Module: Gitlab::Cache::Import::Caching

Defined in:
lib/gitlab/cache/import/caching.rb

Constant Summary collapse

TIMEOUT =

The default timeout of the cache keys.

24.hours.to_i
WRITE_IF_GREATER_SCRIPT =
<<-EOF.strip_heredoc.freeze
local key, value, ttl = KEYS[1], tonumber(ARGV[1]), ARGV[2]
local existing = tonumber(redis.call("get", key))

if existing == nil or value > existing then
  redis.call("set", key, value)
  redis.call("expire", key, ttl)
  return true
else
  return false
end
EOF

Class Method Summary collapse

Class Method Details

.cache_key_for(raw_key) ⇒ Object


165
166
167
# File 'lib/gitlab/cache/import/caching.rb', line 165

def self.cache_key_for(raw_key)
  "#{Redis::Cache::CACHE_NAMESPACE}:#{raw_key}"
end

.expire(raw_key, timeout) ⇒ Object

Sets the expiration time of a key.

raw_key - The key for which to change the timeout. timeout - The new timeout.


137
138
139
140
141
142
143
# File 'lib/gitlab/cache/import/caching.rb', line 137

def self.expire(raw_key, timeout)
  key = cache_key_for(raw_key)

  Redis::Cache.with do |redis|
    redis.expire(key, timeout)
  end
end

.increment(raw_key, timeout: TIMEOUT) ⇒ Object

Increment the integer value of a key by one. Sets the value to zero if missing before incrementing

key - The cache key to increment. timeout - The time after which the cache key should expire.

Returns:

    • the incremented value


79
80
81
82
83
84
85
86
# File 'lib/gitlab/cache/import/caching.rb', line 79

def self.increment(raw_key, timeout: TIMEOUT)
  key = cache_key_for(raw_key)

  Redis::Cache.with do |redis|
    redis.incr(key)
    redis.expire(key, timeout)
  end
end

.read(raw_key, timeout: TIMEOUT) ⇒ Object

Reads a cache key.

If the key exists and has a non-empty value its TTL is refreshed automatically.

raw_key - The cache key to read. timeout - The new timeout of the key if the key is to be refreshed.


30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
# File 'lib/gitlab/cache/import/caching.rb', line 30

def self.read(raw_key, timeout: TIMEOUT)
  key = cache_key_for(raw_key)
  value = Redis::Cache.with { |redis| redis.get(key) }

  if value.present?
    # We refresh the expiration time so frequently used keys stick
    # around, removing the need for querying the database as much as
    # possible.
    #
    # A key may be empty when we looked up a GitHub user (for example) but
    # did not find a matching GitLab user. In that case we _don't_ want to
    # refresh the TTL so we automatically pick up the right data when said
    # user were to register themselves on the GitLab instance.
    Redis::Cache.with { |redis| redis.expire(key, timeout) }
  end

  value
end

.read_integer(raw_key, timeout: TIMEOUT) ⇒ Object

Reads an integer from the cache, or returns nil if no value was found.

See Caching.read for more information.


52
53
54
55
56
# File 'lib/gitlab/cache/import/caching.rb', line 52

def self.read_integer(raw_key, timeout: TIMEOUT)
  value = read(raw_key, timeout: timeout)

  value.to_i if value.present?
end

.set_add(raw_key, value, timeout: TIMEOUT) ⇒ Object

Adds a value to a set.

raw_key - The key of the set to add the value to. value - The value to add to the set. timeout - The new timeout of the key.


93
94
95
96
97
98
99
100
101
102
# File 'lib/gitlab/cache/import/caching.rb', line 93

def self.set_add(raw_key, value, timeout: TIMEOUT)
  key = cache_key_for(raw_key)

  Redis::Cache.with do |redis|
    redis.multi do |m|
      m.sadd(key, value)
      m.expire(key, timeout)
    end
  end
end

.set_includes?(raw_key, value) ⇒ Boolean

Returns true if the given value is present in the set.

raw_key - The key of the set to check. value - The value to check for.

Returns:

  • (Boolean)

108
109
110
111
112
113
114
# File 'lib/gitlab/cache/import/caching.rb', line 108

def self.set_includes?(raw_key, value)
  key = cache_key_for(raw_key)

  Redis::Cache.with do |redis|
    redis.sismember(key, value)
  end
end

.write(raw_key, value, timeout: TIMEOUT) ⇒ Object

Sets a cache key to the given value.

key - The cache key to write. value - The value to set. timeout - The time after which the cache key should expire.


63
64
65
66
67
68
69
70
71
# File 'lib/gitlab/cache/import/caching.rb', line 63

def self.write(raw_key, value, timeout: TIMEOUT)
  key = cache_key_for(raw_key)

  Redis::Cache.with do |redis|
    redis.set(key, value, ex: timeout)
  end

  value
end

.write_if_greater(raw_key, value, timeout: TIMEOUT) ⇒ Object

Sets a key to the given integer but only if the existing value is smaller than the given value.

This method uses a Lua script to ensure the read and write are atomic.

raw_key - The key to set. value - The new value for the key. timeout - The key timeout in seconds.

Returns true when the key was overwritten, false otherwise.


155
156
157
158
159
160
161
162
163
# File 'lib/gitlab/cache/import/caching.rb', line 155

def self.write_if_greater(raw_key, value, timeout: TIMEOUT)
  key = cache_key_for(raw_key)
  val = Redis::Cache.with do |redis|
    redis
      .eval(WRITE_IF_GREATER_SCRIPT, keys: [key], argv: [value, timeout])
  end

  val ? true : false
end

.write_multiple(mapping, key_prefix: nil, timeout: TIMEOUT) ⇒ Object

Sets multiple keys to given values.

mapping - A Hash mapping the cache keys to their values. key_prefix - prefix inserted before each key timeout - The time after which the cache key should expire.


121
122
123
124
125
126
127
128
129
130
131
# File 'lib/gitlab/cache/import/caching.rb', line 121

def self.write_multiple(mapping, key_prefix: nil, timeout: TIMEOUT)
  Redis::Cache.with do |redis|
    redis.pipelined do |multi|
      mapping.each do |raw_key, value|
        key = cache_key_for("#{key_prefix}#{raw_key}")

        multi.set(key, value, ex: timeout)
      end
    end
  end
end