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Update the search to use a reversed graph

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Reverse the graph before searching so we are only working with
    a single possible destination. A DFS is used to initially prune
    down the graph.
This commit is contained in:
Chris Roberts 2022-02-07 14:39:47 -08:00 committed by Paul Hinze
parent 3865008b89
commit b0f59c40f6
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GPG Key ID: B69DEDF2D55501C0
1 changed files with 69 additions and 41 deletions
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110
plugins/commands/serve/mappers/internal/graph/search.rb
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@ -39,14 +39,55 @@ module VagrantPlugins
logger.debug("finding path #{src} -> #{dst}")
@root = src
logger.trace("generating list of required vertices for path #{src} -> #{dst}")
# Generate list of required vertices from the graph
required_vertices = generate_path(src, dst)
# We know the root is our final destination, so flop the graph before searching
graph.reverse!
# Perform an initial DFS to prune the graph down
vertices = []
descender = lambda { |v|
graph.depth_first_visit(v) { |vrt|
vertices << vrt
}
vertices.uniq!
vertices.each do |vrt|
if vrt.incoming_edges_required
graph.out_vertices(vrt).each do |ov|
if !vertices.include?(ov)
descender.call(ov)
end
end
end
end
}
descender.call(dst)
# Remove excess vertices from the graph
(graph.vertices - vertices).each { |v|
graph.remove_vertex(v)
}
logger.trace("graph after DFS reduction:\n#{graph.reverse.inspect}")
logger.trace("generating list of required vertices for path #{src} -> #{dst}")
if !graph.vertices.include?(src)
raise NoPathError,
"Graph no longer includes source vertex #{src}"
end
if !graph.vertices.include?(dst)
raise NoPathError,
"Graph no longer includes destination vertex #{dst}"
end
# Generate list of required vertices from the graph
required_vertices = generate_path(dst, src)
# If not vertices were returned, then the path generation failed
if required_vertices.nil?
raise NoPathError,
"Path generation failed to reach destination (#{src} -> #{dst&.type&.inspect})"
end
logger.trace("required vertices list generation complete for path #{src} -> #{dst}")
# Remove all extraneous vertices
@ -54,36 +95,10 @@ module VagrantPlugins
graph.remove_vertex(vrt)
end
if !graph.acyclic?
logger.debug("cycles detected in graph, removing...")
begin
require 'rgl/dot'
graph.write_to_graphic_file('jpg', 'graph-cyclic')
rescue
#
end
graph.reverse!
graph.break_cycles!(src) if !graph.acyclic?
graph.break_cycles!(src)
logger.debug("cycles removed from graph")
if !graph.acyclic?
logger.error("path generation for #{src} -> #{dst} resulted in cyclic graph")
begin
# If the graph ends up with a cycle, attempt to
# draw the graph for inspection. We don't care if
# this fails as it's only for debugging and will
# only be successful if graphviz is installed.
require 'rgl/dot'
graph.write_to_graphic_file('jpg', 'vagrant-graph-cyclic')
rescue
# ignore
end
raise NoPathError,
"Failed to create an acyclic graph for path generation"
end
end
logger.debug("graph after acyclic breakage:\n#{graph.reverse.inspect}")
# Apply topological sort to the graph so we have
# a proper order for execution
@ -105,6 +120,14 @@ module VagrantPlugins
end
result
end
rescue NoPathError
begin
require 'rgl/dot'
graph.reverse.write_to_graphic_file('jpg', 'graph-no-path')
rescue
#
end
raise
end
protected
@ -112,15 +135,15 @@ module VagrantPlugins
def generate_path(src, dst)
begin
path = graph.shortest_path(src, dst)
o = Array(path).map { |v|
o = Array(path).reverse.map { |v|
" #{v} ->"
}.join("\n")
logger.trace("path generation #{src} -> #{dst}\n#{o}")
logger.trace("path generation #{dst} -> #{src}\n#{o}")
if path.nil?
raise NoPathError,
"Path generation failed to reach destination (#{src} -> #{dst&.type&.inspect})"
"Path generation failed to reach destination (#{dst} -> #{src})"
end
expand_path(path, src, graph)
expand_path(path, dst, graph)
rescue InvalidVertex => err
logger.trace("invalid vertex in path, removing (#{err.vertex})")
graph.remove_vertex(err.vertex)
@ -128,19 +151,24 @@ module VagrantPlugins
end
end
def expand_path(path, src, graph)
def expand_path(path, dst, graph)
new_path = []
path.each do |v|
new_path << v
next if !v.incoming_edges_required
logger.trace("validating incoming edges for vertex #{v}")
ins = graph.in_vertices(v)
outs = graph.out_vertices(v)
g = graph.clone
g.remove_vertex(v)
ins.each do |dst|
outs.each do |src|
ipath = g.shortest_path(src, dst)
raise InvalidVertex.new(v) if ipath.nil? || ipath.empty?
ipath = expand_path(ipath, src, g)
if ipath.nil? || ipath.empty?
logger.trace("failed to find validating path from #{dst} -> #{src}")
raise InvalidVertex.new(v)
else
logger.trace("found validating path from #{dst} -> #{src}")
end
ipath = expand_path(ipath, dst, g)
new_path += ipath
end
logger.trace("incoming edge validation complete for vertex #{v}")