========== Blueprints ========== Blueprints are python classes that dynamically build CloudFormation templates. Where you would specify a raw Cloudformation template in a stack using the ``template_path`` key, you instead specify a blueprint python file using the ``class_path`` key. Traditionally blueprints are built using troposphere_, but that is not absolutely necessary. You are encouraged to check out the library of publicly shared Blueprints in the stacker_blueprints_ package. Making your own should be easy, and you can take a lot of examples from stacker_blueprints_. In the end, all that is required is that the Blueprint is a subclass of *stacker.blueprints.base* and it have the following methods: .. code-block:: python # Initializes the blueprint def __init__(self, name, context, mappings=None): # Updates self.template to create the actual template def create_template(self): # Returns a tuple: (version, rendered_template) def render_template(self): Variables ========= A Blueprint can define a ``VARIABLES`` property that defines the variables it accepts from the `Config Variables `_. ``VARIABLES`` should be a dictionary of ``: ``. The variable definition should be a dictionary which supports the following optional keys: **type:** The type for the variable value. This can either be a native python type or one of the `Variable Types`_. **default:** The default value that should be used for the variable if none is provided in the config. **description:** A string that describes the purpose of the variable. **validator:** An optional function that can do custom validation of the variable. A validator function should take a single argument, the value being validated, and should return the value if validation is successful. If there is an issue validating the value, an exception (``ValueError``, ``TypeError``, etc) should be raised by the function. **no_echo:** Only valid for variables whose type subclasses ``CFNType``. Whether to mask the parameter value whenever anyone makes a call that describes the stack. If you set the value to true, the parameter value is masked with asterisks (*****). **allowed_values:** Only valid for variables whose type subclasses ``CFNType``. The set of values that should be allowed for the CloudFormation Parameter. **allowed_pattern:** Only valid for variables whose type subclasses ``CFNType``. A regular expression that represents the patterns you want to allow for the CloudFormation Parameter. **max_length:** Only valid for variables whose type subclasses ``CFNType``. The maximum length of the value for the CloudFormation Parameter. **min_length:** Only valid for variables whose type subclasses ``CFNType``. The minimum length of the value for the CloudFormation Parameter. **max_value:** Only valid for variables whose type subclasses ``CFNType``. The max value for the CloudFormation Parameter. **min_value:** Only valid for variables whose type subclasses ``CFNType``. The min value for the CloudFormation Parameter. **constraint_description:** Only valid for variables whose type subclasses ``CFNType``. A string that explains the constraint when the constraint is violated for the CloudFormation Parameter. Variable Types ============== Any native python type can be specified as the ``type`` for a variable. You can also use the following custom types: TroposphereType --------------- The ``TroposphereType`` can be used to generate resources for use in the blueprint directly from user-specified configuration. Which case applies depends on what ``type`` was chosen, and how it would be normally used in the blueprint (and CloudFormation in general). Resource Types ^^^^^^^^^^^^^^ When ``type`` is a `Resource Type`_, the value specified by the user in the configuration file must be a dictionary, but with two possible structures. When ``many`` is disabled, the top-level dictionary keys correspond to parameters of the ``type`` constructor. The key-value pairs will be used directly, and one object will be created and stored in the variable. When ``many`` is enabled, the top-level dictionary *keys* are resource titles, and the corresponding *values* are themselves dictionaries, to be used as parameters for creating each of multiple ``type`` objects. A list of those objects will be stored in the variable. Property Types ^^^^^^^^^^^^^^ When ``type`` is a `Property Type`_ the value specified by the user in the configuration file must be a dictionary or a list of dictionaries. When ``many`` is disabled, the top-level dictionary keys correspond to parameters of the ``type`` constructor. The key-value pairs will be used directly, and one object will be created and stored in the variable. When ``many`` is enabled, a list of dictionaries is expected. For each element, one corresponding call will be made to the ``type`` constructor, and all the objects produced will be stored (also as a list) in the variable. Optional variables ^^^^^^^^^^^^^^^^^^ In either case, when ``optional`` is enabled, the variable may have no value assigned, or be explicitly assigned a null value. When that happens the variable's final value will be ``None``. Example ^^^^^^^ Below is an annotated example: .. code-block:: python from stacker.blueprints.base import Blueprint from stacker.blueprints.variables.types import TroposphereType from troposphere import s3, sns class Buckets(Blueprint): VARIABLES = { # Specify that Buckets will be a list of s3.Bucket types. # This means the config should a dictionary of dictionaries # which will be converted into troposphere buckets. "Buckets": { "type": TroposphereType(s3.Bucket, many=True), "description": "S3 Buckets to create.", }, # Specify that only a single bucket can be passed. "SingleBucket": { "type": TroposphereType(s3.Bucket), "description": "A single S3 bucket", }, # Specify that Subscriptions will be a list of sns.Subscription types. # Note: sns.Subscription is the property type, not the standalone # sns.SubscriptionResource. "Subscriptions": { "type": TroposphereType(sns.Subscription, many=True), "description": "Multiple SNS subscription designations" }, # Specify that only a single subscription can be passed, and that it # is made optional. "SingleOptionalSubscription": { "type": TroposphereType(sns.Subscription, optional=True), "description": "A single, optional SNS subscription designation" } } def create_template(self): t = self.template variables = self.get_variables() # The Troposphere s3 buckets have already been created when we access variables["Buckets"], we just need to add them as resources to the template. [t.add_resource(bucket) for bucket in variables["Buckets"]] # Add the single bucket to the template. You can use `Ref(single_bucket)` to pass CloudFormation references to the bucket just as you would with any other Troposphere type. single_bucket = variables["SingleBucket"] t.add_resource(single_bucket) subscriptions = variables["Subscriptions"] optional_subscription = variables["SingleOptionalSubscription"] # Handle it in some special way... if optional_subscription is not None: subscriptions.append(optional_subscription) t.add_resource(sns.Topic( TopicName="one-test", Subscriptions=)) t.add_resource(sns.Topic( TopicName="another-test", Subscriptions=subscriptions)) A sample config for the above: .. code-block:: yaml stacks: - name: buckets class_path: path.to.above.Buckets variables: Buckets: # resource name (title) that will be added to CloudFormation. FirstBucket: # name of the s3 bucket BucketName: my-first-bucket SecondBucket: BucketName: my-second-bucket SingleBucket: # resource name (title) that will be added to CloudFormation. MySingleBucket: BucketName: my-single-bucket Subscriptions: - Endpoint: one-lambda Protocol: lambda - Endpoint: another-lambda Protocol: lambda # The following could be ommited entirely SingleOptionalSubscription: Endpoint: a-third-lambda Protocol: lambda CFNType ------- The ``CFNType`` can be used to signal that a variable should be submitted to CloudFormation as a Parameter instead of only available to the Blueprint when rendering. This is useful if you want to leverage AWS- Specific Parameter types (e.g. ``List``) or Systems Manager Parameter Store values (e.g. ``AWS::SSM::Parameter::Value``). See ``stacker.blueprints.variables.types`` for available subclasses of the ``CFNType``. Example ^^^^^^^ Below is an annotated example: .. code-block:: python from stacker.blueprints.base import Blueprint from stacker.blueprints.variables.types import ( CFNString, EC2AvailabilityZoneNameList, ) class SampleBlueprint(Blueprint): VARIABLES = { "String": { "type": str, "description": "Simple string variable", }, "List": { "type": list, "description": "Simple list variable", }, "CloudFormationString": { "type": CFNString, "description": "A variable which will create a CloudFormation Parameter of type String", }, "CloudFormationSpecificType": { "type": EC2AvailabilityZoneNameList, "description": "A variable which will create a CloudFormation Parameter of type List" }, } def create_template(self): t = self.template # `get_variables` returns a dictionary of : . For the subclasses of `CFNType`, the values are instances of `CFNParameter` which have a `ref` helper property which will return a troposphere `Ref` to the parameter name. variables = self.get_variables() t.add_output(Output("StringOutput", variables["String"])) # variables["List"] is a native list for index, value in enumerate(variables["List"]): t.add_output(Output("ListOutput:{}".format(index), value)) # `CFNParameter` values (which wrap variables with a `type` that is a `CFNType` subclass) can be converted to troposphere `Ref` objects with the `ref` property t.add_output(Output("CloudFormationStringOutput", variables["CloudFormationString"].ref)) t.add_output(Output("CloudFormationSpecificTypeOutput", variables["CloudFormationSpecificType"].ref)) Utilizing Stack name within your Blueprint ========================================== Sometimes your blueprint might want to utilize the already existing stack name within your blueprint. Stacker provides access to both the fully qualified stack name matching what’s shown in the CloudFormation console, in addition to the stacks short name you have set in your YAML config. Referencing Fully Qualified Stack name -------------------------------------- The fully qualified name is a combination of the Stacker namespace + the short name (what you set as `name` in your YAML config file). If your stacker namespace is `StackerIsCool` and the stacks short name is `myAwesomeEC2Instance`, the fully qualified name would be: ``StackerIsCool-myAwesomeEC2Instance`` To use this in your blueprint, you can get the name from context. The ``self.context.get_fqn(self.name)`` Referencing the Stack short name -------------------------------- The Stack short name is the name you specified for the stack within your YAML config. It does not include the namespace. If your stacker namespace is `StackerIsCool` and the stacks short name is `myAwesomeEC2Instance`, the short name would be: ``myAwesomeEC2Instance`` To use this in your blueprint, you can get the name from self.name: ``self.name`` Example ^^^^^^^ Below is an annotated example creating a security group: .. code-block:: python # we are importing Ref to allow for CFN References in the EC2 resource. Tags # will be used to set the Name tag from troposphere import Ref, ec2, Tags from stacker.blueprints.base import Blueprint # CFNString is imported to allow for stand alone stack use from stacker.blueprints.variables.types import CFNString class SampleBlueprint(Blueprint): # VpcId set here to allow for blueprint to be reused VARIABLES = { "VpcId": { "type": CFNString, "description": "The VPC to create the Security group in", } } def create_template(self): template = self.template # Assigning the variables to a variable variables = self.get_variables() # now adding a SecurityGroup resource named `SecurityGroup` to the CFN template template.add_resource( ec2.SecurityGroup( "SecurityGroup", # Refering the VpcId set as the varible VpcId=variables['VpcId'].ref, # Setting the group description as the fully qualified name GroupDescription=self.context.get_fqn(self.name), # setting the Name tag to be the stack short name Tags=Tags( Name=self.name ) ) ) Testing Blueprints ================== When writing your own blueprints its useful to write tests for them in order to make sure they behave the way you expect they would, especially if there is any complex logic inside. To this end, a sub-class of the `unittest.TestCase` class has been provided: `stacker.blueprints.testutil.BlueprintTestCase`. You use it like the regular TestCase class, but it comes with an addition assertion: `assertRenderedBlueprint`. This assertion takes a Blueprint object and renders it, then compares it to an expected output, usually in `tests/fixtures/blueprints`. Examples of using the `BlueprintTestCase` class can be found in the stacker_blueprints repo. For example, see the tests used to test the `Route53 DNSRecords Blueprint`_ and the accompanying `output results`_: Yaml (stacker) format tests --------------------------- In order to wrap the `BlueprintTestCase` tests in a format similar to stacker's stack format, the `YamlDirTestGenerator` class is provided. When subclassed in a directory, it will search for yaml files in that directory with certain structure and execute a test case for it. As an example: .. code-block:: yaml --- namespace: test stacks: - name: test_stack class_path: stacker_blueprints.s3.Buckets variables: var1: val1 When run from tests, this will create a template fixture file called test_stack.json containing the output from the `stacker_blueprints.s3.Buckets` template. Examples of using the `YamlDirTestGenerator` class can be found in the stacker_blueprints repo. For example, see the tests used to test the `s3.Buckets`_ class and the accompanying `fixture`_. These are generated from a `subclass of YamlDirTestGenerator`_. .. _troposphere: https://github.com/cloudtools/troposphere .. _stacker_blueprints: https://github.com/cloudtools/stacker_blueprints .. _Route53 DNSRecords Blueprint: https://github.com/cloudtools/stacker_blueprints/blob/master/tests/test_route53.py .. _output results: https://github.com/cloudtools/stacker_blueprints/tree/master/tests/fixtures/blueprints .. _Resource Type: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-template-resource-type-ref.html .. _Property Type: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-product-property-reference.html .. _s3.Buckets: https://github.com/cloudtools/stacker_blueprints/blob/master/tests/test_s3.yaml .. _fixture: https://github.com/cloudtools/stacker_blueprints/blob/master/tests/fixtures/blueprints/s3_static_website.json .. _subclass of YamlDirTestGenerator: https://github.com/cloudtools/stacker_blueprints/blob/master/tests/__init__.py