Hi Andrew, hi all, I'm further investigating dlm lockspace hangs I described in https://www.redhat.com/archives/cluster-devel/2011-August/msg00133.html and in the thread starting from https://lists.linux-foundation.org/pipermail/openais/2011-September/016701.html .
What I described there is setup which involves pacemaker-1.1.6 with corosync-1.4.1 and dlm_controld.pcmk from cluster-3.0.17 (without cman). I use openais stack for pacemaker. I found that it is possible to reproduce dlm kern_stop state across a whole cluster with iptables on just one node, it is sufficient to block all (or just corosync-specific) incoming/outgoing UDP for several seconds (that time probably depends on corosync settings). I my case I reproduced hang with 3-seconds traffic block: iptables -I INPUT 1 -p udp -j REJECT; \ iptables -I OUTPUT 1 -p udp -j REJECT; \ sleep 3; \ iptables -D INPUT 1; \ iptables -D OUTPUT 1 I tried to make dlm_controld schedule fencing on CPG_REASON_NODEDOWN event (just to look if it helps with problems I described in posts referenced above), but without much success, following code does not work: int fd = pcmk_cluster_fd; int rc = crm_terminate_member_no_mainloop(nodeid, NULL, &fd); I get "Could not kick node XXX from the cluster" message accompanied with "No connection to the cluster". That means that attrd_update_no_mainloop() fails. Andrew, could you please give some pointers why may it fail? I'd then try to fix dlm_controld. I do not see any other uses of that function except than in dlm_controld.pcmk. I agree with Jiaju (https://lists.linux-foundation.org/pipermail/openais/2011-September/016713.html), that could be solely pacemaker problem, because it probably should originate fencing itself is such situation I think. So, using pacemaker/dlm with openais stack is currently risky due to possible hangs of dlm_lockspaces. Originally I got it due to heavy load on one cluster nodes (actually on a host which has that cluster node running as virtual guest). Ok, I switched to cman to see if it helps. Fencing is configured in pacemaker, not in cluster.conf. Things became even worse ;( . Although it took 25 seconds instead of 3 to break the cluster (I understand, this is almost impossible to load host so much, but anyways), then I got a real nightmare: two nodes of 3-node cluster had cman stopped (and pacemaker too because of cman connection loss) - they asked to kick_node_from_cluster() for each other, and that succeeded. But fencing didn't happen (I still need to look why, but this is cman specific). Remaining node had pacemaker hanged, it doesn't even notice cluster infrastructure change, down nodes were listed as a online, one of them was a DC, all resources are marked as started on all (down too) nodes. No log entries from pacemaker at all. So, from my PoV cman+pacemaker is not currently suitable for HA tasks too. That means that both possible alternatives are currently unusable if one needs self-repairing pacemaker cluster with dlm support ;( That is really regrettable. I can provide all needed information and really hope that it is possible to fix both issues: * dlm blockage with openais and * pacemaker lock with cman and no fencing from within dlm_controld I think both issues are really high priority, because it is definitely not acceptable when problems with load on one cluster node (or with link to that node) lead to a total cluster lock or even crash. I also offer any possible assistance from my side (f.e. patch trials etc.) to get that all fixed. I can run either openais or cman and can quickly switch between that stacks. Sorry for not being brief, Best regards, Vladislav _______________________________________________ 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