60 lines
1.9 KiB
Ruby
60 lines
1.9 KiB
Ruby
# frozen_string_literal: true
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# Released under the MIT License.
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# Copyright, 2024, by Samuel Williams.
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module Async
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# A load balancing mechanism that can be used process work when the system is idle.
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class Idler
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# Create a new idler.
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#
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# @public Since *Async v2*.
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#
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# @parameter maximum_load [Numeric] The maximum load before we start shedding work.
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# @parameter backoff [Numeric] The initial backoff time, used for delaying work.
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# @parameter parent [Interface(:async) | Nil] The parent task to use for async operations.
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def initialize(maximum_load = 0.8, backoff: 0.01, parent: nil)
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@maximum_load = maximum_load
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@backoff = backoff
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@parent = parent
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end
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# Wait until the system is idle, then execute the given block in a new task.
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#
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# @asynchronous Executes the given block concurrently.
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#
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# @parameter arguments [Array] The arguments to pass to the block.
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# @parameter parent [Interface(:async) | Nil] The parent task to use for async operations.
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# @parameter options [Hash] The options to pass to the task.
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# @yields {|task| ...} When the system is idle, the block will be executed in a new task.
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def async(*arguments, parent: (@parent or Task.current), **options, &block)
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wait
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# It is crucial that we optimistically execute the child task, so that we prevent a tight loop invoking this method from consuming all available resources.
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parent.async(*arguments, **options, &block)
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end
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# Wait until the system is idle, according to the maximum load specified.
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#
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# If the scheduler is overloaded, this method will sleep for an exponentially increasing amount of time.
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def wait
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scheduler = Fiber.scheduler
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backoff = nil
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while true
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load = scheduler.load
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break if load < @maximum_load
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if backoff
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sleep(backoff)
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backoff *= 2.0
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else
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scheduler.yield
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backoff = @backoff
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end
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end
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end
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end
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end
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