Concurrent writes: optimistic concurrency (version + If-Match → 412) so a co-editor's save is never lost silently
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已经有一个关联 PR 被合并了。
- #562 来自 @silverbackdan —— 已合并
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- 难度
- 5/5
- 预计耗时
- 一周以上
- 新手友好度
- 35/100
调研方向
Start by tracing LastWriteResolver and how writable resources are serialized and updated; the payload does not name source files or tests. Check how versions could cover drafts, published resources, publish, and order changes, then review ETag and CORS handling. Done means writes with stale If-Match return 412 with the current resource, while writes without it continue to work.
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描述
Two admins saving the same field of the same resource at the same moment lose one save silently. Found while porting the TipTap co-editing reference (components-web-app/cwa-nuxt-module#429) with @cwa/nuxt 2.0.0-alpha.28 and this bundle at 2.0.0-alpha.35.
Reproduced
One HtmlContent draft open in two tabs (each with its own X-CWA-Client-Id), both typing in the same editor:
- The two PATCHes went out 1 ms apart, and both returned 200.
- Each body was the tab's whole
html, built from what that tab had before the other's save, so the second commit replaced the first. Neither client can tell that its save was overwritten. - In one run the PATCH responses carried
lastWrite.at17:00:36.235 (A) and 17:00:36.219 (B), and the stored html was A's.
Why the module can't settle it alone
lastWrite.at is stamped the first time the resource is serialised in the request (LastWriteResolver), not in commit order. With two workers a few milliseconds apart, the save that commits last can carry the earlier time. The module drops an update older than its stored copy, so a tab can drop the update that actually won and stay out of step with the stored data. That happened on the template stack in 3/3 runs.
Proposal: optimistic concurrency on writes
- Every writable resource exposes a version that changes on each write. Doctrine's
#[ORM\Version]integer would do, or an opaque token. Serialise it, for example in_metadata, and send it as the responseETag. - A PATCH (and PUT/DELETE) with
If-Matchsucceeds only if the stored version still matches; otherwise 412 Precondition Failed, with the current resource in the body so the client does not need a second request. - Without
If-Match, writes behave as now, so non-realtime clients keep working. - The version on Mercure updates lets a client order updates by version instead of by
lastWrite.at. - To decide: whether the version covers draft and published as one resource (the module treats them as one for conflicts), and how a publish (a draft's PATCH that removes the draft) and the order PATCH /
/movetake part. - CORS: expose
ETagand allowIf-Matchfor cross-origin apps.
Module side, once released
The module sends If-Match from the stored version on each save. On a 412 it shows the field's existing conflict (Use theirs / Keep mine) with the body as theirs, and Keep mine re-sends with the new version. It orders Mercure updates by version.
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components-web-app/api-components-bundle 的其他 Issue
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难度 5/5 一周以上 新手友好度 30/100
components-web-app/api-components-bundle#333 · 3 条评论 ·
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components-web-app/api-components-bundle#325 · 1 条评论 ·
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components-web-app/api-components-bundle#259 · 1 条评论 ·
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难度 4/5 3-5 天 新手友好度 48/100
components-web-app/api-components-bundle#186 ·
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