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Re: [Libvir] Proposal: Block device and network stats

Daniel Veillard wrote:
   wr_bytes :-)

Duh :-(

  int64_t errs;   // In Xen this returns the mysterious 'oo_req'.
typedef struct _virDomainBlockStats *virDomainBlockStatsPtr;

  then yes that's okay.
Those interfaces are what I suggested as the low level ones, I guess
they are needed even if tehy don't really scale as the number of domain and more importantly the number of node increases. But it allows
to build higher level monitoring implementations.
My current POV based on previous monitoring work is that if you are monitoring
up to a few dozen machines then aggregating the data to the monitoring application is fine, where you can then apply the user based policy to
raise the events (and subsequent rules or UI alerts), but if you want
to scale you have to export the monitoring down to each node, and push
the policies there, just gathering the events/alerts at the monitoring
application or console level.
In any case having the low level API is needed so something like those
entry points are needed.


The other issue is remote, where we make 2 * nr_domains round trips. We're already making some k * nr_domains round trips to get the other info (eg. domain names, state, VCPU usage, ...) so there is an argument for being able to aggregate remote requests. The easiest thing would seem to be to allow remote to pipeline requests and responses. Pipelining would get rid of the round trip delays. The remote protocol allows pipelining already, but needs some mucky coding on top to make it actually work.


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