This section describes the high-level architecture of STACKL, referring to other sections for a more in-depth explanation. The architecture shows how STACKL enables users to flexibly and easily model, describe, and automate their application orchestration workflow.
This workflow is supported as follows:
- An operator, any entity that can submit tasks, uses STACKL as a tool to model, describe, and automate applications by using it as (1) a datastore of application configuration and infrastructure model data and (2) a platform that employs this data to provide autonomous application orchestration.
- Authorized operators interact through an API specification to submit tasks, which are handled atomically to produce consistent end-results. Tasks are mainly submitting documents that model the IT environment and describe applications and that request the instantiation or management of applications.
- Tasks are executed in STACKL through pluggable modules for authorization, storage, processing, automation endpoint execution, and monitoring and reporting.
- STACKL thus has a Single Source Of Truth document datastore that contains a consistent model of the available IT environment to provide end-to-end application orchestration for users.
This section describes each element in the above diagram and its responsibilities.
An Operator is an entity that uses the STACKL API to make requests and receives the result or a confirmation in return. Requests can be queries for information, retrieving documents, storing or changing documents, and application orchestration. A operator can be anything that is capable of issuing HTTP requests, including other tools or real-life users.
The API Interface is a frontend for access to STACKL and ensures requests are authorized, submitted to STACKL as tasks, and the result delivered back to the requestor. This API is based on HTTP and REST and provides a web frontend.
The Authorization Module ensures that requests for STACKL are both allowed and delegated to the correct parties. This is a WIP that is intended to be offloaded to a policy-driven system managed by an Open Policy Agent.
The Task Broker and Workers ensure the correct, consistent, and timely end-to-end processing of the tasks. This includes delegating it to multiple workers for horizontal scalability, reporting the result of the work, rolling back any changes in case of failure, and interacting with third parties, such as agents, if needed. Workers contain the core logic needed to process the work, such as constraint solving and matching application requirements and infrastructure capabilities.
The Document Datastore stores and provides documents for workers to execute their tasks. It ensures typed and eventual consistent documents, and thus forms a SSOT to model an IT enterprise environment and application configuration data.
The Monitoring Module assists in the monitoring, logging, and maintenance of the IT enterprise environment and how it is modelled in the document datastore. It interacts with the task broker and agents to ensure both are consistent and queryable. This is a WIP that is intended to be offloaded to a policy-driven system managed by an Open Policy Agent.
The Agent Broker and Agents enable STACKL to execute work and queries in a (remote) IT enterprise environment. The Agent Broker is an interface that allows to interact with user-side agents. Agents do the further processing of the task, such as executing invocations on automation endpoints.