Commit b0b5346d authored by Stan Hu's avatar Stan Hu

Merge branch 'mk/asymmetric-exists-cache' into 'master'

Resolve "Geo: Does not mark repositories as missing on primary due to stale cache"

Closes #50211 and #44044

See merge request gitlab-org/gitlab-ce!21789
parents c02057b4 f2fa7c10
...@@ -510,7 +510,7 @@ class Repository ...@@ -510,7 +510,7 @@ class Repository
raw_repository.exists? raw_repository.exists?
end end
cache_method :exists? cache_method_asymmetrically :exists?
# We don't need to cache the output of this method because both exists? and # We don't need to cache the output of this method because both exists? and
# has_visible_content? are already memoized and cached. There's no guarantee # has_visible_content? are already memoized and cached. There's no guarantee
...@@ -612,7 +612,7 @@ class Repository ...@@ -612,7 +612,7 @@ class Repository
Licensee::License.new(license_key) Licensee::License.new(license_key)
end end
cache_method :license, memoize_only: true memoize_method :license
def gitignore def gitignore
file_on_head(:gitignore) file_on_head(:gitignore)
...@@ -1029,6 +1029,10 @@ class Repository ...@@ -1029,6 +1029,10 @@ class Repository
@cache ||= Gitlab::RepositoryCache.new(self) @cache ||= Gitlab::RepositoryCache.new(self)
end end
def request_store_cache
@request_store_cache ||= Gitlab::RepositoryCache.new(self, backend: Gitlab::SafeRequestStore)
end
def tags_sorted_by_committed_date def tags_sorted_by_committed_date
tags.sort_by do |tag| tags.sort_by do |tag|
# Annotated tags can point to any object (e.g. a blob), but generally # Annotated tags can point to any object (e.g. a blob), but generally
......
---
title: 'Resolve "Geo: Does not mark repositories as missing on primary due to stale
cache"'
merge_request: 21789
author:
type: fixed
...@@ -29,5 +29,21 @@ module Gitlab ...@@ -29,5 +29,21 @@ module Gitlab
def read(key) def read(key)
backend.read(cache_key(key)) backend.read(cache_key(key))
end end
def write(key, value)
backend.write(cache_key(key), value)
end
def fetch_without_caching_false(key, &block)
value = read(key)
return value if value
value = yield
# Don't cache false values
write(key, value) if value
value
end
end end
end end
module Gitlab module Gitlab
module RepositoryCacheAdapter module RepositoryCacheAdapter
extend ActiveSupport::Concern extend ActiveSupport::Concern
include Gitlab::Utils::StrongMemoize
class_methods do class_methods do
# Wraps around the given method and caches its output in Redis and an instance # Caches and strongly memoizes the method.
# variable.
# #
# This only works for methods that do not take any arguments. # This only works for methods that do not take any arguments.
def cache_method(name, fallback: nil, memoize_only: false) #
original = :"_uncached_#{name}" # name - The name of the method to be cached.
# fallback - A value to fall back to if the repository does not exist, or
# in case of a Git error. Defaults to nil.
def cache_method(name, fallback: nil)
uncached_name = alias_uncached_method(name)
define_method(name) do
cache_method_output(name, fallback: fallback) do
__send__(uncached_name) # rubocop:disable GitlabSecurity/PublicSend
end
end
end
alias_method(original, name) # Caches truthy values from the method. All values are strongly memoized,
# and cached in RequestStore.
#
# Currently only used to cache `exists?` since stale false values are
# particularly troublesome. This can occur, for example, when an NFS mount
# is temporarily down.
#
# This only works for methods that do not take any arguments.
#
# name - The name of the method to be cached.
def cache_method_asymmetrically(name)
uncached_name = alias_uncached_method(name)
define_method(name) do define_method(name) do
cache_method_output(name, fallback: fallback, memoize_only: memoize_only) do cache_method_output_asymmetrically(name) do
__send__(original) # rubocop:disable GitlabSecurity/PublicSend __send__(uncached_name) # rubocop:disable GitlabSecurity/PublicSend
end end
end end
end end
# Strongly memoizes the method.
#
# This only works for methods that do not take any arguments.
#
# name - The name of the method to be memoized.
# fallback - A value to fall back to if the repository does not exist, or
# in case of a Git error. Defaults to nil. The fallback value
# is not memoized.
def memoize_method(name, fallback: nil)
uncached_name = alias_uncached_method(name)
define_method(name) do
memoize_method_output(name, fallback: fallback) do
__send__(uncached_name) # rubocop:disable GitlabSecurity/PublicSend
end
end
end
# Prepends "_uncached_" to the target method name
#
# Returns the uncached method name
def alias_uncached_method(name)
uncached_name = :"_uncached_#{name}"
alias_method(uncached_name, name)
uncached_name
end
end
# RequestStore-backed RepositoryCache to be used. Should be overridden by
# the including class
def request_store_cache
raise NotImplementedError
end end
# RepositoryCache to be used. Should be overridden by the including class # RepositoryCache to be used. Should be overridden by the including class
...@@ -30,65 +87,93 @@ module Gitlab ...@@ -30,65 +87,93 @@ module Gitlab
raise NotImplementedError raise NotImplementedError
end end
# Caches the supplied block both in a cache and in an instance variable. # Caches and strongly memoizes the supplied block.
# #
# The cache key and instance variable are named the same way as the value of # name - The name of the method to be cached.
# the `key` argument. # fallback - A value to fall back to if the repository does not exist, or
# in case of a Git error. Defaults to nil.
def cache_method_output(name, fallback: nil, &block)
memoize_method_output(name, fallback: fallback) do
cache.fetch(name, &block)
end
end
# Caches truthy values from the supplied block. All values are strongly
# memoized, and cached in RequestStore.
# #
# This method will return `nil` if the corresponding instance variable is also # Currently only used to cache `exists?` since stale false values are
# set to `nil`. This ensures we don't keep yielding the block when it returns # particularly troublesome. This can occur, for example, when an NFS mount
# `nil`. # is temporarily down.
# #
# key - The name of the key to cache the data in. # name - The name of the method to be cached.
# fallback - A value to fall back to in the event of a Git error. def cache_method_output_asymmetrically(name, &block)
def cache_method_output(key, fallback: nil, memoize_only: false, &block) memoize_method_output(name) do
ivar = cache_instance_variable_name(key) request_store_cache.fetch(name) do
cache.fetch_without_caching_false(name, &block)
if instance_variable_defined?(ivar)
instance_variable_get(ivar)
else
# If the repository doesn't exist and a fallback was specified we return
# that value inmediately. This saves us Rugged/gRPC invocations.
return fallback unless fallback.nil? || cache.repository.exists?
begin
value =
if memoize_only
yield
else
cache.fetch(key, &block)
end
instance_variable_set(ivar, value)
rescue Gitlab::Git::Repository::NoRepository
# Even if the above `#exists?` check passes these errors might still
# occur (for example because of a non-existing HEAD). We want to
# gracefully handle this and not cache anything
fallback
end end
end end
end end
# Strongly memoizes the supplied block.
#
# name - The name of the method to be memoized.
# fallback - A value to fall back to if the repository does not exist, or
# in case of a Git error. Defaults to nil. The fallback value is
# not memoized.
def memoize_method_output(name, fallback: nil, &block)
no_repository_fallback(name, fallback: fallback) do
strong_memoize(memoizable_name(name), &block)
end
end
# Returns the fallback value if the repository does not exist
def no_repository_fallback(name, fallback: nil, &block)
# Avoid unnecessary gRPC invocations
return fallback if fallback && fallback_early?(name)
yield
rescue Gitlab::Git::Repository::NoRepository
# Even if the `#exists?` check in `fallback_early?` passes, these errors
# might still occur (for example because of a non-existing HEAD). We
# want to gracefully handle this and not memoize anything.
fallback
end
# Expires the caches of a specific set of methods # Expires the caches of a specific set of methods
def expire_method_caches(methods) def expire_method_caches(methods)
methods.each do |key| methods.each do |name|
unless cached_methods.include?(key.to_sym) unless cached_methods.include?(name.to_sym)
Rails.logger.error "Requested to expire non-existent method '#{key}' for Repository" Rails.logger.error "Requested to expire non-existent method '#{name}' for Repository"
next next
end end
cache.expire(key) cache.expire(name)
ivar = cache_instance_variable_name(key) clear_memoization(memoizable_name(name))
remove_instance_variable(ivar) if instance_variable_defined?(ivar)
end end
expire_request_store_method_caches(methods)
end end
private private
def cache_instance_variable_name(key) def memoizable_name(name)
:"@#{key.to_s.tr('?!', '')}" "#{name.to_s.tr('?!', '')}"
end
def expire_request_store_method_caches(methods)
methods.each do |name|
request_store_cache.expire(name)
end
end
# All cached repository methods depend on the existence of a Git repository,
# so if the repository doesn't exist, we already know not to call it.
def fallback_early?(method_name)
# Avoid infinite loop
return false if method_name == :exists?
!exists?
end end
end end
end end
...@@ -90,6 +90,11 @@ describe Projects::PipelinesController do ...@@ -90,6 +90,11 @@ describe Projects::PipelinesController do
context 'when performing gitaly calls', :request_store do context 'when performing gitaly calls', :request_store do
it 'limits the Gitaly requests' do it 'limits the Gitaly requests' do
# Isolate from test preparation (Repository#exists? is also cached in RequestStore)
RequestStore.end!
RequestStore.clear!
RequestStore.begin!
expect { get_pipelines_index_json } expect { get_pipelines_index_json }
.to change { Gitlab::GitalyClient.get_request_count }.by(2) .to change { Gitlab::GitalyClient.get_request_count }.by(2)
end end
......
...@@ -65,6 +65,144 @@ describe Gitlab::RepositoryCacheAdapter do ...@@ -65,6 +65,144 @@ describe Gitlab::RepositoryCacheAdapter do
end end
end end
describe '#cache_method_output_asymmetrically', :use_clean_rails_memory_store_caching, :request_store do
let(:request_store_cache) { repository.send(:request_store_cache) }
context 'with a non-existing repository' do
let(:project) { create(:project) } # No repository
let(:object) { double }
subject do
repository.cache_method_output_asymmetrically(:cats) do
object.cats_call_stub
end
end
it 'returns the output of the original method' do
expect(object).to receive(:cats_call_stub).and_return('output')
expect(subject).to eq('output')
end
end
context 'with a method throwing a non-existing-repository error' do
subject do
repository.cache_method_output_asymmetrically(:cats) do
raise Gitlab::Git::Repository::NoRepository
end
end
it 'returns nil' do
expect(subject).to eq(nil)
end
it 'does not cache the data' do
subject
expect(repository.instance_variable_defined?(:@cats)).to eq(false)
expect(cache.exist?(:cats)).to eq(false)
end
end
context 'with an existing repository' do
let(:object) { double }
context 'when it returns truthy' do
before do
expect(object).to receive(:cats).once.and_return('truthy output')
end
it 'caches the output in RequestStore' do
expect do
repository.cache_method_output_asymmetrically(:cats) { object.cats }
end.to change { request_store_cache.read(:cats) }.from(nil).to('truthy output')
end
it 'caches the output in RepositoryCache' do
expect do
repository.cache_method_output_asymmetrically(:cats) { object.cats }
end.to change { cache.read(:cats) }.from(nil).to('truthy output')
end
end
context 'when it returns false' do
before do
expect(object).to receive(:cats).once.and_return(false)
end
it 'caches the output in RequestStore' do
expect do
repository.cache_method_output_asymmetrically(:cats) { object.cats }
end.to change { request_store_cache.read(:cats) }.from(nil).to(false)
end
it 'does NOT cache the output in RepositoryCache' do
expect do
repository.cache_method_output_asymmetrically(:cats) { object.cats }
end.not_to change { cache.read(:cats) }.from(nil)
end
end
end
end
describe '#memoize_method_output' do
let(:fallback) { 10 }
context 'with a non-existing repository' do
let(:project) { create(:project) } # No repository
subject do
repository.memoize_method_output(:cats, fallback: fallback) do
repository.cats_call_stub
end
end
it 'returns the fallback value' do
expect(subject).to eq(fallback)
end
it 'avoids calling the original method' do
expect(repository).not_to receive(:cats_call_stub)
subject
end
it 'does not set the instance variable' do
subject
expect(repository.instance_variable_defined?(:@cats)).to eq(false)
end
end
context 'with a method throwing a non-existing-repository error' do
subject do
repository.memoize_method_output(:cats, fallback: fallback) do
raise Gitlab::Git::Repository::NoRepository
end
end
it 'returns the fallback value' do
expect(subject).to eq(fallback)
end
it 'does not set the instance variable' do
subject
expect(repository.instance_variable_defined?(:@cats)).to eq(false)
end
end
context 'with an existing repository' do
it 'sets the instance variable' do
repository.memoize_method_output(:cats, fallback: fallback) do
'block output'
end
expect(repository.instance_variable_get(:@cats)).to eq('block output')
end
end
end
describe '#expire_method_caches' do describe '#expire_method_caches' do
it 'expires the caches of the given methods' do it 'expires the caches of the given methods' do
expect(cache).to receive(:expire).with(:rendered_readme) expect(cache).to receive(:expire).with(:rendered_readme)
......
...@@ -47,4 +47,89 @@ describe Gitlab::RepositoryCache do ...@@ -47,4 +47,89 @@ describe Gitlab::RepositoryCache do
expect(backend).to have_received(:fetch).with("baz:#{namespace}", &p) expect(backend).to have_received(:fetch).with("baz:#{namespace}", &p)
end end
end end
describe '#fetch_without_caching_false', :use_clean_rails_memory_store_caching do
let(:key) { :foo }
let(:backend) { Rails.cache }
it 'requires a block' do
expect do
cache.fetch_without_caching_false(key)
end.to raise_error(LocalJumpError)
end
context 'when the 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_without_caching_false(key) { true }
expect(result).to be true
end
it 'caches the value' do
expect(backend).to receive(:write).with("#{key}:#{namespace}", true)
cache.fetch_without_caching_false(key) { true }
end
end
context 'when the result of the block is falsey' do
let(:p) { -> { false } }
it 'returns the result of the block' do
result = cache.fetch_without_caching_false(key, &p)
expect(result).to be false
end
it 'does not cache the value' do
expect(backend).not_to receive(:write).with("#{key}:#{namespace}", true)
cache.fetch_without_caching_false(key, &p)
end
end
end
context 'when the cached value is truthy' do
before do
backend.write("#{key}:#{namespace}", true)
end
it 'returns the cached value' do
result = cache.fetch_without_caching_false(key) { 'block result' }
expect(result).to be true
end
it 'does not execute the block' do
expect do |b|
cache.fetch_without_caching_false(key, &b)
end.not_to yield_control
end
it 'does not write to the cache' do
expect(backend).not_to receive(:write)
cache.fetch_without_caching_false(key) { 'block result' }
end
end
context 'when the cached value is falsey' do
before do
backend.write("#{key}:#{namespace}", false)
end
it 'returns the result of the block' do
result = cache.fetch_without_caching_false(key) { 'block result' }
expect(result).to eq 'block result'
end
it 'writes the truthy value to the cache' do
expect(backend).to receive(:write).with("#{key}:#{namespace}", 'block result')
cache.fetch_without_caching_false(key) { 'block result' }
end
end
end
end end
...@@ -1044,6 +1044,47 @@ describe Repository do ...@@ -1044,6 +1044,47 @@ describe Repository do
expect_to_raise_storage_error { broken_repository.exists? } expect_to_raise_storage_error { broken_repository.exists? }
end end
end end
context 'asymmetric caching', :use_clean_rails_memory_store_caching, :request_store do
let(:cache) { repository.send(:cache) }
let(:request_store_cache) { repository.send(:request_store_cache) }
context 'when it returns true' do
before do
expect(repository.raw_repository).to receive(:exists?).once.and_return(true)
end
it 'caches the output in RequestStore' do
expect do
repository.exists?
end.to change { request_store_cache.read(:exists?) }.from(nil).to(true)
end
it 'caches the output in RepositoryCache' do
expect do
repository.exists?
end.to change { cache.read(:exists?) }.from(nil).to(true)
end
end
context 'when it returns false' do
before do
expect(repository.raw_repository).to receive(:exists?).once.and_return(false)
end
it 'caches the output in RequestStore' do
expect do
repository.exists?
end.to change { request_store_cache.read(:exists?) }.from(nil).to(false)
end
it 'does NOT cache the output in RepositoryCache' do
expect do
repository.exists?
end.not_to change { cache.read(:exists?) }.from(nil)
end
end
end
end end
describe '#has_visible_content?' do describe '#has_visible_content?' do
...@@ -1716,12 +1757,19 @@ describe Repository do ...@@ -1716,12 +1757,19 @@ describe Repository do
describe '#expire_exists_cache' do describe '#expire_exists_cache' do
let(:cache) { repository.send(:cache) } let(:cache) { repository.send(:cache) }
let(:request_store_cache) { repository.send(:request_store_cache) }
it 'expires the cache' do it 'expires the cache' do
expect(cache).to receive(:expire).with(:exists?) expect(cache).to receive(:expire).with(:exists?)
repository.expire_exists_cache repository.expire_exists_cache
end end
it 'expires the request store cache', :request_store do
expect(request_store_cache).to receive(:expire).with(:exists?)
repository.expire_exists_cache
end
end end
describe '#xcode_project?' do describe '#xcode_project?' do
...@@ -1892,7 +1940,7 @@ describe Repository do ...@@ -1892,7 +1940,7 @@ describe Repository do
match[1].to_sym if match match[1].to_sym if match
end.compact end.compact
expect(methods).to match_array(Repository::CACHED_METHODS + Repository::MEMOIZED_CACHED_METHODS) expect(Repository::CACHED_METHODS + Repository::MEMOIZED_CACHED_METHODS).to include(*methods)
end end
end end
......
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