fix: add fsync to writePEM before close (PILOT-138)

[matthew-pilot]

What failed

writePEM in pilot-ca/main.go deferred f.Close() after pem.Encode with no intervening fsync. A process crash between the Encode and the deferred Close would lose the newly-issued certificate, leaving a partial or missing PEM file on disk.

Why this fix

• Added f.Sync() after pem.Encode to flush data to durable storage.
• Added parent-directory Sync() so the directory entry is committed before writePEM returns.
• Added TestWritePEM_FsyncBeforeClose regression test that writes a PEM block and reads it back immediately.

Verification

go build ./...   → OK
go vet ./...     → OK
go test ./...    → OK (9/9 tests pass)

Files changed

• main.go — +9 lines in writePEM
• zz_pilot_ca_test.go — +31 lines (new regression test)

Closes PILOT-138

[codecov]

Codecov Report

❌ Patch coverage is 60.00000% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
main.go	60.00%	1 Missing and 1 partial ⚠️

📢 Thoughts on this report? Let us know!

[matthew-pilot]

🦾 Matthew PR Check — #4 PILOT-138

Status

• State: OPEN · MERGEABLE ⚠️ (unstable)
• CI: 1/2 green — test ✅ · codecov/patch ❌
• Canary: not run
• Jira: PILOT-138

CI Details

Check	Result
test	✅ success
codecov/patch	❌ failure

Mergeability

• Mergeable: yes (underlying state: unstable)
• Blocked by: codecov/patch failure
• Draft: no
• Labels: none

Recommendation

🟡 Not ready to merge — codecov/patch check is failing. This is likely a coverage threshold delta (the added code may have reduced patch coverage). Review whether the test coverage is adequate or if the coverage threshold needs adjustment.

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Matthew PR Worker · 2026-05-28 15:25 UTC

[matthew-pilot]

🦾 Matthew PR Explain — #4 PILOT-138

What changed

Adds durability guarantees to PEM certificate writes in the pilot-ca service.

Files

File	Δ	What
main.go	+9	Added f.Sync() + parent-directory Sync() after pem.Encode in writePEM
zz_pilot_ca_test.go	+31	New TestWritePEM_FsyncBeforeClose regression test

Why

writePEM previously deferred f.Close() after pem.Encode without an intervening fsync. A process crash between the Encode and the deferred Close would lose the newly-issued certificate, leaving a partial or missing PEM file on disk. This fix ensures data is flushed to durable storage and the directory entry is committed before writePEM returns.

Verification

go build ./...   → OK
go vet ./...     → OK
go test ./...    → OK (9/9 tests pass)

CI

• test ✅ — all tests pass
• codecov/patch ❌ — coverage delta below threshold (expected for durability code that's hard to cover in unit tests)

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Matthew PR Worker · 2026-05-28 15:25 UTC