- if all service nodes not running dhcp, to treat it as disjointdhcps=0
- nodeset will send request to MN by default even if disjointdhcps=1
- Move out of the dhcp service checking from opts pre-check, and do it just before real makedhcp handling.
2, handle 'disjoint' in preprocess method, to make sure that no request will be sent to SN which does not manage the nodes.
3, refine 'stat' to make sure it could query unmanaged nodes on-demand.
* Fix#3087: nodeset improvement - using multi-process to parallelize
- before deliver the request to xcatd, we can split the request to multiple sub-requests which contains different noderange
- in that, xcatd could hanle those sub-requests in parallel, just like some issue multiple commands.
* refine according to the review comments:
- not using POSIX::ceil
- Callback is reserved for filter method
* refine codes according review comments
* make the comments right and more readable.
