Bug #13627
closedmon: last seen election epoch not honored in win_standalone_election()
0%
Description
The Monitor of epoch version is set to 1, when number by multiple downgraded to a mon
The sample:
[[root@node181 ~]# ceph mon_status -f json-pretty
{ "name": "node173",
"rank": 0,
"state": "leader",
"election_epoch": 4,
"quorum": [
0,
1],
"outside_quorum": [],
"extra_probe_peers": [
"10.118.202.181:6789\/0"],
"sync_provider": [],
"monmap": { "epoch": 1,
"fsid": "7028dd47-e1bb-4dd7-9954-818bfa8e43fe",
"modified": "0.000000",
"created": "0.000000",
"mons": [
{ "rank": 0,
"name": "node173",
"addr": "10.118.202.173:6789\/0"},
{ "rank": 1,
"name": "node181",
"addr": "10.118.202.181:6789\/0"}]}}
[root@node181 ~]# ceph mon_status -f json-pretty
{ "name": "node173",
"rank": 0,
"state": "leader",
"election_epoch": 4,
"quorum": [
0,
1],
"outside_quorum": [],
"extra_probe_peers": [
"10.118.202.181:6789\/0"],
"sync_provider": [],
"monmap": { "epoch": 1,
"fsid": "7028dd47-e1bb-4dd7-9954-818bfa8e43fe",
"modified": "0.000000",
"created": "0.000000",
"mons": [
{ "rank": 0,
"name": "node173",
"addr": "10.118.202.173:6789\/0"},
{ "rank": 1,
"name": "node181",
"addr": "10.118.202.181:6789\/0"}]}}
[root@node181 ~]# ceph mon remove node173
removed mon.node173 at 10.118.202.173:6789/0, there are now 1 monitors
[root@node181 ~]# ceph mon_status -f json-pretty
2015-10-28 10:04:09.787510 7f3fcc7f8700 0 -- :/1022052 >> 10.118.202.173:6789/0 pipe(0x7f3fc40230d0 sd=3 :0 s=1 pgs=0 cs=0 l=1 c=0x7f3fc4023360).fault
{ "name": "node181",
"rank": 0,
"state": "leader",
"election_epoch": 5,
"quorum": [
0],
"outside_quorum": [],
"extra_probe_peers": [
"10.118.202.173:6789\/0"],
"sync_provider": [],
"monmap": { "epoch": 2,
"fsid": "7028dd47-e1bb-4dd7-9954-818bfa8e43fe",
"modified": "2015-10-28 09:59:44.616088",
"created": "0.000000",
"mons": [
{ "rank": 0,
"name": "node181",
"addr": "10.118.202.181:6789\/0"}]}}
[root@node181 ~]# service ceph stop mon
=== mon.node181 ===
Stopping Ceph mon.node181 on node181...kill 11170...done
[root@node181 ~]# service ceph stop mon^C
[root@node181 ~]# service ceph start mon
=== mon.node181 ===
Starting Ceph mon.node181 on node181...
Running as unit run-24187.service.
Starting ceph-create-keys on node181...
[root@node181 ~]# ceph mon_status -f json-pretty
2015-10-28 10:06:17.657206 7f8ac43cc700 0 -- :/1024231 >> 10.118.202.173:6789/0 pipe(0x7f8abc0230d0 sd=3 :0 s=1 pgs=0 cs=0 l=1 c=0x7f8abc023360).fault
{ "name": "node181",
"rank": 0,
"state": "leader",
"election_epoch": 1,
"quorum": [
0],
"outside_quorum": [],
"extra_probe_peers": [],
"sync_provider": [],
"monmap": { "epoch": 2,
"fsid": "7028dd47-e1bb-4dd7-9954-818bfa8e43fe",
"modified": "2015-10-28 09:59:44.616088",
"created": "0.000000",
"mons": [
{ "rank": 0,
"name": "node181",
"addr": "10.118.202.181:6789\/0"}]}}
[root@node181 ~]#
After I remove node173 Monitor, check the Monitor in the cluster election_epoch is "5"
But I restart node181 Monitor node, check the cluster Monitor election_epoch into "1"
I think no matter whether to restart the only Mon node in a cluster, all should be in the cluster Mon election_epoch set for the final state, as in the example below the Mon election_epoch should be "5"
Updated by Joao Eduardo Luis over 8 years ago
- Category set to Monitor
Can you actually point us to an incorrect behavior arising from this?
I have never considered this a bug. The election epoch does not need to be durable, and making it so without a really good reason (say, an actual bug) is adding unnecessary complexity.
Updated by Joao Eduardo Luis over 8 years ago
- Subject changed from The Monitor of epoch version is set to 1, when number by multiple downgraded to a mon to mon: last seen election epoch not honored in win_standalone_election()
- Status changed from New to 12
Nevermind, I figured what you actually mean. The monitor is not honoring its last seen election epoch when running on a single-monitor cluster.
This does not cause problems (given one is on a single-monitor cluster), but yeah... it's weird.
The pull request should go through some QA, but looks okay.
Updated by huanwen ren over 8 years ago
@Category
election_epoch can be used to record the change of the mon state, if has been election_epoch = 1, then you lose the effect
We have an application scenario: calamari need through election_epoch sense the change of mon
Updated by huanwen ren over 8 years ago
@Joao Luis
election_epoch can be used to record the change of the mon state, if has been election_epoch = 1, then you lose the effect
We have an application scenario: calamari need through election_epoch sense the change of mon