[ClusterLabs] Possible circular constraints

David Parker dparker at utica.edu
Fri Mar 30 23:10:31 EDT 2018


I have a two-node cluster running MySQL with DRBD.  I recently tried to
fail over from the first node (mysql1) to the second (mysql2) but it failed
because the promotion of DRBD on mysql2 failed.  After the failure, I found
this in the Corosync log:

(drbd_r0:0_promote_0) on mysql2 failed (target: 0 vs. rc: -2): Error

While looking into the problem, I discovered what appears to be a circular
colocation dependency between my MySQL resource group and my DRBD
resource.  There's an order constraint which says DRBD should go first,
though, so I'm not positive this is the problem.  I was hoping for a second
opinion before I go making any changes.

The constraints in the CIB are as follows:

      <rsc_colocation id="drbd-mysql-ha" rsc="ms-drbd_r0" rsc-role="Master"
score="INFINITY" with-rsc="mysql_resources"/>
      <rsc_order id="drbd-before-mysql" first="ms-drbd_r0"
first-action="promote" score="INFINITY" then="mysql_resources"
      <meta_attributes id="rsc-options">
        <nvpair id="rsc-options-resource-stickiness"
name="resource-stickiness" value="100"/>

And from crm_resource:

root at mysql1:~# crm_resource -a -r ms-drbd_r0
* ms-drbd_r0
    mysql_resources                                (score=INFINITY,
root at mysql1:~# crm_resource -a -r mysql_resources
    ms-drbd_r0                                     (score=INFINITY,
* mysql_resources



Dave Parker '11
Database & Systems Administrator
Utica College
Integrated Information Technology Services
(315) 792-3229
Registered Linux User #408177
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