Conditional room saves, so a stale save never overwrites another writer #5

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oss merged 1 commit from feat/XSH-1-conditional-saves into selfhost

2026-11-11 12:52:08 +01:00

oss commented

2026-11-06 00:43:34 +01:00

Owner

Part of Kaneo Live region shares for Excalidraw boards (XSH-1).

saveToFirebase (excalidraw-app/data/httpStorage.ts) used to snapshot the scene, read the room, and then PUT unconditionally. A save from another writer between that read and that PUT was overwritten. The other writer could be a second tab or the live-share bridge saving a guest's edit.

It now reads the room with its ETag, reconciles exactly as before, and PUTs with If-Match (or If-None-Match: * for a new room). On 412 it re-reads, reconciles and retries, up to 5 times. Against a backend without ETags it falls back to the previous unconditional PUT, so it can deploy in either order relative to oss/excalidraw-storage-backend#15.

The new test excalidraw-app/tests/httpStorage.test.ts races two saves on one room against an ETag-aware backend double. Both elements are kept. On the previous code the same test loses one. Typecheck, ESLint and Prettier are clean, and all 7 app tests pass. Reviewed by GPT-6.1-Sol: PASS.

🤖 Generated with Claude Code

Part of Kaneo *Live region shares for Excalidraw boards* (XSH-1). `saveToFirebase` (`excalidraw-app/data/httpStorage.ts`) used to snapshot the scene, read the room, and then PUT unconditionally. A save from another writer between that read and that PUT was overwritten. The other writer could be a second tab or the live-share bridge saving a guest's edit. It now reads the room with its ETag, reconciles exactly as before, and PUTs with `If-Match` (or `If-None-Match: *` for a new room). On 412 it re-reads, reconciles and retries, up to 5 times. Against a backend without ETags it falls back to the previous unconditional PUT, so it can deploy in either order relative to [oss/excalidraw-storage-backend#15](https://git.ossalali.com/oss/excalidraw-storage-backend/pulls/15). The new test `excalidraw-app/tests/httpStorage.test.ts` races two saves on one room against an ETag-aware backend double. Both elements are kept. On the previous code the same test loses one. Typecheck, ESLint and Prettier are clean, and all 7 app tests pass. Reviewed by GPT-6.1-Sol: PASS. 🤖 Generated with [Claude Code](https://claude.com/claude-code)

oss added 1 commit

2026-11-06 00:43:34 +01:00

fix(selfhost): conditional room saves with retry, so a stale save never overwrites another writer's

upkeep / dispatch (pull_request_target) Has been skipped

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b692afd2b0

oss referenced this pull request

2026-11-06 10:35:57 +01:00

Open the region-share page from Start session, link prefilled #12

oss merged commit 6cd7be0e1c into selfhost

2026-11-11 12:52:08 +01:00

oss deleted branch feat/XSH-1-conditional-saves