The following terms will be used through the rest of the Sceptre documentation:
The directory which stores the top level config directory.
Command Path The Stack or StackGroup that you want to execute a Sceptre command against. For example, if you want to launch
vpc.yamlin the example below the command path would be
. └── config └── dev ├── config.yaml └── vpc.yaml
Where as if you wanted to
account-1in the example below the command path would be
. └── config └── account-1 └── dev └── eu-west-1 ├── config.yaml └── vpc.yaml
Unless you go looking in the code, or you use Sceptre as a python module, you
won’t need to worry about
SceptreContext is a place where we hold information that is relevant to the
project, including references to the project paths such as the path to your
Sceptre project, templates path, config path, and the default names for your
If you are adding functionality to the CLI or you want to use Sceptre as a
module you will need to create a
SceptreContext and pass it an absolute
path to your Sceptre project directory and the “command_path” - the path you
are going to execute commands on.
SceptreContext you shouldn’t need to interact with
most of the time.
SceptrePlan takes a
SceptreContext and constructs everything you will
need to execute a command against your project. After creating a
SceptrePlan you will be able to call all available methods for your stacks
and access the results from each stack. For example,
plan = SceptrePlan(context) responses = plan.launch()
You won’t be able to interact with the
SceptrePlanExecutor directly but
this part of the code is responsible for taking a
SceptrePlan and ensuring
all commands on every stack, are executed in the correct order, concurrently.
The executor algorithm focuses on correctness over maximal concurrency. It knows
what to execute and when based on a
StackGraph which is created when a
SceptrePlan is created.
StackGraph is a Directed Acyclic Graph where the nodes hold
objects and the edges represent a “depends on” relationship. The graph is
created when a
SceptrePlan is instantiated and is then used during the
execution phase to ensure that stack dependency relationships are complete and
correct. Previously, in
v1 stack dependencies were available between
Environments and even within
Environments they could be temperamental,
this concept resolves this issue.
StackActions class takes a
Stack object and uses the data held on
Stack when calling AWS. StackActions is used by the
SceptrePlanExecutor. To add new functionality you can add a method to
StackActions and it will become available to all
Stacks in Sceptre.