Trait GenerationBackend 

pub trait GenerationBackend {
    // Required methods
    fn current(&self) -> Result<GenerationId, Outcome>;
    fn boot_entries(&self) -> Result<Vec<GenerationId>, Outcome>;
    fn boot_default(&self) -> Result<GenerationId, Outcome>;
    fn last_booted(&self) -> Result<GenerationId, Outcome>;
    fn stage(
        &self,
        owner: &PinnedSource,
        overrides: &OverrideSet,
    ) -> Result<StagedSource, Outcome>;
    fn source_hash(&self, owner: &PinnedSource) -> Result<Hash, Outcome>;
    fn evaluate(
        &self,
        src: &StagedSource,
    ) -> Result<EvaluatedGeneration, Outcome>;
    fn build(&self, eval: &EvaluatedGeneration) -> Result<Built, Outcome>;
    fn verify_candidate(
        &self,
        path: &StorePath,
        nar: Option<&Hash>,
    ) -> Result<bool, Outcome>;
    fn pending_jobs(&self) -> Result<Vec<JobId>, Outcome>;
    fn jobs_tagged(&self, op: &OpId) -> Result<Option<Vec<JobId>>, Outcome>;
    fn override_hash(&self) -> Result<Hash, Outcome>;
    fn activate_live(&self, g: GenerationId, op: &OpId) -> Outcome;
    fn publish_boot(&self, g: GenerationId, op: &OpId) -> Outcome;
    fn protect(&self, g: GenerationId, op: &OpId) -> Outcome;
    fn cancel(&self, job: &JobId, op: &OpId) -> Outcome;
    fn swap_override(&self, from: &Hash, to: &Hash, op: &OpId) -> Outcome;
    fn path_of(&self, g: GenerationId) -> Result<StorePath, Outcome>;
    fn evaluate_built(
        &self,
        path: &StorePath,
    ) -> Result<EvaluatedGeneration, Outcome>;
    fn read_overrides(&self) -> Result<(OverrideSet, Hash), Outcome>;
    fn remember_override(&self, set: &OverrideSet) -> Result<Hash, Outcome>;
    fn override_for(&self, g: GenerationId) -> Result<Option<Hash>, Outcome>;
    fn record_override(
        &self,
        g: GenerationId,
        hash: &Hash,
    ) -> Result<(), Outcome>;
    fn release_root(&self, root: &str) -> bool;
    fn collect_garbage(
        &self,
        protect: &[GenerationId],
        emergency: bool,
        op: &OpId,
    ) -> Outcome;
    fn gc_plan(
        &self,
        protect: &[GenerationId],
        emergency: bool,
    ) -> Result<GcPlan, Outcome>;
    fn space_report(&self) -> Option<SpaceReport>;

    // Provided methods
    fn untracked(&self, _owner: &PinnedSource) -> Vec<String> { ... }
    fn dry_activation(
        &self,
        _path: &StorePath,
    ) -> Result<ActivationPlan, Outcome> { ... }
    fn publish_boot_once(
        &self,
        _g: GenerationId,
        _keep: GenerationId,
        _op: &OpId,
    ) -> Outcome { ... }
    fn created_by(&self, _g: GenerationId) -> Option<(u32, Timestamp)> { ... }
    fn one_shot_pending(&self) -> Result<Option<GenerationId>, Outcome> { ... }
    fn override_content(&self, _h: &Hash) -> Result<OverrideSet, Outcome> { ... }
    fn age_out_build_roots(&self) -> Vec<String> { ... }
}

Required Methods

fn current(&self) -> Result<GenerationId, Outcome>

fn boot_entries(&self) -> Result<Vec<GenerationId>, Outcome>

fn boot_default(&self) -> Result<GenerationId, Outcome>

fn last_booted(&self) -> Result<GenerationId, Outcome>

fn stage( &self, owner: &PinnedSource, overrides: &OverrideSet, ) -> Result<StagedSource, Outcome>

fn source_hash(&self, owner: &PinnedSource) -> Result<Hash, Outcome>

Recompute the NAR hash of the owner’s Nix-visible source now (stale check, §9 step 6).

fn evaluate(&self, src: &StagedSource) -> Result<EvaluatedGeneration, Outcome>

fn build(&self, eval: &EvaluatedGeneration) -> Result<Built, Outcome>

Store-only; roots its own output.

fn verify_candidate( &self, path: &StorePath, nar: Option<&Hash>, ) -> Result<bool, Outcome>

The path is a whole system, its contents still hash to what the store recorded, and, when nar is given (the transaction built it), that is the NAR hash recorded at build (§9 step 3, C6).

fn pending_jobs(&self) -> Result<Vec<JobId>, Outcome>

fn jobs_tagged(&self, op: &OpId) -> Result<Option<Vec<JobId>>, Outcome>

None: the backend cannot say whether work tagged with op exists.

fn override_hash(&self) -> Result<Hash, Outcome>

The override file’s current content hash (promotion compares against it, §9 step 4).

fn activate_live(&self, g: GenerationId, op: &OpId) -> Outcome

switch-to-configuration test.

fn publish_boot(&self, g: GenerationId, op: &OpId) -> Outcome

Boot entry only; no re-activation.

fn protect(&self, g: GenerationId, op: &OpId) -> Outcome

fn cancel(&self, job: &JobId, op: &OpId) -> Outcome

fn swap_override(&self, from: &Hash, to: &Hash, op: &OpId) -> Outcome

Atomically replace the live override file with the content whose hash is to, but only if its current hash is from. Idempotent: if it already hashes to to, succeed without writing.

fn path_of(&self, g: GenerationId) -> Result<StorePath, Outcome>

The system store path of a known generation.

fn evaluate_built( &self, path: &StorePath, ) -> Result<EvaluatedGeneration, Outcome>

Evaluate an already-built generation from its store path (its exported manifest), for SwitchGeneration / Revert / Rollback.

fn read_overrides(&self) -> Result<(OverrideSet, Hash), Outcome>

The live override set and its content hash.

fn remember_override(&self, set: &OverrideSet) -> Result<Hash, Outcome>

Keep override content addressable by hash, so swap_override can write it.

fn override_for(&self, g: GenerationId) -> Result<Option<Hash>, Outcome>

The override content recorded for a generation when it was committed.

fn record_override(&self, g: GenerationId, hash: &Hash) -> Result<(), Outcome>

fn release_root(&self, root: &str) -> bool

Remove a GC root symlink this backend created.

fn collect_garbage( &self, protect: &[GenerationId], emergency: bool, op: &OpId, ) -> Outcome

Collect generations under the §12b bounds (gc::plan), never touching protect (I3), then collect store garbage. Mutating.

fn gc_plan( &self, protect: &[GenerationId], emergency: bool, ) -> Result<GcPlan, Outcome>

What collect_garbage would delete now. Read-only.

fn space_report(&self) -> Option<SpaceReport>

The last collection’s result.

Provided Methods

fn untracked(&self, _owner: &PinnedSource) -> Vec<String>

The owner’s files Nix cannot see now (untracked in a git flake), to report with the stale check: one added during the build was not there at staging (§9 step 1).

fn dry_activation(&self, _path: &StorePath) -> Result<ActivationPlan, Outcome>

What switching from the running generation to an existing one would start, stop, restart and reload (its dry activation), for SwitchGeneration / Revert / Rollback (§11, R04). An activation that failed, timed out or was cut short is an error, never a smaller plan.

fn publish_boot_once( &self, _g: GenerationId, _keep: GenerationId, _op: &OpId, ) -> Outcome

The boot-only path (§12 step 7, §12f): g boots once, at the next boot; keep stays the default. All or nothing.

fn created_by(&self, _g: GenerationId) -> Option<(u32, Timestamp)>

Who created generation g and when (its profile link’s owner and time): the provenance of a rebuild made outside Planarian (§15).

fn one_shot_pending(&self) -> Result<Option<GenerationId>, Outcome>

The generation a one-shot entry will boot next, if one is pending.

fn override_content(&self, _h: &Hash) -> Result<OverrideSet, Outcome>

The override content remember_override kept under this hash.

fn age_out_build_roots(&self) -> Vec<String>

Remove build roots no transaction can still use: older than the longest a candidate may wait (§12f), a crashed build’s included. At startup and before every collection (§9 step 5, C4). Returns them.

Implementors