[Linux-cluster] how to handle fence for a simple apache active/passive cluster with virtual ip on 2 virtual machine
nik600
nik600 at gmail.com
Sat Feb 1 21:11:45 UTC 2014
Ok but is not possible to ignore fence?
Il 01/feb/2014 22:09 "Digimer" <lists at alteeve.ca> ha scritto:
> Ooooh, I'm not sure what option you have then. I suppose
> fence_virtd/fence_xvm is your best option, but you're going to need to have
> the admin configure the fence_virtd side.
>
> On 01/02/14 03:50 PM, nik600 wrote:
>
>> My problem is that i don't have root access at host level.
>>
>> Il 01/feb/2014 19:49 "Digimer" <lists at alteeve.ca
>> <mailto:lists at alteeve.ca>> ha scritto:
>>
>> On 01/02/14 01:35 PM, nik600 wrote:
>>
>> Dear all
>>
>> i need some clarification about clustering with rhel 6.4
>>
>> i have a cluster with 2 node in active/passive configuration, i
>> simply
>> want to have a virtual ip and migrate it between 2 nodes.
>>
>> i've noticed that if i reboot or manually shut down a node the
>> failover
>> works correctly, but if i power-off one node the cluster doesn't
>> failover on the other node.
>>
>> Another stange situation is that if power off all the nodes and
>> then
>> switch on only one the cluster doesn't start on the active node.
>>
>> I've read manual and documentation at
>>
>> https://access.redhat.com/__site/documentation/en-US/Red__
>> _Hat_Enterprise_Linux/6/html/__Cluster_Administration/index.__html
>> <https://access.redhat.com/site/documentation/en-US/Red_
>> Hat_Enterprise_Linux/6/html/Cluster_Administration/index.html>
>>
>> and i've understand that the problem is related to fencing, but
>> the
>> problem is that my 2 nodes are on 2 virtual machine , i can't
>> control
>> hardware and can't issue any custom command on the host-side.
>>
>> I've tried to use fence_xvm but i'm not sure about it because if
>> my VM
>> has powered-off, how can it reply to fence_vxm messags?
>>
>> Here my logs when i power off the VM:
>>
>> ==> /var/log/cluster/fenced.log <==
>> Feb 01 18:50:22 fenced fencing node mynode02
>> Feb 01 18:50:53 fenced fence mynode02 dev 0.0 agent fence_xvm
>> result:
>> error from agent
>> Feb 01 18:50:53 fenced fence mynode02 failed
>>
>> I've tried to force the manual fence with:
>>
>> fence_ack_manual mynode02
>>
>> and in this case the failover works properly.
>>
>> The point is: as i'm not using any shared filesystem but i'm only
>> sharing apache with a virtual ip, i won't have any split-brain
>> scenario
>> so i don't need fencing, or not?
>>
>> So, is there the possibility to have a simple "dummy" fencing?
>>
>> here is my config.xml:
>>
>> <?xml version="1.0"?>
>> <cluster config_version="20" name="hacluster">
>> <fence_daemon clean_start="0" post_fail_delay="0"
>> post_join_delay="0"/>
>> <cman expected_votes="1" two_node="1"/>
>> <clusternodes>
>> <clusternode name="mynode01" nodeid="1"
>> votes="1">
>> <fence>
>> <method name="mynode01">
>> <device
>> domain="mynode01"
>> name="mynode01"/>
>> </method>
>> </fence>
>> </clusternode>
>> <clusternode name="mynode02" nodeid="2"
>> votes="1">
>> <fence>
>> <method name="mynode02">
>> <device
>> domain="mynode02"
>> name="mynode02"/>
>> </method>
>> </fence>
>> </clusternode>
>> </clusternodes>
>> <fencedevices>
>> <fencedevice agent="fence_xvm" name="mynode01"/>
>> <fencedevice agent="fence_xvm" name="mynode02"/>
>> </fencedevices>
>> <rm log_level="7">
>> <failoverdomains>
>> <failoverdomain name="MYSERVICE"
>> nofailback="0"
>> ordered="0" restricted="0">
>> <failoverdomainnode
>> name="mynode01"
>> priority="1"/>
>> <failoverdomainnode
>> name="mynode02"
>> priority="2"/>
>> </failoverdomain>
>> </failoverdomains>
>> <resources/>
>> <service autostart="1" exclusive="0"
>> name="MYSERVICE"
>> recovery="relocate">
>> <ip address="192.168.1.239"
>> monitor_link="on"
>> sleeptime="2"/>
>> <apache config_file="conf/httpd.conf" name="apache"
>> server_root="/etc/httpd" shutdown_wait="0"/>
>> </service>
>> </rm>
>> </cluster>
>>
>> Thanks to all in advance.
>>
>>
>> The fence_virtd/fence_xvm agent works by using multicast to talk to
>> the VM host. So the "off" confirmation comes from the hypervisor,
>> not the target.
>>
>> Depending on your setup, you might find better luck with fence_virsh
>> (I have to use this as there is a known multicast issue with Fedora
>> hosts). Can you try, as a test if nothing else, if 'fence_virsh'
>> will work for you?
>>
>> fence_virsh -a <host ip> -l root -p <host root pw> -n <virsh name
>> for target vm> -o status
>>
>> If this works, it should be trivial to add to cluster.conf. If that
>> works, then you have a working fence method. However, I would
>> recommend switching back to fence_xvm if you can. The fence_virsh
>> agent is dependent on libvirtd running, which some consider a risk.
>>
>> hth
>>
>> --
>> Digimer
>> Papers and Projects: https://alteeve.ca/w/
>> What if the cure for cancer is trapped in the mind of a person
>> without access to education?
>>
>> --
>> Linux-cluster mailing list
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>>
>>
>>
>>
>
> --
> Digimer
> Papers and Projects: https://alteeve.ca/w/
> What if the cure for cancer is trapped in the mind of a person without
> access to education?
>
> --
> Linux-cluster mailing list
> Linux-cluster at redhat.com
> https://www.redhat.com/mailman/listinfo/linux-cluster
>
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