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forge-test gate: keep GOCACHE off the virtiofs cache mount (Go mmap fails) #730

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opened 2026-10-06 17:00:58 +00:00 by hexajon · 1 comment

hexajon commented

2026-10-06 17:00:58 +00:00

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In testing, a go test -tags forge build with the caches on the VM's local disk passes; the same build with the caches on the virtiofs mount fails at import. The forge matrix passes end to end only with local-disk caches.

What to do

The gate step that runs the forge tests in the VM must set GOCACHE and GOMODCACHE to a VM-local path, not the virtiofs cache mount. The downloaded forge binaries are executed, and the kernel memory-maps an executable, so they are likely to hit the same limit on virtiofs; keep the resolved-binary cache off the virtiofs mount too, or enable virtiofs DAX on the mount and confirm a build passes.

Acceptance

The forge-test gate step runs go test -tags forge in the VM with the build and module caches on VM-local disk, and it passes.
The persistent-cache design still warms what it can across runs without breaking the build, and the doc states which caches live where.

Blocks #692.

The forge-test Incus VM mounts a persistent host cache over virtiofs so caches survive the per-run snapshot reset. A Go build that points GOCACHE or GOMODCACHE at that mount fails: every import reports "could not import <pkg> (no such device)" (ENXIO). Go memory-maps its cache artifacts and the virtiofs mount rejects mmap; a plain read of the same file works, so the failure looks like a filesystem fault rather than a build error. In testing, a `go test -tags forge` build with the caches on the VM's local disk passes; the same build with the caches on the virtiofs mount fails at import. The forge matrix passes end to end only with local-disk caches. ## What to do The gate step that runs the forge tests in the VM must set GOCACHE and GOMODCACHE to a VM-local path, not the virtiofs cache mount. The downloaded forge binaries are executed, and the kernel memory-maps an executable, so they are likely to hit the same limit on virtiofs; keep the resolved-binary cache off the virtiofs mount too, or enable virtiofs DAX on the mount and confirm a build passes. ## Acceptance - The forge-test gate step runs `go test -tags forge` in the VM with the build and module caches on VM-local disk, and it passes. - The persistent-cache design still warms what it can across runs without breaking the build, and the doc states which caches live where. Blocks #692.

hexajon added a new dependency

2026-10-06 17:01:17 +00:00

#692 gate: run the forge tests only inside an Incus VM

hexajon referenced this issue

2026-10-06 18:46:35 +00:00

docs(adr): 0052 keeps forge-test caches on VM-local disk #734

hexajon referenced this issue from a commit

2026-10-06 18:46:36 +00:00

docs(adr): 0052 keeps forge-test caches on VM-local disk

hexajon referenced this issue

2026-10-06 19:25:07 +00:00

feat(testforge): #692 bring the forge-test VM standup into the repo #735

hexajon commented

2026-10-14 17:58:21 +00:00

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Resolved. The persistent virtiofs cache mount this is about is gone. It was a stray gocache disk device (a host cache dir mounted at /cache); provision.sh now strips any device that is not the NIC or root disk and asserts the set. The runner keeps GOCACHE, GOMODCACHE, and the binary cache at the test user's $HOME on VM-local disk, and go test -tags forge ./internal/testforge/... passes green in the VM (PR #760). ADR 0052 accepted that local-disk caches give up cross-run warming for a correct build, so no virtiofs cache mount is left to keep GOCACHE off.

Resolved. The persistent virtiofs cache mount this is about is gone. It was a stray `gocache` disk device (a host cache dir mounted at /cache); provision.sh now strips any device that is not the NIC or root disk and asserts the set. The runner keeps GOCACHE, GOMODCACHE, and the binary cache at the test user's $HOME on VM-local disk, and `go test -tags forge ./internal/testforge/...` passes green in the VM (PR #760). ADR 0052 accepted that local-disk caches give up cross-run warming for a correct build, so no virtiofs cache mount is left to keep GOCACHE off.

hexajon closed this issue

2026-10-14 17:58:21 +00:00

hexajon referenced this issue

2026-10-17 16:48:29 +00:00

bug(forge-test): the throwaway-forge binary download times out after a base-snapshot reset #796

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#692 gate: run the forge tests only inside an Incus VM

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sixfold-space/madtea#730

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