Class: Async::Node

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

Overview

A node in a tree, used for implementing the task hierarchy.

Direct Known Subclasses

Scheduler, Task

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(parent = nil, annotation: nil, transient: false) ⇒ Node

Create a new node in the tree.



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# File 'lib/async/node.rb', line 73

def initialize(parent = nil, annotation: nil, transient: false)
  @parent = nil
  @children = nil
  
  @annotation = annotation
  @object_name = nil
  
  @transient = transient
  
  @head = nil
  @tail = nil
  
  if parent
    parent.add_child(self)
  end
end

Instance Attribute Details

#A useful identifier for the current node.(usefulidentifier) ⇒ Object (readonly) 



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# File 'lib/async/node.rb', line 108

attr :annotation

#annotation ⇒ Object (readonly)

Returns the value of attribute annotation.



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# File 'lib/async/node.rb', line 108

def annotation
  @annotation
end

#children ⇒ Object (readonly)

Returns the value of attribute children.



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# File 'lib/async/node.rb', line 105

def children
  @children
end

#head ⇒ Object 



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# File 'lib/async/node.rb', line 96

def head
  @head
end

#Optional list of children.(listofchildren.) ⇒ Object (readonly) 



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# File 'lib/async/node.rb', line 105

attr :children

#parent ⇒ Object

Returns the value of attribute parent.



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# File 'lib/async/node.rb', line 102

def parent
  @parent
end

#tail ⇒ Object 



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# File 'lib/async/node.rb', line 99

def tail
  @tail
end

Instance Method Details

#annotate(annotation) ⇒ Object

Annotate the node with a description.



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# File 'lib/async/node.rb', line 142

def annotate(annotation)
  if block_given?
    begin
      current_annotation = @annotation
      @annotation = annotation
      return yield
    ensure
      @annotation = current_annotation
    end
  else
    @annotation = annotation
  end
end

#backtrace(*arguments) ⇒ Object

Provides a backtrace for nodes that have an active execution context.



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# File 'lib/async/node.rb', line 174

def backtrace(*arguments)
  nil
end

#children? ⇒ Boolean

Whether this node has any children.

Returns:

  • (Boolean) 


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# File 'lib/async/node.rb', line 112

def children?
  @children && !@children.empty?
end

#consume ⇒ Object

If the node has a parent, and is #finished?, then remove this node from the parent.



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# File 'lib/async/node.rb', line 228

def consume
  if parent = @parent and finished?
    parent.remove_child(self)
    
    # If we have children, then we need to move them to our the parent if they are not finished:
    if @children
      while child = @children.shift
        if child.finished?
          child.set_parent(nil)
        else
          parent.add_child(child)
        end
      end
      
      @children = nil
    end
    
    parent.consume
  end
end

#description ⇒ Object

A description of the node, including the annotation and object name.



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# File 'lib/async/node.rb', line 159

def description
  @object_name ||= "#{self.class}:#{format '%#018x', object_id}#{@transient ? ' transient' : nil}"
  
  if annotation = self.annotation
    "#{@object_name} #{annotation}"
  elsif line = self.backtrace(0, 1)&.first
    "#{@object_name} #{line}"
  else
    @object_name
  end
end

#finished? ⇒ Boolean

Whether the node can be consumed (deleted) safely. By default, checks if the children set is empty.

Returns:

  • (Boolean) 


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# File 'lib/async/node.rb', line 222

def finished?
  @children.nil? || @children.finished?
end

#print_hierarchy(out = $stdout, backtrace: true) ⇒ Object

Print the hierarchy of the task tree from the given node.



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# File 'lib/async/node.rb', line 304

def print_hierarchy(out = $stdout, backtrace: true)
  self.traverse do |node, level|
    indent = "\t" * level
    
    out.puts "#{indent}#{node}"
    
    print_backtrace(out, indent, node) if backtrace
  end
end

#root ⇒ Object 



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# File 'lib/async/node.rb', line 91

def root
  @parent&.root || self
end

#stop(later = false) ⇒ Object

Attempt to stop the current node immediately, including all non-transient children. Invokes #stop_children to stop all children.



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# File 'lib/async/node.rb', line 283

def stop(later = false)
  # The implementation of this method may defer calling `stop_children`.
  stop_children(later)
end

#stopped? ⇒ Boolean

Whether the node has been stopped.

Returns:

  • (Boolean) 


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# File 'lib/async/node.rb', line 296

def stopped?
  @children.nil?
end

#terminate ⇒ Object

Immediately terminate all children tasks, including transient tasks. Internally invokes ‘stop(false)` on all children. This should be considered a last ditch effort and is used when closing the scheduler.



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# File 'lib/async/node.rb', line 268

def terminate
  # Attempt to stop the current task immediately, and all children:
  stop(false)
  
  # If that doesn't work, take more serious action:
  @children&.each do |child|
    child.terminate
  end
  
  return @children.nil?
end

#The parent node.=(parentnode. = (value)) ⇒ Object 



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# File 'lib/async/node.rb', line 102

attr :parent

#to_s ⇒ Object Also known as: inspect 



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# File 'lib/async/node.rb', line 179

def to_s
  "\#<#{self.description}>"
end

#transient=(value) ⇒ Object

Change the transient state of the node.

A transient node is not considered when determining if a node is finished, and propagates up if the parent is consumed.



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# File 'lib/async/node.rb', line 131

def transient=(value)
  if @transient != value
    @transient = value
    
    @parent&.children&.adjust_transient_count(value)
  end
end

#transient? ⇒ Boolean

Represents whether a node is transient. Transient nodes are not considered when determining if a node is finished. This is useful for tasks which are internal to an object rather than explicit user concurrency. For example, a child task which is pruning a connection pool is transient, because it is not directly related to the parent task, and should not prevent the parent task from finishing.

Returns:

  • (Boolean) 


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# File 'lib/async/node.rb', line 122

def transient?
  @transient
end

#traverse(&block) ⇒ Object

Traverse the task tree.



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# File 'lib/async/node.rb', line 253

def traverse(&block)
  return enum_for(:traverse) unless block_given?
  
  self.traverse_recurse(&block)
end