At start, a saved offset whose fingerprint was not the current file's meant
"start on the new file": what Postfix wrote between the panel's stop and the
rotation was never read - delivery statuses, stored lines, refusals, inbound
journal rows, the deferred counter.
- tracker.resume marks the case (behind, prev); follow calls readRotated
before the new file: it opens mail.log.1 (delaycompress leaves it plain),
checks by fingerprint that it is the file the place belongs to, reads it
from the saved offset to its end through handle (catching up: the
once-protections apply) and flushes the stored lines.
- Not found, not that file, or the offset past its end (rotated twice):
logged, with the saved place's time - from when nothing was read.
- The fingerprint gains the file's identity (device.inode, fileid_unix.go;
empty elsewhere): two logs that begin alike are two files - the
review-2026-08-followups row on collisions. A fingerprint saved before
(hash alone) still matches by its hash (sameLog), so the first start after
the upgrade resumes where it was.
- store.LogtailState reads back updated_at.
Tests: stop, append, rotate, append, start - both halves read, once each,
the earlier line not again; a mail.log.1 that is another file is not read
from the place; sameLog with an old and a new fingerprint.
CHANGELOG [Unreleased], audit plan line ticked, roadmap 23/62.
Evidence: GOOS=linux go vet ./internal/logtail clean; go test ./internal/logtail
ok on Windows but for TestFollowTailsAndRotates; the server run follows
before the push.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
mixandClaude Opus 5.5
4678015bbd