On Fri, Sep 3, 2010 at 9:38 AM, Lars Ellenberg <lars.ellenb...@linbit.com> wrote: > On Thu, Sep 02, 2010 at 09:33:59PM +0200, Andrew Beekhof wrote: >> On Thu, Sep 2, 2010 at 4:05 PM, Lars Ellenberg >> <lars.ellenb...@linbit.com> wrote: >> > On Thu, Sep 02, 2010 at 11:00:12AM +0200, Bernd Schubert wrote: >> >> On Thursday, September 02, 2010, Andrew Beekhof wrote: >> >> > On Wed, Sep 1, 2010 at 11:59 AM, Bernd Schubert >> >> > > My proposal is to rip out all network code out of pingd and to add >> >> > > slightly modified files from 'iputils'. >> >> > >> >> > Close, but thats not portable. >> >> > Instead use ocf:pacemaker:ping which goes a step further and ditches >> >> > the daemon piece altogether. >> >> >> >> Hmm, we are already using that for now temporarily. But I don't think the >> >> ping >> >> RA is suitable for larger clusters. The ping script RA runs everything >> >> serially and only in intervals when called by lrmd. Now lets assume we >> >> have a >> >> 20 node cluster. >> >> >> >> nodes = 20 >> >> timeout = 2 >> >> attempts = 2 >> >> >> >> Makes 80s for a single run with default already rather small timeouts, >> >> which >> >> is IMHO a bit large. And with a shell script I don't see a way to improve >> >> that. While we could send the pings in parallel, I have no idea how to >> >> lock >> >> the variable of active nodes (active=`expr $active + 1`). I don't think >> >> that >> >> the simple sh or even bash have a semaphore or mutex lock. So IMHO, we >> >> need a >> >> language that supports that, rewriting the pingd RA is one choice, >> >> rewriting >> >> the ping RA into python is another. >> > >> > how about an fping RA ? >> > active=$(fping -a -i 5 -t 250 -B1 -r1 $host_list 2>/dev/null | wc -l) >> > >> > terminates in about 3 seconds for a hostlist of 100 (on the LAN, 29 of >> > which are alive). >> >> Happy to add if someone writes it :-) > > I thought so ;-) > Additional note to whomever is going to: > > With fping you can get fancy about "better connectivity", > you are not limited to the measure "number of nodes responding". > You could also use the statistics on packet loss and rtt provided on > stderr for -c or -C mode (example output below, chose what you think is > easier to parse), then do some scoring scheme on average or max packet loss, > rtt, or whatever else makes sense to you. > (If a switch starts dying, it may produce increasing packet loss first...)
This sounds great. I think we want the ping RA to use fping where available. > > Or start a smokeping daemon, > and use the triggers there to change pacemaker attributes. > Uhm, well, thats probably no longer maintainable, though ;-) > > # fping -q -i 5 -t 250 -B1 -r2 -C5 -g 10.9.9.50 10.9.9.70 > 10.9.9.50 : 0.14 0.14 0.16 0.12 0.15 > 10.9.9.51 : - - - - - > 10.9.9.52 : - - - - - > 10.9.9.53 : 0.37 0.34 0.36 0.34 0.34 > 10.9.9.54 : 0.13 0.12 0.13 0.12 0.13 > 10.9.9.55 : 0.17 0.15 0.16 0.12 0.22 > 10.9.9.56 : 0.32 0.32 0.31 0.41 0.36 > 10.9.9.57 : 0.35 0.33 0.32 0.34 0.32 > 10.9.9.58 : - - - - - > 10.9.9.59 : - - - - - > 10.9.9.60 : - - - - - > 10.9.9.61 : - - - - - > 10.9.9.62 : - - - - - > 10.9.9.63 : - - - - - > 10.9.9.64 : - - - - - > 10.9.9.65 : 1.92 0.33 0.33 0.33 0.34 > 10.9.9.66 : - - - - - > 10.9.9.67 : - - - - - > 10.9.9.68 : - - - - - > 10.9.9.69 : 0.15 0.14 0.17 0.13 0.14 > 10.9.9.70 : - - - - - > > # fping -q -i 5 -t 250 -B1 -r2 -c5 -g 10.9.9.50 10.9.9.70 > 10.9.9.50 : xmt/rcv/%loss = 5/5/0%, min/avg/max = 0.11/0.13/0.15 > 10.9.9.51 : xmt/rcv/%loss = 5/0/100% > 10.9.9.52 : xmt/rcv/%loss = 5/0/100% > 10.9.9.53 : xmt/rcv/%loss = 5/5/0%, min/avg/max = 0.33/0.34/0.37 > 10.9.9.54 : xmt/rcv/%loss = 5/5/0%, min/avg/max = 0.10/0.11/0.13 > 10.9.9.55 : xmt/rcv/%loss = 5/5/0%, min/avg/max = 0.13/0.16/0.20 > 10.9.9.56 : xmt/rcv/%loss = 5/5/0%, min/avg/max = 0.34/0.36/0.41 > 10.9.9.57 : xmt/rcv/%loss = 5/5/0%, min/avg/max = 0.16/0.25/0.33 > 10.9.9.58 : xmt/rcv/%loss = 5/0/100% > 10.9.9.59 : xmt/rcv/%loss = 5/0/100% > 10.9.9.60 : xmt/rcv/%loss = 5/0/100% > 10.9.9.61 : xmt/rcv/%loss = 5/0/100% > 10.9.9.62 : xmt/rcv/%loss = 5/0/100% > 10.9.9.63 : xmt/rcv/%loss = 5/0/100% > 10.9.9.64 : xmt/rcv/%loss = 5/0/100% > 10.9.9.65 : xmt/rcv/%loss = 5/5/0%, min/avg/max = 0.28/0.32/0.34 > 10.9.9.66 : xmt/rcv/%loss = 5/0/100% > 10.9.9.67 : xmt/rcv/%loss = 5/0/100% > 10.9.9.68 : xmt/rcv/%loss = 5/0/100% > 10.9.9.69 : xmt/rcv/%loss = 5/5/0%, min/avg/max = 0.13/0.14/0.15 > 10.9.9.70 : xmt/rcv/%loss = 5/0/100% > >> >> So in fact my first proposal also only was the first step - first add >> >> better >> >> network code and then to make it multi-threaded - each ping host gets its >> >> own >> >> thread. >> > >> > A working pingd daemon has the additional advantage that it can ask its >> > peers for their ping node count, before actually updating the attribute, >> > which should help with the "dampen race". >> >> That happens at the attrd level in both cases. pingd adds nothing here. > > I thought pingd did the dampening itself, even communicated with its peer > pingd's, and there was no more dampening in attrd involved after that. Nope. All in attrd. I dont like writing things twice :-) > But If you say so. I never looked at pingd too closely. > >> >> PS: (*) As you insist ;) on quorum with n/2 + 1 nodes, we use ping as >> >> replacement. We simply cannot fulfill n/2 + 1, as controller failure takes >> >> down 50% of the systems (virtual machines) and the systems (VMs) of the >> >> 2nd >> >> controller are then supposed to take over failed services. I see that n/2 >> >> + 1 >> >> is optimal and also required for a few nodes. But if you have a larger >> >> set of >> >> system (e.g. minimum 6 with the VM systems I have in my mind) n/2 + 1 is >> >> sufficient, IMHO. >> > >> > You meant to say you consider == n/2 sufficient, instead of > n/2 ? > > So you have a two node virtualization stuff, each hosting n/2 VMs, > and do the pacemaker clustering between those VMs? > > I'm sure you could easily add "somewhere else" a very bare bone VM > (or real) server, that is dedicated member of your cluster, but > never takes any resources? Just serves as arbitrator? as your "+1"? > > May be easier, safer, and more transparent than > no-quorum=ignore plus some ping attribute based auto-shutdown. > > -- > : Lars Ellenberg > : LINBIT | Your Way to High Availability > : DRBD/HA support and consulting http://www.linbit.com > > DRBD® and LINBIT® are registered trademarks of LINBIT, Austria. > > _______________________________________________ > Pacemaker mailing list: Pacemaker@oss.clusterlabs.org > http://oss.clusterlabs.org/mailman/listinfo/pacemaker > > Project Home: http://www.clusterlabs.org > Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf > Bugs: > http://developerbugs.linux-foundation.org/enter_bug.cgi?product=Pacemaker > _______________________________________________ Pacemaker mailing list: Pacemaker@oss.clusterlabs.org http://oss.clusterlabs.org/mailman/listinfo/pacemaker Project Home: http://www.clusterlabs.org Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf Bugs: http://developerbugs.linux-foundation.org/enter_bug.cgi?product=Pacemaker
