require_dependency 'rate_limiter/limit_exceeded' require_dependency 'rate_limiter/on_create_record' # A redis backed rate limiter. class RateLimiter attr_reader :max, :secs, :user, :key def self.key_prefix "l-rate-limit3:" end def self.disable @disabled = true end def self.enable @disabled = false end # We don't observe rate limits in test mode def self.disabled? @disabled end # Only used in test, only clears current namespace, does not clear globals def self.clear_all! $redis.delete_prefixed(RateLimiter.key_prefix) end def self.clear_all_global! $redis.without_namespace.keys("GLOBAL::#{key_prefix}*").each do |k| $redis.without_namespace.del k end end def build_key(type) "#{RateLimiter.key_prefix}:#{@user && @user.id}:#{type}" end def initialize(user, type, max, secs, global: false) @user = user @type = type @key = build_key(type) @max = max @secs = secs @global = global end def clear! redis.del(prefixed_key) end def can_perform? rate_unlimited? || is_under_limit? end # reloader friendly unless defined? PERFORM_LUA PERFORM_LUA = <<~LUA local now = tonumber(ARGV[1]) local secs = tonumber(ARGV[2]) local max = tonumber(ARGV[3]) local key = KEYS[1] if ((tonumber(redis.call("LLEN", key)) < max) or (now - tonumber(redis.call("LRANGE", key, -1, -1)[1])) > secs) then redis.call("LPUSH", key, now) redis.call("LTRIM", key, 0, max - 1) redis.call("EXPIRE", key, secs * 2) return 1 else return 0 end LUA PERFORM_LUA_SHA = Digest::SHA1.hexdigest(PERFORM_LUA) end def performed! return if rate_unlimited? now = Time.now.to_i if eval_lua(PERFORM_LUA, PERFORM_LUA_SHA, [prefixed_key], [now, @secs, @max]) == 0 raise RateLimiter::LimitExceeded.new(seconds_to_wait, @type) end rescue Redis::CommandError => e if e.message =~ /READONLY/ # TODO,switch to in-memory rate limiter else raise end end def rollback! return if RateLimiter.disabled? redis.lpop(prefixed_key) end def remaining return @max if @user && @user.staff? arr = redis.lrange(prefixed_key, 0, @max) || [] t0 = Time.now.to_i arr.reject! { |a| (t0 - a.to_i) > @secs } @max - arr.size end private def prefixed_key if @global "GLOBAL::#{key}" else $redis.namespace_key(key) end end def redis $redis.without_namespace end def seconds_to_wait @secs - age_of_oldest end def age_of_oldest # age of oldest event in buffer, in seconds Time.now.to_i - redis.lrange(prefixed_key, -1, -1).first.to_i end def is_under_limit? # number of events in buffer less than max allowed? OR (redis.llen(prefixed_key) < @max) || # age bigger than silding window size? (age_of_oldest > @secs) end def rate_unlimited? !!(RateLimiter.disabled? || (@user && @user.staff?)) end def eval_lua(lua, sha, keys, args) redis.evalsha(sha, keys, args) rescue Redis::CommandError => e if e.to_s =~ /^NOSCRIPT/ redis.eval(lua, keys, args) else raise end end end