Class: Puppet::SimpleGraph

Inherits:
Object show all
Defined in:
lib/vendor/puppet/simple_graph.rb

Overview

A hopefully-faster graph class to replace the use of GRATR.

Direct Known Subclasses

Resource::Catalog

Defined Under Namespace

Classes: VertexWrapper

Class Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ SimpleGraph

All public methods of this class must maintain (assume ^ ensure) the following invariants, where “=~=” means equiv. up to order:

@in_to.keys =~= @out_to.keys =~= all vertices
@in_to.values.collect { |x| x.values }.flatten =~= @out_from.values.collect { |x| x.values }.flatten =~= all edges
@in_to[v1][v2] =~= @out_from[v2][v1] =~= all edges from v1 to v2
@in_to   [v].keys =~= vertices with edges leading to   v
@out_from[v].keys =~= vertices with edges leading from v
no operation may shed reference loops (for gc)
recursive operation must scale with the depth of the spanning trees, or better (e.g. no recursion over the set
    of all vertices, etc.)

This class is intended to be used with DAGs. However, if the graph has a cycle, it will not cause non-termination of any of the algorithms.



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# File 'lib/vendor/puppet/simple_graph.rb', line 24

def initialize
  @in_to = {}
  @out_from = {}
  @upstream_from = {}
  @downstream_from = {}
end

Class Attribute Details

.use_new_yaml_format ⇒ Object

Returns the value of attribute use_new_yaml_format.



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# File 'lib/vendor/puppet/simple_graph.rb', line 480

def use_new_yaml_format
  @use_new_yaml_format
end

Instance Method Details

#add_edge(e, *a) ⇒ Object

Add a new edge. The graph user has to create the edge instance, since they have to specify what kind of edge it is.



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# File 'lib/vendor/puppet/simple_graph.rb', line 291

def add_edge(e,*a)
  return add_relationship(e,*a) unless a.empty?
  @upstream_from.clear
  @downstream_from.clear
  add_vertex(e.source)
  add_vertex(e.target)
  @in_to[   e.target][e.source] ||= []; @in_to[   e.target][e.source] |= [e]
  @out_from[e.source][e.target] ||= []; @out_from[e.source][e.target] |= [e]
end

#add_relationship(source, target, label = nil) ⇒ Object 



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# File 'lib/vendor/puppet/simple_graph.rb', line 301

def add_relationship(source, target, label = nil)
  add_edge Puppet::Relationship.new(source, target, label)
end

#add_vertex(vertex) ⇒ Object

Add a new vertex to the graph.



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# File 'lib/vendor/puppet/simple_graph.rb', line 264

def add_vertex(vertex)
  @in_to[vertex]    ||= {}
  @out_from[vertex] ||= {}
end

#adjacent(v, options = {}) ⇒ Object

Find adjacent edges.



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# File 'lib/vendor/puppet/simple_graph.rb', line 334

def adjacent(v, options = {})
  return [] unless ns = (options[:direction] == :in) ? @in_to[v] : @out_from[v]
  (options[:type] == :edges) ? ns.values.flatten : ns.keys
end

#clear ⇒ Object

Clear our graph.



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# File 'lib/vendor/puppet/simple_graph.rb', line 32

def clear
  @in_to.clear
  @out_from.clear
  @upstream_from.clear
  @downstream_from.clear
end

#dependencies(resource) ⇒ Object

Which resources depend upon the given resource.



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# File 'lib/vendor/puppet/simple_graph.rb', line 40

def dependencies(resource)
  vertex?(resource) ? upstream_from_vertex(resource).keys : []
end

#dependents(resource) ⇒ Object 



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# File 'lib/vendor/puppet/simple_graph.rb', line 44

def dependents(resource)
  vertex?(resource) ? downstream_from_vertex(resource).keys : []
end

#direct_dependencies_of(v) ⇒ Object 



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# File 'lib/vendor/puppet/simple_graph.rb', line 392

def direct_dependencies_of(v)
  (@in_to[v] || {}).keys 
end

#direct_dependents_of(v) ⇒ Object 



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# File 'lib/vendor/puppet/simple_graph.rb', line 378

def direct_dependents_of(v)
  (@out_from[v] || {}).keys 
end

#directed? ⇒ Boolean

Whether our graph is directed. Always true. Used to produce dot files.

Returns:

  • (Boolean) 


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# File 'lib/vendor/puppet/simple_graph.rb', line 49

def directed?
  true
end

#dotty(params = {}, dotfile = 'graph.dot') ⇒ Object

Call dotty for the graph which is written to the file ‘graph.dot’ in the # current directory.



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# File 'lib/vendor/puppet/simple_graph.rb', line 458

def dotty (params = {}, dotfile = 'graph.dot')
  File.open(dotfile, 'w') {|f| f << to_dot(params) }
  system('dotty', dotfile)
end

#downstream_from_vertex(v) ⇒ Object 



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# File 'lib/vendor/puppet/simple_graph.rb', line 368

def downstream_from_vertex(v)
  return @downstream_from[v] if @downstream_from[v]
  result = @downstream_from[v] = {}
  @out_from[v].keys.each do |node|
    result[node] = 1
    result.update(downstream_from_vertex(node))
  end
  result
end

#each_edge ⇒ Object 



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# File 'lib/vendor/puppet/simple_graph.rb', line 319

def each_edge
  @in_to.each { |t,ns| ns.each { |s,es| es.each { |e| yield e }}}
end

#edge?(source, target) ⇒ Boolean

Is there an edge between the two vertices?

Returns:

  • (Boolean) 


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# File 'lib/vendor/puppet/simple_graph.rb', line 311

def edge?(source, target)
  vertex?(source) and vertex?(target) and @out_from[source][target]
end

#edges ⇒ Object 



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# File 'lib/vendor/puppet/simple_graph.rb', line 315

def edges
  @in_to.values.collect { |x| x.values }.flatten
end

#edges_between(source, target) ⇒ Object

Find all matching edges.



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# File 'lib/vendor/puppet/simple_graph.rb', line 306

def edges_between(source, target)
  (@out_from[source] || {})[target] || []
end

#find_cycles_in_graph ⇒ Object

Find all cycles in the graph by detecting all the strongly connected components, then eliminating everything with a size of one as uninteresting - which it is, because it can’t be a cycle. :)

This has an unhealthy relationship with the ‘tarjan’ method above, which it uses to implement the detection of strongly connected components.



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# File 'lib/vendor/puppet/simple_graph.rb', line 160

def find_cycles_in_graph
  state = {
    :number => 0, :index => {}, :lowlink => {}, :scc => [],
    :stack => [], :seen => {}
  }

  # we usually have a disconnected graph, must walk all possible roots
  vertices.each do |vertex|
    if ! state[:index][vertex] then
      tarjan vertex, state
    end
  end

  # To provide consistent results to the user, given that a hash is never
  # assured to return the same order, and given our graph processing is
  # based on hash tables, we need to sort the cycles internally, as well as
  # the set of cycles.
  #
  # Given we are in a failure state here, any extra cost is more or less
  # irrelevant compared to the cost of a fix - which is on a human
  # time-scale.
  state[:scc].select { |c| c.length > 1 }.map {|x| x.sort }.sort
end

#instance_variable_get(v) ⇒ Object

instance_variable_get is used by Object.to_zaml to get instance variables. Override it so that we can simulate the presence of instance variables @edges and @vertices for serialization.



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# File 'lib/vendor/puppet/simple_graph.rb', line 501

def instance_variable_get(v)
  case v.to_s
  when '@edges' then
    edges
  when '@vertices' then
    if self.class.use_new_yaml_format
      vertices
    else
      result = {}
      vertices.each do |vertex|
        adjacencies = {}
        [:in, :out].each do |direction|
          adjacencies[direction] = {}
          adjacent(vertex, :direction => direction, :type => :edges).each do |edge|
            other_vertex = direction == :in ? edge.source : edge.target
            (adjacencies[direction][other_vertex] ||= Set.new).add(edge)
          end
        end
        result[vertex] = Puppet::SimpleGraph::VertexWrapper.new(vertex, adjacencies)
      end
      result
    end
  else
    super(v)
  end
end

#leaves(vertex, direction = :out) ⇒ Object

Determine all of the leaf nodes below a given vertex.



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# File 'lib/vendor/puppet/simple_graph.rb', line 54

def leaves(vertex, direction = :out)
  tree_from_vertex(vertex, direction).keys.find_all { |c| adjacent(c, :direction => direction).empty? }
end

#matching_edges(event, base = nil) ⇒ Object

Collect all of the edges that the passed events match. Returns an array of edges.



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# File 'lib/vendor/puppet/simple_graph.rb', line 60

def matching_edges(event, base = nil)
  source = base || event.resource

  unless vertex?(source)
    Puppet.warning "Got an event from invalid vertex #{source.ref}"
    return []
  end
  # Get all of the edges that this vertex should forward events
  # to, which is the same thing as saying all edges directly below
  # This vertex in the graph.
  @out_from[source].values.flatten.find_all { |edge| edge.match?(event.name) }
end

#path_between(f, t) ⇒ Object

Return an array of the edge-sets between a series of n+1 vertices (f=v0,v1,v2…t=vn)

connecting the two given verticies.  The ith edge set is an array containing all the
edges between v(i) and v(i+1); these are (by definition) never empty.

  * if f == t, the list is empty
  * if they are adjacent the result is an array consisting of
    a single array (the edges from f to t)
  * and so on by induction on a vertex m between them
  * if there is no path from f to t, the result is nil

This implementation is not particularly efficient; it’s used in testing where clarity

is more important than last-mile efficiency.



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# File 'lib/vendor/puppet/simple_graph.rb', line 409

def path_between(f,t)
  if f==t
    []
  elsif direct_dependents_of(f).include?(t)
    [edges_between(f,t)]
  elsif dependents(f).include?(t)
    m = (dependents(f) & direct_dependencies_of(t)).first
    path_between(f,m) + path_between(m,t)
  else
    nil
  end
end

#paths_in_cycle(cycle, max_paths = 1) ⇒ Object

Perform a BFS on the sub graph representing the cycle, with a view to generating a sufficient set of paths to report the cycle meaningfully, and ideally usefully, for the end user.

BFS is preferred because it will generally report the shortest paths through the graph first, which are more likely to be interesting to the user. I think; it would be interesting to verify that. –daniel 2011-01-23

Raises:

  • (ArgumentError) 


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# File 'lib/vendor/puppet/simple_graph.rb', line 191

def paths_in_cycle(cycle, max_paths = 1)
  raise ArgumentError, "negative or zero max_paths" if max_paths < 1

  # Calculate our filtered outbound vertex lists...
  adj = {}
  cycle.each do |vertex|
    adj[vertex] = adjacent(vertex).select{|s| cycle.member? s}
  end

  found = []

  # frame struct is vertex, [path]
  stack = [[cycle.first, []]]
  while frame = stack.shift do
    if frame[1].member?(frame[0]) then
      found << frame[1] + [frame[0]]
      break if found.length >= max_paths
    else
      adj[frame[0]].each do |to|
        stack.push [to, frame[1] + [frame[0]]]
      end
    end
  end

  return found.sort
end

#remove_edge!(e) ⇒ Object

Remove an edge from our graph.



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# File 'lib/vendor/puppet/simple_graph.rb', line 324

def remove_edge!(e)
  if edge?(e.source,e.target)
    @upstream_from.clear
    @downstream_from.clear
    @in_to   [e.target].delete e.source if (@in_to   [e.target][e.source] -= [e]).empty?
    @out_from[e.source].delete e.target if (@out_from[e.source][e.target] -= [e]).empty?
  end
end

#remove_vertex!(v) ⇒ Object

Remove a vertex from the graph.



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# File 'lib/vendor/puppet/simple_graph.rb', line 270

def remove_vertex!(v)
  return unless vertex?(v)
  @upstream_from.clear
  @downstream_from.clear
  (@in_to[v].values+@out_from[v].values).flatten.each { |e| remove_edge!(e) }
  @in_to.delete(v)
  @out_from.delete(v)
end

#report_cycles_in_graph ⇒ Object

Raises:



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# File 'lib/vendor/puppet/simple_graph.rb', line 218

def report_cycles_in_graph
  cycles = find_cycles_in_graph
  n = cycles.length           # where is "pluralize"? --daniel 2011-01-22
  return if n == 0
  s = n == 1 ? '' : 's'

  message = "Found #{n} dependency cycle#{s}:\n"
  cycles.each do |cycle|
    paths = paths_in_cycle(cycle)
    message += paths.map{ |path| '(' + path.join(" => ") + ')'}.join("\n") + "\n"
  end

  if Puppet[:graph] then
    filename = write_cycles_to_graph(cycles)
    message += "Cycle graph written to #{filename}."
  else
    message += "Try the '--graph' option and opening the "
    message += "resulting '.dot' file in OmniGraffle or GraphViz"
  end

  raise Puppet::Error, message
end

#reversal ⇒ Object

Return a reversed version of this graph.



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# File 'lib/vendor/puppet/simple_graph.rb', line 74

def reversal
  result = self.class.new
  vertices.each { |vertex| result.add_vertex(vertex) }
  edges.each do |edge|
    result.add_edge edge.class.new(edge.target, edge.source, edge.label)
  end
  result
end

#size ⇒ Object

Return the size of the graph.



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# File 'lib/vendor/puppet/simple_graph.rb', line 84

def size
  vertices.size
end

#tarjan(root, s) ⇒ Object

This is a simple implementation of Tarjan’s algorithm to find strongly connected components in the graph; this is a fairly ugly implementation, because I can’t just decorate the vertices themselves.

This method has an unhealthy relationship with the find_cycles_in_graph method below, which contains the knowledge of how the state object is maintained.



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# File 'lib/vendor/puppet/simple_graph.rb', line 99

def tarjan(root, s)
  # initialize the recursion stack we use to work around the nasty lack of a
  # decent Ruby stack.
  recur = [{ :node => root }]

  while not recur.empty? do
    frame = recur.last
    vertex = frame[:node]

    case frame[:step]
    when nil then
      s[:index][vertex]   = s[:number]
      s[:lowlink][vertex] = s[:number]
      s[:number]          = s[:number] + 1

      s[:stack].push(vertex)
      s[:seen][vertex] = true

      frame[:children] = adjacent(vertex)
      frame[:step]     = :children

    when :children then
      if frame[:children].length > 0 then
        child = frame[:children].shift
        if ! s[:index][child] then
          # Never seen, need to recurse.
          frame[:step] = :after_recursion
          frame[:child] = child
          recur.push({ :node => child })
        elsif s[:seen][child] then
          s[:lowlink][vertex] = [s[:lowlink][vertex], s[:index][child]].min
        end
      else
        if s[:lowlink][vertex] == s[:index][vertex] then
          this_scc = []
          begin
            top = s[:stack].pop
            s[:seen][top] = false
            this_scc << top
          end until top == vertex
          s[:scc] << this_scc
        end
        recur.pop               # done with this node, finally.
      end

    when :after_recursion then
      s[:lowlink][vertex] = [s[:lowlink][vertex], s[:lowlink][frame[:child]]].min
      frame[:step] = :children

    else
      fail "#{frame[:step]} is an unknown step"
    end
  end
end

#to_a ⇒ Object 



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# File 'lib/vendor/puppet/simple_graph.rb', line 88

def to_a
  vertices
end

#to_dot(params = {}) ⇒ Object

Output the dot format as a string



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# File 'lib/vendor/puppet/simple_graph.rb', line 454

def to_dot (params={}) to_dot_graph(params).to_s; end

#to_dot_graph(params = {}) ⇒ Object

Return a DOT::DOTDigraph for directed graphs or a DOT::DOTSubgraph for an undirected Graph. params can contain any graph property specified in rdot.rb. If an edge or vertex label is a kind of Hash then the keys which match dot properties will be used as well.



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# File 'lib/vendor/puppet/simple_graph.rb', line 428

def to_dot_graph (params = {})
  params['name'] ||= self.class.name.gsub(/:/,'_')
  fontsize   = params['fontsize'] ? params['fontsize'] : '8'
  graph      = (directed? ? DOT::DOTDigraph : DOT::DOTSubgraph).new(params)
  edge_klass = directed? ? DOT::DOTDirectedEdge : DOT::DOTEdge
  vertices.each do |v|
    name = v.to_s
    params = {'name'     => '"'+name+'"',
      'fontsize' => fontsize,
      'label'    => name}
    v_label = v.to_s
    params.merge!(v_label) if v_label and v_label.kind_of? Hash
    graph << DOT::DOTNode.new(params)
  end
  edges.each do |e|
    params = {'from'     => '"'+ e.source.to_s + '"',
      'to'       => '"'+ e.target.to_s + '"',
      'fontsize' => fontsize }
    e_label = e.to_s
    params.merge!(e_label) if e_label and e_label.kind_of? Hash
    graph << edge_klass.new(params)
  end
  graph
end

#to_yaml_properties ⇒ Object 



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# File 'lib/vendor/puppet/simple_graph.rb', line 528

def to_yaml_properties
  other_vars = instance_variables.
    map {|v| v.to_s}.
    reject { |v| %w{@in_to @out_from @upstream_from @downstream_from}.include?(v) }

  (other_vars + %w{@vertices @edges}).sort.uniq
end

#tree_from_vertex(start, direction = :out) ⇒ Object

A different way of walking a tree, and a much faster way than the one that comes with GRATR.



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# File 'lib/vendor/puppet/simple_graph.rb', line 360

def tree_from_vertex(start, direction = :out)
  predecessor={}
  walk(start, direction) do |parent, child|
    predecessor[child] = parent
  end
  predecessor
end

#upstream_from_vertex(v) ⇒ Object 



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# File 'lib/vendor/puppet/simple_graph.rb', line 382

def upstream_from_vertex(v)
  return @upstream_from[v] if @upstream_from[v]
  result = @upstream_from[v] = {}
  @in_to[v].keys.each do |node|
    result[node] = 1
    result.update(upstream_from_vertex(node))
  end
  result
end

#vertex?(v) ⇒ Boolean

Test whether a given vertex is in the graph.

Returns:

  • (Boolean) 


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# File 'lib/vendor/puppet/simple_graph.rb', line 280

def vertex?(v)
  @in_to.include?(v)
end

#vertices ⇒ Object

Return a list of all vertices.



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# File 'lib/vendor/puppet/simple_graph.rb', line 285

def vertices
  @in_to.keys
end

#walk(source, direction) ⇒ Object

Just walk the tree and pass each edge.



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# File 'lib/vendor/puppet/simple_graph.rb', line 340

def walk(source, direction)
  # Use an iterative, breadth-first traversal of the graph. One could do
  # this recursively, but Ruby's slow function calls and even slower
  # recursion make the shorter, recursive algorithm cost-prohibitive.
  stack = [source]
  seen = Set.new
  until stack.empty?
    node = stack.shift
    next if seen.member? node
    connected = adjacent(node, :direction => direction)
    connected.each do |target|
      yield node, target
    end
    stack.concat(connected)
    seen << node
  end
end

#write_cycles_to_graph(cycles) ⇒ Object 



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# File 'lib/vendor/puppet/simple_graph.rb', line 241

def write_cycles_to_graph(cycles)
  # This does not use the DOT graph library, just writes the content
  # directly.  Given the complexity of this, there didn't seem much point
  # using a heavy library to generate exactly the same content. --daniel 2011-01-27
  Puppet.settings.use(:graphing)

  graph = ["digraph Resource_Cycles {"]
  graph << '  label = "Resource Cycles"'

  cycles.each do |cycle|
    paths_in_cycle(cycle, 10).each do |path|
      graph << path.map { |v| '"' + v.to_s.gsub(/"/, '\\"') + '"' }.join(" -> ")
    end
  end

  graph << '}'

  filename = File.join(Puppet[:graphdir], "cycles.dot")
  File.open(filename, "w") { |f| f.puts graph }
  return filename
end

#write_graph(name) ⇒ Object

Produce the graph files if requested.



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# File 'lib/vendor/puppet/simple_graph.rb', line 464

def write_graph(name)
  return unless Puppet[:graph]

  Puppet.settings.use(:graphing)

  file = File.join(Puppet[:graphdir], "#{name}.dot")
  File.open(file, "w") { |f|
    f.puts to_dot("name" => name.to_s.capitalize)
  }
end

#yaml_initialize(tag, var) ⇒ Object 



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# File 'lib/vendor/puppet/simple_graph.rb', line 536

def yaml_initialize(tag, var)
  initialize()
  vertices = var.delete('vertices')
  edges = var.delete('edges')
  if vertices.is_a?(Hash)
    # Support old (2.6) format
    vertices = vertices.keys
  end
  vertices.each { |v| add_vertex(v) }
  edges.each { |e| add_edge(e) }
  var.each do |varname, value|
    instance_variable_set("@#{varname}", value)
  end
end