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| | # -*- encoding: binary -*-
# Copyright (C) 2013-2016 all contributors <yahns-public@yhbt.net>
# License: GPL-3.0+ (https://www.gnu.org/licenses/gpl-3.0.txt)
# frozen_string_literal: true
class Yahns::Worker # :nodoc:
attr_accessor :nr
attr_reader :to_io
def initialize(nr)
@nr = nr
@to_io, @wr = Kgio::Pipe.new
begin
# F_SETPIPE_SZ = 1031, PAGE_SIZE = 4096
# (fcntl will handle minimum size on platforms where PAGE_SIZE > 4096)
@to_io.fcntl(1031, 4096)
rescue SystemCallError
# old kernel (EINVAL, EPERM)
end if RUBY_PLATFORM =~ /\blinux\b/
end
def atfork_child
@wr = @wr.close # nil @wr to save space in worker process
end
def atfork_parent
@to_io = @to_io.close
self
end
# used in the worker process.
# This causes the worker to gracefully exit if the master
# dies unexpectedly.
def yahns_step
case buf = @to_io.kgio_tryread(4)
when String
# unpack the buffer and trigger the signal handler
signum = buf.unpack('l')
fake_sig(signum[0])
# keep looping, more signals may be queued
when nil # EOF: master died, but we are at a safe place to exit
fake_sig(:QUIT)
@to_io.close
return :ignore
when :wait_readable # keep waiting
return :ignore
end while true # loop, as multiple signals may be sent
end
# worker objects may be compared to just plain Integers
def ==(other_nr) # :nodoc:
@nr == other_nr
end
# call a signal handler immediately without triggering EINTR
# We do not use the more obvious Process.kill(sig, $$) here since
# that signal delivery may be deferred. We want to avoid signal delivery
# while the Rack app.call is running because some database drivers
# (e.g. ruby-pg) may cancel pending requests.
def fake_sig(sig) # :nodoc:
old_cb = trap(sig, "IGNORE")
old_cb.call
ensure
trap(sig, old_cb)
end
# master sends fake signals to children
def soft_kill(signum) # :nodoc:
# writing and reading 4 bytes on a pipe is atomic on all POSIX platforms
# Do not care in the odd case the buffer is full, here.
@wr.kgio_trywrite([signum].pack('l'))
rescue Errno::EPIPE
# worker will be reaped soon
end
end
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