Concurrently is a concurrency framework for Ruby and mruby built upon fibers. With it code can be evaluated independently in its own execution context similar to a thread. Execution contexts are called evaluations in Concurrently and are created with Kernel#concurrently:
hello = concurrently do
wait 0.2 # seconds
"hello"
end
world = concurrently do
wait 0.1 # seconds
"world"
end
puts "#{hello.await_result} #{world.await_result}" In this example we have three evaluations: The root evaluation and two more concurrent evaluations started by said root evaluation. The root evaluation waits until both concurrent evaluations were concluded and then prints "hello world".
Evaluations can be synchronized with certain events by waiting for them. These events are:
- an elapsed time period (Kernel#wait),
- readability and writability of IO (IO#await_readable, IO#await_writable) and
- the result of another evaluation (Concurrently::Proc::Evaluation#await_result).
Since evaluations run independently they are not blocking other evaluations while waiting.
When doing I/O it is important to do it non-blocking. If the IO object is not ready use IO#await_readable and IO#await_writable to await readiness.
For more about non-blocking I/O, see the core ruby docs for IO#read_nonblock and IO#write_nonblock.
This is a little server reading from an IO and printing the received messages:
# Let's start with creating a pipe to connect client and server
r,w = IO.pipe
# Server:
# We let the server code run concurrently so it runs independently. It reads
# from the pipe non-blocking and awaits readability if the pipe is not readable.
concurrently do
while true
begin
puts r.read_nonblock 32
rescue IO::WaitReadable
r.await_readable
retry
end
end
end
# Client:
# The client writes to the pipe every 0.5 seconds
puts "#{Time.now.strftime('%H:%M:%S.%L')} (Start time)"
while true
wait 0.5
w.write Time.now.strftime('%H:%M:%S.%L')
endThe root evaluation is effectively blocked by waiting or writing messages. But since the server runs concurrently it is not affected by this and happily prints its received messages.
This is the output:
23:20:42.357 (Start time)
23:20:42.858
23:20:43.359
23:20:43.860
23:20:44.360
...
- Ruby 2.2.7+
- mruby 1.3+
Copyright 2016-present Christopher Aue
Concurrently is licensed under the Apache License, Version 2.0. Please see the file called LICENSE.