New RateLimitedService module

This module is responsible for handling rate
limit checking and throttling with a focus on
services.

app/services/concerns/rate_limited_service.rb

+# frozen_string_literal: true
+
+module RateLimitedService
+  extend ActiveSupport::Concern
+
+  RateLimitedNotSetupError = Class.new(StandardError)
+
+  class RateLimitedError < StandardError
+    def initialize(key:, rate_limiter:)
+      @key = key
+      @rate_limiter = rate_limiter
+    end
+
+    def headers
+      # TODO: This will be fleshed out in https://gitlab.com/gitlab-org/gitlab/-/issues/342370
+      {}
+    end
+
+    def log_request(request, current_user)
+      rate_limiter.class.log_request(request, "#{key}_request_limit".to_sym, current_user)
+    end
+
+    private
+
+    attr_reader :key, :rate_limiter
+  end
+
+  class RateLimiterScopedAndKeyed
+    attr_reader :key, :opts, :rate_limiter_klass
+
+    def initialize(key:, opts:, rate_limiter_klass:)
+      @key = key
+      @opts = opts
+      @rate_limiter_klass = rate_limiter_klass
+    end
+
+    def rate_limit!(service)
+      evaluated_scope = evaluated_scope_for(service)
+      return if feature_flag_disabled?(evaluated_scope[:project])
+
+      rate_limiter = new_rate_limiter(evaluated_scope)
+      if rate_limiter.throttled?
+        raise RateLimitedError.new(key: key, rate_limiter: rate_limiter), _('This endpoint has been requested too many times. Try again later.')
+      end
+    end
+
+    private
+
+    def users_allowlist
+      @users_allowlist ||= opts[:users_allowlist] ? opts[:users_allowlist].call : []
+    end
+
+    def evaluated_scope_for(service)
+      opts[:scope].each_with_object({}) do |var, all|
+        all[var] = service.public_send(var) # rubocop: disable GitlabSecurity/PublicSend
+      end
+    end
+
+    def feature_flag_disabled?(project)
+      Feature.disabled?("rate_limited_service_#{key}", project, default_enabled: :yaml)
+    end
+
+    def new_rate_limiter(evaluated_scope)
+      rate_limiter_klass.new(key, **opts.merge(scope: evaluated_scope.values, users_allowlist: users_allowlist))
+    end
+  end
+
+  prepended do
+    attr_accessor :rate_limiter_bypassed
+    cattr_accessor :rate_limiter_scoped_and_keyed
+
+    def self.rate_limit(key:, opts:, rate_limiter_klass: ::Gitlab::ApplicationRateLimiter)
+      self.rate_limiter_scoped_and_keyed = RateLimiterScopedAndKeyed.new(key: key,
+                                                                         opts: opts,
+                                                                         rate_limiter_klass: rate_limiter_klass)
+    end
+  end
+
+  def execute_without_rate_limiting(*args, **kwargs)
+    self.rate_limiter_bypassed = true
+    execute(*args, **kwargs)
+  ensure
+    self.rate_limiter_bypassed = false
+  end
+
+  def execute(*args, **kwargs)
+    raise RateLimitedNotSetupError if rate_limiter_scoped_and_keyed.nil?
+
+    rate_limiter_scoped_and_keyed.rate_limit!(self) unless rate_limiter_bypassed
+
+    super
+  end
+end

app/services/issues/create_service.rb

@@ -3,6 +3,10 @@
 module Issues
   class CreateService < Issues::BaseService
     include ResolveDiscussions
+    prepend RateLimitedService
+
+    rate_limit key: :issues_create,
+               opts: { scope: [:project, :current_user], users_allowlist: -> { [User.support_bot.username] } }
 
     # NOTE: For Issues::CreateService, we require the spam_params and do not default it to nil, because
     # spam_checking is likely to be necessary.  However, if there is not a request available in scope

spec/services/concerns/rate_limited_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe RateLimitedService do
+  let(:key) { :issues_create }
+  let(:scope) { [:project, :current_user] }
+  let(:opts) { { scope: scope, users_allowlist: -> { [User.support_bot.username] } } }
+  let(:rate_limiter_klass) { ::Gitlab::ApplicationRateLimiter }
+  let(:rate_limiter_instance) { rate_limiter_klass.new(key, **opts) }
+
+  describe 'RateLimitedError' do
+    subject { described_class::RateLimitedError.new(key: key, rate_limiter: rate_limiter_instance) }
+
+    describe '#headers' do
+      it 'returns a Hash of HTTP headers' do
+        # TODO: This will be fleshed out in https://gitlab.com/gitlab-org/gitlab/-/issues/342370
+        expected_headers = {}
+
+        expect(subject.headers).to eq(expected_headers)
+      end
+    end
+
+    describe '#log_request' do
+      it 'logs the request' do
+        request = instance_double(Grape::Request)
+        user = instance_double(User)
+
+        expect(rate_limiter_klass).to receive(:log_request).with(request, "#{key}_request_limit".to_sym, user)
+
+        subject.log_request(request, user)
+      end
+    end
+  end
+
+  describe 'RateLimiterScopedAndKeyed' do
+    subject { described_class::RateLimiterScopedAndKeyed.new(key: key, opts: opts, rate_limiter_klass: rate_limiter_klass) }
+
+    describe '#rate_limit!' do
+      let(:project_with_feature_enabled) { create(:project) }
+      let(:project_without_feature_enabled) { create(:project) }
+
+      let(:project) { nil }
+
+      let(:current_user) { create(:user) }
+      let(:service) { instance_double(Issues::CreateService, project: project, current_user: current_user) }
+      let(:evaluated_scope) { [project, current_user] }
+      let(:evaluated_opts) { { scope: evaluated_scope, users_allowlist: %w[support-bot] } }
+      let(:rate_limited_service_issues_create_feature_enabled) { nil }
+
+      before do
+        allow(rate_limiter_klass).to receive(:new).with(key, **evaluated_opts).and_return(rate_limiter_instance)
+        stub_feature_flags(rate_limited_service_issues_create: rate_limited_service_issues_create_feature_enabled)
+      end
+
+      shared_examples 'a service that does not attempt to throttle' do
+        it 'does not attempt to throttle' do
+          expect(rate_limiter_instance).not_to receive(:throttled?)
+
+          expect(subject.rate_limit!(service)).to be_nil
+        end
+      end
+
+      shared_examples 'a service that does attempt to throttle' do
+        before do
+          allow(rate_limiter_instance).to receive(:throttled?).and_return(throttled)
+        end
+
+        context 'when rate limiting is not in effect' do
+          let(:throttled) { false }
+
+          it 'does not raise an exception' do
+            expect(subject.rate_limit!(service)).to be_nil
+          end
+        end
+
+        context 'when rate limiting is in effect' do
+          let(:throttled) { true }
+
+          it 'raises a RateLimitedError exception' do
+            expect { subject.rate_limit!(service) }.to raise_error(described_class::RateLimitedError, 'This endpoint has been requested too many times. Try again later.')
+          end
+        end
+      end
+
+      context 'when :rate_limited_service_issues_create feature is globally disabled' do
+        let(:rate_limited_service_issues_create_feature_enabled) { false }
+
+        it_behaves_like 'a service that does not attempt to throttle'
+      end
+
+      context 'when :rate_limited_service_issues_create feature is globally enabled' do
+        let(:throttled) { nil }
+        let(:rate_limited_service_issues_create_feature_enabled) { true }
+        let(:project) { project_without_feature_enabled }
+
+        it_behaves_like 'a service that does attempt to throttle'
+      end
+
+      context 'when :rate_limited_service_issues_create feature is enabled for project_with_feature_enabled' do
+        let(:throttled) { nil }
+        let(:rate_limited_service_issues_create_feature_enabled) { project_with_feature_enabled }
+
+        context 'for project_without_feature_enabled' do
+          let(:project) { project_without_feature_enabled }
+
+          it_behaves_like 'a service that does not attempt to throttle'
+        end
+
+        context 'for project_with_feature_enabled' do
+          let(:project) { project_with_feature_enabled }
+
+          it_behaves_like 'a service that does attempt to throttle'
+        end
+      end
+    end
+  end
+
+  describe '#execute_without_rate_limiting' do
+    let(:rate_limiter_scoped_and_keyed) { instance_double(RateLimitedService::RateLimiterScopedAndKeyed) }
+    let(:subject) do
+      local_key = key
+      local_opts = opts
+
+      Class.new do
+        prepend RateLimitedService
+
+        rate_limit key: local_key, opts: local_opts
+
+        def execute(*args, **kwargs)
+          'main logic here'
+        end
+      end.new
+    end
+
+    before do
+      allow(RateLimitedService::RateLimiterScopedAndKeyed).to receive(:new).with(key: key, opts: opts, rate_limiter_klass: rate_limiter_klass).and_return(rate_limiter_scoped_and_keyed)
+    end
+
+    context 'bypasses rate limiting' do
+      it 'calls super' do
+        expect(rate_limiter_scoped_and_keyed).not_to receive(:rate_limit!).with(subject)
+
+        expect(subject.execute_without_rate_limiting).to eq('main logic here')
+      end
+    end
+  end
+
+  describe '#execute' do
+    context 'when rate_limit has not been called' do
+      let(:subject) { Class.new { prepend RateLimitedService }.new }
+
+      it 'raises an RateLimitedNotSetupError exception' do
+        expect { subject.execute }.to raise_error(described_class::RateLimitedNotSetupError)
+      end
+    end
+
+    context 'when rate_limit has been called' do
+      let(:rate_limiter_scoped_and_keyed) { instance_double(RateLimitedService::RateLimiterScopedAndKeyed) }
+      let(:subject) do
+        local_key = key
+        local_opts = opts
+
+        Class.new do
+          prepend RateLimitedService
+
+          rate_limit key: local_key, opts: local_opts
+
+          def execute(*args, **kwargs)
+            'main logic here'
+          end
+        end.new
+      end
+
+      before do
+        allow(RateLimitedService::RateLimiterScopedAndKeyed).to receive(:new).with(key: key, opts: opts, rate_limiter_klass: rate_limiter_klass).and_return(rate_limiter_scoped_and_keyed)
+      end
+
+      context 'and applies rate limiting' do
+        it 'raises an RateLimitedService::RateLimitedError exception' do
+          expect(rate_limiter_scoped_and_keyed).to receive(:rate_limit!).with(subject).and_raise(RateLimitedService::RateLimitedError.new(key: key, rate_limiter: rate_limiter_instance))
+
+          expect { subject.execute }.to raise_error(RateLimitedService::RateLimitedError)
+        end
+      end
+
+      context 'but does not apply rate limiting' do
+        it 'calls super' do
+          expect(rate_limiter_scoped_and_keyed).to receive(:rate_limit!).with(subject).and_return(nil)
+
+          expect(subject.execute).to eq('main logic here')
+        end
+      end
+    end
+  end
+end

spec/services/issues/create_service_spec.rb

@@ -10,6 +10,25 @@ RSpec.describe Issues::CreateService do
 
   let(:spam_params) { double }
 
+  describe '.rate_limiter_scoped_and_keyed' do
+    it 'is set via the rate_limit call' do
+      expect(described_class.rate_limiter_scoped_and_keyed).to be_a(RateLimitedService::RateLimiterScopedAndKeyed)
+
+      expect(described_class.rate_limiter_scoped_and_keyed.key).to eq(:issues_create)
+      expect(described_class.rate_limiter_scoped_and_keyed.opts[:scope]).to eq(%i[project current_user])
+      expect(described_class.rate_limiter_scoped_and_keyed.opts[:users_allowlist].call).to eq(%w[support-bot])
+      expect(described_class.rate_limiter_scoped_and_keyed.rate_limiter_klass).to eq(Gitlab::ApplicationRateLimiter)
+    end
+  end
+
+  describe '#rate_limiter_bypassed' do
+    let(:subject) { described_class.new(project: project, spam_params: {}) }
+
+    it 'is nil by default' do
+      expect(subject.rate_limiter_bypassed).to be_nil
+    end
+  end
+
   describe '#execute' do
     let_it_be(:assignee) { create(:user) }
     let_it_be(:milestone) { create(:milestone, project: project) }