[ClusterLabs] Problem with MariaDB cluster

Thomas CAS tcas at ikoula.com
Tue Jan 31 09:45:46 EST 2023


Hello Reid,

What solution can I use while waiting for a fix for this bug?
Modify RA?

Thanks,
Best regards,

Thomas Cas  |  Technicien du support infogérance
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De : Thomas CAS
Envoyé : vendredi 27 janvier 2023 11:28
À : Reid Wahl <nwahl at redhat.com>
Cc : Cluster Labs - All topics related to open-source clustering welcomed <users at clusterlabs.org>
Objet : RE: [ClusterLabs] Problem with MariaDB cluster

Reid,

I have activated the trace mode on the MYSQL resource on my lab and I rebooted Node2, after reboot:

+ echo Node1
+ tr -d
+ master_host=Node1
+ echo Node1
+ [ Node1 -a Node1 != Node2 ]
+ ocf_log info Changing MySQL configuration to replicate from zabbixmysqlmaster01.

I can see that the variable "master_host" is well filled.

In production, I did the same thing and variable "master_host" is not filled:

+ echo
+ tr -d
+ master_host=
+ [  -a  != Node2 ]
+ ocf_log info No MySQL master present - clearing replication state


That is why I would like to know concretely what the variable "$OCF_RESKEY_CRM_meta_notify_master_uname" does.
How is the master_host name retrieved?

Best regards,

Thomas Cas  |  Technicien du support infogérance
PHONE : +33 3 51 25 23 26       WEB : www.ikoula.com/en<https://www.ikoula.com/en>
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De : Reid Wahl <nwahl at redhat.com<mailto:nwahl at redhat.com>>
Envoyé : vendredi 27 janvier 2023 09:32
À : Thomas CAS <tcas at ikoula.com<mailto:tcas at ikoula.com>>
Cc : Cluster Labs - All topics related to open-source clustering welcomed <users at clusterlabs.org<mailto:users at clusterlabs.org>>
Objet : Re: [ClusterLabs] Problem with MariaDB cluster



On Fri, Jan 27, 2023 at 12:23 AM Thomas CAS <tcas at ikoula.com<mailto:tcas at ikoula.com>> wrote:
Hello Reid,

Thank you so much for your answer and bug report.
If it is a bug, I do not understand why the problem is present in production but not on my lab which is identical?

That's a good question. I'm not sure, and I haven't worked much with this resource agent. Does the lab show interesting logs at all from the resource agent during startup? I wonder if it's hitting the same "No MySQL master present" issue but *not* the error that follows. That error is coming from mysql itself, not from the resource agent.

After the agent hits the "No MySQL master present" issue, it calls the unset_master() function. You can take a look at the agent script (in /usr/lib/ocf/resource.d/heartbeat/mysql by default) to see all the things that unset_master() is doing, and try to determine what's behaving differently in production vs. lab.

What does the "$OCF_RESKEY_CRM_meta_notify_master_uname" variable do? (which shell command is done through this variable)

Pacemaker sets it during a resource's notify operation. It's set to some information that's used only during a notify operation, and it's unset otherwise. You can see some other similar meta variables in the mysql_notify() function. The mysql_notify() function gets called during a notify operation, so those variables might be set. They won't be set when mysql_start() is called during a start operation.


Best regards,

Thomas Cas  |  Technicien du support infogérance
PHONE : +33 3 51 25 23 26       WEB : www.ikoula.com/en<https://fra01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.ikoula.com%2Fen&data=05%7C01%7Ctcas%40ikoula.com%7C226d88b9b1754639362e08db00410952%7Ccb7a4a4ea7f747cc931f80db4a66f1c7%7C0%7C0%7C638104051570154976%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=uNarHoMr%2FuGeTV6PG6OWomI%2Fuu80OgcY2ER8IYBXv6s%3D&reserved=0>
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De : Reid Wahl <nwahl at redhat.com<mailto:nwahl at redhat.com>>
Envoyé : jeudi 26 janvier 2023 20:31
À : Cluster Labs - All topics related to open-source clustering welcomed <users at clusterlabs.org<mailto:users at clusterlabs.org>>; Thomas CAS <tcas at ikoula.com<mailto:tcas at ikoula.com>>
Objet : Re: [ClusterLabs] Problem with MariaDB cluster

Vous ne recevez pas souvent de courriers de la part de nwahl at redhat.com<mailto:nwahl at redhat.com>. Découvrez pourquoi cela est important<https://aka.ms/LearnAboutSenderIdentification>


On Thu, Jan 26, 2023 at 7:39 AM Thomas CAS <tcas at ikoula.com<mailto:tcas at ikoula.com>> wrote:
Hello,

I'm having trouble with a MariaDB cluster (2 nodes, master-slave) on Debian 11.
I don't know what to do anymore.

Environment:

Node1:
 OS: Debian 11
Kernel: 5.10.0-21-amd64 #1 SMP Debian 5.10.162-1 (2023-01-21)
Versions: resource-agents (4.7.0-1), pacemaker (2.0.5-2), corosync (3.1.2-2), mariadb (10.5.18-0+deb11u1)

Node2:
 OS: Debian 11
Kernel: 5.10.0-21-amd64 #1 SMP Debian 5.10.162-1 (2023-01-21)
Versions: resource-agents (4.7.0-1), pacemaker (2.0.5-2), corosync (3.1.2-2), mariadb (10.5.18-0+deb11u1)

crm configure show as attachment.

Problem:

When I restart Node2 (which is a slave), it goes up correctly in the cluster:

$ crm status
Cluster Summary:
  * Stack: corosync
  * Current DC: Node1 (version 2.0.5-ba59be7122) - partition with quorum
  * Last updated: Thu Jan 26 12:04:57 2023
  * Last change:  Thu Jan 26 11:39:58 2023 by root via cibadmin on Node2
  * 2 nodes configured
  * 3 resource instances configured

Node List:
  * Online: [ Node1 Node2 ]

Full List of Resources:
  * VIP (ocf::heartbeat:IPaddr2):        Started Node1
  * Clone Set: MYSQLREPLICATOR [MYSQL] (promotable):
    * Masters: [ Node1 ]
    * Slaves: [ Node2 ]

But it does not retrieve the replication information. (SHOW SLAVE STATUS; returns nothing)
In the Node2 logs, I can see this message that explains that replication is not taking place:

Jan 25 16:29:38  mysql(MYSQL)[22862]:    INFO: No MySQL master present - clearing replication state
Jan 25 16:29:39  mysql(MYSQL)[22862]:    WARNING: MySQL Slave IO threads currently not running.
Jan 25 16:29:39  mysql(MYSQL)[22862]:    ERROR: MySQL Slave SQL threads currently not running.
Jan 25 16:29:39  mysql(MYSQL)[22862]:    ERROR: See  for details
Jan 25 16:29:39  mysql(MYSQL)[22862]:    ERROR: ERROR 1200 (HY000) at line 1: Misconfigured slave: MASTER_HOST was not set; Fix in config file or with CHANGE MASTER TO

>From what I see in the following file, Node2 does not seem to find the master name. So it clears its replication information:

/usr/lib/ocf/resource.d/heartbeat/mysql

        master_host=`echo $OCF_RESKEY_CRM_meta_notify_master_uname|tr -d " "`
        if [ "$master_host" -a "$master_host" != ${NODENAME} ]; then
            ocf_log info "Changing MySQL configuration to replicate from $master_host."
            set_master
            start_slave
            if [ $? -ne 0 ]; then
                ocf_exit_reason "Failed to start slave"
                return $OCF_ERR_GENERIC
            fi
        else
            ocf_log info "No MySQL master present - clearing replication state"
            unset_master
        fi

As it is a production environment, I performed a bare metal restore of these machines on 2 LAB machines and I have no problem...
In production, there is a lot of writing but the servers are far from being saturated.

Thank you in advance for all the help you can give me.

Best regards,

I'm sorry you've encountered this.

I don't understand why the resource agent checks $OCF_RESKEY_CRM_meta_notify_master_uname during the start operation. That value gets set only during a notify operation. That looks like a bug in the resource agent.

I've filed an issue against it here: https://github.com/ClusterLabs/resource-agents/issues/1839<https://fra01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FClusterLabs%2Fresource-agents%2Fissues%2F1839&data=05%7C01%7Ctcas%40ikoula.com%7C226d88b9b1754639362e08db00410952%7Ccb7a4a4ea7f747cc931f80db4a66f1c7%7C0%7C0%7C638104051570311189%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=1rZ5TyqG4PhgpfaJr%2FrRp9retwphLm2Ifm669sVx3p4%3D&reserved=0>



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--
Regards,
Reid Wahl (He/Him)
Senior Software Engineer, Red Hat
RHEL High Availability - Pacemaker


--
Regards,
Reid Wahl (He/Him)
Senior Software Engineer, Red Hat
RHEL High Availability - Pacemaker
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