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



214
215
216
217
218
219
220
221
222
 
# File 'lib/mcollective/matcher.rb', line 214

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



17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
 
# 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



135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
 
# File 'lib/mcollective/matcher.rb', line 135

def self.eval_compound_fstatement(function_hash)
  l_compare = execute_function(function_hash)
  r_compare = function_hash["r_compare"]
  operator = function_hash["operator"]

  # Break out early and return false if the function returns nil
  if l_compare.nil?
    return false
  end

  # 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

  # Do a regex comparison if right compare string is a regex
  if 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
      result = l_compare.match(r_compare)
      # Flip return value for != operator
      if function_hash["operator"] == "!=~"
        return !result
      else
        return !!result
      end
    end
    # Otherwise do a normal comparison while taking the type into account
  else
    if l_compare.is_a? String
      r_compare = r_compare.to_s
    elsif r_compare.is_a? String
      if l_compare.is_a? Numeric
        r_compare = r_compare.strip
        begin
          r_compare = Integer(r_compare)
        rescue ArgumentError
          begin
            r_compare = Float(r_compare)
          rescue ArgumentError
            raise ArgumentError, "invalid numeric value: #{r_compare}"
          end
        end
      elsif l_compare.is_a? TrueClass or l_compare.is_a? FalseClass
        r_compare = r_compare.strip
        if r_compare == true.to_s
          r_compare = true
        elsif r_compare == false.to_s
          r_compare = false
        else
          raise ArgumentError, "invalid boolean value: #{r_compare}"
        end
      end
    end
    operator = operator.strip
    if operator =~ /(?:(!=|<=|>=|<|>)|==?)/
      operator = $1 ? $1.to_sym : :==
    else
      raise ArgumentError, "invalid operator: #{operator}"
    end
    result = l_compare.send(operator, r_compare)
    return result
  end
end

.eval_compound_statement(expression) ⇒ Object

Evaluates a compound statement



115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
 
# 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



78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
 
# 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