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Bug 1835717 - pacemaker never promotes a bundle until another transition unblocks it
Summary: pacemaker never promotes a bundle until another transition unblocks it
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 8
Classification: Red Hat
Component: pacemaker
Version: 8.2
Hardware: All
OS: All
high
high
Target Milestone: rc
: 8.4
Assignee: Ken Gaillot
QA Contact: cluster-qe@redhat.com
URL:
Whiteboard:
Depends On: 1885645
Blocks: 1935240 1935241
TreeView+ depends on / blocked
 
Reported: 2020-05-14 11:36 UTC by Michele Baldessari
Modified: 2021-05-18 15:28 UTC (History)
6 users (show)

Fixed In Version: pacemaker-2.0.5-1.el8
Doc Type: Bug Fix
Doc Text:
Cause: When selecting promotable clone instances for promotion on guest nodes, Pacemaker considered whether the guest node itself could run resources, but not whether the guest resource creating it was runnable. Consequence: An unrunnable guest could be chosen for promotion, unnecessarily leaving some instances unpromoted until the next natural transition. Fix: Pacemaker now considers whether a guest node's guest resource is runnable when selecting nodes for promotion. Result: All instances that can be promoted will be.
Clone Of:
: 1935240 1935241 (view as bug list)
Environment:
Last Closed: 2021-05-18 15:26:41 UTC
Type: Bug
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)

Description Michele Baldessari 2020-05-14 11:36:28 UTC 
Description of problem:
So this morning we were testing a few things and we hit this rather odd behavior. We start off from a good condition:
A) Strating point
 * Container bundle set: redis-bundle [cluster.common.tag/rhosp16-openstack-redis:pcmklatest]:
    * redis-bundle-0	(ocf::heartbeat:redis):	 Master controller-0
    * redis-bundle-1	(ocf::heartbeat:redis):	 Slave controller-1
    * redis-bundle-2	(ocf::heartbeat:redis):	 Slave controller-2
  * Container bundle set: ovn-dbs-bundle [cluster.common.tag/rhosp16-openstack-ovn-northd:pcmklatest]:
    * ovn-dbs-bundle-0	(ocf::ovn:ovndb-servers):	 Master controller-0
    * ovn-dbs-bundle-1	(ocf::ovn:ovndb-servers):	 Slave controller-1
    * ovn-dbs-bundle-2	(ocf::ovn:ovndb-servers):	 Slave controller-2

B) So now we want to just move ovn-dbs-bundle master away from controller-0 and we do so by banning the whole bundle (pcs resource ban ovn-dbs-bunle controller-0). But what happens is the following:
  * Container bundle set: redis-bundle [cluster.common.tag/rhosp16-openstack-redis:pcmklatest]:
    * redis-bundle-0	(ocf::heartbeat:redis):	 Master controller-0
    * redis-bundle-1	(ocf::heartbeat:redis):	 Slave controller-1
    * redis-bundle-2	(ocf::heartbeat:redis):	 Slave controller-2
  * Container bundle set: ovn-dbs-bundle [cluster.common.tag/rhosp16-openstack-ovn-northd:pcmklatest]:
    * ovn-dbs-bundle-0	(ocf::ovn:ovndb-servers):	 Stopped
    * ovn-dbs-bundle-1	(ocf::ovn:ovndb-servers):	 Slave controller-1
    * ovn-dbs-bundle-2	(ocf::ovn:ovndb-servers):	 Slave controller-2

Somehow we observe that a promotion just never takes place. But the interesting thing is that pacemaker clearly thinks that the promotion should happen:
 * Start      ovn-dbs-bundle-0     (                     controller-0 )   due to unrunnable ovn-dbs-bundle-podman-0 start (blocked)
 * Start      ovndb_servers:0      (                 ovn-dbs-bundle-0 )   due to unrunnable ovn-dbs-bundle-podman-0 start (blocked)
 * Promote    ovndb_servers:1      ( Slave -> Master ovn-dbs-bundle-1 )  

The problem is that it seems it is never triggered at all?
Now the reason that we suspect that this is a pacemaker bug is the following:
C) When the cluster is in state (B), somehow triggering another unrelated transition makes the seemingly blocked ovndb_servers promotion, unstuck again. So when we run: 'pcs resource ban redis-budle controller-0' we suddenly get what we were wanting at (B):
  * Container bundle set: redis-bundle [cluster.common.tag/rhosp16-openstack-redis:pcmklatest]:
    * redis-bundle-0	(ocf::heartbeat:redis):	 Stopped
    * redis-bundle-1	(ocf::heartbeat:redis):	 Master controller-1
    * redis-bundle-2	(ocf::heartbeat:redis):	 Slave controller-2
  * Container bundle set: ovn-dbs-bundle [cluster.common.tag/rhosp16-openstack-ovn-northd:pcmklatest]:
    * ovn-dbs-bundle-0	(ocf::ovn:ovndb-servers):	 Stopped
    * ovn-dbs-bundle-1	(ocf::ovn:ovndb-servers):	 Master controller-1
    * ovn-dbs-bundle-2	(ocf::ovn:ovndb-servers):	 Slave controller-2

And now crm_simulate only shows the expected blocked bundles (due to the bans):
Transition Summary:                                                                                                
 * Start      redis-bundle-0     (     controller-0 )   due to unrunnable redis-bundle-podman-0 start (blocked)    
 * Start      redis:0            (   redis-bundle-0 )   due to unrunnable redis-bundle-podman-0 start (blocked)    
 * Start      ovn-dbs-bundle-0   (     controller-0 )   due to unrunnable ovn-dbs-bundle-podman-0 start (blocked)  
 * Start      ovndb_servers:0    ( ovn-dbs-bundle-0 )   due to unrunnable ovn-dbs-bundle-podman-0 start (blocked)  


I.e. it is as if in (B) it knows it wants to promote ovndbs_servers but somehow never ends up doing it (we did wait
for a longer time as well just to understand if this is not some other issue)


Version-Release number of selected component (if applicable):
pacemaker-2.0.3-5.el8.x86_64
Comment 2 Ken Gaillot 2020-05-15 15:34:32 UTC 
This is definitely a pacemaker scheduler bug
Comment 5 Ken Gaillot 2020-09-10 14:30:00 UTC 
Fixed upstream as of commit 8c9ee257
Comment 8 Ken Gaillot 2020-09-10 16:45:10 UTC 
A workaround until the fix is available would be waiting a few seconds after the ban, then changing any configuration value (such as a dummy node attribute) to trigger a new transition. For testing purposes I use a bash alias that does

 attrd_updater -N "$(hostname)" -n trigger-transition -v "$(date)"

(my test nodes are named the same as their hostname, you can use any node name)
Comment 12 pkomarov 2020-11-03 10:22:03 UTC 
Verified , 

(undercloud) [stack@undercloud-0 ~]$ ansible controller -b -mshell -a'pcs cluster status'|grep version
[WARNING]: Found both group and host with same name: undercloud
   * Current DC: controller-1 (version 2.0.5-2.el8-31aa4f5515) - partition with quorum
   * Current DC: controller-1 (version 2.0.5-2.el8-31aa4f5515) - partition with quorum
   * Current DC: controller-1 (version 2.0.5-2.el8-31aa4f5515) - partition with quorum

  * Container bundle set: ovn-dbs-bundle [cluster.common.tag/rhosp16-openstack-ovn-northd:pcmklatest]:
    * ovn-dbs-bundle-0  (ocf::ovn:ovndb-servers):        Master controller-2
    * ovn-dbs-bundle-1  (ocf::ovn:ovndb-servers):        Slave controller-0
    * ovn-dbs-bundle-2  (ocf::ovn:ovndb-servers):        Slave controller-1

[root@controller-2 ~]# pcs resource ban ovn-dbs-bundle controller-2


  * Container bundle set: ovn-dbs-bundle [cluster.common.tag/rhosp16-openstack-ovn-northd:pcmklatest]:
    * ovn-dbs-bundle-0  (ocf::ovn:ovndb-servers):        Stopped controller-2
    * ovn-dbs-bundle-1  (ocf::ovn:ovndb-servers):        Slave controller-0
[..]

  * Container bundle set: ovn-dbs-bundle [cluster.common.tag/rhosp16-openstack-ovn-northd:pcmklatest]:
    * ovn-dbs-bundle-0  (ocf::ovn:ovndb-servers):        Stopped
    * ovn-dbs-bundle-1  (ocf::ovn:ovndb-servers):        Master controller-0
    * ovn-dbs-bundle-2  (ocf::ovn:ovndb-servers):        Slave controller-1
Comment 16 errata-xmlrpc 2021-05-18 15:26:41 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 (pacemaker 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/RHEA-2021:1782
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