This document describes the Fuchsia API Council, which is a group of people who are accountable for the quality and long-term health of the Fuchsia API Surface. The council will collaborate constructively with the people who create and modify Fuchsia’s APIs to help guide the evolution of those APIs. The council will communicate its decisions clearly, including the underlying rationale, and will document best practices by contributing to Fuchsia’s API readability rubrics.
The Fuchsia System Interface is the binary interface that the Fuchsia operating system presents to software running on the system. For example, the entry points into the vDSO as well as all the FIDL protocols used by the system are part of the Fuchsia System Interface.
A client library is a library that people writing software for Fuchsia might choose to use rather than interfacing directly with the Fuchsia System Interface. For example, FDIO is a client library that provides a POSIX-like abstraction over the underlying fuchsia.io protocol in the Fuchsia System Interface.
The Fuchsia IDK is a collection of libraries, metadata, and tools that the Fuchsia project provides to people writing software for Fuchsia. Among other things, the Fuchsia IDK contains a definition of the Fuchsia System Interface as well as a number of client libraries.
The Fuchsia API Surface is the collection of artifacts that we include in the IDK. This includes, but is not limited to, the Fuchsia System Interface, the client libraries included in the Fuchsia IDK, the IDK metadata, and the core Fuchsia developer tools.
Fuchsia contributors are people who are involved in creating the Fuchsia operating system, including people who work for Google and people who do not.
Fuchsia API designers are people who create or modify the Fuchsia API Surface, including people who work for Google and people who do not.
End-developers are people who write software that consumes the Fuchsia API Surface.
Users are people who use devices that run the Fuchsia operating system.
Ultimately, the end-goal of the Fuchsia API Council is to foster a healthy software ecosystem around the Fuchsia operating system. Fostering a healthy ecosystem requires balancing many concerns, including growing the ecosystem and guiding the ecosystem towards particular outcomes.
The ecosystem has many participants who play many different roles. Ideally, we would be able to design APIs that meet the needs of everyone in the ecosystem simultaneously, but API designers are often called upon to make decisions that involve trade-offs. The council should help API designers make these decisions in a way that respects the following priority of constituencies:
- API designers
- Council members
For example, we should design APIs that protect user privacy, even at the expense of not fulfilling all the desires of end-developers. Similarly, we should design APIs that are better for end-developers even if those designs place a higher burden on the people implementing the APIs.
These values help guide the ecosystem towards meeting the needs of users, which promotes the health and growth of the ecosystem in the long run because users are more likely to join, and remain in, an ecosystem that meets their needs.
To achieve these goals, the council focus on the following metrics:
Functionality. The council is accountable for the functionality of the Fuchsia API Surface. Specifically, functionality refers to whether the APIs meet the needs of the ecosystem participants. For example, the council is accountable for how well our APIs protect the privacy of users, how well our APIs help end-developers accomplish a given task, and how well our APIs let Fuchsia contributors improve their implementations over time.
Usability. The council is accountable for the usability of the Fuchsia API Surface. For example, the council should strive for consistency in how similar concepts are expressed in our APIs, which makes our APIs easier for end-developers to learn. Similarly, the council should ensure that our APIs are well-documented and that the semantics of interfaces are intuitive from their declaration.
System impact. The council is accountable for the burden on the system as a whole incurred through the use of the Fuchsia API Surface, including both intended and unintended usage. For example, APIs that use polling impose a large burden on the system because they require their clients to run continuously to monitor changes in conditions. Assessing system impact requires a significant amount of judgement and experience, especially to predict unintended uses of APIs.
Communication clarity. The council is responsible for clearly communicating decisions and the rationale behind those decisions to Fuchsia contributors. This communication should provide transparency about the decision-making process and should help educate API designers about how to create high-quality APIs. For example, the council should document best practices by contributing to Fuchsia’s API readability rubrics.
Customer satisfaction. The council is responsible for collaborating constructively with API designers. The council should foster an environment in which council members and API designers work in partnership to improve the Fuchsia API Surface. API designers should see the council as providing positive value, helping them make better APIs, rather than as bureaucratic burden. For example, council members should respond promptly and respectfully to requests for API reviews.
The council is comprised of Fuchsia contributors who have demonstrated:
Good judgement about the quality and long-term health of APIs, either within Fuchsia or in their past work with other platforms.
Strong communication and collaboration skills, as viewed by API designers (i.e., their collaborators).
Members are appointed by each functional area of the project.
The council is overseen by the Fuchsia Eng Council.
The council has a chair, who is appointed by Fuchsia leadership and facilitates the operations of the Fuchsia Eng council. The chair has the following responsibilities:
- Schedules meetings.
- Sets the agenda for each meeting.
- Assesses if the council has reached rough consensus.
As the project evolves, the list of functional areas (and therefore the makeup of the council) will evolve as well. The list of functional areas is maintained by Fuchsia leadership.
When considering adding an area, the council considers:
- Coverage. Is this area already covered by one of the other areas, or is there a gap?
- Scope. Is this area sufficiently large to warrant a dedicated appointee?
- Consistent need.. Has the need to have this as an area arisen before?
If the council is called upon to make a decision, the decision process is as follows. The council member for the area in question is the primary decision maker, but the council as a whole is the final decision maker. The council as a whole makes decisions by rough consensus, as assessed by the chair.
The primary decision maker can defer a decision, in which case the council will make the decision. If the council fails to reach rough consensus, the chair will make the final decision.
A council member can ask the council to overrule the primary decision maker. If the council fails to reach rough consensus, the decision made by the primary decision maker stands.
The council has two major functions: API review and API calibration.
Every change to the Fuchsia API Surface requires approval from a council member. A change in a particular functional area should typically be approved by the council member responsible for that area, but any council member can approve the change if the responsible council member is unavailable.
Before being merged, every change that modifies the Fuchsia API Surface must receive an API-Review+1 from a member of email@example.com in addition to the usual Code-Review+2. The same person can provide both API-Review+1 and Code-Review+2 for a given change, but someone cannot give their own CLs API-Review+1. See Review Labels for documentation about this Gerrit feature.
For small API changes, especially incremental refinements to existing APIs, a code review is usually sufficient for an API reviewer to give the change API-Review+1. However, for larger changes, especially those that expand the API surface significantly, the API designer should write an API Design Document (see Fuchsia API Design Template), which explains the design of the API, including use cases and examples, as well as security and privacy considerations. An API reviewer can always request the API designer to write an API Design Document, even for small changes if the API reviewer does not feel comfortable approving the change purely through code review.
For inclusion in the Fuchsia SDK, an API must clear two hurdles: there must be a ready and willing customer, and the API must have gone through API calibration.
API designers are also encouraged to seek early feedback from council members. For example, API designers should consider sharing work-in-progress API Design Documents with council members to get input early in the design process. Council members should engage in these discussions with the goal of partnering with API designers to help design the best API. API designers can also seek feedback early in the design process from the full council by asking the chair for a slot in the agenda for an upcoming API calibration session (see the next section).
The API reviewer should work with the API designer to improve the API Design Document to the point where the API reviewer feels comfortable approving the document. An approved document serves as the plan of record for the API in question. However, individual CLs that modify the API surface still need to review API-Review+1 before being merged. API designers should expect that CLs that follow the plan laid out in an approved API Design Document should review API-Review+1 quite easily, even from other council members.
API designers or reviewers can refer a API Design Document to the full council by asking the chair for a slot in the agenda for an upcoming API calibration session (see the next section). For example, an API reviewer might refer a document to the full council if the API reviewer does not feel sufficiently calibrated, if the API is particularly complex or important, or if the reviewer feels pressured by looming deadlines or other teams.
Periodically, the API council will meet for API calibration. The purpose of API calibration is to promote consistency of API reviews across the project and to improve the quality of API reviews by cross-pollinating best practices across the council. These meetings often have a facilitator, who keeps the meeting on topic and helps ensure each participant has a chance to provide their feedback.
Fuchsia contributors can observe API calibration meetings. Observing these meetings can be a good way to learn best practices about evolving our API surface.
Review API Design Documents
The first priority in API calibration is to review any API Design Documents that have been referred to the full council. If there are multiple pending documents, the chair will select the order in which the council works through the documents.
The API designer who wrote the document should present the document, providing the council with the necessary context to understand the issues at stake. Afterwards, the person who referred the document should lead a discussion of the areas of the API design for which they are seeking feedback. Council members are encouraged to focus their feedback on those areas but are free to provide feedback about the document as a whole.
The Fuchsia API Surface contains a large number of APIs that were designed before the council was formed. The council will work through that backlog of API reviews, eventually reaching the point where every API in the Fuchsia API Surface has been reviewed. Ideally, the council will have a chance to review the entire Fuchsia API Surface before Fuchsia commits to the backwards compatibility of its APIs.
The chair selects the order in which the council works through the backlog, attempting to balance reviewing APIs from diverse areas of the project with the urgency to review APIs that are accreting a large number of clients.
When reviewing an API, the council member who is responsible for the area that contains the API (hereafter the responsible member) will present the API, providing the council with the necessary context to understand the use cases and motivation for the API. The responsible member can invite one or more subject matter experts to help provide additional context and technical details. Ideally, the responsible member will have pre-reviewed the API and will have a list of proposed modifications.
The council will also cycle through the functional areas of the project, performing a secondary review of changes to the API surface for each area since the last cycle. This activity lets the council provide feedback to members on their recent API reviews.
The chair will select the order in which the areas are reviewed, attempting to balance reviewing APIs from diverse areas of the project with the urgency to review APIs that have a large volume of changes.
During secondary review, the council member who was the primary reviewer for the API change will present the change as well as any associated API Design Documents, providing the council with the necessary context to understand the use cases and motivation for the changes. The API designer who made the change in question is also encouraged (but not required) to attend.
Generally, the council should respect the decisions made during the primary API review, but council members are encouraged to provide feedback about how the API could have been improved, which benefits future reviews. Depending on the maturity of the API, the primary reviewer might decide to incorporate these improvements into the API. In rare cases, the council can overrule the primary reviewer, per the council’s decision process.
This document draws heavily from the governance structure used by the Android API Council, the Web API OWNERS, the W3C, and the IETF. Special thanks to Jeff Brown, Dimitri Glazkov, Jeremy Manson, Rebecca Silberstein, and Greg Simon for sharing their experience with API governance and for their thoughtful feedback on early drafts of this document.