Add the clean race and the end of a preview to the roadmap

roadmap/README.md

@@ -50,6 +50,11 @@ The parts, their tasks, and the order of the PRs are in [v8.1/README.md](v8.1/RE
 
 These do not depend on the six parts. Each can be a separate PR to `main`, in a patch release or in 8.1.
 
+- **`clean` while a publish runs.** `publish-content` lists the `_files_` keys that are in storage, uploads only the files that are not there, and writes the index at the end. `clean` deletes each `_files_` key that no index refers to. If `clean` runs during a publish, two things can occur:
+   - `clean` deletes files that the publish uploaded, because the new index is not written yet.
+   - `clean` deletes a file that no index used, but that the publish found in its list and did not upload again. The new index then refers to a file that does not exist.
+
+   In both cases, the published collection has files that the server cannot find. A CI job that runs `clean` on a schedule, and a job for each PR that publishes a preview, can easily run at the same time. Possible fixes, to decide while building: a warning in the README and in `clean --help` (do not run `clean` while a publish can run; in GitHub Actions, put both jobs in the same `concurrency` group); `clean` keeps the files that were uploaded in the last N minutes (S3 has `LastModified`; the KV Store has no time, so the metadata would need one); or a lock entry in storage.
 - **Remove the Beta label of S3-compatible storage** in 8.1: in `README.md`, `README.short.md`, `MIGRATING.md`, the CLI help text, the CLI log messages, and the code comments.
 - **Retry an empty body** (follow-up to #116 and #52). If storage returns an empty body for a file whose size is not 0, `checkBodyLength()` throws before the response starts, and the client gets a `500`. Instead, the server could read the entry again for the same request. First, collect data from the log message `expected N bytes, got 0` to find how frequently this occurs.
 - **Run only the end-to-end tests that use real services.** Each `describe` in `test/e2e` skips with `skipUnlessFastlyCli()` or `skipUnlessEnv()`. Thus, with credentials, the local tests always run too. Idea: an environment variable such as `CJSP_TEST_SKIP_LOCAL=1` in `test/e2e/helpers.js`.

roadmap/v8.1/README.md

@@ -63,6 +63,7 @@ The `plain` template has no collection selection yet. Part 2 adds it.
 - 2.4 **`resolveCollection()`**, one function for all templates, and **`previewUrl()`**, which gives the link for a collection.
 - 2.5 **`collectionSelection`** in `static-publish.rc.js`: select a collection by a hostname, a path, a query parameter, a cookie, or a header, with settings in place of code. `allow`, `sticky`, `onMissing`. Responses from previews get `noindex` and `Cache-Control: private`.
 - 2.6 **Connect it to the `plain` template**, plus the `scaffold` flags. The scaffolded app supports previews with no code.
+- 2.7 **The end of a preview.** In 8.0.0, nothing removes a preview when its branch or PR closes: `--expires-in` stops serving it, but its index stays in storage until `clean --delete-expired-collections`, and its files stay until `clean`. The README has no CI example for it. Add a CI example that, when a PR closes, runs `collections delete` for its preview, and then `clean` (see [`clean` while a publish runs](../README.md#separate-from-the-six-parts-80x-or-81) for when `clean` is safe). Decide while building: only docs, or also a command or a flag that does both steps.
 
 The `collectionSelector` helpers and custom selectors continue to work, for customers who need a rule that the config does not have.