Struct NewGeneration 

pub struct NewGeneration {
    pub stop_after: StopAfter,
}

GC into a new generation, keeping the old one until the new one is proven.

repo.znippy becomes repo.g1.znippy, then repo.g2.znippy, and so on. The old file is unlinked only after the new one has been read back in full.

The sequence, and why each step is where it is:

1. link(archive, work) — a hard link, so the work name and the archive name are the same inode and not one byte is copied. This is what lets step 2 be compact_archive verbatim (LAW 5) while the archive’s own name stays untouched: compact_archive renames over the name it was given, and the name it is given here is the work link, not the archive.
2. compact_archive(work) — stages beside work and renames over it. The archive’s inode is still fully referenced by the archive’s own name throughout, so every reader of repo.znippy is unaffected.
3. verify — [verify_archive_integrity] over the new file, plus a manifest set comparison against the original. Both are read back off disk.
4. rename(work, repo.gN.znippy) — atomic; the new generation now has its permanent name.
5. unlink(repo.znippy) — the old index and old data go, and only now.

A death at any point leaves at least one complete, readable archive: before 4 the original under its own name (plus debris), after 4 and before 5 both of them, after 5 the new generation. Asserted, per step, in [tests::an_interruption_at_every_step_leaves_a_readable_archive].

Fields

stop_after: StopAfter

Test-only interruption point. StopAfter::Never in every real run.

Implementations

impl NewGeneration

pub fn new() -> Self

pub fn stopping_after(stop: StopAfter) -> Self

Stop the run at stop, leaving the filesystem as a crash there would.

Trait Implementations

impl Clone for NewGeneration

fn clone(&self) -> NewGeneration

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for NewGeneration

impl Debug for NewGeneration

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for NewGeneration

fn default() -> NewGeneration

Returns the “default value” for a type.

impl Gc for NewGeneration

fn run(&self, archive: &Path) -> Result<GcReport>

fn name(&self) -> &'static str