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|
# frozen_string_literal: true
require "json"
require "fileutils"
module Dispatch
module Adapter
class RateLimiter
def initialize(rate_limit_path:, min_request_interval:, rate_limit:)
validate_min_request_interval!(min_request_interval)
validate_rate_limit!(rate_limit)
@rate_limit_path = rate_limit_path
@min_request_interval = min_request_interval
@rate_limit = rate_limit
end
def wait!
return if disabled?
loop do
wait_time = 0.0
File.open(rate_limit_file, File::RDWR | File::CREAT) do |file|
file.flock(File::LOCK_EX)
state = read_state(file)
now = Time.now.to_f
wait_time = compute_wait(state, now)
if wait_time <= 0
record_request(state, now)
write_state(file, state)
return
end
end
sleep(wait_time)
end
end
private
def disabled?
effective_min_interval.nil? && @rate_limit.nil?
end
def effective_min_interval
return nil if @min_request_interval.nil?
return nil if @min_request_interval.zero?
@min_request_interval
end
def rate_limit_file
FileUtils.mkdir_p(File.dirname(@rate_limit_path))
File.chmod(0o600, @rate_limit_path) if File.exist?(@rate_limit_path)
@rate_limit_path
end
def read_state(file)
file.rewind
content = file.read
return default_state if content.nil? || content.strip.empty?
parsed = JSON.parse(content)
{
"last_request_at" => parsed["last_request_at"]&.to_f,
"request_log" => Array(parsed["request_log"]).map(&:to_f)
}
rescue JSON::ParserError
default_state
end
def default_state
{ "last_request_at" => nil, "request_log" => [] }
end
def write_state(file, state)
file.rewind
file.truncate(0)
file.write(JSON.generate(state))
file.flush
File.chmod(0o600, @rate_limit_path)
end
def compute_wait(state, now)
cooldown_wait = compute_cooldown_wait(state, now)
window_wait = compute_window_wait(state, now)
[cooldown_wait, window_wait].max
end
def compute_cooldown_wait(state, now)
interval = effective_min_interval
return 0.0 if interval.nil?
last = state["last_request_at"]
return 0.0 if last.nil?
elapsed = now - last
remaining = interval - elapsed
remaining > 0 ? remaining : 0.0
end
def compute_window_wait(state, now)
return 0.0 if @rate_limit.nil?
max_requests = @rate_limit[:requests]
period = @rate_limit[:period]
window_start = now - period
log = state["request_log"].select { |t| t > window_start }
return 0.0 if log.size < max_requests
oldest_in_window = log.min
wait = oldest_in_window + period - now
wait > 0 ? wait : 0.0
end
def record_request(state, now)
state["last_request_at"] = now
state["request_log"] << now
prune_log(state, now)
end
def prune_log(state, now)
if @rate_limit
period = @rate_limit[:period]
cutoff = now - period
state["request_log"] = state["request_log"].select { |t| t > cutoff }
else
state["request_log"] = []
end
end
def validate_min_request_interval!(value)
return if value.nil?
unless value.is_a?(Numeric)
raise ArgumentError,
"min_request_interval must be nil or a Numeric >= 0, got #{value.inspect}"
end
return unless value.negative?
raise ArgumentError,
"min_request_interval must be nil or a Numeric >= 0, got #{value.inspect}"
end
def validate_rate_limit!(value)
return if value.nil?
unless value.is_a?(Hash)
raise ArgumentError,
"rate_limit must be nil or a Hash with :requests and :period keys, got #{value.inspect}"
end
unless value.key?(:requests) && value[:requests].is_a?(Integer) && value[:requests].positive?
raise ArgumentError,
"rate_limit[:requests] must be a positive Integer, got #{value[:requests].inspect}"
end
return if value.key?(:period) && value[:period].is_a?(Numeric) && value[:period].positive?
raise ArgumentError,
"rate_limit[:period] must be a positive Numeric, got #{value[:period].inspect}"
end
end
end
end
|
