Module: Concurrent

Defined in:
lib/concurrent.rb,
lib/concurrent/map.rb,
lib/concurrent/set.rb,
lib/concurrent/atom.rb,
lib/concurrent/hash.rb,
lib/concurrent/ivar.rb,
lib/concurrent/mvar.rb,
lib/concurrent/tvar.rb,
lib/concurrent/agent.rb,
lib/concurrent/array.rb,
lib/concurrent/async.rb,
lib/concurrent/delay.rb,
lib/concurrent/maybe.rb,
lib/concurrent/tuple.rb,
lib/concurrent/errors.rb,
lib/concurrent/future.rb,
lib/concurrent/options.rb,
lib/concurrent/promise.rb,
lib/concurrent/version.rb,
lib/concurrent/dataflow.rb,
lib/concurrent/promises.rb,
lib/concurrent/constants.rb,
lib/concurrent/exchanger.rb,
lib/concurrent/re_include.rb,
lib/concurrent/timer_task.rb,
lib/concurrent/atomic/event.rb,
lib/concurrent/configuration.rb,
lib/concurrent/mutable_struct.rb,
lib/concurrent/scheduled_task.rb,
lib/concurrent/utility/engine.rb,
lib/concurrent/concern/logging.rb,
lib/concurrent/settable_struct.rb,
lib/concurrent/synchronization.rb,
lib/concurrent/utility/at_exit.rb,
lib/concurrent/atomic/semaphore.rb,
lib/concurrent/immutable_struct.rb,
lib/concurrent/thread_safe/util.rb,
lib/concurrent/concern/obligation.rb,
lib/concurrent/concern/observable.rb,
lib/concurrent/executor/timer_set.rb,
lib/concurrent/concern/deprecation.rb,
lib/concurrent/atomic/atomic_fixnum.rb,
lib/concurrent/synchronization/lock.rb,
lib/concurrent/atomic/atomic_boolean.rb,
lib/concurrent/atomic/cyclic_barrier.rb,
lib/concurrent/atomic/mutex_semaphore.rb,
lib/concurrent/atomic/read_write_lock.rb,
lib/concurrent/synchronization/object.rb,
lib/concurrent/thread_safe/util/adder.rb,
lib/concurrent/utility/monotonic_time.rb,
lib/concurrent/utility/native_integer.rb,
lib/concurrent/atomic/atomic_reference.rb,
lib/concurrent/atomic/count_down_latch.rb,
lib/concurrent/atomic/thread_local_var.rb,
lib/concurrent/concern/dereferenceable.rb,
lib/concurrent/synchronization/volatile.rb,
lib/concurrent/executor/executor_service.rb,
lib/concurrent/synchronization/condition.rb,
lib/concurrent/thread_safe/util/volatile.rb,
lib/concurrent/utility/processor_counter.rb,
lib/concurrent/atomic/mutex_atomic_fixnum.rb,
lib/concurrent/collection/lock_free_stack.rb,
lib/concurrent/executor/fixed_thread_pool.rb,
lib/concurrent/synchronization/mri_object.rb,
lib/concurrent/synchronization/rbx_object.rb,
lib/concurrent/thread_safe/util/striped64.rb,
lib/concurrent/atomic/mutex_atomic_boolean.rb,
lib/concurrent/executor/cached_thread_pool.rb,
lib/concurrent/executor/immediate_executor.rb,
lib/concurrent/executor/safe_task_executor.rb,
lib/concurrent/atomic/java_count_down_latch.rb,
lib/concurrent/atomic/java_thread_local_var.rb,
lib/concurrent/atomic/ruby_thread_local_var.rb,
lib/concurrent/synchronization/jruby_object.rb,
lib/concurrent/atomic/mutex_count_down_latch.rb,
lib/concurrent/atomic_reference/mutex_atomic.rb,
lib/concurrent/executor/serialized_execution.rb,
lib/concurrent/executor/thread_pool_executor.rb,
lib/concurrent/collection/map/mri_map_backend.rb,
lib/concurrent/executor/java_executor_service.rb,
lib/concurrent/executor/ruby_executor_service.rb,
lib/concurrent/executor/single_thread_executor.rb,
lib/concurrent/synchronization/abstract_object.rb,
lib/concurrent/synchronization/abstract_struct.rb,
lib/concurrent/synchronization/lockable_object.rb,
lib/concurrent/thread_safe/util/cheap_lockable.rb,
lib/concurrent/utility/native_extension_loader.rb,
lib/concurrent/atomic/abstract_thread_local_var.rb,
lib/concurrent/atomic/atomic_markable_reference.rb,
lib/concurrent/atomic/reentrant_read_write_lock.rb,
lib/concurrent/executor/serial_executor_service.rb,
lib/concurrent/executor/simple_executor_service.rb,
lib/concurrent/thread_safe/util/data_structures.rb,
lib/concurrent/thread_safe/util/xor_shift_random.rb,
lib/concurrent/executor/abstract_executor_service.rb,
lib/concurrent/executor/java_thread_pool_executor.rb,
lib/concurrent/executor/ruby_thread_pool_executor.rb,
lib/concurrent/synchronization/truffleruby_object.rb,
lib/concurrent/thread_safe/synchronized_delegator.rb,
lib/concurrent/synchronization/rbx_lockable_object.rb,
lib/concurrent/thread_safe/util/power_of_two_tuple.rb,
lib/concurrent/atomic_reference/numeric_cas_wrapper.rb,
lib/concurrent/executor/indirect_immediate_executor.rb,
lib/concurrent/executor/java_single_thread_executor.rb,
lib/concurrent/executor/ruby_single_thread_executor.rb,
lib/concurrent/collection/copy_on_write_observer_set.rb,
lib/concurrent/synchronization/jruby_lockable_object.rb,
lib/concurrent/synchronization/mutex_lockable_object.rb,
lib/concurrent/collection/copy_on_notify_observer_set.rb,
lib/concurrent/collection/map/synchronized_map_backend.rb,
lib/concurrent/executor/serialized_execution_delegator.rb,
lib/concurrent/collection/non_concurrent_priority_queue.rb,
lib/concurrent/synchronization/abstract_lockable_object.rb,
lib/concurrent/collection/map/non_concurrent_map_backend.rb,
lib/concurrent/collection/map/atomic_reference_map_backend.rb,
lib/concurrent/collection/java_non_concurrent_priority_queue.rb,
lib/concurrent/collection/ruby_non_concurrent_priority_queue.rb,
lib-edge/concurrent/edge.rb,
lib-edge/concurrent/actor.rb,
lib-edge/concurrent/channel.rb,
lib-edge/concurrent/actor/core.rb,
lib-edge/concurrent/actor/root.rb,
lib-edge/concurrent/actor/utils.rb,
lib-edge/concurrent/actor/errors.rb,
lib-edge/concurrent/channel/tick.rb,
lib-edge/concurrent/actor/context.rb,
lib-edge/concurrent/edge/promises.rb,
lib-edge/concurrent/edge/throttle.rb,
lib-edge/concurrent/lazy_register.rb,
lib-edge/concurrent/actor/envelope.rb,
lib-edge/concurrent/actor/behaviour.rb,
lib-edge/concurrent/actor/reference.rb,
lib-edge/concurrent/actor/type_check.rb,
lib-edge/concurrent/actor/utils/pool.rb,
lib-edge/concurrent/channel/selector.rb,
lib-edge/concurrent/edge/cancellation.rb,
lib-edge/concurrent/actor/utils/ad_hoc.rb,
lib-edge/concurrent/channel/buffer/base.rb,
lib-edge/concurrent/actor/utils/balancer.rb,
lib-edge/concurrent/channel/buffer/timer.rb,
lib-edge/concurrent/edge/lock_free_queue.rb,
lib-edge/concurrent/actor/utils/broadcast.rb,
lib-edge/concurrent/channel/buffer/ticker.rb,
lib-edge/concurrent/edge/processing_actor.rb,
lib-edge/concurrent/actor/behaviour/awaits.rb,
lib-edge/concurrent/actor/behaviour/buffer.rb,
lib-edge/concurrent/channel/buffer/sliding.rb,
lib-edge/concurrent/actor/behaviour/linking.rb,
lib-edge/concurrent/actor/behaviour/pausing.rb,
lib-edge/concurrent/channel/buffer/buffered.rb,
lib-edge/concurrent/channel/buffer/dropping.rb,
lib-edge/concurrent/actor/behaviour/abstract.rb,
lib-edge/concurrent/actor/public_delegations.rb,
lib-edge/concurrent/channel/buffer/unbuffered.rb,
lib-edge/concurrent/edge/lock_free_linked_set.rb,
lib-edge/concurrent/actor/internal_delegations.rb,
lib-edge/concurrent/actor/behaviour/supervising.rb,
lib-edge/concurrent/actor/behaviour/termination.rb,
lib-edge/concurrent/channel/selector/put_clause.rb,
lib-edge/concurrent/actor/behaviour/sets_results.rb,
lib-edge/concurrent/channel/selector/take_clause.rb,
lib-edge/concurrent/edge/old_channel_integration.rb,
lib-edge/concurrent/actor/behaviour/removes_child.rb,
lib-edge/concurrent/channel/selector/after_clause.rb,
lib-edge/concurrent/channel/selector/error_clause.rb,
lib-edge/concurrent/edge/lock_free_linked_set/node.rb,
lib-edge/concurrent/channel/selector/default_clause.rb,
lib-edge/concurrent/actor/behaviour/executes_context.rb,
lib-edge/concurrent/edge/lock_free_linked_set/window.rb,
lib-edge/concurrent/actor/default_dead_letter_handler.rb,
lib-edge/concurrent/actor/behaviour/errors_on_unknown_message.rb

Overview

Concurrent Ruby

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Modern concurrency tools for Ruby. Inspired by Erlang, Clojure, Scala, Haskell, F#, C#, Java, and classic concurrency patterns.

The design goals of this gem are:

  • Be an 'unopinionated' toolbox that provides useful utilities without debating which is better or why
  • Remain free of external gem dependencies
  • Stay true to the spirit of the languages providing inspiration
  • But implement in a way that makes sense for Ruby
  • Keep the semantics as idiomatic Ruby as possible
  • Support features that make sense in Ruby
  • Exclude features that don't make sense in Ruby
  • Be small, lean, and loosely coupled
  • Thread-safety
  • Backward compatibility

Contributing

This gem depends on contributions and we appreciate your help. Would you like to contribute? Great! Have a look at issues with looking-for-contributor label. And if you pick something up let us know on the issue.

Thread Safety

Concurrent Ruby makes one of the strongest thread safety guarantees of any Ruby concurrency library, providing consistent behavior and guarantees on all three of the main Ruby interpreters (MRI/CRuby, JRuby, Rubinius, TruffleRuby).

Every abstraction in this library is thread safe. Specific thread safety guarantees are documented with each abstraction.

It is critical to remember, however, that Ruby is a language of mutable references. No concurrency library for Ruby can ever prevent the user from making thread safety mistakes (such as sharing a mutable object between threads and modifying it on both threads) or from creating deadlocks through incorrect use of locks. All the library can do is provide safe abstractions which encourage safe practices. Concurrent Ruby provides more safe concurrency abstractions than any other Ruby library, many of which support the mantra of "Do not communicate by sharing memory; instead, share memory by communicating". Concurrent Ruby is also the only Ruby library which provides a full suite of thread safe and immutable variable types and data structures.

We've also initiated discussion to document memory model of Ruby which would provide consistent behaviour and guarantees on all four of the main Ruby interpreters (MRI/CRuby, JRuby, Rubinius, TruffleRuby).

Features & Documentation

The primary site for documentation is the automatically generated API documentation which is up to date with latest release. This readme matches the master so may contain new stuff not yet released.

We also have a IRC (gitter).

Versioning

  • concurrent-ruby uses Semantic Versioning
  • concurrent-ruby-ext has always same version as concurrent-ruby
  • concurrent-ruby-edge will always be 0.y.z therefore following point 4 applies "Major version zero (0.y.z) is for initial development. Anything may change at any time. The public API should not be considered stable." However we additionally use following rules:
    • Minor version increment means incompatible changes were made
    • Patch version increment means only compatible changes were made

General-purpose Concurrency Abstractions

  • Async: A mixin module that provides simple asynchronous behavior to a class. Loosely based on Erlang's gen_server.
  • ScheduledTask: Like a Future scheduled for a specific future time.
  • TimerTask: A Thread that periodically wakes up to perform work at regular intervals.
  • Promises: Unified implementation of futures and promises which combines features of previous Future, Promise, IVar, Event, dataflow, Delay, and (partially) TimerTask into a single framework. It extensively uses the new synchronization layer to make all the features non-blocking and lock-free, with the exception of obviously blocking operations like #wait, #value. It also offers better performance.

Thread-safe Value Objects, Structures, and Collections

Collection classes that were originally part of the (deprecated) thread_safe gem:

  • Array A thread-safe subclass of Ruby's standard Array.
  • Hash A thread-safe subclass of Ruby's standard Hash.
  • Set A thread-safe subclass of Ruby's standard Set.
  • Map A hash-like object that should have much better performance characteristics, especially under high concurrency, than Concurrent::Hash.
  • Tuple A fixed size array with volatile (synchronized, thread safe) getters/setters.

Value objects inspired by other languages:

Structure classes derived from Ruby's Struct:

  • ImmutableStruct Immutable struct where values are set at construction and cannot be changed later.
  • MutableStruct Synchronized, mutable struct where values can be safely changed at any time.
  • SettableStruct Synchronized, write-once struct where values can be set at most once, either at construction or any time thereafter.

Thread-safe variables:

  • Agent: A way to manage shared, mutable, asynchronous, independent state. Based on Clojure's Agent.
  • Atom: A way to manage shared, mutable, synchronous, independent state. Based on Clojure's Atom.
  • AtomicBoolean A boolean value that can be updated atomically.
  • AtomicFixnum A numeric value that can be updated atomically.
  • AtomicReference An object reference that may be updated atomically.
  • Exchanger A synchronization point at which threads can pair and swap elements within pairs. Based on Java's Exchanger.
  • MVar A synchronized single element container. Based on Haskell's MVar and Scala's MVar.
  • ThreadLocalVar A variable where the value is different for each thread.
  • TVar A transactional variable implementing software transactional memory (STM). Based on Clojure's Ref.

Java-inspired ThreadPools and Other Executors

  • See the thread pool overview, which also contains a list of other Executors available.

Thread Synchronization Classes and Algorithms

  • CountDownLatch A synchronization object that allows one thread to wait on multiple other threads.
  • CyclicBarrier A synchronization aid that allows a set of threads to all wait for each other to reach a common barrier point.
  • Event Old school kernel-style event.
  • ReadWriteLock A lock that supports multiple readers but only one writer.
  • ReentrantReadWriteLock A read/write lock with reentrant and upgrade features.
  • Semaphore A counting-based locking mechanism that uses permits.
  • AtomicMarkableReference

Deprecated

Deprecated features are still available and bugs are being fixed, but new features will not be added.

  • Future: An asynchronous operation that produces a value. Replaced by Promises.
    • .dataflow: Built on Futures, Dataflow allows you to create a task that will be scheduled when all of its data dependencies are available. Replaced by Promises.
  • Promise: Similar to Futures, with more features. Replaced by Promises.
  • Delay Lazy evaluation of a block yielding an immutable result. Based on Clojure's delay. Replaced by Promises.
  • IVar Similar to a "future" but can be manually assigned once, after which it becomes immutable. Replaced by Promises.

Edge Features

These are available in the concurrent-ruby-edge companion gem.

These features are under active development and may change frequently. They are expected not to keep backward compatibility (there may also lack tests and documentation). Semantic versions will be obeyed though. Features developed in concurrent-ruby-edge are expected to move to concurrent-ruby when final.

  • Actor: Implements the Actor Model, where concurrent actors exchange messages. Status: Partial documentation and tests; depends on new future/promise framework; stability is good.
  • Channel: Communicating Sequential Processes (CSP). Functionally equivalent to Go channels with additional inspiration from Clojure core.async. Status: Partial documentation and tests.
  • LazyRegister
  • LockFreeLinkedSet Status: will be moved to core soon.
  • LockFreeStack Status: missing documentation and tests.

Supported Ruby versions

  • MRI 2.0 and above
  • JRuby 9000
  • TruffleRuby are supported.
  • Any Ruby interpreter that is compliant with Ruby 2.0 or newer.

Actually we still support mri 1.9.3 and jruby 1.7.27 but we are looking at ways how to drop the support. Java 8 is preferred for JRuby but every Java version on which JRuby 9000 runs is supported.

The legacy support for Rubinius is kept but it is no longer maintained, if you would like to help please respond to #739.

Usage

Everything within this gem can be loaded simply by requiring it:

require 'concurrent'

Requiring only specific abstractions from Concurrent Ruby is not yet supported.

To use the tools in the Edge gem it must be required separately:

require 'concurrent-edge'

If the library does not behave as expected, Concurrent.use_stdlib_logger(Logger::DEBUG) could help to reveal the problem.

Installation

gem install concurrent-ruby

or add the following line to Gemfile:

gem 'concurrent-ruby', require: 'concurrent'

and run bundle install from your shell.

Edge Gem Installation

The Edge gem must be installed separately from the core gem:

gem install concurrent-ruby-edge

or add the following line to Gemfile:

gem 'concurrent-ruby-edge', require: 'concurrent-edge'

and run bundle install from your shell.

C Extensions for MRI

Potential performance improvements may be achieved under MRI by installing optional C extensions. To minimise installation errors the C extensions are available in the concurrent-ruby-ext extension gem. concurrent-ruby and concurrent-ruby-ext are always released together with same version. Simply install the extension gem too:

gem install concurrent-ruby-ext

or add the following line to Gemfile:

gem 'concurrent-ruby-ext'

and run bundle install from your shell.

In code it is only necessary to

require 'concurrent'

The concurrent-ruby gem will automatically detect the presence of the concurrent-ruby-ext gem and load the appropriate C extensions.

Note For gem developers

No gems should depend on concurrent-ruby-ext. Doing so will force C extensions on your users. The best practice is to depend on concurrent-ruby and let users to decide if they want C extensions.

Maintainers

Special Thanks to

and to the past maintainers

License and Copyright

Concurrent Ruby is free software released under the MIT License.

The Concurrent Ruby logo was designed by David Jones. It is Copyright © 2014 Jerry D'Antonio. All Rights Reserved.

Defined Under Namespace

Modules: Actor, Async, Concern, Edge, ImmutableStruct, MutableStruct, Promises, ReInclude, SettableStruct, Synchronization, Utility Classes: Agent, Array, Atom, AtomicBoolean, AtomicFixnum, AtomicMarkableReference, AtomicReference, CachedThreadPool, Cancellation, Channel, ConcurrentUpdateError, CountDownLatch, CyclicBarrier, Delay, Event, Exchanger, FixedThreadPool, Future, Hash, IVar, ImmediateExecutor, IndirectImmediateExecutor, LazyRegister, LockFreeStack, MVar, Map, Maybe, MultipleAssignmentError, MultipleErrors, ProcessingActor, Promise, ReadWriteLock, ReentrantReadWriteLock, SafeTaskExecutor, ScheduledTask, Semaphore, SerializedExecution, SerializedExecutionDelegator, Set, SimpleExecutorService, SingleThreadExecutor, TVar, ThreadLocalVar, ThreadPoolExecutor, Throttle, TimerSet, TimerTask, Transaction, Tuple

Constant Summary collapse

Error = 
Class.new(StandardError)
ConfigurationError =

Raised when errors occur during configuration.

Class.new(Error)
CancelledOperationError =

Raised when an asynchronous operation is cancelled before execution.

Class.new(Error)
LifecycleError =

Raised when a lifecycle method (such as stop) is called in an improper sequence or when the object is in an inappropriate state.

Class.new(Error)
ImmutabilityError =

Raised when an attempt is made to violate an immutability guarantee.

Class.new(Error)
IllegalOperationError =

Raised when an operation is attempted which is not legal given the receiver's current state

Class.new(Error)
InitializationError =

Raised when an object's methods are called when it has not been properly initialized.

Class.new(Error)
MaxRestartFrequencyError =

Raised when an object with a start/stop lifecycle has been started an excessive number of times. Often used in conjunction with a restart policy or strategy.

Class.new(Error)
RejectedExecutionError =

Raised by an Executor when it is unable to process a given task, possibly because of a reject policy or other internal error.

Class.new(Error)
ResourceLimitError =

Raised when any finite resource, such as a lock counter, exceeds its maximum limit/threshold.

Class.new(Error)
TimeoutError =

Raised when an operation times out.

Class.new(Error)
PromiseExecutionError = 
Class.new(StandardError)
VERSION = 
'1.1.4'
EDGE_VERSION = 
'0.4.1'
NULL_LOGGER =

Suppresses all output when used for logging.

lambda { |level, progname, message = nil, &block| }

Class Method Summary collapse

Class Method Details

.abort_transaction ⇒ undocumented

Abort a currently running transaction - see Concurrent::atomically.

Raises:



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# File 'lib/concurrent/tvar.rb', line 150

def abort_transaction
  raise Transaction::AbortError.new
end

.atomically ⇒ undocumented

Run a block that reads and writes TVars as a single atomic transaction. With respect to the value of TVar objects, the transaction is atomic, in that it either happens or it does not, consistent, in that the TVar objects involved will never enter an illegal state, and isolated, in that transactions never interfere with each other. You may recognise these properties from database transactions.

There are some very important and unusual semantics that you must be aware of:

  • Most importantly, the block that you pass to atomically may be executed more than once. In most cases your code should be free of side-effects, except for via TVar.

  • If an exception escapes an atomically block it will abort the transaction.

  • It is undefined behaviour to use callcc or Fiber with atomically.

  • If you create a new thread within an atomically, it will not be part of the transaction. Creating a thread counts as a side-effect.

Transactions within transactions are flattened to a single transaction.

Examples:

a = new TVar(100_000)
b = new TVar(100)

Concurrent::atomically do
  a.value -= 10
  b.value += 10
end

Raises:

  • (ArgumentError) 


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# File 'lib/concurrent/tvar.rb', line 93

def atomically
  raise ArgumentError.new('no block given') unless block_given?

  # Get the current transaction

  transaction = Transaction::current

  # Are we not already in a transaction (not nested)?

  if transaction.nil?
    # New transaction

    begin
      # Retry loop

      loop do

        # Create a new transaction

        transaction = Transaction.new
        Transaction::current = transaction

        # Run the block, aborting on exceptions

        begin
          result = yield
        rescue Transaction::AbortError => e
          transaction.abort
          result = Transaction::ABORTED
        rescue Transaction::LeaveError => e
          transaction.abort
          break result
        rescue => e
          transaction.abort
          raise e
        end
        # If we can commit, break out of the loop

        if result != Transaction::ABORTED
          if transaction.commit
            break result
          end
        end
      end
    ensure
      # Clear the current transaction

      Transaction::current = nil
    end
  else
    # Nested transaction - flatten it and just run the block

    yield
  end
end

.call_dataflow(method, executor, *inputs, &block) ⇒ undocumented

Raises:

  • (ArgumentError) 


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# File 'lib/concurrent/dataflow.rb', line 56

def call_dataflow(method, executor, *inputs, &block)
  raise ArgumentError.new('an executor must be provided') if executor.nil?
  raise ArgumentError.new('no block given') unless block_given?
  unless inputs.all? { |input| input.is_a? IVar }
    raise ArgumentError.new("Not all dependencies are IVars.\nDependencies: #{ inputs.inspect }")
  end

  result = Future.new(executor: executor) do
    values = inputs.map { |input| input.send(method) }
    block.call(*values)
  end

  if inputs.empty?
    result.execute
  else
    counter = DependencyCounter.new(inputs.size) { result.execute }

    inputs.each do |input|
      input.add_observer counter
    end
  end

  result
end

.create_simple_logger(level = Logger::FATAL, output = $stderr) ⇒ Logger

Returns Logger with provided level and output.

Returns:

  • (Logger) —

    Logger with provided level and output.



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# File 'lib/concurrent/configuration.rb', line 19

def self.create_simple_logger(level = Logger::FATAL, output = $stderr)
  # TODO (pitr-ch 24-Dec-2016): figure out why it had to be replaced, stdlogger was deadlocking
  lambda do |severity, progname, message = nil, &block|
    return false if severity < level

    message           = block ? block.call : message
    formatted_message = case message
                        when String
                          message
                        when Exception
                          format "%s (%s)\n%s",
                                 message.message, message.class, (message.backtrace || []).join("\n")
                        else
                          message.inspect
                        end

    output.print format "[%s] %5s -- %s: %s\n",
                        Time.now.strftime('%Y-%m-%d %H:%M:%S.%L'),
                        Logger::SEV_LABEL[severity],
                        progname,
                        formatted_message
    true
  end
end

.create_stdlib_logger(level = Logger::FATAL, output = $stderr) ⇒ Logger

Deprecated.

Returns Logger with provided level and output.

Returns:

  • (Logger) —

    Logger with provided level and output.



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# File 'lib/concurrent/configuration.rb', line 51

def self.create_stdlib_logger(level = Logger::FATAL, output = $stderr)
  logger           = Logger.new(output)
  logger.level     = level
  logger.formatter = lambda do |severity, datetime, progname, msg|
    formatted_message = case msg
                        when String
                          msg
                        when Exception
                          format "%s (%s)\n%s",
                                 msg.message, msg.class, (msg.backtrace || []).join("\n")
                        else
                          msg.inspect
                        end
    format "[%s] %5s -- %s: %s\n",
           datetime.strftime('%Y-%m-%d %H:%M:%S.%L'),
           severity,
           progname,
           formatted_message
  end

  lambda do |loglevel, progname, message = nil, &block|
    logger.add loglevel, message, progname, &block
  end
end

.dataflow(*inputs) {|inputs| ... } ⇒ Object

Dataflow allows you to create a task that will be scheduled when all of its data dependencies are available. Data dependencies are Future values. The dataflow task itself is also a Future value, so you can build up a graph of these tasks, each of which is run when all the data and other tasks it depends on are available or completed.

Our syntax is somewhat related to that of Akka's flow and Habanero Java's DataDrivenFuture. However unlike Akka we don't schedule a task at all until it is ready to run, and unlike Habanero Java we pass the data values into the task instead of dereferencing them again in the task.

The theory of dataflow goes back to the 70s. In the terminology of the literature, our implementation is coarse-grained, in that each task can be many instructions, and dynamic in that you can create more tasks within other tasks.

Example

A dataflow task is created with the dataflow method, passing in a block.

task = Concurrent::dataflow { 14 }

This produces a simple Future value. The task will run immediately, as it has no dependencies. We can also specify Future values that must be available before a task will run. When we do this we get the value of those futures passed to our block. 

a = Concurrent::dataflow { 1 }
b = Concurrent::dataflow { 2 }
c = Concurrent::dataflow(a, b) { |av, bv| av + bv }

Using the dataflow method you can build up a directed acyclic graph (DAG) of tasks that depend on each other, and have the tasks run as soon as their dependencies are ready and there is CPU capacity to schedule them. This can help you create a program that uses more of the CPU resources available to you.

Derivation

This section describes how we could derive dataflow from other primitives in this library.

Consider a naive fibonacci calculator.

def fib(n)
  if n < 2
    n
  else
    fib(n - 1) + fib(n - 2)
  end
end

puts fib(14) #=> 377

We could modify this to use futures.

def fib(n)
  if n < 2
    Concurrent::Future.new { n }
  else
    n1 = fib(n - 1).execute
    n2 = fib(n - 2).execute
    Concurrent::Future.new { n1.value + n2.value }
  end
end

f = fib(14) #=> #<Concurrent::Future:0x000001019ef5a0 ...
f.execute   #=> #<Concurrent::Future:0x000001019ef5a0 ...

sleep(0.5)

puts f.value #=> 377

One of the drawbacks of this approach is that all the futures start, and then most of them immediately block on their dependencies. We know that there's no point executing those futures until their dependencies are ready, so let's not execute each future until all their dependencies are ready.

To do this we'll create an object that counts the number of times it observes a future finishing before it does something - and for us that something will be to execute the next future. 

class CountingObserver

  def initialize(count, &block)
    @count = count
    @block = block
  end

  def update(time, value, reason)
    @count -= 1

    if @count <= 0
      @block.call()
    end
  end

end

def fib(n)
  if n < 2
    Concurrent::Future.new { n }.execute
  else
    n1 = fib(n - 1)
    n2 = fib(n - 2)

    result = Concurrent::Future.new { n1.value + n2.value }

    barrier = CountingObserver.new(2) { result.execute }
    n1.add_observer barrier
    n2.add_observer barrier

    n1.execute
    n2.execute

    result
  end
end

We can wrap this up in a dataflow utility.

f = fib(14) #=> #<Concurrent::Future:0x00000101fca308 ...
sleep(0.5)

puts f.value #=> 377

def dataflow(*inputs, &block)
  result = Concurrent::Future.new(&block)

  if inputs.empty?
    result.execute
  else
    barrier = CountingObserver.new(inputs.size) { result.execute }

    inputs.each do |input|
      input.add_observer barrier
    end
  end

  result
end

def fib(n)
  if n < 2
    dataflow { n }
  else
    n1 = fib(n - 1)
    n2 = fib(n - 2)
    dataflow(n1, n2) { n1.value + n2.value }
  end
end

f = fib(14) #=> #<Concurrent::Future:0x00000101fca308 ...
sleep(0.5)

puts f.value #=> 377

Since we know that the futures the dataflow computation depends on are already going to be available when the future is executed, we might as well pass the values into the block so we don't have to reference the futures inside the block. This allows us to write the dataflow block as straight non-concurrent code without reference to futures. 

def dataflow(*inputs, &block)
  result = Concurrent::Future.new do
    values = inputs.map { |input| input.value }
    block.call(*values)
  end

  if inputs.empty?
    result.execute
  else
    barrier = CountingObserver.new(inputs.size) { result.execute }

    inputs.each do |input|
      input.add_observer barrier
    end
  end

  result
end

def fib(n)
  if n < 2
    Concurrent::dataflow { n }
  else
    n1 = fib(n - 1)
    n2 = fib(n - 2)
    Concurrent::dataflow(n1, n2) { |v1, v2| v1 + v2 }
  end
end

f = fib(14) #=> #<Concurrent::Future:0x000001019a26d8 ...
sleep(0.5)

puts f.value #=> 377

Parameters:

  • inputs (Future) —

    zero or more Future operations that this dataflow depends upon

Yields:

  • The operation to perform once all the dependencies are met

Yield Parameters:

  • inputs (Future) —

    each of the Future inputs to the dataflow

Yield Returns:

  • (Object) —

    the result of the block operation

Returns:

  • (Object) —

    the result of all the operations

Raises:

  • (ArgumentError) —

    if any of the inputs are not IVars

  • (ArgumentError) —

    if no block is given



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# File 'lib/concurrent/dataflow.rb', line 34

def dataflow(*inputs, &block)
  dataflow_with(Concurrent.global_io_executor, *inputs, &block)
end

.dataflow!(*inputs, &block) ⇒ undocumented 



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# File 'lib/concurrent/dataflow.rb', line 44

def dataflow!(*inputs, &block)
  dataflow_with!(Concurrent.global_io_executor, *inputs, &block)
end

.dataflow_with(executor, *inputs, &block) ⇒ undocumented 



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# File 'lib/concurrent/dataflow.rb', line 39

def dataflow_with(executor, *inputs, &block)
  call_dataflow(:value, executor, *inputs, &block)
end

.dataflow_with!(executor, *inputs, &block) ⇒ undocumented 



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# File 'lib/concurrent/dataflow.rb', line 49

def dataflow_with!(executor, *inputs, &block)
  call_dataflow(:value!, executor, *inputs, &block)
end

.disable_at_exit_handlers! ⇒ undocumented

Note:

this option should be needed only because of at_exit ordering issues which may arise when running some of the testing frameworks. E.g. Minitest's test-suite runs itself in at_exit callback which executes after the pools are already terminated. Then auto termination needs to be disabled and called manually after test-suite ends.

Note:

This method should never be called from within a gem. It should only be used from within the main application and even then it should be used only when necessary.

Disables AtExit handlers including pool auto-termination handlers. When disabled it will be the application programmer's responsibility to ensure that the handlers are shutdown properly prior to application exit by calling AtExitImplementation.new.install.run method.

See Also:

  • AtExit


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# File 'lib/concurrent/configuration.rb', line 129

def self.disable_at_exit_handlers!
  AtExit.enabled = false
end

.executor(executor_identifier) ⇒ Executor

General access point to global executors.

Parameters:

Returns:

  • (Executor) 


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# File 'lib/concurrent/configuration.rb', line 164

def self.executor(executor_identifier)
  Options.executor(executor_identifier)
end

.global_fast_executor ⇒ ThreadPoolExecutor

Global thread pool optimized for short, fast operations.

Returns:



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# File 'lib/concurrent/configuration.rb', line 136

def self.global_fast_executor
  GLOBAL_FAST_EXECUTOR.value
end

.global_immediate_executor ⇒ undocumented 



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# File 'lib/concurrent/configuration.rb', line 147

def self.global_immediate_executor
  GLOBAL_IMMEDIATE_EXECUTOR
end

.global_io_executor ⇒ ThreadPoolExecutor

Global thread pool optimized for long, blocking (IO) tasks.

Returns:



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# File 'lib/concurrent/configuration.rb', line 143

def self.global_io_executor
  GLOBAL_IO_EXECUTOR.value
end

.global_logger ⇒ undocumented 



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# File 'lib/concurrent/configuration.rb', line 91

def self.global_logger
  GLOBAL_LOGGER.value
end

.global_logger=(value) ⇒ undocumented 



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# File 'lib/concurrent/configuration.rb', line 95

def self.global_logger=(value)
  GLOBAL_LOGGER.value = value
end

.global_timer_set ⇒ Concurrent::TimerSet

Global thread pool user for global timers.

Returns:



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# File 'lib/concurrent/configuration.rb', line 154

def self.global_timer_set
  GLOBAL_TIMER_SET.value
end

.leave_transaction ⇒ undocumented

Leave a transaction without committing or aborting - see Concurrent::atomically.

Raises:



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# File 'lib/concurrent/tvar.rb', line 155

def leave_transaction
  raise Transaction::LeaveError.new
end

.monotonic_time ⇒ Float

Note:

Time calculations on all platforms and languages are sensitive to changes to the system clock. To alleviate the potential problems associated with changing the system clock while an application is running, most modern operating systems provide a monotonic clock that operates independently of the system clock. A monotonic clock cannot be used to determine human-friendly clock times. A monotonic clock is used exclusively for calculating time intervals. Not all Ruby platforms provide access to an operating system monotonic clock. On these platforms a pure-Ruby monotonic clock will be used as a fallback. An operating system monotonic clock is both faster and more reliable than the pure-Ruby implementation. The pure-Ruby implementation should be fast and reliable enough for most non-realtime operations. At this time the common Ruby platforms that provide access to an operating system monotonic clock are MRI 2.1 and above and JRuby (all versions).

Returns the current time a tracked by the application monotonic clock.

Returns:

  • (Float) —

    The current monotonic time since some unspecified starting point

See Also:



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# File 'lib/concurrent/utility/monotonic_time.rb', line 53

def monotonic_time
  GLOBAL_MONOTONIC_CLOCK.get_time
end

.new_fast_executor(opts = {}) ⇒ undocumented 



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# File 'lib/concurrent/configuration.rb', line 168

def self.new_fast_executor(opts = {})
  FixedThreadPool.new(
      [2, Concurrent.processor_count].max,
      auto_terminate:  opts.fetch(:auto_terminate, true),
      idletime:        60, # 1 minute
      max_queue:       0, # unlimited
      fallback_policy: :abort # shouldn't matter -- 0 max queue
  )
end

.new_io_executor(opts = {}) ⇒ undocumented 



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# File 'lib/concurrent/configuration.rb', line 178

def self.new_io_executor(opts = {})
  CachedThreadPool.new(
      auto_terminate:  opts.fetch(:auto_terminate, true),
      fallback_policy: :abort # shouldn't matter -- 0 max queue
  )
end

.physical_processor_count ⇒ undocumented 



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# File 'lib/concurrent/utility/processor_counter.rb', line 155

def self.physical_processor_count
  processor_counter.physical_processor_count
end

.processor_count ⇒ undocumented 



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# File 'lib/concurrent/utility/processor_counter.rb', line 151

def self.processor_count
  processor_counter.processor_count
end

.use_simple_logger(level = Logger::FATAL, output = $stderr) ⇒ undocumented

Use logger created by #create_simple_logger to log concurrent-ruby messages.



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# File 'lib/concurrent/configuration.rb', line 45

def self.use_simple_logger(level = Logger::FATAL, output = $stderr)
  Concurrent.global_logger = create_simple_logger level, output
end

.use_stdlib_logger(level = Logger::FATAL, output = $stderr) ⇒ undocumented

Deprecated.

Use logger created by #create_stdlib_logger to log concurrent-ruby messages.



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# File 'lib/concurrent/configuration.rb', line 78

def self.use_stdlib_logger(level = Logger::FATAL, output = $stderr)
  Concurrent.global_logger = create_stdlib_logger level, output
end