Operators in Metadata

[ForbiddenEra]

Would the authors consider allowing operators in metadata?

ie:

[X-fleet]
MachineMetadata=ram>=2048

This + way to update metadata easier = dynamic metadata, awesome? lame? opinions?

thanks

[ForbiddenEra]

I was doing some reading last night, and it turns out systemd actually supports some of this (similar) already in unit files.

Here's the article I was reading (look under the header of "Language Issues")
http://lwn.net/Articles/584176/

Though I'm guessing something like..

[X-fleet]
MachineMetadata=!ram=1024

..wouldn't work..?

[bcwaldon]

I don't really have an issue with this, but we need to put some effort into design before we can move forward.

[HarryR]

Variable expansion in the MachineMetadata field would be a good use case too, for example in a template I could specify that no two units will be placed in the same datacenter or on a machine which is already running the service.

[X-Fleet]
MachineMetadata=dc!=$METADATA_DC
MachineMetadata=role!=db
MachineMetadata=cores>=4
Conflicts=$NAME

[iby]

That would be pretty awesome indeed. Is there a way of dealing with list values at all? For example, if I have several groups, like app, lb, postgres and mongo, where a host may be present in more than one group, then I'd like to have group='app,lb,postgres' metadata set on it. But the only way to describe this with fleet would be more like group_app=true, group_lb=true, group_postgres=true, right?

Would you also consider supporting lists and contains or in operator? Or maybe even better (for consistency sake) support repeating keys in metadata, combine items with repeated keys into a list, and use same operators, e.g., group==lb would check if an item is present in the list, group!=mongo that it's not, etc.

[jbguerraz]

@ianbytchek +1
list values (typically for groups/roles usage) is definitely something needed