Class: Async::Pool::Controller

Inherits:
Object
  • Object
show all
Defined in:
lib/async/pool/controller.rb

Overview

A resource pool controller.

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(constructor, limit: nil, concurrency: (limit || 1), policy: nil, tags: nil) ⇒ Controller

Create a new resource pool.



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# File 'lib/async/pool/controller.rb', line 31

def initialize(constructor, limit: nil, concurrency: (limit || 1), policy: nil, tags: nil)
  @constructor = constructor
  @limit = limit
  
  # This semaphore is used to limit the number of concurrent tasks which are creating new resources.
  @guard = Async::Semaphore.new(concurrency)
  
  @policy = policy
  @gardener = nil
  
  @tags = tags
  
  # All available resources:
  @resources = {}
  
  # Resources which may be available to be acquired:
  # This list may contain false positives, or resources which were okay but have since entered a state which is unusuable.
  @available = []
  
  # Used to signal when a resource has been released:
  @mutex = Thread::Mutex.new
  @condition = Thread::ConditionVariable.new
end

Instance Attribute Details

#all allocated resources, and their associated usage.(allocatedresources) ⇒ Object (readonly) 



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# File 'lib/async/pool/controller.rb', line 99

attr :resources

#constructor ⇒ Object (readonly)

Returns the value of attribute constructor.



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# File 'lib/async/pool/controller.rb', line 56

def constructor
  @constructor
end

#limit ⇒ Object

Returns the value of attribute limit.



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# File 'lib/async/pool/controller.rb', line 59

def limit
  @limit
end

#policy ⇒ Object

Returns the value of attribute policy.



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# File 'lib/async/pool/controller.rb', line 96

def policy
  @policy
end

#resources ⇒ Object (readonly)

Returns the value of attribute resources.



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# File 'lib/async/pool/controller.rb', line 99

def resources
  @resources
end

#tags ⇒ Object

Returns the value of attribute tags.



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# File 'lib/async/pool/controller.rb', line 102

def tags
  @tags
end

#The constructor used to create new resources.(constructorusedtocreatenewresources.) ⇒ Object (readonly) 



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# File 'lib/async/pool/controller.rb', line 56

attr :constructor

#The maximum number of concurrent tasks that can be creating a new resource.(maximumnumberofconcurrenttasksthatcanbecreatinganewresource.) ⇒ Object (readonly) 



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# File 'lib/async/pool/controller.rb', line 86

def concurrency
  @guard.limit
end

#The maximum number of resources that this pool can have at any given time.(maximumnumberofresourcesthatthispoolcanhaveatanygiventime.) ⇒ Object (readonly) 



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# File 'lib/async/pool/controller.rb', line 59

attr_accessor :limit

#The name of the pool.(nameofthepool.) ⇒ Object (readonly) 



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# File 'lib/async/pool/controller.rb', line 102

attr_accessor :tags

Class Method Details

.wrap(**options, &block) ⇒ Object

Create a new resource pool, using the given block to create new resources.



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# File 'lib/async/pool/controller.rb', line 21

def self.wrap(**options, &block)
  self.new(block, **options)
end

Instance Method Details

#acquire ⇒ Object

Acquire a resource from the pool. If a block is provided, the resource will be released after the block has been executed.



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# File 'lib/async/pool/controller.rb', line 154

def acquire
  resource = wait_for_resource
  
  return resource unless block_given?
  
  begin
    yield resource
  ensure
    release(resource)
  end
end

#active? ⇒ Boolean

Whether the pool has any active resources.

Returns:

  • (Boolean) 


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# File 'lib/async/pool/controller.rb', line 110

def active?
  !@resources.empty?
end

#as_json ⇒ Object

Generate a JSON representation of the pool.



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# File 'lib/async/pool/controller.rb', line 71

def as_json(...)
  {
    limit: @limit,
    concurrency: @guard.limit,
    usage: @resources.size,
    availability_summary: self.availability_summary,
  }
end

#available? ⇒ Boolean

Whether there are available resources, i.e. whether #acquire can reuse an existing resource.

Returns:

  • (Boolean) 


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# File 'lib/async/pool/controller.rb', line 124

def available?
  @available.any?
end

#busy? ⇒ Boolean

Whether there are resources which are currently in use.

Returns:

  • (Boolean) 


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# File 'lib/async/pool/controller.rb', line 115

def busy?
  @resources.collect do |_, usage|
    return true if usage > 0
  end
  
  return false
end

#close ⇒ Object

Drain the pool, clear all resources, and stop the gardener.



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# File 'lib/async/pool/controller.rb', line 191

def close
  self.drain
  
  @available.clear
  @gardener&.stop
end

#concurrency ⇒ Object 



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# File 'lib/async/pool/controller.rb', line 86

def concurrency
  @guard.limit
end

#concurrency=(value) ⇒ Object

Set the maximum number of concurrent tasks that can be creating a new resource.



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# File 'lib/async/pool/controller.rb', line 91

def concurrency= value
  @guard.limit = value
end

#drain ⇒ Object

Drain the pool, closing all resources.



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# File 'lib/async/pool/controller.rb', line 181

def drain
  Console.debug(self, "Draining pool...", size: @resources.size)
  
  # Enumerate all existing resources and retire them:
  while resource = acquire_existing_resource
    retire(resource)
  end
end

#empty? ⇒ Boolean

Whether the pool is empty.

Returns:

  • (Boolean) 


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# File 'lib/async/pool/controller.rb', line 149

def empty?
  @resources.empty?
end

#prune(retain = 0) ⇒ Object

Retire (and close) all unused resources. If a block is provided, it should implement the desired functionality for unused resources.



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# File 'lib/async/pool/controller.rb', line 201

def prune(retain = 0)
  unused = []
  
  # This code must not context switch:
  @resources.each do |resource, usage|
    if usage.zero?
      unused << resource
    end
  end
  
  # It's okay for this to context switch:
  unused.each do |resource|
    if block_given?
      yield resource
    else
      retire(resource)
    end
    
    break if @resources.size <= retain
  end
  
  # Update availability list:
  @available.clear
  @resources.each do |resource, usage|
    if usage < resource.concurrency and resource.reusable?
      @available << resource
    end
  end
  
  return unused.size
end

#release(resource) ⇒ Object

Make the resource resources and let waiting tasks know that there is something resources.



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# File 'lib/async/pool/controller.rb', line 167

def release(resource)
  processed = false
  
  # A resource that is not good should also not be reusable.
  if resource.reusable?
    processed = reuse(resource)
  end
  
  # @policy.released(self, resource)
ensure
  retire(resource) unless processed
end

#retire(resource) ⇒ Object

Retire a specific resource.



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# File 'lib/async/pool/controller.rb', line 234

def retire(resource)
  Console.debug(self){"Retire #{resource}"}
  
  @resources.delete(resource)
  
  resource.close
  
  @mutex.synchronize{@condition.broadcast}
  
  return true
end

#size ⇒ Object

The number of resources in the pool.



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# File 'lib/async/pool/controller.rb', line 105

def size
  @resources.size
end

#The pool policy.=(poolpolicy. = (value)) ⇒ Object 



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# File 'lib/async/pool/controller.rb', line 96

attr_accessor :policy

#to_json ⇒ Object

Generate a JSON representation of the pool.



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# File 'lib/async/pool/controller.rb', line 81

def to_json(...)
  as_json.to_json(...)
end

#to_s ⇒ Object

Generate a human-readable representation of the pool.



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# File 'lib/async/pool/controller.rb', line 62

def to_s
  if @resources.empty?
    "\#<#{self.class}(#{usage_string})>"
  else
    "\#<#{self.class}(#{usage_string}) #{availability_summary.join(';')}>"
  end
end

#wait ⇒ Object

Deprecated.

Use #wait_until_free instead.

Wait until a pool resource has been freed.



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# File 'lib/async/pool/controller.rb', line 130

def wait
  @mutex.synchronize do
    @condition.wait(@mutex)
  end
end

#wait_until_free ⇒ Object

Wait until the pool is not busy (no resources in use).



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# File 'lib/async/pool/controller.rb', line 137

def wait_until_free
  @mutex.synchronize do
    if busy?
      yield self if block_given?
      
      # Wait until the pool is not busy:
      @condition.wait(@mutex) while busy?
    end
  end
end