Design Document Template

Introduction

Purpose

State the purpose of the document; something like: this is functional specificationS of feature "..." which has Jira ID CS-xyzw

References

• relevant links

Document History

Glossary

Feature Specifications

• put a summary or a brief description of the feature in question 
• list what is deliberately not supported or what the feature will not offer - to clear any prospective ambiguities
• list all open items or unresolved issues the developer is unable to decide about without further discussion
• quality risks (test guidelines)
  • functional
  • non functional: performance, scalability, stability, overload scenarios, etc
  • corner cases and boundary conditions
  • negative usage scenarios
• specify supportability characteristics:
  • what new logging (or at least the important one) is introduced
  • how to debug and troubleshoot
  • what are the audit events 
  • list JMX interfaces
  • graceful failure and recovery scenarios
  • possible fallback or work around route if feature does not work as expected, if those workarounds do exist ofcourse.
  • if feature depends other run-time environment related requirements, provide sanity check list for support people to run
• explain configuration characteristics:
  • configuration parameters or files introduced/changed
  • branding parameters or files introduced/changed
  • highlight parameters for performance tweaking
  • highlight how installation/upgrade scenarios change
• deployment requirements (fresh install vs. upgrade) if any
• system requirements: memory, CPU, desk space, etc
• interoperability and compatibility requirements:
  • OS
  • xenserver, hypervisors
  • storage, networks, other
• list localization and internationalization specifications 
• explain the impact and possible upgrade/migration solution introduced by the feature 
• explain performance & scalability implications when feature is used from small scale to large scale
• explain security specifications
  • list your evaluation of possible security attacks against the feature and the answers in your design* *
• explain marketing specifications
• explain levels or types of users communities of this feature (e.g. admin, user, etc)

Use cases

put the relevant use case/stories to explain how the feature is going to be used/work

Architecture and Design description

• discussion of alternatives amongst design ideas, their resources/time tradeoffs and limitations. Explain why a certain design idea is chosen over others
• highlight architectural patterns being used (queues, async/sync, state machines, etc)
• talk about main algorithms used
• explain what components are being changed and what the dependent components are
• regarding database: talk about tables being added/modified
• performance implications: what are the improvements or risks introduced to capacity, response time, resources usage and other relevant KPIs
• preferably show class diagrams, sequence diagrams and state diagrams
• if possible, publish signatures of all methods classes and interfaces implement, and the explain the object information of different classes

API and Schema Changes

list changes to existing web services APIs and new APIs introduced with signatures and throughout documentation

Service Layer Changes

Describe business/service layer changes, changes in frameworks, plugins ...

UI Changes

• One
• Two
• Three

Marvin Tests

For this feature, the following test cases or QA considerations must be made:

• CRUD tests as user or root admin for all features listed above in API section
• ...

IP Clearance

• what dependencies will you be adding to the project?
• are you expecting to include any code developed outside the Apache CloudStack project?

Usage Impact

• Are there any entities being created that require usage reporting for billing purposes? 

• Does this change any existing entities for which usage is being tracked already?

Appendix

Appendix A:

Appendix B: