Traceback when running 'check --repair' on a repository

[Ernest0x]

I got the following when running 'check --repair' on a repository. It seems that the code found some damage that could not handle.

...
Archive metadata damage detected
Traceback (most recent call last):
  File "/usr/local/bin/attic", line 5, in <module>
    pkg_resources.run_script('Attic==0.13', 'attic')
  File "/usr/lib/python3/dist-packages/pkg_resources.py", line 499, in run_script
    self.require(requires)[0].run_script(script_name, ns)
  File "/usr/lib/python3/dist-packages/pkg_resources.py", line 1236, in run_script
    exec(compile(open(script_filename).read(), script_filename, 'exec'), namespace, namespace)
  File "/usr/local/lib/python3.2/dist-packages/Attic-0.13-py3.2-linux-x86_64.egg/EGG-INFO/scripts/attic", line 3, in <module>
    main()
  File "/usr/local/lib/python3.2/dist-packages/Attic-0.13-py3.2-linux-x86_64.egg/attic/archiver.py", line 715, in main
    exit_code = archiver.run(sys.argv[1:])
  File "/usr/local/lib/python3.2/dist-packages/Attic-0.13-py3.2-linux-x86_64.egg/attic/archiver.py", line 705, in run
    return args.func(args)
  File "/usr/local/lib/python3.2/dist-packages/Attic-0.13-py3.2-linux-x86_64.egg/attic/archiver.py", line 84, in do_check
    if not args.repo_only and not ArchiveChecker().check(repository, repair=args.repair):
  File "/usr/local/lib/python3.2/dist-packages/Attic-0.13-py3.2-linux-x86_64.egg/attic/archive.py", line 494, in check
    self.rebuild_refcounts()
  File "/usr/local/lib/python3.2/dist-packages/Attic-0.13-py3.2-linux-x86_64.egg/attic/archive.py", line 646, in rebuild_refcounts
    items_buffer.add(item)
  File "/usr/local/lib/python3.2/dist-packages/Attic-0.13-py3.2-linux-x86_64.egg/attic/archive.py", line 69, in add
    self.buffer.write(self.packer.pack(StableDict(item)))
TypeError: cannot convert dictionary update sequence element #0 to a sequence

[ThomasWaldmann]

Could you use attic 0.14 and try again? Just to make sure we do not look at already fixed bugs.

[Ernest0x]

Could you use attic 0.14 and try again? Just to make sure we do not look at already fixed bugs.

The same error occurs with attic 0.14 too.

[ThomasWaldmann]

If you could add a little code and look for the output, it would help analysing the problem:

In file /usr/local/lib/python3.2/dist-packages/Attic-0.13-py3.2-linux-x86_64.egg/attic/archive.py", before line 69 (self.buffer.write(self.packer.pack(StableDict(item)))), add:

print(repr(item))
print(repr(StableDict(item)))

Indent these lines same as the following line. Post the output here (should show up at top of the traceback)).

[Ernest0x]

The traceback occurs when trying to analyze a specific archive. Here is the output just before the traceback, after adding the print() calls above:

Analyzing archive binlogs_2015-03-09-02:25 (364/2074)
{b'path': b'var/lib/mysql/binlog.020441', b'gid': 108, b'group': b'mysql', b'mode': 33200, b'mtime': 1425027901071324160}
{b'path': b'var/lib/mysql/binlog.020441', b'gid': 108, b'group': b'mysql', b'mode': 33200, b'mtime': 1425027901071324160}
b'uid'

[Ernest0x]

Also, unfortunately, I have been left without options, as I cannot even delete the damaged archive. This is because the first thing that all operations are trying to do is triggering that 'analyzing' step on each archive, which always crashes when reaching the damaged archive.

[Ernest0x]

When trying to delete the damaged archive (with the delete operation) I do not get a traceback, but this:

Analyzing archive: binlogs_2015-03-09-02:25
attic: Error: Object with key b'c`e\x959\x12iGF<\xd9\x84=\xc6l\x86\xd9\x08n\r) %\xe2\xf5\xa2\xc5\xa1L\x8c*\x99' not found in repository modcom-db

[Ernest0x]

For clarity, I included in the beggining of the lines what is actually printed with the print() calls above:

item: {b'path': b'var/lib/mysql/binlog.020441', b'gid': 108, b'group': b'mysql', b'mode': 33200, b'mtime': 1425027901071324160}
StableDict(item): {b'path': b'var/lib/mysql/binlog.020441', b'gid': 108, b'group': b'mysql', b'mode': 33200, b'mtime': 1425027901071324160}
item: b'uid'

In the code, it seems that robust_iterator() handles only the cases when an archive item is missing (?). However, in my case the item does exist, but has not the correct format: it is a bytestring instead of a dict, which cannot be converted later to a StableDict object, and the traceback occurs. So, would a type check for dict on archive items make the robust_iterator() more, well... robust? I am not sure how that item got packed in the msgpack stream in the first place, but at Ieast, it should be possible to ignore it. Or perhaps, it would be safer to delete the whole archive from the repository. What do you think?

[ThomasWaldmann]

your analysis is correct IMHO. I added a type check and a warning.

@Ernest0x try that: https://paste.thinkmo.de/2jRZKJyy#fix_232.diff

Test if check now works, and also test delete again.

@jborg look here ^^ and there vv. Would be a nice fix for next release and it is not yet finished/committed.

[Ernest0x]

@ThomasWaldmann your patch did the job. attic check --repair did the repairing and attic delete deleted the archive. Thanks.

That said, however, I am not sure if the best place to put the check is where you put it in the patch. For example, the check operation uses a custom msgpack unpacker class named "RobustUnpacker", which it does try to check for correct format (see the comment: "Abort early if the data does not look like a serialized dict"), but it seems it does not catch my case. The relevant code in 'cache.py', on the other hand, uses msgpack's Unpacker class.