Class: Build::Graph::Walker

Inherits:
Object
  • Object
show all
Defined in:
lib/build/graph/walker.rb

Overview

A walker walks over a graph and applies a task to each node.

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(logger: nil, &block) ⇒ Walker

Returns a new instance of Walker.



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# File 'lib/build/graph/walker.rb', line 43

def initialize(logger: nil, &block)
	# Node -> Task mapping.
	@tasks = {}
	
	@update = block
	
	@outputs = {}
	
	@parents = {}
	
	# Failed output paths:
	@failed_tasks = []
	@failed_outputs = Set.new
	
	@logger = logger || Logger.new(nil)
	@monitor = Files::Monitor.new(logger: @logger)
end

Instance Attribute Details

#count ⇒ Object (readonly)

Returns the value of attribute count.



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# File 'lib/build/graph/walker.rb', line 68

def count
  @count
end

#dirty ⇒ Object (readonly)

Returns the value of attribute dirty.



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# File 'lib/build/graph/walker.rb', line 69

def dirty
  @dirty
end

#failed_outputs ⇒ Object (readonly)

Returns the value of attribute failed_outputs.



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# File 'lib/build/graph/walker.rb', line 66

def failed_outputs
  @failed_outputs
end

#failed_tasks ⇒ Object (readonly)

Returns the value of attribute failed_tasks.



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# File 'lib/build/graph/walker.rb', line 65

def failed_tasks
  @failed_tasks
end

#monitor ⇒ Object (readonly)

Returns the value of attribute monitor.



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# File 'lib/build/graph/walker.rb', line 73

def monitor
  @monitor
end

#outputs ⇒ Object (readonly)

Returns the value of attribute outputs.



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# File 'lib/build/graph/walker.rb', line 63

def outputs
  @outputs
end

#parents ⇒ Object (readonly)

Returns the value of attribute parents.



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# File 'lib/build/graph/walker.rb', line 71

def parents
  @parents
end

#tasks ⇒ Object (readonly)

=> Task



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# File 'lib/build/graph/walker.rb', line 61

def tasks
  @tasks
end

Class Method Details

.for(task_class, *args, **options) ⇒ Object 



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# File 'lib/build/graph/walker.rb', line 33

def self.for(task_class, *args, **options)
	self.new(**options) do |walker, node|
		task = task_class.new(walker, node, *args)
		
		task.visit do
			task.update
		end
	end
end

Instance Method Details

#call(node) ⇒ Object 



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# File 'lib/build/graph/walker.rb', line 81

def call(node)
	# We try to fetch the task if it has already been invoked, otherwise we create a new task.
	@tasks.fetch(node) do
		@logger.debug{"Update: #{node}"}
		
		@update.call(self, node)
		
		# This should now be defined:
		@tasks[node]
	end
end

#clear_failed ⇒ Object 



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# File 'lib/build/graph/walker.rb', line 196

def clear_failed
	@failed_tasks.each do |task|
		self.delete(task.node)
	end if @failed_tasks
	
	@failed_tasks = []
	@failed_outputs = Set.new
end

#delete(node) ⇒ Object 



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# File 'lib/build/graph/walker.rb', line 188

def delete(node)
	@logger.debug{">-< #{node.process}"}

	if task = @tasks.delete(node)
		@monitor.delete(task)
	end
end

#enter(task) ⇒ Object 



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# File 'lib/build/graph/walker.rb', line 146

def enter(task)
	@logger.debug{"--> #{task.node.process}"}
	
	@tasks[task.node] = task
	
	# In order to wait on outputs, they must be known before entering the task. This might seem odd, but unless we know outputs are being generated, waiting for them to complete is impossible - unless this was somehow specified ahead of time. The implications of this logic is that all tasks must be sequential in terms of output -> input chaning. This is not a problem in practice.
	if outputs = task.outputs
		outputs.each do |path|
			@outputs[path.to_s] = []
		end
	end
end

#exit(task) ⇒ Object 



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# File 'lib/build/graph/walker.rb', line 159

def exit(task)
	@logger.debug{"<-- #{task.node.process}"}
	
	# Fail outputs if the node failed:
	if task.failed?
		@failed_tasks << task
		
		if task.outputs
			@failed_outputs += task.outputs.collect{|path| path.to_s}
		end
	end
	
	# Clean the node's outputs:
	task.outputs.each do |path|
		path = path.to_s
		
		if edges = @outputs.delete(path)
			edges.each{|edge| edge.traverse(task)}
		end
	end
	
	# Notify the parent nodes that the child is done:
	if parents = @parents.delete(task.node)
		parents.each{|edge| edge.traverse(task)}
	end
	
	@monitor.add(task)
end

#failed? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/build/graph/walker.rb', line 93

def failed?
	@failed_tasks.size > 0
end

#run(**options) ⇒ Object 



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# File 'lib/build/graph/walker.rb', line 205

def run(**options)
	yield
	
	monitor.run(**options) do
		yield
	end
end

#update(nodes) ⇒ Object 



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# File 'lib/build/graph/walker.rb', line 75

def update(nodes)
	Array(nodes).each do |node|
		self.call(node)
	end
end

#wait_for_children(parent, children) ⇒ Object

A parent task only completes once all it’s children are complete.



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# File 'lib/build/graph/walker.rb', line 121

def wait_for_children(parent, children)
	# Consider only incomplete/failed children:
	children = children.select{|child| !child.complete?}
	
	# If there are no children like this, then done:
	return true if children.size == 0
	
	# Otherwise, construct an edge to track state changes:
	edge = Edge.new
	
	children.each do |child|
		if child.failed?
			edge.skip!(child)
		else
			# We are waiting for this child to finish:
			edge.increment!
			
			@parents[child.node] ||= []
			@parents[child.node] << edge
		end
	end
	
	return edge.wait
end

#wait_on_paths(paths) ⇒ Object 



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# File 'lib/build/graph/walker.rb', line 97

def wait_on_paths(paths)
	# If there are no paths, we are done:
	return true if paths.count == 0
	
	# We create a new directed hyper-graph edge which waits for all paths to be ready (or failed):
	edge = Edge.new
	
	paths = paths.collect(&:to_s)
	
	paths.each do |path|
		# Is there a task generating this output?
		if outputs = @outputs[path]
			# When the output is ready, trigger this edge:
			outputs << edge
			edge.increment!
		end
	end
	
	failed = paths.any?{|path| @failed_outputs.include? path}
	
	return edge.wait && !failed
end