class Ractor

Returns total count of Ractors currently running.

Ractor.count                   #=> 1
r = Ractor.new(name: 'example') { Ractor.yield(1) }
Ractor.count                   #=> 2 (main + example ractor)
r.take                         # wait for Ractor.yield(1)
r.take                         # wait till r will finish
Ractor.count                   #=> 1

# File ractor.rb, line 291
def self.count
  __builtin_cexpr! %q{
    ULONG2NUM(GET_VM()->ractor.cnt);
  }
end

Returns the currently executing Ractor.

Ractor.current #=> #<Ractor:#1 running>

# File ractor.rb, line 277
def self.current
  __builtin_cexpr! %q{
    rb_ractor_self(rb_ec_ractor_ptr(ec));
  }
end

returns main ractor

# File ractor.rb, line 837
def self.main
  __builtin_cexpr! %q{
    rb_ractor_self(GET_VM()->ractor.main_ractor);
  }
end

Make obj shareable between ractors.

obj and all the objects it refers to will be frozen, unless they are already shareable.

If copy keyword is true, the method will copy objects before freezing them This is safer option but it can take be slower.

Note that the specification and implementation of this method are not mature and may be changed in the future.

obj = ['test']
Ractor.shareable?(obj)     #=> false
Ractor.make_shareable(obj) #=> ["test"]
Ractor.shareable?(obj)     #=> true
obj.frozen?                #=> true
obj[0].frozen?             #=> true

# Copy vs non-copy versions:
obj1 = ['test']
obj1s = Ractor.make_shareable(obj1)
obj1.frozen?                        #=> true
obj1s.object_id == obj1.object_id   #=> true
obj2 = ['test']
obj2s = Ractor.make_shareable(obj2, copy: true)
obj2.frozen?                        #=> false
obj2s.frozen?                       #=> true
obj2s.object_id == obj2.object_id   #=> false
obj2s[0].object_id == obj2[0].object_id #=> false

See also the “Shareable and unshareable objects” section in the Ractor class docs.

# File ractor.rb, line 814
def self.make_shareable obj, copy: false
  if copy
    __builtin_cexpr! %q{
      rb_ractor_make_shareable_copy(obj);
    }
  else
    __builtin_cexpr! %q{
      rb_ractor_make_shareable(obj);
    }
  end
end

Create a new Ractor with args and a block.

A block (Proc) will be isolated (can’t access to outer variables). self inside the block will refer to the current Ractor.

r = Ractor.new { puts "Hi, I am #{self.inspect}" }
r.take
# Prints "Hi, I am #<Ractor:#2 test.rb:1 running>"

args passed to the method would be propagated to block args by the same rules as objects passed through send/Ractor.receive: if args are not shareable, they will be copied (via deep cloning, which might be inefficient).

arg = [1, 2, 3]
puts "Passing: #{arg} (##{arg.object_id})"
r = Ractor.new(arg) {|received_arg|
  puts "Received: #{received_arg} (##{received_arg.object_id})"
}
r.take
# Prints:
#   Passing: [1, 2, 3] (#280)
#   Received: [1, 2, 3] (#300)

Ractor’s name can be set for debugging purposes:

r = Ractor.new(name: 'my ractor') {}
p r
#=> #<Ractor:#3 my ractor test.rb:1 terminated>

# File ractor.rb, line 262
def self.new(*args, name: nil, &block)
  b = block # TODO: builtin bug
  raise ArgumentError, "must be called with a block" unless block
  if __builtin_cexpr!("RBOOL(ruby_single_main_ractor)")
    warn("Ractor is experimental, and the behavior may change in future versions of Ruby! " \
         "Also there are many implementation issues.", uplevel: 0, category: :experimental)
  end
  loc = caller_locations(1, 1).first
  loc = "#{loc.path}:#{loc.lineno}"
  __builtin_ractor_create(loc, name, args, b)
end

Receive an incoming message from the current Ractor’s incoming port’s queue, which was sent there by send.

r = Ractor.new do
  v1 = Ractor.receive
  puts "Received: #{v1}"
end
r.send('message1')
r.take
# Here will be printed: "Received: message1"

Alternatively, private instance method receive may be used:

r = Ractor.new do
  v1 = receive
  puts "Received: #{v1}"
end
r.send('message1')
r.take
# Here will be printed: "Received: message1"

The method blocks if the queue is empty.

r = Ractor.new do
  puts "Before first receive"
  v1 = Ractor.receive
  puts "Received: #{v1}"
  v2 = Ractor.receive
  puts "Received: #{v2}"
end
wait
puts "Still not received"
r.send('message1')
wait
puts "Still received only one"
r.send('message2')
r.take

Output:

Before first receive
Still not received
Received: message1
Still received only one
Received: message2

If close_incoming was called on the ractor, the method raises Ractor::ClosedError if there are no more messages in incoming queue:

Ractor.new do
  close_incoming
  receive
end
wait
# in `receive': The incoming port is already closed => #<Ractor:#2 test.rb:1 running> (Ractor::ClosedError)

# File ractor.rb, line 419
def self.receive
  __builtin_cexpr! %q{
    ractor_receive(ec, rb_ec_ractor_ptr(ec))
  }
end

Receive only a specific message.

Instead of Ractor.receive, Ractor.receive_if can provide a pattern by a block and you can choose the receiving message.

r = Ractor.new do
  p Ractor.receive_if{|msg| msg.match?(/foo/)} #=> "foo3"
  p Ractor.receive_if{|msg| msg.match?(/bar/)} #=> "bar1"
  p Ractor.receive_if{|msg| msg.match?(/baz/)} #=> "baz2"
end
r << "bar1"
r << "baz2"
r << "foo3"
r.take

This will output:

foo3
bar1
baz2

If the block returns a truthy value, the message will be removed from the incoming queue and returned. Otherwise, the message remains in the incoming queue and the following received messages are checked by the given block.

If there are no messages left in the incoming queue, the method will block until new messages arrive.

If the block is escaped by break/return/exception/throw, the message is removed from the incoming queue as if a truthy value had been returned.

r = Ractor.new do
  val = Ractor.receive_if{|msg| msg.is_a?(Array)}
  puts "Received successfully: #{val}"
end

r.send(1)
r.send('test')
wait
puts "2 non-matching sent, nothing received"
r.send([1, 2, 3])
wait

Prints:

2 non-matching sent, nothing received
Received successfully: [1, 2, 3]

Note that you can not call receive/receive_if in the given block recursively. It means that you should not do any tasks in the block.

Ractor.current << true
Ractor.receive_if{|msg| Ractor.receive}
#=> `receive': can not call receive/receive_if recursively (Ractor::Error)

# File ractor.rb, line 497
def self.receive_if &b
  Primitive.ractor_receive_if b
end

Waits for the first ractor to have something in its outgoing port, reads from this ractor, and returns that ractor and the object received.

r1 = Ractor.new {Ractor.yield 'from 1'}
r2 = Ractor.new {Ractor.yield 'from 2'}

r, obj = Ractor.select(r1, r2)

puts "received #{obj.inspect} from #{r.inspect}"
# Prints: received "from 1" from #<Ractor:#2 test.rb:1 running>

If one of the given ractors is the current ractor, and it would be selected, r will contain :receive symbol instead of the ractor object.

r1 = Ractor.new(Ractor.current) do |main|
  main.send 'to main'
  Ractor.yield 'from 1'
end
r2 = Ractor.new do
  Ractor.yield 'from 2'
end

r, obj = Ractor.select(r1, r2, Ractor.current)
puts "received #{obj.inspect} from #{r.inspect}"
# Prints: received "to main" from :receive

If yield_value is provided, that value may be yielded if another Ractor is calling take. In this case, the pair [:yield, nil] would be returned:

r1 = Ractor.new(Ractor.current) do |main|
  puts "Received from main: #{main.take}"
end

puts "Trying to select"
r, obj = Ractor.select(r1, Ractor.current, yield_value: 123)
wait
puts "Received #{obj.inspect} from #{r.inspect}"

This will print:

Trying to select
Received from main: 123
Received nil from :yield

move boolean flag defines whether yielded value should be copied (default) or moved.

# File ractor.rb, line 346
def self.select(*ractors, yield_value: yield_unspecified = true, move: false)
  raise ArgumentError, 'specify at least one ractor or `yield_value`' if yield_unspecified && ractors.empty?

  __builtin_cstmt! %q{
    const VALUE *rs = RARRAY_CONST_PTR_TRANSIENT(ractors);
    VALUE rv;
    VALUE v = ractor_select(ec, rs, RARRAY_LENINT(ractors),
                            yield_unspecified == Qtrue ? Qundef : yield_value,
                            (bool)RTEST(move) ? true : false, &rv);
    return rb_ary_new_from_args(2, rv, v);
  }
end

Checks if the object is shareable by ractors.

Ractor.shareable?(1)            #=> true -- numbers and other immutable basic values are frozen
Ractor.shareable?('foo')        #=> false, unless the string is frozen due to # freeze_string_literals: true
Ractor.shareable?('foo'.freeze) #=> true

See also the “Shareable and unshareable objects” section in the Ractor class docs.

# File ractor.rb, line 773
def self.shareable? obj
  __builtin_cexpr! %q{
    RBOOL(rb_ractor_shareable_p(obj));
  }
end

Send a message to the current ractor’s outgoing port to be consumed by take.

r = Ractor.new {Ractor.yield 'Hello from ractor'}
puts r.take
# Prints: "Hello from ractor"

The method is blocking, and will return only when somebody consumes the sent message.

r = Ractor.new do
  Ractor.yield 'Hello from ractor'
  puts "Ractor: after yield"
end
wait
puts "Still not taken"
puts r.take

This will print:

Still not taken
Hello from ractor
Ractor: after yield

If the outgoing port was closed with close_outgoing, the method will raise:

r = Ractor.new do
  close_outgoing
  Ractor.yield 'Hello from ractor'
end
wait
# `yield': The outgoing-port is already closed (Ractor::ClosedError)

The meaning of move argument is the same as for send.

# File ractor.rb, line 630
def self.yield(obj, move: false)
  __builtin_cexpr! %q{
    ractor_yield(ec, rb_ec_ractor_ptr(ec), obj, move)
  }
end

get a value from ractor-local storage

# File ractor.rb, line 827
def [](sym)
  Primitive.ractor_local_value(sym)
end

set a value in ractor-local storage

# File ractor.rb, line 832
def []=(sym, val)
  Primitive.ractor_local_value_set(sym, val)
end

Closes the incoming port and returns its previous state. All further attempts to Ractor.receive in the ractor, and send to the ractor will fail with Ractor::ClosedError.

r = Ractor.new {sleep(500)}
r.close_incoming  #=> false
r.close_incoming  #=> true
r.send('test')
# Ractor::ClosedError (The incoming-port is already closed)

# File ractor.rb, line 737
def close_incoming
  __builtin_cexpr! %q{
    ractor_close_incoming(ec, RACTOR_PTR(self));
  }
end

Closes the outgoing port and returns its previous state. All further attempts to Ractor.yield in the ractor, and take from the ractor will fail with Ractor::ClosedError.

r = Ractor.new {sleep(500)}
r.close_outgoing  #=> false
r.close_outgoing  #=> true
r.take
# Ractor::ClosedError (The outgoing-port is already closed)

# File ractor.rb, line 756
def close_outgoing
  __builtin_cexpr! %q{
    ractor_close_outgoing(ec, RACTOR_PTR(self));
  }
end

The name set in Ractor.new, or nil.

# File ractor.rb, line 716
def name
  __builtin_cexpr! %q{RACTOR_PTR(self)->name}
end

Send a message to a Ractor’s incoming queue to be consumed by Ractor.receive.

r = Ractor.new do
  value = Ractor.receive
  puts "Received #{value}"
end
r.send 'message'
# Prints: "Received: message"

The method is non-blocking (will return immediately even if the ractor is not ready to receive anything):

r = Ractor.new {sleep(5)}
r.send('test')
puts "Sent successfully"
# Prints: "Sent successfully" immediately

Attempt to send to ractor which already finished its execution will raise Ractor::ClosedError.

r = Ractor.new {}
r.take
p r
# "#<Ractor:#6 (irb):23 terminated>"
r.send('test')
# Ractor::ClosedError (The incoming-port is already closed)

If close_incoming was called on the ractor, the method also raises Ractor::ClosedError.

r =  Ractor.new do
  sleep(500)
  receive
end
r.close_incoming
r.send('test')
# Ractor::ClosedError (The incoming-port is already closed)
# The error would be raised immediately, not when ractor will try to receive

If the obj is unshareable, by default it would be copied into ractor by deep cloning. If the move: true is passed, object is moved into ractor and becomes inaccessible to sender.

r = Ractor.new {puts "Received: #{receive}"}
msg = 'message'
r.send(msg, move: true)
r.take
p msg

This prints:

Received: message
in `p': undefined method `inspect' for #<Ractor::MovedObject:0x000055c99b9b69b8>

All references to the object and its parts will become invalid in sender.

r = Ractor.new {puts "Received: #{receive}"}
s = 'message'
ary = [s]
copy = ary.dup
r.send(ary, move: true)

s.inspect
# Ractor::MovedError (can not send any methods to a moved object)
ary.class
# Ractor::MovedError (can not send any methods to a moved object)
copy.class
# => Array, it is different object
copy[0].inspect
# Ractor::MovedError (can not send any methods to a moved object)
# ...but its item was still a reference to `s`, which was moved

If the object was shareable, move: true has no effect on it:

r = Ractor.new {puts "Received: #{receive}"}
s = 'message'.freeze
r.send(s, move: true)
s.inspect #=> "message", still available

# File ractor.rb, line 586
def send(obj, move: false)
  __builtin_cexpr! %q{
    ractor_send(ec, RACTOR_PTR(self), obj, move)
  }
end

Take a message from ractor’s outgoing port, which was put there by Ractor.yield or at ractor’s finalization.

r = Ractor.new do
  Ractor.yield 'explicit yield'
  'last value'
end
puts r.take #=> 'explicit yield'
puts r.take #=> 'last value'
puts r.take # Ractor::ClosedError (The outgoing-port is already closed)

The fact that the last value is also put to outgoing port means that take can be used as some analog of Thread#join (“just wait till ractor finishes”), but don’t forget it will raise if somebody had already consumed everything ractor have produced.

If the outgoing port was closed with close_outgoing, the method will raise Ractor::ClosedError.

r = Ractor.new do
  sleep(500)
  Ractor.yield 'Hello from ractor'
end
r.close_outgoing
r.take
# Ractor::ClosedError (The outgoing-port is already closed)
# The error would be raised immediately, not when ractor will try to receive

If an uncaught exception is raised in the Ractor, it is propagated on take as a Ractor::RemoteError.

r = Ractor.new {raise "Something weird happened"}

begin
  r.take
rescue => e
  p e              #  => #<Ractor::RemoteError: thrown by remote Ractor.>
  p e.ractor == r  # => true
  p e.cause        # => #<RuntimeError: Something weird happened>
end

Ractor::ClosedError is a descendant of StopIteration, so the closing of the ractor will break the loops without propagating the error:

r = Ractor.new do
  3.times {|i| Ractor.yield "message #{i}"}
  "finishing"
end

loop {puts "Received: " + r.take}
puts "Continue successfully"

This will print:

Received: message 0
Received: message 1
Received: message 2
Received: finishing
Continue successfully

# File ractor.rb, line 697
def take
  __builtin_cexpr! %q{
    ractor_take(ec, RACTOR_PTR(self))
  }
end

same as Ractor.receive

# File ractor.rb, line 430
        def receive
  __builtin_cexpr! %q{
    ractor_receive(ec, rb_ec_ractor_ptr(ec))
  }
end