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Javier de la TorreandJavier de la Torre
df89afbef4
* volume: repair an unindexed .dat tail at load instead of loading read-only A needle write appends the needle to the .dat, then its entry to the .idx, then answers the client. A crash between the two appends leaves a .dat that ends past the last indexed needle; on the next start CheckVolumeDataIntegrity reports "actual N bytes expected M bytes" and the volume loads read-only, and a complete needle in that tail cannot be read because nothing indexes it. After a process crash those bytes belong to a write that was never answered; after a power loss a complete needle can survive in the .dat while its .idx entry did not, although the client was answered. So complete needles are re-indexed rather than cut. CheckVolumeDataIntegrity now repairs the tail before the existing check, which then runs on the repaired files as before. The repair: - acts only on a local, version 3 volume within MaxPossibleVolumeSize, with a whole number of .idx entries, that is about to load writable (neither noWriteOrDelete nor noWriteCanDelete is set); - requires the needle at the highest indexed offset to match its entry (id, size, whole record, CRC); - walks from the end of that needle to the real end of the file and gives every complete needle (header, body, checksum, timestamp and padding inside the file, CRC valid, append timestamp later than the needle before it) the .idx entry the volume server would have written, in .dat order; a size 0 record, which is how a delete is appended, is indexed as a tombstone; - cuts only an incomplete last record: fewer bytes than a header, a record running past the end of the file, or a last record whose CRC fails; - changes nothing otherwise (a damaged record with more data after it, a header with id 0 or a negative size, append timestamps going backwards), so the volume loads read-only exactly as before. The .idx entries are written and synced before the .dat is truncated and synced, so a crash during the repair leaves the needles indexed and the remainder still past them; the next load cuts it. One warning per repaired volume names the needles re-indexed and the bytes cut. Tests: volume_checking_tail_repair_test.go reloads volumes through the normal load path. Repaired: one and two complete unindexed needles, an unindexed delete, a partial header, a partial body, a complete needle followed by a partial one, a last needle with a bad CRC, a partial needle after an indexed tombstone; each reloads clean afterwards. Left read-only and unchanged: the last indexed needle with a wrong id or a bad CRC, a bad CRC followed by more data, zero bytes past the last needle, an index past the data, a volume persisted read-only, a partial .idx entry, and a clean volume. TestCheckVolumeDataIntegrityVerifiesDeletionTail now also checks that on a writable volume its 64 zero bytes are reported and kept. Fixes #11864 * volume: fail the integrity check when a tail repair cannot complete A repair that wrote the .idx or cut the .dat and then failed to sync only logged the error; the check that followed saw the repaired files and the volume loaded writable on a repair that may not be on disk. Any repair error other than an unexplained tail now fails the check, so the volume loads read-only, and the next load repairs again. A failed .idx append could leave part of an entry behind, which made every later load reject the .idx as a partial entry. The appended bytes are truncated away again before the error is returned. * volume: do not cut a tail record that could not be read The walk cut a last record whose read failed for any reason, so an I/O error (EIO) on a complete record erased it. Only a record whose bytes are damaged (needle.ErrorCorrupted: a CRC mismatch or a body that does not parse) is cut now; any other read error is returned with both files left as they are, and the volume loads read-only. * volume: treat a sized tail record with no data as damaged A needle with no data is written with size 0. A tail record whose header gives a body but whose data size field reads 0 parsed as an empty needle, and ReadBytes checks the CRC only when there is data, so the repair indexed it with its positive size and reads returned an empty body. Such a record is now damaged like one with a bad CRC: cut when it is the last record, otherwise the tail is left alone and the volume loads read-only. * volume: keep an unindexed empty write as an empty needle A delete and a write with no data both append a size 0 record, and the repair indexed every size 0 record in the tail as a tombstone, so an acknowledged empty write whose .idx entry was lost read back as deleted. A delete is only appended for a needle that is live, so a size 0 record of a needle that is absent or deleted (in the .idx and in the tail before it) is an empty write and is re-indexed with size 0. One of a live needle stays a tombstone, the reading weed fix and the backup's index regeneration already give it. The .idx is scanned only when the tail holds a size 0 record. * volume: cut torn-tail test records inside their body, not at +40 The partial-record cases cut the .dat 40 bytes into a record. A needle with up to 7 bytes of data is a 40-byte record, so newRandomNeedle's random length (1..1023) left it whole about once in 150 runs per case: the repair then correctly re-indexed it and cut nothing, and the test failed on the .dat size. The cut now lands halfway through the record's body, which is always past its header and short of its end. --------- Co-authored-by: Javier de la Torre <jatorre@lakehousebox.com>