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    Hosts in a pool have gone offline after reboot

    Scheduled Pinned Locked Moved Management
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    • A Offline
      Aeoran @Danp
      last edited by

      @Danp Sorry about the cross post. I realised I might have put it in the wrong section of the forum, as this might not be related to XO management. But that's where I first encountered it, so good enough.

      All of the hosts are running the most up to date version, and the patches are all up to date as of right now. I cannot be absolutely certain that the slaves were not rebooted before the master - I was adopting a new slave a week or two ago, which failed at first. So that might have been rebooted first.

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      • DanpD Offline
        Danp Pro Support Team
        last edited by

        Is the pool master up and running?

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        • A Offline
          Aeoran
          last edited by

          No, the pool master is not running. The logs posted are from the machine that was the pool master.

          The machine boots but the management interface (console) has no NIC, and no network.

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          • DanpD Offline
            Danp Pro Support Team
            last edited by

            Have you checked to see if there are any pending updates on the pool master by running yum update?

            I've never encountered this particular error, but here are some other things you could try --

            • Emergency network reset, which can be done from the CLI or from within xsconsole

            • Force one of your slaves to become the new master using xe pool-emergency-transition-to-master. You can read more about this in this thread.

            I hope that you have good backups of your VMs. 😉

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            • A Offline
              Aeoran @Danp
              last edited by

              @Danp I did a yum update and a xe-toolstack-restart on all three hosts, made no difference.

              I also tried doing an emergency network reset on just the master, but no difference. I think that XAPI isn't up at all because of the database.

              Will a reinstall of XCP work? Some forum entries seem to suggest so, but I'm leery of how fragile this seems to be.

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              • A Offline
                Aeoran @Danp
                last edited by

                @Danp So the saga continues:

                I designated the sole running host as the new master. It did this happily and in fact also discovered one of the other hosts - the one that was not the old master. So far so good.

                I was able to then take a look at the list of VMs, then force any VMs "running" on the dead host (the old master) to be halted. Now the dead host only has the XCP control plane running.

                All that is left is to get the dead host forgotten from the pool and then rejoin the pool, right?

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                • DanpD Offline
                  Danp Pro Support Team @Aeoran
                  last edited by

                  @Aeoran Yes, that sounds like a good plan.

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                  • A Offline
                    Aeoran @Danp
                    last edited by

                    @Danp Is there some documentation you would recommend on how to safely forget a host? I'm confronted with dire warnings on how this will permanently destroy the SRs used by the VMs that used to run on the dead host. So, I want to make really sure I won't be doing something wrong here.

                    Thanks!

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                    • nikadeN Offline
                      nikade Top contributor
                      last edited by

                      Shared storage should belong to the pool, only local SR should be affected when you forget the old master.
                      Just make sure all the slaves know about the new master before doing anything to the old one.

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                      • A Offline
                        Aeoran @nikade
                        last edited by

                        @nikade It looks like I cannot get the dead host to rejoin the pool using xe pool-join:

                        You attempted an operation that was not allowed.
                        reason: Host is already part of a pool
                        

                        Will I have problems if I try to force it to join with xe pool-join force? A forum post seems to suggest that this may propagate data corruption errors from the dead host to the pool, which is obviously undesireable. So how would I avoid that?

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                        • nikadeN Offline
                          nikade Top contributor
                          last edited by

                          Not really sure, I'd ask @olivierlambert to be sure.

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                          • DanpD Offline
                            Danp Pro Support Team
                            last edited by

                            What actions did you initially perform to remove the host from the pool?

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                            • A Offline
                              Aeoran @Danp
                              last edited by

                              @Danp I didn't do anything. The master host failed on its own and stopped responding to XO.

                              I've rebooted the host and the hardware all seems fine. The logs suggest that XAPI is not running because the database is missing a column (see above, first comment).

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                              • DanpD Offline
                                Danp Pro Support Team
                                last edited by

                                You probably need to forget the host using xe host-forget uuid=UUID where UUID belongs to the old pool master.

                                See prior discussion on this topic -- https://xcp-ng.org/forum/topic/6164/remove-a-host-from-a-pool/14

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                                • A Offline
                                  Aeoran @Danp
                                  last edited by

                                  @Danp How can I preserve or recover the local SRs of the dead host?

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                                  • DanpD Offline
                                    Danp Pro Support Team @Aeoran
                                    last edited by

                                    @Aeoran AFAIK, the XAPI database gets wiped whenever you add or remove the host from a pool. You may be able to restore metadata to the old master once it is no longer belongs to the pool, but I can't guarantee that this will work or not produce other issues.

                                    If you don't have backups of the VMs, then you should be able to copy the VHD files to another location by accessing the directory /run/sr-mount/<SR UUID>/ on the old master.

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