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 


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# 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.


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# 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


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# 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.


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# 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.


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# 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.


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# 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) 

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# 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.


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# 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.


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# 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.


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# 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