Module: MCollective::Matcher

Defined in:
lib/mcollective/matcher.rb,
lib/mcollective/matcher/parser.rb,
lib/mcollective/matcher/scanner.rb

Overview

A parser and scanner that creates a stack machine for a simple fact and class matching language used on the CLI to facilitate a rich discovery language

Language EBNF

compound = [“(”] expression [“)”] expression [“)”] expression = [!|not]statement [“and”|“or”] [!|not] statement char = A-Z | a-z | < | > | => | =< | _ | - |* | / { A-Z | a-z | < | > | => | =< | _ | - | * | / | } int = 0|1|2|3|4|5|6|7|8|9{|0|1|2|3|4|5|6|7|8|9|0}

Defined Under Namespace

Classes: Parser, Scanner

Class Method Summary collapse

Class Method Details

.create_compound_callstack(call_string) ⇒ Object

Creates a callstack to be evaluated from a compound evaluation string



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# File 'lib/mcollective/matcher.rb', line 181

def self.create_compound_callstack(call_string)
  callstack = Matcher::Parser.new(call_string).execution_stack
  callstack.each_with_index do |statement, i|
    if statement.keys.first == "fstatement"
      callstack[i]["fstatement"] = create_function_hash(statement.values.first)
    end
  end
  callstack
end

.create_function_hash(function_call) ⇒ Object

Helper creates a hash from a function call string



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# File 'lib/mcollective/matcher.rb', line 17

def self.create_function_hash(function_call)
  func_hash = {}
  f = ""
  func_parts = function_call.split(/(!=|>=|<=|<|>|=)/)
  func_hash["r_compare"] = func_parts.pop
  func_hash["operator"] = func_parts.pop
  func = func_parts.join

  # Deal with dots in function parameters and functions without dot values
  if func.match(/^.+\(.*\)$/)
    f = func
  else
    func_parts = func.split(".")
    func_hash["value"] = func_parts.pop
    f = func_parts.join(".")
  end

  # Deal with regular expression matches
  if func_hash["r_compare"] =~ /^\/.*\/$/
    func_hash["operator"] = "=~" if func_hash["operator"] == "="
    func_hash["operator"] = "!=~" if func_hash["operator"] == "!="
    func_hash["r_compare"] = Regexp.new(func_hash["r_compare"].gsub(/^\/|\/$/, ""))
  # Convert = operators to == so they can be propperly evaluated
  elsif func_hash["operator"] == "="
    func_hash["operator"] = "=="
  end

  # Grab function name and parameters from left compare string
  func_hash["name"], func_hash["params"] = f.split("(")
  if func_hash["params"] == ")"
    func_hash["params"] = nil
  else

    # Walk the function parameters from the front and from the
    # back removing the first and last instances of single of
    # double qoutes. We do this to handle the case where params
    # contain escaped qoutes.
    func_hash["params"] = func_hash["params"].gsub(")", "")
    func_quotes = func_hash["params"].split(/('|")/)

    func_quotes.each_with_index do |item, i|
      if item.match(/'|"/)
        func_quotes.delete_at(i)
        break
      end
    end

    func_quotes.reverse.each_with_index do |item,i|
      if item.match(/'|"/)
        func_quotes.delete_at(func_quotes.size - i - 1)
        break
      end
    end

    func_hash["params"] = func_quotes.join
  end

  func_hash
end

.eval_compound_fstatement(function_hash) ⇒ Object

Returns the result of an evaluated compound statement that includes a function



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# File 'lib/mcollective/matcher.rb', line 135

def self.eval_compound_fstatement(function_hash)
  l_compare = execute_function(function_hash)

  # Break out early and return false if the function returns nil
  return false unless l_compare

  # Prevent unwanted discovery by limiting comparison operators
  # on Strings and Booleans
  if((l_compare.is_a?(String) || l_compare.is_a?(TrueClass) || l_compare.is_a?(FalseClass)) && function_hash["operator"].match(/<|>/))
    Log.debug "Cannot do > and < comparison on Booleans and Strings '#{l_compare} #{function_hash["operator"]} #{function_hash["r_compare"]}'"
    return false
  end

  # Prevent backticks in function parameters
  if function_hash["params"] =~ /`/
    Log.debug("Cannot use backticks in function parameters")
    return false
  end

  # Escape strings for evaluation
  function_hash["r_compare"] = "\"#{function_hash["r_compare"]}\"" if(l_compare.is_a?(String)  && !(function_hash["operator"] =~ /=~|!=~/))

  # Do a regex comparison if right compare string is a regex
  if function_hash["operator"] =~ /(=~|!=~)/
    # Fail if left compare value isn't a string
    unless l_compare.is_a?(String)
      Log.debug("Cannot do a regex check on a non string value.")
      return false
    else
      compare_result = l_compare.match(function_hash["r_compare"])
      # Flip return value for != operator
      if function_hash["operator"] == "!=~"
        !((compare_result.nil?) ? false : true)
      else
        (compare_result.nil?) ? false : true
      end
    end
    # Otherwise evaluate the logical comparison
  else
    l_compare = "\"#{l_compare}\"" if l_compare.is_a?(String)
    result = eval("#{l_compare} #{function_hash["operator"]} #{function_hash["r_compare"]}")
    (result.nil?) ? false : result
  end
end

.eval_compound_statement(expression) ⇒ Object

Evaluates a compound statement



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# File 'lib/mcollective/matcher.rb', line 115

def self.eval_compound_statement(expression)
  if expression.values.first =~ /^\//
    return Util.has_cf_class?(expression.values.first)
  elsif expression.values.first =~ />=|<=|=|<|>/
    optype = expression.values.first.match(/>=|<=|=|<|>/)
    name, value = expression.values.first.split(optype[0])
    unless value.split("")[0] == "/"
      optype[0] == "=" ? optype = "==" : optype = optype[0]
    else
      optype = "=~"
    end

    return Util.has_fact?(name,value, optype).to_s
  else
    return Util.has_cf_class?(expression.values.first)
  end
end

.execute_function(function_hash) ⇒ Object

Returns the result of an executed function



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# File 'lib/mcollective/matcher.rb', line 78

def self.execute_function(function_hash)
  # In the case where a data plugin isn't present there are two ways we can handle
  # the raised exception. The function result can either be false or the entire
  # expression can fail.
  #
  # In the case where we return the result as false it opens us op to unexpected
  # negation behavior.
  #
  #   !foo('bar').name = bar
  #
  # In this case the user would expect discovery to match on all machines where
  # the name value of the foo function does not equal bar. If a non existent function
  # returns false then it is posible to match machines where the name value of the
  # foo function is bar.
  #
  # Instead we raise a DDLValidationError to prevent this unexpected behavior from
  # happening.

  result = Data.send(function_hash["name"], function_hash["params"])

  if function_hash["value"]
    begin
      eval_result = result.send(function_hash["value"])
    rescue
      # If data field has not been set we set the comparison result to nil
      eval_result = nil
    end
    return eval_result
  else
    return result
  end
rescue NoMethodError
  Log.debug("cannot execute discovery function '#{function_hash["name"]}'. data plugin not found")
  raise DDLValidationError
end