[redirecting to the mailing list] On Tue, May 22, 2012 at 5:38 PM, Doug Hellmann <doug.hellm...@dreamhost.com>wrote:
> Cool. That's not what I was expecting, but I hadn't gotten far enough to > dig into libvirt yet. We can definitely make cumulative messages work, and > that does eliminate a lot of my concern about missing a message here or > there. > > > On Tue, May 22, 2012 at 5:36 PM, James R Penick <pen...@yahoo-inc.com>wrote: > >> Libvirt statistics are all cumulative, my collection agent stores them >> all in a sqlite db, and my monitoring agent compares deltas to determine >> resource utilization and send alerts. >> >> -James >> >> >> -----Original Message----- >> *From:* Doug Hellmann [doug.hellm...@dreamhost.com] >> *Received:* Tuesday, 22 May 2012, 2:32pm >> *To:* James R Penick [pen...@yahoo-inc.com] >> *CC:* Nick Barcet [nick.bar...@canonical.com]; >> openstack@lists.launchpad.net [openstack@lists.launchpad.net] >> *Subject:* Re: [Openstack] [metering] high-level design proposal >> >> >> >> On Tue, May 22, 2012 at 4:35 PM, James R Penick <pen...@yahoo-inc.com>wrote: >> >>> >>-> In addition to a signature, I think we would need a sequence number >>> >>to be embedded by the agent for each message sent, so that loss of >>> >>messages, or forgery of messages, can be detected by the collector and >>> >>further audit process. >>> >>> >OK. We have a message id, but I assumed those would be used to eliminate >>> >duplicates so this sounds like something different or new. It implies >>> >that the agent knows its own id (not hard) and keeps up >with a sequence >>> >counter (more difficult, though not impossible). >>> >Did you have something in mind for how to implement that? >>> >>> >>> If we're submitting messages every given node with a predictable >>> frequency, we should be able to determine that a message was lost simply >>> by noting a gap in the timestamps. Also, if we're sending cumulative >>> statistics then the loss of a single message (or even a fair number of >>> them) shouldn't impact our ability to meter too much. >>> >> >> I don't know if we have cumulative statistics. What does libvirt >> actually give us? >> >> >>> >>> -James >>> >>> >> >
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