templates: add fork-only template registry and promotion lifecycle#213
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templates: add fork-only template registry and promotion lifecycle#213sjmiller609 wants to merge 1 commit intomainfrom
sjmiller609 wants to merge 1 commit intomainfrom
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Introduces a templates package and Standby-instance promotion path so later PRs can wire fork-from-template into firecracker. The registry persists one JSON file per template under <data>/templates/<id>/, with fork refcount accounting and Delete-blocked-when-in-use. The instance manager owns the registry because template lifecycle is coupled to instance lifecycle: promotion guards on Standby+HasSnapshot, deletion clears IsTemplate on the source instance, and forks (PR 3) will increment the refcount. Hypervisor wire-up is deferred — this PR ships the registry, the StoredMetadata flags, and the manager helpers (templateGuard, templateForFork, validateForkResolvedFromTemplate) so PR 3 can plug in.
This was referenced May 8, 2026
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Summary
lib/templatespackage with a JSON file-backedRegistry(Save/Get/GetByName/List/Delete + IncrementForkCount/DecrementForkCount).Templatemodel with hypervisor type/version, image+digest, vCPU/memory, fork refcount, and a reservedHotPagesPathfield for PR 8.lib/instancestemplate plumbing: promote/list/get/delete pluspaths.TemplatesDir()etc.IsTemplate/TemplateID/ForkOfTemplateon instance metadata; the manager owns atemplates.Registryit constructs at startup.Why
Foundation for snapshot fan-out: templates are the durable "tagged Standby instance promoted to fork-only parent" record that downstream PRs (shared mem-file, GC, UFFD page server) hang off of. Splitting it out keeps each follow-up reviewable.
Test plan
go test ./lib/templates/...go test ./lib/instances/...for unit coverage of new metadata fields🤖 Generated with Claude Code