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batched_udp_sink.rb
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batched_udp_sink.rb
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# frozen_string_literal: true
module StatsD
module Instrument
# @note This class is part of the new Client implementation that is intended
# to become the new default in the next major release of this library.
class BatchedUDPSink
DEFAULT_THREAD_PRIORITY = 100
DEFAULT_BUFFER_CAPACITY = 5_000
# https://docs.datadoghq.com/developers/dogstatsd/high_throughput/?code-lang=ruby#ensure-proper-packet-sizes
DEFAULT_MAX_PACKET_SIZE = 1472
def self.for_addr(addr, **kwargs)
host, port_as_string = addr.split(":", 2)
new(host, Integer(port_as_string), **kwargs)
end
attr_reader :host, :port
class << self
def finalize(dispatcher)
proc { dispatcher.shutdown }
end
end
def initialize(
host,
port,
thread_priority: DEFAULT_THREAD_PRIORITY,
buffer_capacity: DEFAULT_BUFFER_CAPACITY,
max_packet_size: DEFAULT_MAX_PACKET_SIZE
)
@host = host
@port = port
@dispatcher = Dispatcher.new(
host,
port,
buffer_capacity,
thread_priority,
max_packet_size,
)
ObjectSpace.define_finalizer(self, self.class.finalize(@dispatcher))
end
def sample?(sample_rate)
sample_rate == 1.0 || rand < sample_rate
end
def <<(datagram)
@dispatcher << datagram
self
end
def shutdown(*args)
@dispatcher.shutdown(*args)
end
class Buffer < SizedQueue
def push_nonblock(item)
push(item, true)
rescue ThreadError, ClosedQueueError
nil
end
def inspect
"<#{self.class.name}:#{object_id} capacity=#{max} size=#{size}>"
end
def pop_nonblock
pop(true)
rescue ThreadError
nil
end
end
class Dispatcher
def initialize(host, port, buffer_capacity, thread_priority, max_packet_size)
@udp_sink = UDPSink.new(host, port)
@interrupted = false
@thread_priority = thread_priority
@max_packet_size = max_packet_size
@buffer_capacity = buffer_capacity
@buffer = Buffer.new(buffer_capacity)
@dispatcher_thread = Thread.new { dispatch }
@pid = Process.pid
end
def <<(datagram)
if !thread_healthcheck || !@buffer.push_nonblock(datagram)
# The buffer is full or the thread can't be respaned,
# we'll send the datagram synchronously
@udp_sink << datagram
end
self
end
def shutdown(wait = 2)
@interrupted = true
@buffer.close
if @dispatcher_thread&.alive?
@dispatcher_thread.join(wait)
end
flush(blocking: false)
end
private
NEWLINE = "\n".b.freeze
def flush(blocking:)
packet = "".b
next_datagram = nil
until @buffer.closed? && @buffer.empty? && next_datagram.nil?
if blocking
next_datagram ||= @buffer.pop
break if next_datagram.nil? # queue was closed
else
next_datagram ||= @buffer.pop_nonblock
break if next_datagram.nil? # no datagram in buffer
end
packet << next_datagram
next_datagram = nil
unless packet.bytesize > @max_packet_size
while (next_datagram = @buffer.pop_nonblock)
if @max_packet_size - packet.bytesize - 1 > next_datagram.bytesize
packet << NEWLINE << next_datagram
else
break
end
end
end
@udp_sink << packet
packet.clear
end
end
def thread_healthcheck
# TODO: We have a race condition on JRuby / Truffle here. It could cause multiple
# dispatcher threads to be spawned, which would cause problems.
# However we can't simply lock here as we might be called from a trap context.
unless @dispatcher_thread&.alive?
# If the main the main thread is dead the VM is shutting down so we won't be able
# to spawn a new thread, so we fallback to sending our datagram directly.
return false unless Thread.main.alive?
# If the dispatcher thread is dead, it might be because the process was forked.
# So to avoid sending datagrams twice we clear the buffer.
if @pid != Process.pid
StatsD.logger.info { "[#{self.class.name}] Restarting the dispatcher thread after fork" }
@pid = Process.pid
@buffer.clear
else
StatsD.logger.info { "[#{self.class.name}] Restarting the dispatcher thread" }
end
@dispatcher_thread = Thread.new { dispatch }.tap { |t| t.priority = @thread_priority }
end
true
end
def dispatch
until @interrupted
begin
flush(blocking: true)
rescue => error
report_error(error)
end
end
flush(blocking: false)
end
def report_error(error)
StatsD.logger.error do
"[#{self.class.name}] The dispatcher thread encountered an error #{error.class}: #{error.message}"
end
end
end
end
end
end