Port Gitlab::JsonCache to CE

lib/gitlab/json_cache.rb

+# frozen_string_literal: true
+
+module Gitlab
+  class JsonCache
+    attr_reader :backend, :cache_key_with_version, :namespace
+
+    def initialize(options = {})
+      @backend = options.fetch(:backend, Rails.cache)
+      @namespace = options.fetch(:namespace, nil)
+      @cache_key_with_version = options.fetch(:cache_key_with_version, true)
+    end
+
+    def active?
+      if backend.respond_to?(:active?)
+        backend.active?
+      else
+        true
+      end
+    end
+
+    def cache_key(key)
+      expanded_cache_key = [namespace, key].compact
+
+      if cache_key_with_version
+        expanded_cache_key << Rails.version
+      end
+
+      expanded_cache_key.join(':')
+    end
+
+    def expire(key)
+      backend.delete(cache_key(key))
+    end
+
+    def read(key, klass = nil)
+      value = backend.read(cache_key(key))
+      value = parse_value(value, klass) if value
+      value
+    end
+
+    def write(key, value, options = nil)
+      backend.write(cache_key(key), value.to_json, options)
+    end
+
+    def fetch(key, options = {}, &block)
+      klass = options.delete(:as)
+      value = read(key, klass)
+
+      return value unless value.nil?
+
+      value = yield
+
+      write(key, value, options)
+
+      value
+    end
+
+    private
+
+    def parse_value(raw, klass)
+      value = ActiveSupport::JSON.decode(raw)
+
+      case value
+      when Hash then parse_entry(value, klass)
+      when Array then parse_entries(value, klass)
+      else
+        value
+      end
+    rescue ActiveSupport::JSON.parse_error
+      nil
+    end
+
+    def parse_entry(raw, klass)
+      klass.new(raw) if valid_entry?(raw, klass)
+    end
+
+    def valid_entry?(raw, klass)
+      return false unless klass && raw.is_a?(Hash)
+
+      (raw.keys - klass.attribute_names).empty?
+    end
+
+    def parse_entries(values, klass)
+      values.map { |value| parse_entry(value, klass) }.compact
+    end
+  end
+end

spec/lib/gitlab/json_cache_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::JsonCache do
+  let(:backend) { double('backend').as_null_object }
+  let(:namespace) { 'geo' }
+  let(:key) { 'foo' }
+  let(:expanded_key) { "#{namespace}:#{key}:#{Rails.version}" }
+  let(:broadcast_message) { create(:broadcast_message) }
+
+  subject(:cache) { described_class.new(namespace: namespace, backend: backend) }
+
+  describe '#active?' do
+    context 'when backend respond to active? method' do
+      it 'delegates to the underlying cache implementation' do
+        backend = double('backend', active?: false)
+
+        cache = described_class.new(namespace: namespace, backend: backend)
+
+        expect(cache.active?).to eq(false)
+      end
+    end
+
+    context 'when backend does not respond to active? method' do
+      it 'returns true' do
+        backend = double('backend')
+
+        cache = described_class.new(namespace: namespace, backend: backend)
+
+        expect(cache.active?).to eq(true)
+      end
+    end
+  end
+
+  describe '#cache_key' do
+    context 'when namespace is not defined' do
+      it 'expands out the key with Rails version' do
+        cache = described_class.new(cache_key_with_version: true)
+
+        cache_key = cache.cache_key(key)
+
+        expect(cache_key).to eq("#{key}:#{Rails.version}")
+      end
+    end
+
+    context 'when cache_key_with_version is true' do
+      it 'expands out the key with namespace and Rails version' do
+        cache = described_class.new(namespace: namespace, cache_key_with_version: true)
+
+        cache_key = cache.cache_key(key)
+
+        expect(cache_key).to eq("#{namespace}:#{key}:#{Rails.version}")
+      end
+    end
+
+    context 'when cache_key_with_version is false' do
+      it 'expands out the key with namespace' do
+        cache = described_class.new(namespace: namespace, cache_key_with_version: false)
+
+        cache_key = cache.cache_key(key)
+
+        expect(cache_key).to eq("#{namespace}:#{key}")
+      end
+    end
+
+    context 'when namespace is nil, and cache_key_with_version is false' do
+      it 'returns the key' do
+        cache = described_class.new(namespace: nil, cache_key_with_version: false)
+
+        cache_key = cache.cache_key(key)
+
+        expect(cache_key).to eq(key)
+      end
+    end
+  end
+
+  describe '#expire' do
+    it 'expires the given key from the cache' do
+      cache.expire(key)
+
+      expect(backend).to have_received(:delete).with(expanded_key)
+    end
+  end
+
+  describe '#read' do
+    it 'reads the given key from the cache' do
+      cache.read(key)
+
+      expect(backend).to have_received(:read).with(expanded_key)
+    end
+
+    it 'returns the cached value when there is data in the cache with the given key' do
+      allow(backend).to receive(:read)
+        .with(expanded_key)
+        .and_return("true")
+
+      expect(cache.read(key)).to eq(true)
+    end
+
+    it 'returns nil when there is no data in the cache with the given key' do
+      allow(backend).to receive(:read)
+        .with(expanded_key)
+        .and_return(nil)
+
+      expect(cache.read(key)).to be_nil
+    end
+
+    context 'when the cached value is a hash' do
+      it 'parses the cached value' do
+        allow(backend).to receive(:read)
+          .with(expanded_key)
+          .and_return(broadcast_message.to_json)
+
+        expect(cache.read(key, BroadcastMessage)).to eq(broadcast_message)
+      end
+
+      it 'returns nil when klass is nil' do
+        allow(backend).to receive(:read)
+          .with(expanded_key)
+          .and_return(broadcast_message.to_json)
+
+        expect(cache.read(key)).to be_nil
+      end
+
+      it 'gracefully handles bad cached entry' do
+        allow(backend).to receive(:read)
+          .with(expanded_key)
+          .and_return('{')
+
+        expect(cache.read(key, BroadcastMessage)).to be_nil
+      end
+
+      it 'gracefully handles an empty hash' do
+        allow(backend).to receive(:read)
+          .with(expanded_key)
+          .and_return('{}')
+
+        expect(cache.read(key, BroadcastMessage)).to be_a(BroadcastMessage)
+      end
+
+      it 'gracefully handles unknown attributes' do
+        allow(backend).to receive(:read)
+          .with(expanded_key)
+          .and_return(broadcast_message.attributes.merge(unknown_attribute: 1).to_json)
+
+        expect(cache.read(key, BroadcastMessage)).to be_nil
+      end
+    end
+
+    context 'when the cached value is an array' do
+      it 'parses the cached value' do
+        allow(backend).to receive(:read)
+          .with(expanded_key)
+          .and_return([broadcast_message].to_json)
+
+        expect(cache.read(key, BroadcastMessage)).to eq([broadcast_message])
+      end
+
+      it 'returns an empty array when klass is nil' do
+        allow(backend).to receive(:read)
+          .with(expanded_key)
+          .and_return([broadcast_message].to_json)
+
+        expect(cache.read(key)).to eq([])
+      end
+
+      it 'gracefully handles bad cached entry' do
+        allow(backend).to receive(:read)
+          .with(expanded_key)
+          .and_return('[')
+
+        expect(cache.read(key, BroadcastMessage)).to be_nil
+      end
+
+      it 'gracefully handles an empty array' do
+        allow(backend).to receive(:read)
+          .with(expanded_key)
+          .and_return('[]')
+
+        expect(cache.read(key, BroadcastMessage)).to eq([])
+      end
+
+      it 'gracefully handles unknown attributes' do
+        allow(backend).to receive(:read)
+          .with(expanded_key)
+          .and_return([{ unknown_attribute: 1 }, broadcast_message.attributes].to_json)
+
+        expect(cache.read(key, BroadcastMessage)).to eq([broadcast_message])
+      end
+    end
+  end
+
+  describe '#write' do
+    it 'writes value to the cache with the given key' do
+      cache.write(key, true)
+
+      expect(backend).to have_received(:write).with(expanded_key, "true", nil)
+    end
+
+    it 'writes a string containing a JSON representation of the value to the cache' do
+      cache.write(key, broadcast_message)
+
+      expect(backend).to have_received(:write)
+        .with(expanded_key, broadcast_message.to_json, nil)
+    end
+
+    it 'passes options the underlying cache implementation' do
+      cache.write(key, true, expires_in: 15.seconds)
+
+      expect(backend).to have_received(:write)
+        .with(expanded_key, "true", expires_in: 15.seconds)
+    end
+
+    it 'passes options the underlying cache implementation when options is empty' do
+      cache.write(key, true, {})
+
+      expect(backend).to have_received(:write)
+        .with(expanded_key, "true", {})
+    end
+
+    it 'passes options the underlying cache implementation when options is nil' do
+      cache.write(key, true, nil)
+
+      expect(backend).to have_received(:write)
+        .with(expanded_key, "true", nil)
+    end
+  end
+
+  describe '#fetch', :use_clean_rails_memory_store_caching do
+    let(:backend) { Rails.cache }
+
+    it 'requires a block' do
+      expect { cache.fetch(key) }.to raise_error(LocalJumpError)
+    end
+
+    it 'passes options the underlying cache implementation' do
+      expect(backend).to receive(:write)
+        .with(expanded_key, "true", expires_in: 15.seconds)
+
+      cache.fetch(key, expires_in: 15.seconds) { true }
+    end
+
+    context 'when the given key does not exist in the cache' do
+      context 'when the result of the block is truthy' do
+        it 'returns the result of the block' do
+          result = cache.fetch(key) { true }
+
+          expect(result).to eq(true)
+        end
+
+        it 'caches the value' do
+          expect(backend).to receive(:write).with(expanded_key, "true", {})
+
+          cache.fetch(key) { true }
+        end
+      end
+
+      context 'when the result of the block is false' do
+        it 'returns the result of the block' do
+          result = cache.fetch(key) { false }
+
+          expect(result).to eq(false)
+        end
+
+        it 'caches the value' do
+          expect(backend).to receive(:write).with(expanded_key, "false", {})
+
+          cache.fetch(key) { false }
+        end
+      end
+
+      context 'when the result of the block is nil' do
+        it 'returns the result of the block' do
+          result = cache.fetch(key) { nil }
+
+          expect(result).to eq(nil)
+        end
+
+        it 'caches the value' do
+          expect(backend).to receive(:write).with(expanded_key, "null", {})
+
+          cache.fetch(key) { nil }
+        end
+      end
+    end
+
+    context 'when the given key exists in the cache' do
+      context 'when the cached value is a hash' do
+        before do
+          backend.write(expanded_key, broadcast_message.to_json)
+        end
+
+        it 'parses the cached value' do
+          result = cache.fetch(key, as: BroadcastMessage) { 'block result' }
+
+          expect(result).to eq(broadcast_message)
+        end
+
+        it "returns the result of the block when 'as' option is nil" do
+          result = cache.fetch(key, as: nil) { 'block result' }
+
+          expect(result).to eq('block result')
+        end
+
+        it "returns the result of the block when 'as' option is not informed" do
+          result = cache.fetch(key) { 'block result' }
+
+          expect(result).to eq('block result')
+        end
+      end
+
+      context 'when the cached value is a array' do
+        before do
+          backend.write(expanded_key, [broadcast_message].to_json)
+        end
+
+        it 'parses the cached value' do
+          result = cache.fetch(key, as: BroadcastMessage) { 'block result' }
+
+          expect(result).to eq([broadcast_message])
+        end
+
+        it "returns an empty array when 'as' option is nil" do
+          result = cache.fetch(key, as: nil) { 'block result' }
+
+          expect(result).to eq([])
+        end
+
+        it "returns an empty array when 'as' option is not informed" do
+          result = cache.fetch(key) { 'block result' }
+
+          expect(result).to eq([])
+        end
+      end
+
+      context 'when the cached value is true' do
+        before do
+          backend.write(expanded_key, "true")
+        end
+
+        it 'returns the cached value' do
+          result = cache.fetch(key) { 'block result' }
+
+          expect(result).to eq(true)
+        end
+
+        it 'does not execute the block' do
+          expect { |block| cache.fetch(key, &block) }.not_to yield_control
+        end
+
+        it 'does not write to the cache' do
+          expect(backend).not_to receive(:write)
+
+          cache.fetch(key) { 'block result' }
+        end
+      end
+
+      context 'when the cached value is false' do
+        before do
+          backend.write(expanded_key, "false")
+        end
+
+        it 'returns the cached value' do
+          result = cache.fetch(key) { 'block result' }
+
+          expect(result).to eq(false)
+        end
+
+        it 'does not execute the block' do
+          expect { |block| cache.fetch(key, &block) }.not_to yield_control
+        end
+
+        it 'does not write to the cache' do
+          expect(backend).not_to receive(:write)
+
+          cache.fetch(key) { 'block result' }
+        end
+      end
+
+      context 'when the cached value is nil' do
+        before do
+          backend.write(expanded_key, "null")
+        end
+
+        it 'returns the result of the block' do
+          result = cache.fetch(key) { 'block result' }
+
+          expect(result).to eq('block result')
+        end
+
+        it 'writes the result of the block to the cache' do
+          expect(backend).to receive(:write)
+            .with(expanded_key, 'block result'.to_json, {})
+
+          cache.fetch(key) { 'block result' }
+        end
+      end
+    end
+  end
+end