etcd-io/etcd

Explicit client versioning

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#10246 opened on Nov 8, 2018

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Description

Hi all,

I can't find any precise documentation around compatibility of v3 clients with given versions and v3 servers with given versions.

While it may be possible to take entire Etcd clusters down and replace them at once, doing that with a larger set of clients is somewhat unrealistic.

Are there any backwards or forwards compatibility guarantees across the client API? For example:

  • Backwards compatibility: Will any new version of a v3 client work with any older v3 version of Etcd? For instance, will existing grpc/protobuf messages only add optional fields, such that old messages are still understood, and those fields can be ignored? Will responses change across minor versions? In essence what guarantees can be provided if any? This allows upgrading clients first and then Etcd.
  • Forwards compatibility: Will any old version of a v3 client work with any new v3 version of Etcd? For instance, will new versions of Etcd be able to interpret old protobuf client messages with missing optional fields correctly? This allows Etcd to be updated first and then clients to be updated individually over time.

It would be great if you could provide some information about how the Etcd team plans for such scenarios and how you attempt to maintain compatibility, if at all. If not, that should be documented as well.

Thanks!

Contributor guide

Tech stack
go
Domain
documentationbackend
Issue type
documentation
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
basic understanding of etcdfamiliarity with gRPC and protobuf versioning
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Review etcd's existing release notes and upgrade guides for compatibility statements. Examine the protobuf definitions in the etcd codebase, especially any optional fields or deprecation markers. Look at the changelog for the etcd client go library to understand past changes. The issue asks for explicit documentation of backwards and forwards compatibility guarantees, so the research should focus on summarizing the current ad hoc practices and proposing a formal compatibility policy.