Bug #18482
closed
Fiber can not disable scheduler
Description
class Fiber can not disable scheduler with it's parameter.
When parameter is false:
require 'fiber'
require 'io/nonblock'
class SimpleScheduler
def initialize
@readable = {}
@writable = {}
@waiting = {}
@ready = []
@blocking = 0
@urgent = IO.pipe
end
def run
while @readable.any? or @writable.any? or @waiting.any? or @blocking.positive? or @ready.any?
readable, writable = IO.select(@readable.keys + [@urgent.first], @writable.keys, [], 0)
readable&.each do |io|
if fiber = @readable.delete(io)
fiber.resume
end
end
writable&.each do |io|
if fiber = @writable.delete(io)
fiber.resume
end
end
@waiting.keys.each do |fiber|
if current_time > @waiting[fiber]
@waiting.delete(fiber)
fiber.resume
end
end
ready, @ready = @ready, []
ready.each do |fiber|
fiber.resume
end
end
end
def io_wait(io, events, timeout)
unless (events & IO::READABLE).zero?
@readable[io] = Fiber.current
end
unless (events & IO::WRITABLE).zero?
@writable[io] = Fiber.current
end
Fiber.yield
return events
end
def kernel_sleep(duration = nil)
block(:sleep, duration)
return true
end
def block(blocker, timeout = nil)
if timeout
@waiting[Fiber.current] = current_time + timeout
begin
Fiber.yield
ensure
@waiting.delete(Fiber.current)
end
else
@blocking += 1
begin
Fiber.yield
ensure
@blocking -= 1
end
end
end
def unblock(blocker, fiber)
@ready << fiber
io = @urgent.last
io.write_nonblock('.')
end
def close
run
@urgent.each(&:close)
@urgent = nil
end
private
def current_time
Process.clock_gettime(Process::CLOCK_MONOTONIC)
end
end
scheduler = SimpleScheduler.new
Fiber.set_scheduler(scheduler)
puts "Go to sleep!"
f = Fiber.new(false) do
puts "Going to sleep"
sleep(1)
puts "I slept well"
end
f.resume
puts "Wakey-wakey, sleepyhead"
Result:
Go to sleep!
Going to sleep
Wakey-wakey, sleepyhead
I slept well
And when parameter is true:
require 'fiber'
require 'io/nonblock'
class SimpleScheduler
def initialize
@readable = {}
@writable = {}
@waiting = {}
@ready = []
@blocking = 0
@urgent = IO.pipe
end
def run
while @readable.any? or @writable.any? or @waiting.any? or @blocking.positive? or @ready.any?
readable, writable = IO.select(@readable.keys + [@urgent.first], @writable.keys, [], 0)
readable&.each do |io|
if fiber = @readable.delete(io)
fiber.resume
end
end
writable&.each do |io|
if fiber = @writable.delete(io)
fiber.resume
end
end
@waiting.keys.each do |fiber|
if current_time > @waiting[fiber]
@waiting.delete(fiber)
fiber.resume
end
end
ready, @ready = @ready, []
ready.each do |fiber|
fiber.resume
end
end
end
def io_wait(io, events, timeout)
unless (events & IO::READABLE).zero?
@readable[io] = Fiber.current
end
unless (events & IO::WRITABLE).zero?
@writable[io] = Fiber.current
end
Fiber.yield
return events
end
def kernel_sleep(duration = nil)
block(:sleep, duration)
return true
end
def block(blocker, timeout = nil)
if timeout
@waiting[Fiber.current] = current_time + timeout
begin
Fiber.yield
ensure
@waiting.delete(Fiber.current)
end
else
@blocking += 1
begin
Fiber.yield
ensure
@blocking -= 1
end
end
end
def unblock(blocker, fiber)
@ready << fiber
io = @urgent.last
io.write_nonblock('.')
end
def close
run
@urgent.each(&:close)
@urgent = nil
end
private
def current_time
Process.clock_gettime(Process::CLOCK_MONOTONIC)
end
end
scheduler = SimpleScheduler.new
Fiber.set_scheduler(scheduler)
puts "Go to sleep!"
f = Fiber.new(true) do
puts "Going to sleep"
sleep(1)
puts "I slept well"
end
f.resume
puts "Wakey-wakey, sleepyhead"
Result (was still the same):
Go to sleep!
Going to sleep
Wakey-wakey, sleepyhead
I slept well
While make the set_scheduler line commented:
scheduler = SimpleScheduler.new
# Fiber.set_scheduler(scheduler) // Here is commented
puts "Go to sleep!"
f = Fiber.new(false) do
puts "Going to sleep"
sleep(1)
puts "I slept well"
end
Result is right:
Go to sleep!
Going to sleep
I slept well
Wakey-wakey, sleepyhead
Maybe in some situation.
I wrote my gem without Scheduler. But user defined its Scheduler for his or her logic code.
It will break the sequence of Fiber which was needed for my gem.
Also, using Fiber in the Enumerator situation will be broke down too:
db.with_each_row_of_result(sql_stmt) do |row|
yield row
end
[[https://blog.appsignal.com/2018/11/27/ruby-magic-fibers-and-enumerators-in-ruby.html]]
It will break the sequence of db rows when doing enum such like python's generator.
========================
Also, another question is that I saw something was talk in:
https://bugs.ruby-lang.org/issues/16786
I think there would be a better way to improve this.
You can see, in c++, std::thread is easy to create and join a new thread.
If someone make a std::thread::scheduler into STL of C++.
And let user to implement its std::thread::handler to implement the virtual methods (interface or callback) to use it.
And std::thread::scheduler holds an independent thread pool which is not separated.
What do you think about this std::thread::scheduler?
What about make a golang's GMP into std::thread or std::coroutine.
Why not STL do that?
Why not STL let std::thread become a self-scheduled module?
Otherwise, the sense of implement Scheduler as async await may be a good idea, but there has module named Ractor can solve it.
Maybe:
IO.async do |readable, writeble|
if readable
# code
end
end
======================
In other programming language, like Python.
Python never let it's Generator mixed with async IO but add async syntax:
async def coro(): # a coroutine function
await smth()
async def asyncgen(): # an asynchronous generator function
await smth()
yield 42
Python goes in a right way. Methods can run async and something like IO.write() can put in it.
async def async_write(data): # a coroutine function
IO.write(data)
async def send(message): # an asynchronous generator function
await async_write("hello " + message)
yield 1
https://www.python.org/dev/peps/pep-0525/#id10
Also, JavaScript use async syntax to identify the async procedure.
Above that, I think the Fiber.scheduler may not be a good idea. Because Ractor is here.
Ractor can run methods async and we can put IO.write in it and make it "async".
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