vine: set file mode for all transmitted file types

[btovar]

Currently local files in taskvine are copied to the workers with the same permissions they have in the machine running the manager. For coffea-casa some files need to be chmod to 0600.

This sounds like a mount option, however, the mode is kept in the file structure; thus it would be easier to add a set_mod to the vine_file. This is specially true for the dask executor, as users only have access to files, but not mounts when specifying extra_files.

[btovar]

Actually the mode is not kept in vine_file, but it is read from stat every time the file is transferred.

[btovar]

A workaround with minitasks:

local_token = m.declare_file("token", cache=True)
do_chmod = vine.Task("chmod 0600 input_file")
do_chmod.add_input(local_token, "input_file")

f = m.declare_minitask(do_chmod, "input_file", cache=True, peer_transfer=True)

t = vine.Task("stat access_token")
t.add_input(f, "access_token")

[dthain]

Interestingly, the worker and the manager-worker protocol all support the notion that the file mode is carried over the network and applied at the worker. We are just missing the opportunity to set the mode appropriately through the API. For a normal file, it can come from the file source. But buffers, urls, and other files sources don't have an obvious way. For example:

cctools/taskvine/src/manager/vine_manager_put.c

Line 235 in 0179753

/* XXX The API does not allow the user to choose the mode bits of the target file, so we make it permissive

Suggest that what we do is add a new file method something like this:

vine_file_set_mode( file, mode );

And then use that saved info throughout vine_manager_put.