nordisk/Skidbladnir

layout — design

Class: design · Function axis: f5 (AIRGAP5). States only the shape we ship.

The prepared directory layout

pub struct Layout { data_dir, log_dir, software_dir, version } (layout.rs:18). Software is partitioned by a date-stamped version so upgrades are generations, not in-place overwrites:

<software_dir>/<version>/<product>/…      ← this generation's files
<software_dir>/current  → <version>       ← atomic symlink to the active generation
<data_dir>/<product>/…                    ← persistent data (survives updates)
<log_dir>/<product>/…                     ← logs (survive updates)

Layout::dated(data_dir, log_dir, software_dir) (layout.rs:34) stamps version with today's YYYYMMDD. Path builders: version_dir (layout.rs:48), product_software(name) (layout.rs:53), product_data(name) (layout.rs:58), product_log(name) (layout.rs:64), current_link (layout.rs:70).

Provisioning

• prepare() (layout.rs:79) — idempotently creates data, log, and software/<version> roots; does not touch current.
• prepare_product(name) -> (software, data, log) (layout.rs:96) — prepare() then the three per-product dirs; idempotent, never clobbers an existing data/<name> or log/<name>.

Atomic upgrade swap

activate() (layout.rs:115, unix) writes a temp symlink .current.tmp pointing at the version, then rename(2)s it onto current — a single atomic op on the same filesystem. The symlink targets the relative version name, so the whole tree is relocatable (layout.rs:121). On non-unix it writes a CURRENT marker file (layout.rs:129).

active_version() -> Option<String> (layout.rs:139) resolves what current points at. current_product_path(software_dir, product) (layout.rs:153) resolves a product path through current, so a running service always follows the active generation.

Rollback

There is no separate rollback() — a swap never deletes the previous generation, so rollback is re-activate()ing an older Layout (the old version dir is retained, asserted at layout.rs:247).

Contract (inject-assert tests)

prepare_product_creates_software_data_and_log_dirs (layout.rs:193), atomic_symlink_swap_on_upgrade (layout.rs:222), dated_version_is_yyyymmdd_and_paths_compose (layout.rs:258), reactivate_same_version_is_idempotent (layout.rs:295).