[WARN] ignoring error reading parent snapshot: TreeStackEmptyError

[vt-alt]

In 0.9.5 I noticed such warning on my tests:

rustic (sisyphus)$ rustic backup .
...
[00:00:00] reading index...               ████████████████████████████████████████          3/3
[00:00:00] getting latest snapshot...     ████████████████████████████████████████          3/3
[INFO] using parent a9f756c6
[INFO] starting to backup . ...
[00:00:00] backing up...                  ████████████████████████████████████░░░░ 450.80 MiB/489.44 MiB 834.63 MiB/s (ETA 0s)
[WARN] ignoring error reading parent snapshot: TreeStackEmptyError
[00:00:03] backing up...                  ████████████████████████████████████████ 489.44 MiB/489.44 MiB 155.93 MiB/s (ETA -)
Files:       0 new, 0 changed, 31508 unchanged
Dirs:        0 new, 0 changed, 5552 unchanged
Added to the repo: 0 B (raw: 0 B)
processed 31508 files, 489.4 MiB
snapshot 96d2a461 successfully saved.
[INFO] backup of . done.

This happens on old and new repositories. The error warnings usually isn't what you want to see in backup software, especially I did nothing suspicious to cause this.

[aawsome]

@vt-alt Thanks for opening this issue. You are right, even though this is "just" related to parent processing such a warning should not come in standard case (I actually thought it will never show up...). Can you please re-run with a higher verbosity, e.g. --log-level=debug and give the output (the last lines before the warning may be sufficient, you can also redact sensitive information, of course)

[vt-alt]

They are just in the middle of test backup of the rustic repo itself (with cargo vendor tree).

rustic$ rustic --log-level=debug backup .
...
[00:00:03] backing up...                  ███████████████████████████████████████░ 484.89 MiB/489.44 MiB 118.58 MiB/s (ETA 0s)                                 
...
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/decompress/zstd_decompress_block.h"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/decompress/zstd_decompress_internal.h"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged tree: "./vendor/zstd-sys/zstd/lib/decompress"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/deprecated/zbuff.h"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/deprecated/zbuff_common.c"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/deprecated/zbuff_compress.c"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/deprecated/zbuff_decompress.c"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged tree: "./vendor/zstd-sys/zstd/lib/deprecated"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/dictBuilder/cover.c"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/dictBuilder/cover.h"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/dictBuilder/divsufsort.c"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/dictBuilder/divsufsort.h"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/dictBuilder/fastcover.c"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/dictBuilder/zdict.c"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged tree: "./vendor/zstd-sys/zstd/lib/dictBuilder"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/legacy/zstd_legacy.h"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/legacy/zstd_v01.c"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/legacy/zstd_v01.h"
[WARN] ignoring error reading parent snapshot: TreeStackEmptyError
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/legacy/zstd_v02.c"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/legacy/zstd_v02.h"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/legacy/zstd_v03.c"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/legacy/zstd_v03.h"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/legacy/zstd_v04.c"
...

Re-run:

[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/dictBuilder/zdict.c"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged tree: "./vendor/zstd-sys/zstd/lib/dictBuilder"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/legacy/zstd_legacy.h"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/legacy/zstd_v01.c"
[DEBUG] (1) rustic_core::archiver::tree_archiver: unchanged file: "./vendor/zstd-sys/zstd/lib/legacy/zstd_v01.h"
[WARN] ignoring error reading parent snapshot: TreeStackEmptyError

So it happened consistently at the same place.