Using xrdcp and http to write extended attributes

General Discussion
1

Hello,

I’m creating files with various bits of metadata, and I’d like to write in the extended metadata too, as fetched from the method in a previous conversation here.

Looking into the EOS source code, it appears that I can pass along eos.xattr as a field, but I can’t figure out the particular format for this value.

How does one format this string such that it’ll work with an xrdcp root://mgm/path/file?eos.xattr=... sequence?

2

Hi David,

I had a quick look at this but I’m afraid there is a bug which makes this functionality unusable for the moment. I’ve pushed this fix and things work file now:
https://gitlab.cern.ch/dss/eos/commit/e971c7ce898005a50b494aa57772be49d0de0c18

For example:
xrdcp -f -d 1 /etc/passwd root://localhost//eos/dev/replica/david1.dat?eos.xattr=user.acl=u:esindril:rwx

Looks like this on the MGM side:

EOS Console [root://localhost] |/eos/dev/replica/> attr ls david1.dat
user.acl="u:esindril:rwx"

Unfortunately, this will require a new release and update of the MGM unless you can build it yourself …
A new release will probably happen next week.

Cheers,
Elvin

1 Like
3

Thank you @esindril. For some reason I never saw an email about this reply, apologies for my delay in getting back to you.

How does one then use to set multiple metadata fields? Specify eos.xattr as a parameter for each extended attribute, so that it reads “?eos.xattr=my.attribute=foo&eos.xattr=your.attribute=baz” ?

4

Hi David,

No worries. Well now, looking at the functionality to add multiple xattrs in one command this can not work since it assumes the “&” is the separator. But the “&” is the default separator for the opaque tokens.
I’ve pushed another fix to use “#” as separator between multiple xattr values. This will be available in 4.5.3:
https://gitlab.cern.ch/dss/eos/commit/ce83d6b347d704c3bf3d486c5ad24367295d1e62

Now, you should be able to set multiple xattrs in one go like this:

sudo xrdcp -f -d 1 /etc/passwd "root://localhost//eos/dev/replica/davida1.dat?eos.xattr=user.acl=u:esindril:rwx#user.mask=700"                                                                                                                           
[3.236kB/3.236kB][100%][==================================================][3.236kB/s]  


EOS Console [root://localhost] |/eos/dev/replica/> attr ls davida1.dat
sys.eos.btime="1563972113.221350554"
user.acl="u:esindril:rwx"
user.mask="700"

Cheers,
Elvin