Architecture Decision RecordAWS Architectural Decision Records Process
An architectural decisioun record (ADR) is a document that describes a chyce the team maks aboot a muckle aspect o the saftware architectur they're plannin tae big. Each ADR describes the architectural decisioun, its context, an its consequences. ADRs hae states an sae follae a lifecycle. For an example o an ADR, see the appendix.
The ADR process ootputs a collection o architectural decisioun records. This collection creates the decisioun log. The decisioun log provides the project context as weel as detailed implementation an design information. Project members skim the headlines o each ADR tae get an owerview o the project context. They read the ADRs tae dive deep intae project implementations an design chyces.
Whan the team accepts an ADR, it becomes immutable. If new insichts require a different decisioun, the team proposes a new ADR. Whan the team accepts the new ADR, it supersedes the previous ADR.
Scope o the ADR process
Project members sud mak an ADR for ilka architecturally significant decisioun that affects the saftware project or product, includin the follaein (Richards an Ford 2020):
Structur (for example, patterns sic as microservices)
Non-functional requirements (security, heich availability, an fault tolerance)
Dependencies (couplin o components)
Interfaces (APIs an publisht contracts)
Constructioun techniques (leebraries, frameworks, tuils, an processes)
Functional an non-functional requirements are the maist common inputs tae the ADR process.
ADR contents
Whan the team identifies a need for an ADR, a team member stairts tae screive the ADR based on a projectwide template. (See the ADR GitHub organisation for example templates.) The template simplifies ADR creation an ensures that the ADR taks doun aw the relevant information. At a minimum, each ADR sud define the context o the decisioun, the decisioun itsel, an the consequences o the decisioun for the project an its deliverables. (For examples o thir sections, see the appendix.) Ane o the maist pouerfu aspects o the ADR structur is that it focuses on the reason for the decisioun raither than hoo the team implementit it. Unnerstaunin why the team made the decisioun maks it easier for ither team members tae adopt the decisioun, an prevents ither architects wha werena involved in the decisioun-makin process frae owerrulin that decisioun in the future.
ADR adoption process
Ilka team member can mak an ADR, but the team sud establish a definition o ownership for an ADR. Each author wha is the awner o an ADR sud actively keep up an communicate the ADR content. Tae clarify this ownership, this guide refers tae ADR authors as ADR awners in the follaein sections. Ither team members can aye contribute tae an ADR. If the content o an ADR chynges afore the team accepts the ADR, the awner sud approve thir chynges.
Efter the team identifies an architectural decisioun an its awner, the ADR awner provides the ADR in the Proposed state at the beginnin o the process. ADRs in the Proposed state are ready for review.
The ADR awner than initiates the review process for the ADR. The aim o the ADR review process is tae decide whether the team accepts the ADR, determines that it needs rework, or rejects the ADR. The project team, includin the awner, reviews the ADR. The review meetin sud stairt wi a dedicatit time slot tae read the ADR. On average, 10 tae 15 minutes sud be eneuch. Durin this time, each team member reads the document an adds comments an questions tae flag unclear topics. Efter the review phase, the ADR awner reads oot an discusses each comment wi the team.
If the team finds action pynts tae improve the ADR, the state o the ADR bides Proposed. The ADR awner formulates the actions, an, in collaboration wi the team, adds an assignee tae each action. Each team member can contribute an resolve the action pynts. It is the responsibility o the ADR awner tae reschedule the review process.
The team can an aw decide tae reject the ADR. In this case, the ADR awner adds a reason for the rejection tae prevent future discussiouns on the same topic. The awner chynges the ADR state tae Rejected.
If the team approves the ADR, the awner adds a timestamp, version, an list o stakeholders. The awner than updates the state tae Accepted.
ADRs an the decisioun log they mak represent decisiouns made bi the team an provide a history o aw decisiouns. The team uises the ADRs as a reference durin code an architectural reviews whaur possible. In addition tae daein code reviews, design tasks, an implementation tasks, team members sud consult ADRs for strategic decisiouns for the product.
As a guid practice, each saftware chynge sud gae throu peer reviews an require at least ane approval. Durin the code review, a code reviewer micht find chynges that violate ane or mair ADRs. In this case, the reviewer asks the author o the code chynge tae update the code, an shares a link tae the ADR. Whan the author updates the code, it is approved bi peer reviewers an merged intae the main code base.
ADR review process
The team sud treat ADRs as immutable documents efter the team accepts or rejects them. Chynges tae an existin ADR requires makin a new ADR, establishin a review process for the new ADR, an approvin the ADR. If the team approves the new ADR, the awner sud chynge the state o the auld ADR tae Superseded.