BrokenPipeError for remote archives

[ThomasWaldmann]

I encountered this issue in a bit strange way, by trying to use zlib level 0.
But I guess this could happen otherwise also, e.g. if data compresses really badly. Or even otherwise.

In attic/key.py (about line 80), there is a line like:

return b''.join([self.TYPE_STR, zlib.compress(data)])

Add compression level 0 there (instead of the implicit default level 6):

return b''.join([self.TYPE_STR, zlib.compress(data, 0)])

Now run the unit tests: fakeroot -u tox

You may have one additional issue in the test log now:

284 test_overwrite (attic.testsuite.archiver.RemoteArchiverTestCase) ... Traceback (most recent call last):
285   File "/usr/lib/python3.4/runpy.py", line 170, in _run_module_as_main
286     "__main__", mod_spec)
287   File "/usr/lib/python3.4/runpy.py", line 85, in _run_code
288     exec(code, run_globals)
289   File "/tmp/merge/.tox/py34/lib/python3.4/site-packages/attic/archiver.py", line 740, in <module>
290     main()
291   File "/tmp/merge/.tox/py34/lib/python3.4/site-packages/attic/archiver.py", line 727, in main
292     exit_code = archiver.run(sys.argv[1:])
293   File "/tmp/merge/.tox/py34/lib/python3.4/site-packages/attic/archiver.py", line 717, in run
294     return args.func(args)
295   File "/tmp/merge/.tox/py34/lib/python3.4/site-packages/attic/archiver.py", line 54, in do_serve
296     return RepositoryServer(restrict_to_paths=args.restrict_to_paths).serve()
297   File "/tmp/merge/.tox/py34/lib/python3.4/site-packages/attic/remote.py", line 58, in serve
298     sys.stdout.buffer.write(msgpack.packb((1, msgid, None, res)))
299 BrokenPipeError: [Errno 32] Broken pipe

It was reproduced by @paolodina on ubuntu 14.10 64bit and me on ubuntu 14.04 64bit.
dcrouch from IRC #attic could not reproduce on centos 6.6.

A special thing to note about zlib level 0 is that output data always will be bigger than input data.

[ThomasWaldmann]

Something within these changes broke it (I used git bisect to find it):

git diff c973040..bd5b72a

[ThomasWaldmann]

it is not in zlib.

i kept zlib default level and just appended >64kB dummy bytes to compression result (and stripped it from end before invoking decompress) - that breaks it in exactly the same way.

[ThomasWaldmann]

I found it is related to pipe I/O, fix coming soon, just doing some final tests.

[ThomasWaldmann]

See PR #234.

[paolodina]

@ThomasWaldmann I run the tests with fakeroot -u tox and confirm the BrokenPipeError disappeared. Good for me on xubuntu 14.10.