The Shaman server is a file storage system that identifies files by
SHA256sum and file length. BAT can send packs there by only uploading
changed/new files. The BAT pack is reproduced at the Shaman server's
checkout directory by creating symlinks to the files in its file
storage.
Retrying sending files:
When we can defer uploading a file (that is, when we have other files to
upload as well, and we could send the current file at a later moment) we
send an `X-Shaman-Can-Defer-Upload: true` header in the file upload
request. In that case, when someone else is already uploading that file,
a `208 Already Reported` response is sent and the connection is closed.
Python's Requests library unfortunately won't give us that response if
we're still streaming the request, and raise a ConnectionError exception
instead. This exception can mean two things:
- If the `X-Shaman-Can-Defer-Upload: true` header was sent: someone else
is currently uploading that file, so defer it.
- If that header was not sent: that file is already completely uploaded
and does not need to be uploaded again.
Instead of retrying each failed file, after a few failures we now just
resend the definition file to get a new list of files to upload, then
send those. This should considerably reduce the number of HTTP calls
when multiple clients are uploading the same set of files.
The target path is just read as string from the CLI now, to allow more
complex targets (such as URLs) that don't directly map to a path.
The Packer subclass now handles the conversion from that string to a
`pathlib.PurePath`, and specific subclasses & transfer classes can convert
those to a `pathlib.Path` to perform actual filesystem operations when
necessary.
This makes BAT skip assets that are referred to with an absolute path.
It is assumed that the receiver of the BAT pack can access those assets
at the same path.
This will cause a nice speedup if the temporary directory happens to be on
the same file system as the target directory for the BAT Pack. This can be
influenced by setting an environment variable; see the documentation for
[tempfile.gettempdir](https://docs.python.org/3/library/tempfile.html#tempfile.gettempdir)
This does introduce some not-so-nice things, like having to annotate each
`__init__` function with `-> None`. However, the benefits of having static
type checking in a complex bit of software like BAT outweigh the downsides.
- Tracer now iterates over blocks in disk order.
- Packer copies files per directory, in a separate thread.
- Packer only copies files if they don't exist yet.
- Packer also copies file permissions.
No path rewriting yet, just simply copying the dependencies. They are
copied to the target directory + the path relative to the current working
directory. For example:
bat pack scenes/05-barber/05_02_C-agent_focused/05_02_C.lighting.blend /tmp/packer
will write to
/tmp/packer/scenes/05-barber/05_02_C-agent_focused/05_02_C.lighting.blend
and will copy ./path/to/file → /tmp/packer/path/to/file
