Z,
You are forcing a byzantine failure, the paxos implemented to form the consensus ring of the mon daemons does not support this kind of failures, that is why you get and erratic behaviour, I believe is the common paxos algorithm implemented in mon daemon code.
If you just gracefully shutdown a mon daemon everything will work fine, but with this you can not prove a split brain situation, because you will force the election of the leader by quorum.
Maybe with 2 mon daemons and closing the communication between each of them every mon daemon will believe that can be a leader because every daemon will have the que quorum of 1 with no other vote.
Just saying :)
On Jul 4, 2017 12:57 AM, "Z Will" <zhao6305@xxxxxxxxx> wrote:
Hi:
I am testing ceph-mon brain split . I have read the code . If I
understand it right , I know it won't be brain split. But I think
there is still another problem. My ceph version is 0.94.10. And here
is my test detail :
3 ceph-mons , there ranks are 0, 1, 2 respectively.I stop the rank 1
mon , and use iptables to block the communication between mon 0 and
mon 1. When the cluster is stable, start mon.1 . I found the 3
monitors will all can not work well. They are all trying to call new
leader election . This means the cluster can't work anymore.
Here is my analysis. Because mon will always respond to leader
election message, so , in my test, communication between mon.0 and
mon.1 is blocked , so mon.1 will always try to be leader, because it
will always see mon.2, and it should win over mon.2. Mon.0 should
always win over mon.2. But mon.2 will always responsd to the election
message issued by mon.1, so this loop will never end. Am I right ?
This should be a problem? Or is it was just designed like this , and
should be handled by human ?
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