class Puppet::Provider

A Provider is an implementation of the actions that manage resources (of some type) on a system. This class is the base class for all implementation of a Puppet Provider.

Concepts:

Constants

Confine

Common module for the Boolean confines. It currently contains just enough code to implement PUP-9336.

Attributes

doc[W]

@!attribute [r] doc

The (full) documentation for this provider class. The documentation for the provider class itself
should be set with the DSL method {desc=}. Setting the documentation with with {doc=} has the same effect
as setting it with {desc=} (only the class documentation part is set). In essence this means that
there is no getter for the class documentation part (since the getter returns the full
documentation when there are additional contributors).

@return [String] Returns the full documentation for the provider.

@see Puppet::Utils::Docs @comment This is puzzling … a write only doc attribute??? The generated setter never seems to be

used, instead the instance variable @doc is set in the `desc` method. This seems wrong. It is instead
documented as a read only attribute (to get the full documentation). Also see doc below for
desc.

@!attribute [w] desc

Sets the documentation of this provider class. (The full documentation is read via the
{doc} attribute).

@dsl type
name[RW]

@return [String] The name of the provider

resource_type[RW]

@todo What is this type? A reference to a Puppet::Type ? @return [Puppet::Type] the resource type (that this provider is … WHAT?)

source[W]

@todo Original = _“The source parameter exists so that providers using the same

source can specify this, so reading doesn't attempt to read the
same package multiple times."_ This seems to be a package type specific attribute. Is this really
used?

@return [???] The source is WHAT?

resource[RW]

@return [???] This resource is what? Is an instance of a provider attached to one particular Puppet::Resource?

Public Class Methods

command(name) click to toggle source

Returns the absolute path to the executable for the command referenced by the given name. @raise [Puppet::DevError] if the name does not reference an existing command. @return [String] the absolute path to the found executable for the command @see which @api public

    # File lib/puppet/provider.rb
125 def self.command(name)
126   name = name.intern
127 
128   command = @commands[name] if defined?(@commands)    
129   command = superclass.command(name) if !command && superclass.respond_to?(:command)
130 
131   unless command
132     raise Puppet::DevError, _("No command %{command} defined for provider %{provider}") % { command: name, provider: self.name }
133   end
134 
135   which(command)
136 end
commands(command_specs) click to toggle source

Confines this provider to be suitable only on hosts where the given commands are present. Also see {Puppet::Confiner#confine} for other types of confinement of a provider by use of other types of predicates.

@note It is preferred if the commands are not entered with absolute paths as this allows puppet

to search for them using the PATH variable.

@param command_specs [Hash{String => String}] Map of name to command that the provider will

be executing on the system. Each command is specified with a name and the path of the executable.

@return [void] @see optional_commands @api public

    # File lib/puppet/provider.rb
151 def self.commands(command_specs)
152   command_specs.each do |name, path|
153     has_command(name, path)
154   end
155 end
declared_feature?(name) click to toggle source

@return [Boolean] Return whether the given feature has been declared or not.

    # File lib/puppet/provider.rb
250 def self.declared_feature?(name)
251   defined?(@declared_features) and @declared_features.include?(name)
252 end
default?() click to toggle source

@return [Boolean] Returns whether this implementation satisfies all of the default requirements or not.

Returns false if there is no matching defaultfor

@see Provider.defaultfor

    # File lib/puppet/provider.rb
258 def self.default?
259   default_match ? true : false
260 end
default_match() click to toggle source

Look through the array of defaultfor hashes and return the first match. @return [Hash<{String => Object}>] the matching hash specified by a defaultfor @see Provider.defaultfor @api private

    # File lib/puppet/provider.rb
266 def self.default_match
267   return nil if some_default_match(@notdefaults) # Blacklist means this provider cannot be a default
268   some_default_match(@defaults)
269 end
defaultfor(hash) click to toggle source

Sets a facts filter that determine which of several suitable providers should be picked by default. This selection only kicks in if there is more than one suitable provider. To filter on multiple facts the given hash may contain more than one fact name/value entry. The filter picks the provider if all the fact/value entries match the current set of facts. (In case there are still more than one provider after this filtering, the first found is picked). @param hash [Hash<{String => Object}>] hash of fact name to fact value. @return [void]

    # File lib/puppet/provider.rb
319 def self.defaultfor(hash)
320   @defaults << hash
321 end
execpipe(*args, &block) click to toggle source

(see Puppet::Util::Execution.execpipe)

    # File lib/puppet/provider.rb
116 def self.execpipe(*args, &block)
117   Puppet::Util::Execution.execpipe(*args, &block)
118 end
execute(*args) click to toggle source

(see Puppet::Util::Execution.execute)

    # File lib/puppet/provider.rb
105 def self.execute(*args)
106   Puppet::Util::Execution.execute(*args)
107 end
fact_match(fact, values) click to toggle source

Compare a fact value against one or more supplied value @param [Symbol] fact a fact to query to match against one of the given values @param [Array, Regexp, String] values one or more values to compare to the

value of the given fact

@return [Boolean] whether or not the fact value matches one of the supplied

values. Given one or more Regexp instances, fact is compared via the basic
pattern-matching operator.
    # File lib/puppet/provider.rb
291 def self.fact_match(fact, values)
292   fact_val = Facter.value(fact).to_s.downcase
293   if fact_val.empty?
294     return false
295   else
296     values = [values] unless values.is_a?(Array)
297     values.any? do |value|
298       if value.is_a?(Regexp)
299         fact_val =~ value
300       else
301         fact_val.intern == value.to_s.downcase.intern
302       end
303     end
304   end
305 end
feature_match(value) click to toggle source
    # File lib/puppet/provider.rb
307 def self.feature_match(value)
308   Puppet.features.send(value.to_s + "?")
309 end
has_command(name, path, &block) click to toggle source

Creates a convenience method for invocation of a command.

This generates a Provider method that allows easy execution of the command. The generated method may take arguments that will be passed through to the executable as the command line arguments when it is invoked.

@example Use it like this:

has_command(:echo, "/bin/echo")
def some_method
  echo("arg 1", "arg 2")
end

@comment the . . . below is intentional to avoid the three dots to become an illegible ellipsis char. @example . . . or like this

has_command(:echo, "/bin/echo") do
  is_optional
  environment :HOME => "/var/tmp", :PWD => "/tmp"
end

@param name [Symbol] The name of the command (will become the name of the generated method that executes the command) @param path [String] The path to the executable for the command @yield [ ] A block that configures the command (see {Puppet::Provider::Command}) @comment a yield [ ] produces {|| …} in the signature, do not remove the space. @note the name ´has_command´ looks odd in an API context, but makes more sense when seen in the internal

DSL context where a Provider is declaratively defined.

@api public

    # File lib/puppet/provider.rb
201 def self.has_command(name, path, &block)
202   name = name.intern
203   command = CommandDefiner.define(name, path, self, &block)
204 
205   @commands[name] = command.executable
206 
207   # Now define the class and instance methods.
208   create_class_and_instance_method(name) do |*args|
209     return command.execute(*args)
210   end
211 end
initvars() click to toggle source

Initializes defaults and commands (i.e. clears them). @return [void]

    # File lib/puppet/provider.rb
350 def self.initvars
351   @defaults = []
352   @notdefaults = []
353   @commands = {}
354 end
instances() click to toggle source

Returns a list of system resources (entities) this provider may/can manage. This is a query mechanism that lists entities that the provider may manage on a given system. It is is directly used in query services, but is also the foundation for other services; prefetching, and purging.

As an example, a package provider lists all installed packages. (In contrast, the File provider does not list all files on the file-system as that would make execution incredibly slow). An implementation of this method should be made if it is possible to quickly (with a single system call) provide all instances.

An implementation of this method should only cache the values of properties if they are discovered as part of the process for finding existing resources. Resource properties that require additional commands (than those used to determine existence/identity) should be implemented in their respective getter method. (This is important from a performance perspective; it may be expensive to compute, as well as wasteful as all discovered resources may perhaps not be managed).

An implementation may return an empty list (naturally with the effect that it is not possible to query for manageable entities).

By implementing this method, it is possible to use the `resources´ resource type to specify purging of all non managed entities.

@note The returned instances are instance of some subclass of Provider, not resources. @return [Array<Puppet::Provider>] a list of providers referencing the system entities @abstract this method must be implemented by a subclass and this super method should never be called as it raises an exception. @raise [Puppet::DevError] Error indicating that the method should have been implemented by subclass. @see prefetch

    # File lib/puppet/provider.rb
383 def self.instances
384   raise Puppet::DevError, _("To support listing resources of this type the '%{provider}' provider needs to implement an 'instances' class method returning the current set of resources. We recommend porting your module to the simpler Resource API instead: https://puppet.com/search/docs?keys=resource+api") % { provider: self.name }
385 end
mk_resource_methods() click to toggle source

Creates getter- and setter- methods for each property supported by the resource type. Call this method to generate simple accessors for all properties supported by the resource type. These simple accessors lookup and sets values in the property hash. The generated methods may be overridden by more advanced implementations if something else than a straight forward getter/setter pair of methods is required. (i.e. define such overriding methods after this method has been called)

An implementor of a provider that makes use of `prefetch` and `flush` can use this method since it uses the internal `@property_hash` variable to store values. An implementation would then update the system state on a call to `flush` based on the current values in the `@property_hash`.

@return [void]

    # File lib/puppet/provider.rb
400 def self.mk_resource_methods
401   [resource_type.validproperties, resource_type.parameters].flatten.each do |attr|
402     attr = attr.intern
403     next if attr == :name
404     define_method(attr) do
405       if @property_hash[attr].nil?
406         :absent
407       else
408         @property_hash[attr]
409       end
410     end
411 
412     define_method(attr.to_s + "=") do |val|
413       @property_hash[attr] = val
414     end
415   end
416 end
new(resource = nil) click to toggle source

Creates a new provider that is optionally initialized from a resource or a hash of properties. If no argument is specified, a new non specific provider is initialized. If a resource is given it is remembered for further operations. If a hash is used it becomes the internal `@property_hash` structure of the provider - this hash holds the current state property values of system entities as they are being discovered by querying or other operations (typically getters).

@todo The use of a hash as a parameter needs a better explanation; why is this done? What is the intent? @param resource [Puppet::Resource, Hash] optional resource or hash

    # File lib/puppet/provider.rb
519 def initialize(resource = nil)
520   if resource.is_a?(Hash)
521     # We don't use a duplicate here, because some providers (ParsedFile, at least)
522     # use the hash here for later events.
523     @property_hash = resource
524   elsif resource
525     @resource = resource
526     @property_hash = {}
527   else
528     @property_hash = {}
529   end
530 end
notdefaultfor(hash) click to toggle source
    # File lib/puppet/provider.rb
323 def self.notdefaultfor(hash)
324   @notdefaults << hash
325 end
optional_commands(hash) click to toggle source

Defines optional commands. Since Puppet 2.7.8 this is typically not needed as evaluation of provider suitability is lazy (when a resource is evaluated) and the absence of commands that will be present after other resources have been applied no longer needs to be specified as optional. @param [Hash{String => String}] hash Named commands that the provider will

be executing on the system. Each command is specified with a name and the path of the executable.

(@see has_command) @see commands @api public

    # File lib/puppet/provider.rb
167 def self.optional_commands(hash)
168   hash.each do |name, target|
169     has_command(name, target) do
170       is_optional
171     end
172   end
173 end
some_default_match(defaultlist) click to toggle source
    # File lib/puppet/provider.rb
271 def self.some_default_match(defaultlist)
272   defaultlist.find do |default|
273     default.all? do |key, values|
274       case key
275         when :feature
276           feature_match(values)
277         else
278           fact_match(key, values)
279       end
280     end
281   end
282 end
source() click to toggle source

@return [String] Returns the data source, which is the provider name if no other source has been set. @todo Unclear what “the source” is used for?

    # File lib/puppet/provider.rb
439 def self.source
440   @source ||= self.name
441 end
specificity() click to toggle source

@return [Integer] Returns a numeric specificity for this provider based on how many requirements it has

and number of _ancestors_. The higher the number the more specific the provider.

The number of requirements is based on the hash size of the matching {Provider.defaultfor}.

The ancestors is the Ruby Module::ancestors method and the number of classes returned is used to boost the score. The intent is that if two providers are equal, but one is more “derived” than the other (i.e. includes more classes), it should win because it is more specific). @note Because of how this value is

calculated there could be surprising side effects if a provider included an excessive amount of classes.
    # File lib/puppet/provider.rb
337 def self.specificity
338   # This strange piece of logic attempts to figure out how many parent providers there
339   # are to increase the score. What is will actually do is count all classes that Ruby Module::ancestors
340   # returns (which can be other classes than those the parent chain) - in a way, an odd measure of the
341   # complexity of a provider).
342   match = default_match
343   length = match ? match.length : 0
344 
345   (length * 100) + ancestors.select { |a| a.is_a? Class }.length
346 end
supports_parameter?(param) click to toggle source

Returns true if the given attribute/parameter is supported by the provider. The check is made that the parameter is a valid parameter for the resource type, and then if all its required features (if any) are supported by the provider.

@param param [Class, Puppet::Parameter] the parameter class, or a parameter instance @return [Boolean] Returns whether this provider supports the given parameter or not. @raise [Puppet::DevError] if the given parameter is not valid for the resource type

    # File lib/puppet/provider.rb
451 def self.supports_parameter?(param)
452   if param.is_a?(Class)
453     klass = param
454   else
455     klass = resource_type.attrclass(param)
456     unless klass
457       raise Puppet::DevError, _("'%{parameter_name}' is not a valid parameter for %{resource_type}") % { parameter_name: param, resource_type: resource_type.name }
458     end
459   end
460   features = klass.required_features
461   return true unless features
462 
463   !!satisfies?(*features)
464 end

Private Class Methods

create_class_and_instance_method(name, &block) click to toggle source

This method is used to generate a method for a command. @return [void] @api private

    # File lib/puppet/provider.rb
424 def self.create_class_and_instance_method(name, &block)
425   unless singleton_class.method_defined?(name)
426     meta_def(name, &block)
427   end
428 
429   unless method_defined?(name)
430     define_method(name) do |*args|
431       self.class.send(name, *args)
432     end
433   end
434 end

Public Instance Methods

<=>(other) click to toggle source

Compares this provider against another provider. Comparison is only possible with another provider (no other class). The ordering is based on the class name of the two providers.

@return [-1,0,+1, nil] A comparison result -1, 0, +1 if this is before other, equal or after other. Returns

nil oif not comparable to other.

@see Comparable

    # File lib/puppet/provider.rb
577 def <=>(other)
578   # We can only have ordering against other providers.
579   return nil unless other.is_a? Puppet::Provider
580   # Otherwise, order by the providers class name.
581   return self.class.name <=> other.class.name
582 end
clear() click to toggle source

Clears this provider instance to allow GC to clean up.

    # File lib/puppet/provider.rb
493 def clear
494   @resource = nil
495 end
command(name) click to toggle source

(see command)

    # File lib/puppet/provider.rb
498 def command(name)
499   self.class.command(name)
500 end
execpipe(*args, &block) click to toggle source

Convenience methods - see class method with the same name. @return (see self.execpipe)

    # File lib/puppet/provider.rb
111 def execpipe(*args, &block)
112   Puppet::Util::Execution.execpipe(*args, &block)
113 end
execute(*args) click to toggle source

Convenience methods - see class method with the same name. @return (see self.execute)

    # File lib/puppet/provider.rb
100 def execute(*args)
101   Puppet::Util::Execution.execute(*args)
102 end
get(param) click to toggle source

Returns the value of a parameter value, or `:absent` if it is not defined. @param param [Puppet::Parameter] the parameter to obtain the value of @return [Object] the value of the parameter or `:absent` if not defined.

    # File lib/puppet/provider.rb
506 def get(param)
507   @property_hash[param.intern] || :absent
508 end
inspect() click to toggle source

@return [String] Returns a human readable string with information about the resource and the provider.

    # File lib/puppet/provider.rb
564 def inspect
565   to_s
566 end
name() click to toggle source

Returns the name of the resource this provider is operating on. @return [String] the name of the resource instance (e.g. the file path of a File). @raise [Puppet::DevError] if no resource is set, or no name defined.

    # File lib/puppet/provider.rb
536 def name
537   n = @property_hash[:name]
538   if n
539     return n
540   elsif self.resource
541     resource.name
542   else
543     raise Puppet::DevError, _("No resource and no name in property hash in %{class_name} instance") % { class_name: self.class.name }
544   end
545 end
set(params) click to toggle source

Sets the given parameters values as the current values for those parameters. Other parameters are unchanged. @param [Array<Puppet::Parameter>] params the parameters with values that should be set @return [void]

    # File lib/puppet/provider.rb
552 def set(params)
553   params.each do |param, value|
554     @property_hash[param.intern] = value
555   end
556 end
to_s() click to toggle source

@return [String] Returns a human readable string with information about the resource and the provider.

    # File lib/puppet/provider.rb
559 def to_s
560   "#{@resource}(provider=#{self.class.name})"
561 end