# NAME Cfn - An object model for CloudFormation documents # DESCRIPTION This module helps parse, manipulate, validate and generate CloudFormation documents in JSON and YAML formats (see stability section for more information on YAML). It creates an object model of a CloudFormation template so you can work with the document as a set of objects. See [https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/template-anatomy.html](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/template-anatomy.html) for more information. It provides full blown objects for all know CloudFormation resources. See [https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-template-resource-type-ref.html](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-template-resource-type-ref.html) for a list of all resource types. These objects live in the `Cfn::Resource` namespace. The module provides a set of objects representing each piece of CloudFormation. Following is a list of all object types in the distribution: # Cfn object The `Cfn` class is the "root" of a CloudFormation document. It represents an entire CloudFormation document. It has attributes and methods to access the parts of a CloudFormation document. use Cfn; my $cfn = Cfn->new; $cfn->addResource('MyRes' => ...); my $res = $cfn->Resource('MyRes'); ## Constructors ### new(Resources => { ... }, Outputs => { }, ...) The default Moose constructor. You can initialize an empty document like this: my $cfn = Cfn->new; print $cfn->as_json; ### from\_hashref CloudFormation documents resemble Perl HashRefs (since they're just JSON datastructures). This method converts a hashref that represents a CloudFormation document into a Cfn object. use Data::Dumper; my $cfn = Cfn->from_hashref({ Resources => { R1 => { Type => '...', Properties => { ... } } } }); print Dumper($cfn->Resource('R1'); ### from\_json This method creates a Cfn object from a JSON string that contains a CloudFormation document in JSON format ### from\_yaml This method creates a Cfn object from a YAML string that contains a CloudFormation document in YAML format ## Attributes ### json When serializing to JSON with `as_json`, the encode method on this object is called passing the documents hashref representation. By default the JSON generated is "ugly", that is, all in one line, but in canonical form (so a given serialization always has attributes in the same order). You can specify your own JSON serializer to control how JSON is generated: my $cfn = Cfn->new(json => JSON->new->canonical->pretty); ... print $cfn->as_json; ### yaml Holds a configured `YAML::PP` parser for use when serializing and deserializing to and from YAML. Methods `load_string` and `dump_string` are called when needed from convert the object model to a YAML document, and to convert a YAML document to a datastructure that can later be coerced into the object model. ### cfn\_options A `Cfn::Internal::Options` object instance that controls how the as\_hashref method converts the Cfn object to a datastructure suitable for CloudFormation (only HashRefs, ArrayRefs and Scalars). You can specify your own options as a hashref with the attributes to `Cfn::Internal::Options` in the constructor. my $cfn = Cfn->new(cfn_options => { custom_resource_rename => 1 }); ... print Dumper($cfn->as_hashref); See the `Cfn::Internal::Options` object for more details ### AWSTemplateFormatVersion A string with the value of the AWSTemplateFormatVersion field of the CloudFormation document. Can be undef. ### Description A string with the value of the Description field of the CloudFormation document. Can be undef. ### Transform An ArrayRef of Strings with the values of the Transform field of the CloudFormation document. Can be undef. ### Parameters A HashRef of `Cfn::Parameter` objects. The keys are the name of the Parameters. There are a set of convenience methods for accessing this attribute: $cfn->Parameter('ParamName') # returns a Cfn::Parameter or undef $cfn->ParameterList # returns a list of the parameters in the document $cfn->ParameterCount # returns the number of parameters in the document ### Mappings A HashRef of `Cfn::Mapping` objects. The keys are the name of the Mappings. There are a set of convenience methods for accessing this attribute: $cfn->Mapping('MappingName') # returns a Cfn::Parameter or undef $cfn->MappingList # returns a list of the mappings in the document $cfn->MappingCount # returns the number of mappings in the document ### Conditions A HashRef of `Cfn::Condition` objects. The keys are the name of the Mappings. There are a set of convenience methods for accessing this attribute: $cfn->Mapping('MappingName') # returns a Cfn::Mapping or undef $cfn->MappingList # returns a list of the mappings in the document $cfn->MappingCount # returns the number of mappings in the document ### Resources A HashRef of `Cfn::Resource` objects. The keys are the name of the Resources. There are a set of convenience methods for accessing this attribute: $cfn->Resource('ResourceName') # returns a Cfn::Resource or undef $cfn->ResourceList # returns a list of the resources in the document $cfn->ResourceCount # returns the number of resources in the document ### Outputs A HashRef of `Cfn::Output` objects. The keys are the name of the Outputs. There are a set of convenience methods for accessing this attribute: $cfn->Output('OutputName') # returns a Cfn::Output or undef $cfn->OutputList # returns a list of the outputs in the document $cfn->OutputCount # returns the number of outputs in the document ### Metadata A HashRef of `Cfn::Value` or subclasses of `Cfn::Value`. Represents the Metadata key of the CloudFormation document. There are a set of convenience methods for accessing this attribute: $cfn->Metadata('MetadataName') # returns a Cfn::Metadata or undef $cfn->MetadataList # returns a list of keys in the document Metadata $cfn->MetadataCount # returns the number of keys in the document Metadata ## Methods ### as\_hashref Returns a Perl HashRef representation of the CloudFormation document. This HashRef has no objects in it. It is suitable for converting to JSON and passing to CloudFormation `as_hashref` triggers the serialization process of the document, which scans the whole object model asking it's components to serialize (calling their `as_hashref`). Objects can decide how they serialize to a hashref. When `$cfn-`as\_hashref> is invoked, all the dynamic values in the Cfn object will be called with the `$cfn` instance as the first parameter to their subroutine $cfn->addResource('R1', 'AWS::IAM::User', Path => Cfn::DynamicValue->new(Value => sub { my $cfn = shift; return $cfn->ResourceCount + 41 })); $cfn->as_hashref->{ Resources }->{ R1 }->{ Properties }->{ Path } # == 42 ### as\_json Returns a JSON representation of the current instance ### as\_yaml Returns a YAML representation of the current instance ### path\_to($path) Given a path in the format `'Resources.R1.Properties.PropName'` it will return the value stored in PropName of the resource R1. Use `'Resource.R1.Properties.ArrayProp.0'` to access Arrays. ### resolve\_dynamicvalues Returns a new `Cfn` object with all `Cfn::DynamicValues` resolved. ### ResourcesOfType($type) Returns a list of all the Resources of a given type. foreach my $iam_user ($cfn->ResourcesOfType('AWS::IAM::User')) { ... } ### addParameter($name, $object) Adds an already instanced `Cfn::Parameter` object. Throws an exception if the parameter already exists. $cfn->addParameter('P1', Cfn::Parameter->new(Type => 'String', MaxLength => 5)); ### addParameter($name, $type, %properties) Adds a named parameter to the document with the specified type and properties. See `Cfn::Parameter` for available properties. Throws an exception if the parameter already exists. $cfn->addParameter('P1', 'String', MaxLength => 5); ### addMapping($name, $object\_or\_hashref); Adds a named mapping to the mappings of the document. The second parameter can be a `Cfn::Mapping` object or a HashRef that will be coerced to a `Cfn::Mapping` object $cfn->addMapping('amis', { 'eu-west-1' => 'ami-12345678' }); $cfn->addMapping('amis', Cfn::Mapping->new(Map => { 'eu-west-1' => 'ami-12345678' })); # $cfn->Mapping('amis') is a Cfn::Mapping object ### addOutput($name, $object) Adds an already instanced `Cfn::Output` object. Throws an exception if the output already exists. $cfn->addParameter('O1', Cfn::Output->new(Value => { Ref => 'R1' }); ### addOutput($name, $output\[, %output\_attributes\]); Adds a named output to the document. See `Cfn::Output` for available output\_attributes. Throws an exception if the output already exists. $cfn->addParameter('O1', { Ref => 'R1' }); $cfn->addParameter('O1', { Ref => 'R1' }, Description => 'Bla bla'); ### addCondition($name, $value) Adds a named condition to the document. The value parameter should be a HashRef that expresses a CloudFormation condition. See [https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/conditions-section-structure.html](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/conditions-section-structure.html) ### addResource($name, $object) Adds a named resource to the document. $object has to be an instance of a subclass of `Cfn::Resource`. Throws an exception if a resource already exists with that name. ### addResource($name, $type, %properties) Adds a named resource to the document, putting the specified properties in the resources properties. See subclasses of `Cfn::Resource` for more details. $cfn->addResource('R1', 'AWS::IAM::User'); $cfn->addResource('R2', 'AWS::IAM::User', Path => '/'); # $cfn->Resource('R2')->Properties->Path is '/' Throws an exception if a resource already exists with that name. ### addResource($name, $name, $properties, $resource\_attributes) Adds a named resource to the document. properties and resource\_attributes are hashrefs. $cfn->addResource('R3', 'AWS::IAM::User', { Path => '/' }); # $cfn->Resource('R3')->Properties->Path is '/' $cfn->addResource('R3', 'AWS::IAM::User', { Path => '/' }, { DependsOn => [ 'R2' ] }); # $cfn->Resource('R3')->DependsOn->[0] is 'R2' Throws an exception if a resource already exists with that name. ### addResourceMetadata($name, %metadata); Adds metadata to the Metadata attribute of a Resource. $cfn->addResourceMetadata('R1', MyMetadataKey1 => 'Value'); # $cfn->Resource('R1')->Metadata->{ MyMedataKey1 } is 'Value' ### addDependsOn($resource\_name, $depends\_on1, $depends\_on2) $cfn->addDependsOn('R1', 'R2', 'R3'); # $cfn->Resource('R1')->DependsOn is [ 'R2', 'R3' ] ### addDeletionPolicy($resource\_name) Adds a DeletionPolicy to the resource. L ### addUpdatePolicy($resource\_name) Adds an UpdatePolicy to the resource. L # Cfn::Value Is a base class for the attributes of Cloudformation values. In Cloudformation you can find that in a resources attributes you can place functions, references, etc. "Attribute": "hello" "Attribute": { "Ref": "R1" } "Attribute": { "Fn::GetAtt": [ "R1", "InstanceId" ] } All value objects in the Cfn toolkit subclass `Cfn::Value` as a common ancestor. Once the object model is built, you can find that a $cfn->addResource('R1', 'AWS::IAM::User', Path => '/'); # $cfn->Resource('R1')->Properties->Path is a Cfn::Value::Primitive $cfn->addResource('R1', 'AWS::IAM::User', Path => { 'Fn::Join' => [ '/', { Ref => 'Param1' }, '/' ] }); # $cfn->Resource('R1')->Properties->Path is a Cfn::Value::Function::Join All `Cfn::Value` subclasses have to implement an `as_hashref` method that returns a HashRef suitable for conversion to JSON for CloudFormation. A attributes of objects that hold `Cfn::Value` subclasses should enable coercion of the attribute so that plain hashrefs can be coerced into the appropiate Cfn::Value objects Here is a Hierarchy of the different Cfn::Value descendant object: Cfn::Value |--Cfn::DynamicValue |--Cfn::Value::Function | |--Cfn::Value::Function::Condition | |--Cfn::Value::Function::Ref | |--Cfn::Value::Function::PseudoParameter | |--Cfn::Value::Function::GetAtt |--Cfn::Value::Array |--Cfn::Value::Hash |--Cfn::Value::Primitive | |--Cfn::Boolean | |--Cfn::Integer | |--Cfn::Long | |--Cfn::String | |--Cfn::Double | |--Cfn::Timestamp |--Cfn::Value::TypedValue ## Cfn::DynamicValue The `Value` attribute of this object is a CodeRef that get's called when as\_hashref is called. $cfn->addResource('R1', 'AWS::IAM::User', Path => Cfn::DynamicValue->new(Value => sub { return 'Hello' }); $cfn->path_to('Resources.R1.Properties.Path') # isa Cfn::DynamicValue $cfn->path_to('Resources.R1.Properties.Path')->as_hashref # eq 'Hello' When `$cfn-`as\_hashref> is invoked, all the dynamic values in the Cfn object will be called with the `$cfn` instance as the first parameter to their subroutine $cfn->addResource('R1', 'AWS::IAM::User', Path => Cfn::DynamicValue->new(Value => sub { my $cfn = shift; return $cfn->ResourceCount + 41 })); $cfn->as_hashref->{ Resources }->{ R1 }->{ Properties }->{ Path } # == 42 ## Cfn::Value::Function All function statements derive from Cfn::Value::Function. The name of the function can be found in the `Function` attribute It's value can be found in the `Value` attribute ## Cfn::Value::Function::Ref Object of this class represent a CloudFormation Ref. You can find the value of the reference in the `Value` attribute. Note that the Value attribute contains another `Cfn::Value`. It derives from `Cfn::Value::Function` $cfn->addResource('R1', 'AWS::IAM::User', Path => { Ref => 'AWS::Region' }); $cfn->path_to('Resources.R1.Properties.Path') # isa Cfn::Value::Function::PseudoParameter ## Cfn::Value::Function::PseudoParameter This is a subclass of `Cfn::Value::Function::Ref` used to hold what CloudFormation calls PseudoParameters. $cfn->addResource('R1', 'AWS::IAM::User', Path => { Ref => 'AWS::Region' }); $cfn->path_to('Resources.R1.Properties.Path') # isa Cfn::Value::Function::PseudoParam ## Cfn::Value::Function::GetAtt This class represents 'Fn::GetAtt' nodes in the object model. It's a subclass of `Cfn::Value::Function`. $cfn->addResource('R1', 'AWS::IAM::User', Path => { 'Fn::GetAtt' => [ 'R1', 'InstanceId' ] }); $cfn->path_to('Resources.R1.Properties.Path') # isa Cfn::Value::Function::GetAtt $cfn->path_to('Resources.R1.Properties.Path')->LogicalId # eq 'R1' $cfn->path_to('Resources.R1.Properties.Path')->Property # eq 'InstanceId' ## Cfn::Value::Array This class represents Arrays in the object model. It's `Value` property is an ArrayRef of `Cfn::Values` or `Cfn::Resource::Properties`. There is also a subtype called `Cfn::Value::ArrayOfPrimitives` that restricts the values in the array to `Cfn::Value::Primitive` types. ## Cfn::Value::Hash This class represents JSON objects whose keys are not defined beforehand (arbitrary keys). It's `Value` property is a HashRef of `Cfn::Value`s. ## Cfn::Value::Primitive This is a base class for any "simple" value (what the CloudFormation spec calls `PrimitiveType`). This classes `Value` attribute has no type constraint, so it actually accepts anything. This class is supposed to only be inherited from, specializing the `Value` attribute to a specific type. ## Cfn::Boolean Used to store and validate CloudFormation `Boolean` values. Has a `stringy` attribute that controls if `as_hashref` returns a string boolean `"true"` or `"false"` or a literal `true` or `false`, since these two boolean forms are accepted in CloudFormation. ## Cfn::Integer Used to store and validate CloudFormation `Integer` values. ## Cfn::Long Used to store and validate CloudFormation `Long` values. ## Cfn::String Used to store and validate CloudFormation `String` values. ## Cfn::Double Used to store and validate CloudFormation `Double` values. ## Cfn::Timestamp Used to store CloudFormation `Timestamp` values. Only validates that it's a string. ## Cfn::Value::TypedValue Used as a base class for structured properties of CloudFormation resources. The subclasses of TypedValue declare Moose attributes that are used to represent and validate that the properties of a CloudFormation resource are well formed. # Cfn::Resource Represents a CloudFormation Resource. All `Cfn::Resource::*` objects (like [Cfn::Resource::AWS::IAM::User](https://metacpan.org/pod/Cfn%3A%3AResource%3A%3AAWS%3A%3AIAM%3A%3AUser)) use `Cfn::Resource` as a base class. ## Attributes for Cfn::Resource objects The attributes for Cfn::Resource objects map to the attributes of CloudFormation Resources. { "Type": "AWS::IAM::User", "Properties": { ... }, "DependsOn": "R2" ... } ### Type Holds a string with the type of the resource. ### Properties Holds a `Cfn::Value::Properties` subclass with the properties of the resource. ### DeletionPolicy Holds the DeletionPolicy. Validates that the DeletionPolicy is valid ### DependsOn Can hold either a single string or an arrayref of strings. This is because CloudFormation supports `DependsOn` in these two forms. Method `DependsOnList` provides a uniform way of accessing the DependsOn attribute. ### Condition Can hold a String identifying the Condition property of a resource ### Metadata Is a `Cfn::Value::Hash` for the resources metadata ### UpdatePolicy Holds the UpdatePolicy. Validates that the UpdatePolicy is valid ### CreationPolicy HashRef with the CreationPolicy. Doesn't validate CreationPolicies. ## Methods for Cfn::Resource objects ### AttributeList Returns an ArrayRef of attributes that can be recalled in CloudFormation via `Fn::GetAtt`. Can also be retrieved as a class method `Cfn::Resource::...-`AttributeList> ### supported\_regions Returns an ArrayRef of the AWS regions where the resource can be provisioned. Can also be retrieved as a class method `Cfn::Resource::...-`supported\_regions> ### DependsOnList Returns a list of dependencies from the DependsOn attribute (it doesn't matter if the DependsOn attribute is a String or an ArrayRef of Strings. my @deps = $cfn->Resource('R1')->DependsOnList; ### hasAttribute($attribute) Returns true if the specified attribute is in the `AttributeList`. Note that some resources (AWS::CloudFormation::CustomResource) can return true for values that are not in AttributeList ### as\_hashref Like `Cfn::Values`, as\_hashref returns a HashRef representation of the object ready for transforming to JSON. # Cfn::Resource::Properties A base class for the objects that the `Properties` attribute of `Cfn::Resource`s hold. Subclasses of `Cfn::Resource::Properties` are used to validate and represent the properties of resources inside the object model. See [Cfn::Resource::Properties::AWS::IAM::User](https://metacpan.org/pod/Cfn%3A%3AResource%3A%3AProperties%3A%3AAWS%3A%3AIAM%3A%3AUser) for an example. Each subclass of `Cfn::Resource::Properties` has to have attributes to hold the values of the properties of the resource it represents. # Cfn::Parameter Represents a Parameter in a CloudFormation document my $cfn = Cfn->new; $cfn->addParameter('P1', 'String', Default => 5); $cfn->Parameter('P1')->Default # 5 $cfn->Parameter('P1')->NoEcho # undef ## Cfn::Parameter Attributes ### Type A string with the type of parameter. Validates that it's a CloudFormation supported parameter type. ### Default Holds the default value for the parameter ### NoEcho Holds the NoEcho property of the parameter ### AllowedValues An ArrayRef of the allowed values of the parameter ### AllowedPattern A String holding the pattern that the value of this parameter can take ### MaxLength, MinLength, MaxValue, MinValue Values holding the MaxLength, MinLength, MaxValue, MinValue of the parameter ### Description A string description of the parameter ### ConstraintDescription A string description of the constraint of the parameter # Cfn::Mapping This object represents the value of the `Mappings` key in a CloudFormation document. It has a `Map` attribute to hold the Mappings in the CloudFormation document. # Cfn::Output Represents an output object in a CloudFormation document ## Attributes for Cfn::Output objects "Outputs": { "Output1": { "Value": { "Ref": "Instance" } } } ### Value Holds the Value key of an output. Is a `Cfn::Value` ### Description Holds a String with the descrption of the output ### Condition Holds a String with the condition of the output ### Export Holds a HashRef with the export definition of the object ## Methods for Cfn::Output objects ### as\_hashref Returns a HashRef representation of the output that is convertible to JSON # STABILITY YAML support is recent, and due to the still evolving YAML::PP module, may break (altough the tests are there to detect that). This distribution will try to keep up as hard as it can with latest YAML::PP developments. # SEE ALSO [https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/template-anatomy.html](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/template-anatomy.html) This module kind of resembles troposphere (python): [https://github.com/cloudtools/troposphere](https://github.com/cloudtools/troposphere). # CLI utils This distribution includes a series of CLI utilities to help you with CloudFormation: ## cfn\_list\_resources \[STRING\] Lists all the resources supported by Cfn. If a string is specified, will filter the ones matching the STRING. ## cfn\_region\_matrix Displays a table of what resource types are supported in each region ## cfn\_region\_compatibility FILE Takes a cloudformation template and calculates in what regions it will be deployable ## cfn\_resource\_properties RESOURCE Outputs information about a resource type: properties accessible via Fn::GetAtt, region availability and it's whole property structure. # AUTHOR Jose Luis Martinez CAPSiDE jlmartinez@capside.com # Contributions Thanks to Sergi Pruneda, Miquel Ruiz, Luis Alberto Gimenez, Eleatzar Colomer, Oriol Soriano, Roi Vazquez for years of work on this module. TINITA for helping make the YAML support possible. First for the YAML::PP module, which is the only Perl module to support sufficiently modern YAML features, and also for helping me in the use of YAML::PP. # BUGS and SOURCE The source code is located here: [https://github.com/pplu/cfn-perl](https://github.com/pplu/cfn-perl) Please report bugs to: [https://github.com/pplu/cfn-perl/issues](https://github.com/pplu/cfn-perl/issues) # COPYRIGHT and LICENSE Copyright (c) 2013 by CAPSiDE This code is distributed under the Apache 2 License. The full text of the license can be found in the LICENSE file included with this module.