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Bug 1891835 - promoting a galera node can fail due to a race in attributes update
Summary: promoting a galera node can fail due to a race in attributes update
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 8
Classification: Red Hat
Component: resource-agents
Version: 8.2
Hardware: Unspecified
OS: Unspecified
unspecified
medium
Target Milestone: rc
: 8.4
Assignee: Oyvind Albrigtsen
QA Contact: cluster-qe@redhat.com
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2020-10-27 13:47 UTC by Damien Ciabrini
Modified: 2021-05-18 15:11 UTC (History)
5 users (show)

Fixed In Version: resource-agents-4.1.1-72.el8
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed: 2021-05-18 15:11:15 UTC
Type: Bug
Target Upstream Version:
Embargoed:
pm-rhel: mirror+

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Github ClusterLabs resource-agents pull 1567 0 None closed galera: set bootstrap attribute before promote 2020-12-07 10:15:42 UTC

Description Damien Ciabrini 2020-10-27 13:47:09 UTC 
Description of problem:
When the master detection takes place, the node chosen for
becoming the master is given two attributes in the CIB:
a master score and a bootstrap flag. The master score makes
pacemaker schedule a promote operation, and the bootstrap flag
drives how the galera server is started.

The order in which we set the attributes is racy; it may happen
that a promote operation is started before the current master
detection function has set the bootstrap flag, in which case
the promotion will fail.


Version-Release number of selected component (if applicable):
resource-agents-4.1.1-44.el8_2.3.x86_64

How reproducible:
Random

Steps to Reproduce:
1. deploy a 3-node galera cluster, start the resource, then stop it
2. ban resource on the two oldest resource
3. restart the remaining resource

Actual results:
sometime the promote operation gets triggered before the bootstrap flag has been set up in the CIB, and the promotion fails

Expected results:
the promotion should finish successfully

Additional info:
Comment 4 Damien Ciabrini 2020-12-04 08:51:51 UTC 
The original bug is hard to reproduce as it is a race. But the fix is really just inverting two line in the agent:

@@ -587,8 +587,8 @@ detect_first_master()
     fi
 
     ocf_log info "Promoting $best_node to be our bootstrap node"
-    set_master_score $best_node
     set_bootstrap_node $best_node
+    set_master_score $best_node
 }

So a simple overcloud deployment is enough to verify that the original behaviour is preserved, and the new line ordering is enough to ensure that the fix will work as expected.
Comment 5 pkomarov 2020-12-04 23:21:35 UTC 
Verified , 

[stack@undercloud-0 ~]$ ansible database -b -mshell -a'podman exec `podman ps -f name=galera-bundle -q`  sh -c "rpm -q resource-agents";rpm -q resource-agents'
[WARNING]: Found both group and host with same name: undercloud
database-0 | CHANGED | rc=0 >>
resource-agents-4.1.1-79.el8.x86_64
resource-agents-4.1.1-79.el8.x86_64
database-2 | CHANGED | rc=0 >>
resource-agents-4.1.1-79.el8.x86_64
resource-agents-4.1.1-79.el8.x86_64
database-1 | CHANGED | rc=0 >>
resource-agents-4.1.1-79.el8.x86_64
resource-agents-4.1.1-79.el8.x86_64

#testing disruptive galera scenario:

git clone -c http.sslVerify=false https://code.engineering.redhat.com/gerrit/openstack-pidone-qe

   ansible-playbook -v  openstack-pidone-qe/CI/ansible_sts/ansible_sts_composable_roles_tests.yaml --tags 06_KILL_ALL_GALERA|& tee ansible_sts_results/06_KILL_ALL_GALERA.log
   ansible-playbook -v  openstack-pidone-qe/CI/ansible_sts/ansible_sts_composable_roles_tests.yaml --tags 07_REMOVE_ALL_GRASTATE_GALERA|& tee ansible_sts_results/07_REMOVE_ALL_GRASTATE_GALERA.log
   ansible-playbook -v  openstack-pidone-qe/CI/ansible_sts/ansible_sts_composable_roles_tests.yaml --tags 09_GENERATE_BIG_DATA_GALERA|& tee ansible_sts_results/09_GENERATE_BIG_DATA_GALERA.log

#agents have recovered after all disruptive galera tests:
    * galera-bundle-0   (ocf::heartbeat:galera):         Master database-2
    * galera-bundle-1   (ocf::heartbeat:galera):         Master database-1
    * galera-bundle-2   (ocf::heartbeat:galera):         Master database-0
Comment 7 errata-xmlrpc 2021-05-18 15:11:15 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (resource-agents bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2021:1736
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