diff options
-rw-r--r-- | changelogs/unreleased/etag-notes-polling.yml | 4 | ||||
-rw-r--r-- | config/initializers/etag_caching.rb | 4 | ||||
-rw-r--r-- | lib/gitlab/etag_caching/middleware.rb | 66 | ||||
-rw-r--r-- | lib/gitlab/etag_caching/store.rb | 32 | ||||
-rw-r--r-- | spec/lib/gitlab/etag_caching/middleware_spec.rb | 163 |
5 files changed, 269 insertions, 0 deletions
diff --git a/changelogs/unreleased/etag-notes-polling.yml b/changelogs/unreleased/etag-notes-polling.yml new file mode 100644 index 00000000000..53990821d25 --- /dev/null +++ b/changelogs/unreleased/etag-notes-polling.yml @@ -0,0 +1,4 @@ +--- +title: Use ETag to improve performance of issue notes polling +merge_request: 9036 +author: diff --git a/config/initializers/etag_caching.rb b/config/initializers/etag_caching.rb new file mode 100644 index 00000000000..eba88801141 --- /dev/null +++ b/config/initializers/etag_caching.rb @@ -0,0 +1,4 @@ +# This middleware has to come after Gitlab::Metrics::RackMiddleware +# in the middleware stack, because it tracks events with +# GitLab Performance Monitoring +Rails.application.config.middleware.use(Gitlab::EtagCaching::Middleware) diff --git a/lib/gitlab/etag_caching/middleware.rb b/lib/gitlab/etag_caching/middleware.rb new file mode 100644 index 00000000000..0f24f9bbfde --- /dev/null +++ b/lib/gitlab/etag_caching/middleware.rb @@ -0,0 +1,66 @@ +module Gitlab + module EtagCaching + class Middleware + RESERVED_WORDS = ProjectPathValidator::RESERVED.map { |word| "/#{word}/" }.join('|') + ROUTE_REGEXP = Regexp.union( + %r(^(?!.*(#{RESERVED_WORDS})).*/noteable/issue/\d+/notes\z) + ) + + def initialize(app) + @app = app + end + + def call(env) + return @app.call(env) unless enabled_for_current_route?(env) + Gitlab::Metrics.add_event(:etag_caching_middleware_used) + + etag, cached_value_present = get_etag(env) + if_none_match = env['HTTP_IF_NONE_MATCH'] + + if if_none_match == etag + Gitlab::Metrics.add_event(:etag_caching_cache_hit) + [304, { 'ETag' => etag }, ['']] + else + track_cache_miss(if_none_match, cached_value_present) + + status, headers, body = @app.call(env) + headers['ETag'] = etag + [status, headers, body] + end + end + + private + + def enabled_for_current_route?(env) + ROUTE_REGEXP.match(env['PATH_INFO']) + end + + def get_etag(env) + cache_key = env['PATH_INFO'] + store = Store.new + current_value = store.get(cache_key) + cached_value_present = current_value.present? + + unless cached_value_present + current_value = store.touch(cache_key, only_if_missing: true) + end + + [weak_etag_format(current_value), cached_value_present] + end + + def weak_etag_format(value) + %Q{W/"#{value}"} + end + + def track_cache_miss(if_none_match, cached_value_present) + if if_none_match.blank? + Gitlab::Metrics.add_event(:etag_caching_header_missing) + elsif !cached_value_present + Gitlab::Metrics.add_event(:etag_caching_key_not_found) + else + Gitlab::Metrics.add_event(:etag_caching_resource_changed) + end + end + end + end +end diff --git a/lib/gitlab/etag_caching/store.rb b/lib/gitlab/etag_caching/store.rb new file mode 100644 index 00000000000..9532e432f78 --- /dev/null +++ b/lib/gitlab/etag_caching/store.rb @@ -0,0 +1,32 @@ +module Gitlab + module EtagCaching + class Store + EXPIRY_TIME = 10.minutes + REDIS_NAMESPACE = 'etag:'.freeze + + def get(key) + Gitlab::Redis.with { |redis| redis.get(redis_key(key)) } + end + + def touch(key, only_if_missing: false) + etag = generate_etag + + Gitlab::Redis.with do |redis| + redis.set(redis_key(key), etag, ex: EXPIRY_TIME, nx: only_if_missing) + end + + etag + end + + private + + def generate_etag + SecureRandom.hex + end + + def redis_key(key) + "#{REDIS_NAMESPACE}#{key}" + end + end + end +end diff --git a/spec/lib/gitlab/etag_caching/middleware_spec.rb b/spec/lib/gitlab/etag_caching/middleware_spec.rb new file mode 100644 index 00000000000..8b5bfc4dbb0 --- /dev/null +++ b/spec/lib/gitlab/etag_caching/middleware_spec.rb @@ -0,0 +1,163 @@ +require 'spec_helper' + +describe Gitlab::EtagCaching::Middleware do + let(:app) { double(:app) } + let(:middleware) { described_class.new(app) } + let(:app_status_code) { 200 } + let(:if_none_match) { nil } + let(:enabled_path) { '/gitlab-org/gitlab-ce/noteable/issue/1/notes' } + + context 'when ETag caching is not enabled for current route' do + let(:path) { '/gitlab-org/gitlab-ce/tree/master/noteable/issue/1/notes' } + + before do + mock_app_response + end + + it 'does not add ETag header' do + _, headers, _ = middleware.call(build_env(path, if_none_match)) + + expect(headers['ETag']).to be_nil + end + + it 'passes status code from app' do + status, _, _ = middleware.call(build_env(path, if_none_match)) + + expect(status).to eq app_status_code + end + end + + context 'when there is no ETag in store for given resource' do + let(:path) { enabled_path } + + before do + mock_app_response + mock_value_in_store(nil) + end + + it 'generates ETag' do + expect_any_instance_of(Gitlab::EtagCaching::Store) + .to receive(:touch).and_return('123') + + middleware.call(build_env(path, if_none_match)) + end + + context 'when If-None-Match header was specified' do + let(:if_none_match) { 'W/"abc"' } + + it 'tracks "etag_caching_key_not_found" event' do + expect(Gitlab::Metrics).to receive(:add_event) + .with(:etag_caching_middleware_used) + expect(Gitlab::Metrics).to receive(:add_event) + .with(:etag_caching_key_not_found) + + middleware.call(build_env(path, if_none_match)) + end + end + end + + context 'when there is ETag in store for given resource' do + let(:path) { enabled_path } + + before do + mock_app_response + mock_value_in_store('123') + end + + it 'returns this value as header' do + _, headers, _ = middleware.call(build_env(path, if_none_match)) + + expect(headers['ETag']).to eq 'W/"123"' + end + end + + context 'when If-None-Match header matches ETag in store' do + let(:path) { enabled_path } + let(:if_none_match) { 'W/"123"' } + + before do + mock_value_in_store('123') + end + + it 'does not call app' do + expect(app).not_to receive(:call) + + middleware.call(build_env(path, if_none_match)) + end + + it 'returns status code 304' do + status, _, _ = middleware.call(build_env(path, if_none_match)) + + expect(status).to eq 304 + end + + it 'tracks "etag_caching_cache_hit" event' do + expect(Gitlab::Metrics).to receive(:add_event) + .with(:etag_caching_middleware_used) + expect(Gitlab::Metrics).to receive(:add_event) + .with(:etag_caching_cache_hit) + + middleware.call(build_env(path, if_none_match)) + end + end + + context 'when If-None-Match header does not match ETag in store' do + let(:path) { enabled_path } + let(:if_none_match) { 'W/"abc"' } + + before do + mock_value_in_store('123') + end + + it 'calls app' do + expect(app).to receive(:call).and_return([app_status_code, {}, ['body']]) + + middleware.call(build_env(path, if_none_match)) + end + + it 'tracks "etag_caching_resource_changed" event' do + mock_app_response + + expect(Gitlab::Metrics).to receive(:add_event) + .with(:etag_caching_middleware_used) + expect(Gitlab::Metrics).to receive(:add_event) + .with(:etag_caching_resource_changed) + + middleware.call(build_env(path, if_none_match)) + end + end + + context 'when If-None-Match header is not specified' do + let(:path) { enabled_path } + + before do + mock_value_in_store('123') + mock_app_response + end + + it 'tracks "etag_caching_header_missing" event' do + expect(Gitlab::Metrics).to receive(:add_event) + .with(:etag_caching_middleware_used) + expect(Gitlab::Metrics).to receive(:add_event) + .with(:etag_caching_header_missing) + + middleware.call(build_env(path, if_none_match)) + end + end + + def mock_app_response + allow(app).to receive(:call).and_return([app_status_code, {}, ['body']]) + end + + def mock_value_in_store(value) + allow_any_instance_of(Gitlab::EtagCaching::Store) + .to receive(:get).and_return(value) + end + + def build_env(path, if_none_match) + { + 'PATH_INFO' => path, + 'HTTP_IF_NONE_MATCH' => if_none_match + } + end +end |