1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
|
# frozen_string_literal: true
module Gitlab
module RepositoryCacheAdapter
extend ActiveSupport::Concern
include Gitlab::Utils::StrongMemoize
class_methods do
# Caches and strongly memoizes the method.
#
# This only works for methods that do not take any arguments.
#
# 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
# 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
cache_method_output_asymmetrically(name) do
__send__(uncached_name) # rubocop:disable GitlabSecurity/PublicSend
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
# RepositoryCache to be used. Should be overridden by the including class
def cache
raise NotImplementedError
end
# List of cached methods. Should be overridden by the including class
def cached_methods
raise NotImplementedError
end
# Caches and strongly memoizes the supplied block.
#
# 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_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.
#
# 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.
#
# name - The name of the method to be cached.
def cache_method_output_asymmetrically(name, &block)
memoize_method_output(name) do
request_store_cache.fetch(name) do
cache.fetch_without_caching_false(name, &block)
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
def expire_method_caches(methods)
methods.each do |name|
unless cached_methods.include?(name.to_sym)
Rails.logger.error "Requested to expire non-existent method '#{name}' for Repository" # rubocop:disable Gitlab/RailsLogger
next
end
cache.expire(name)
clear_memoization(memoizable_name(name))
end
expire_request_store_method_caches(methods)
end
private
def memoizable_name(name)
"#{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
|