304 # not modified
+ env[:body] = cached[:body]
+ end
+
+ if env[:status] == 200 && env[:response_headers]["Etag"] # modified and cacheable
+ @cache.write(cache_key, env)
+ end
+ end
+ end
+ end
+ end
+ end
+end

spec/lru_cache_spec.rb

@@ -0,0 +1,26 @@
+require 'spec_helper'
+
+describe ZendeskAPI::LRUCache do
+ let(:cache){ ZendeskAPI::LRUCache.new(2) }
+
+ it "writes and reads" do
+ cache.write("x", 1).should == 1
+ cache.read("x").should == 1
+ end
+
+ it "drops" do
+ cache.write("x", 1)
+ cache.write("y", 1)
+ cache.write("x", 1)
+ cache.write("z", 1)
+ cache.read("z").should == 1
+ cache.read("x").should == 1
+ cache.read("y").should == nil
+ end
+
+ it "fetches" do
+ cache.fetch("x"){ 1 }.should == 1
+ cache.read("x").should == 1
+ cache.fetch("x"){ 2 }.should == 1
+ end
+end

spec/middleware/request/etag_cache_spec.rb

@@ -0,0 +1,24 @@
+require 'spec_helper'
+
+describe ZendeskAPI::Middleware::Request::EtagCache do
+ def fake_response(data)
+ stub_request(:get, %r{blergh}).to_return(:status => 200, :body => data)
+ response = client.connection.get("blergh")
+ response.status.should == 200
+ response
+ end
+
+ it "caches" do
+ client.config.cache.size = 1
+
+ stub_request(:get, %r{blergh}).to_return(:status => 200, :body => '{"x":1}', :headers => {"Etag" => "x"})
+ response = client.connection.get("blergh")
+ response.status.should == 200
+ response.body.should == {"x"=>1}
+
+ stub_request(:get, %r{blergh}).to_return(:status => 304, :response_headers => {"Etag" => "x"})
+ response = client.connection.get("blergh")
+ response.status.should == 304
+ response.body.should == {"x"=>1}
+ end
+end

spec/spec_helper.rb

@@ -46,6 +46,7 @@ def client
  end
 
  client.config.logger.level = (ENV["LOG"] ? Logger::INFO : Logger::WARN)
+ client.config.cache.size = 0
 
  client
  end