debian-mirror-gitlab/lib/gitlab/github_import/caching.rb

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2018-03-17 18:26:18 +05:30
# frozen_string_literal: true
module Gitlab
module GithubImport
module Caching
# The default timeout of the cache keys.
TIMEOUT = 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
# 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.
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
# Reads an integer from the cache, or returns nil if no value was found.
#
# See Caching.read for more information.
def self.read_integer(raw_key, timeout: TIMEOUT)
value = read(raw_key, timeout: timeout)
value.to_i if value.present?
end
# 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.
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
# 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.
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
# 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.
def self.set_includes?(raw_key, value)
key = cache_key_for(raw_key)
Redis::Cache.with do |redis|
redis.sismember(key, value)
end
end
# Sets multiple keys to a given value.
#
# mapping - A Hash mapping the cache keys to their values.
# timeout - The time after which the cache key should expire.
def self.write_multiple(mapping, timeout: TIMEOUT)
Redis::Cache.with do |redis|
redis.multi do |multi|
mapping.each do |raw_key, value|
multi.set(cache_key_for(raw_key), value, ex: timeout)
end
end
end
end
# Sets the expiration time of a key.
#
# raw_key - The key for which to change the timeout.
# timeout - The new timeout.
def self.expire(raw_key, timeout)
key = cache_key_for(raw_key)
Redis::Cache.with do |redis|
redis.expire(key, timeout)
end
end
# 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.
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
def self.cache_key_for(raw_key)
"#{Redis::Cache::CACHE_NAMESPACE}:#{raw_key}"
end
end
end
end