How to make MariaDB MaxScale High Available

The document shows an example of a Pacemaker / Corosync setup with MariaDB MaxScale based on Linux Centos 6.5, using three virtual servers and unicast heartbeat mode with the following minimum requirements:

  • MariaDB MaxScale process is started/stopped and monitored via /etc/init.d/maxscale script that is LSB compatible in order to be managed by Pacemaker resource manager

  • A Virtual IP is set providing the access to the MariaDB MaxScale process that could be set to one of the cluster nodes

  • Pacemaker/Corosync and crmsh command line tool basic knowledge

Please note the solution is a quick setup example that may not be suited for all production environments.

Clustering Software installation

On each node in the cluster do the following steps:

(1) Add clustering repos to yum

# vi /etc/yum.repos.d/ha-clustering.repo

Add the following to the file

[haclustering]
name=HA Clustering
baseurl=http://download.opensuse.org/repositories/network:/ha-clustering:/Stable/CentOS_CentOS-6/
enabled=1
gpgcheck=0

(2) Install the software

# yum install pacemaker corosync crmsh

Package versions used

Package pacemaker-1.1.10-14.el6_5.3.x86_64
Package corosync-1.4.5-2.4.x86_64
Package crmsh-2.0+git46-1.1.x86_64

(3) Assign hostname on each node

In this example the three names used for the nodes are: node1,node,node3

[root@server1 ~]# hostname node1
...
[root@server2 ~]# hostname node2
...
[root@server3 ~]# hostname node3

(4) For each node add server names in /etc/hosts

[root@node3 ~]# vi /etc/hosts
10.74.14.39     node1
10.228.103.72   node2
10.35.15.26     node3 current-node
...
[root@node1 ~]# vi /etc/hosts
10.74.14.39     node1 current-node
10.228.103.72   node2
10.35.15.26     node3

Please note: add current-node as an alias for the current node in each of the /etc/hosts files.

(5) Prepare authkey for optional cryptographic use

On one of the nodes, say node2 run the corosync-keygen utility and follow

[root@node2 ~]# corosync-keygen

Corosync Cluster Engine Authentication key generator.       Gathering 1024 bits for key from /dev/random.       Press keys on your keyboard to generate entropy.

After completion the key will be found in /etc/corosync/authkey.

(6) Prepare the corosync configuration file

Using node2 as an example:

[root@node2 ~]# vi /etc/corosync/corosync.conf

Add the following to the file:

# Please read the corosync.conf.5 manual page

compatibility: whitetank

totem {
        version: 2
        secauth: off
        interface {
                member {
                        memberaddr: node1
                }
                member {
                        memberaddr: node2
                }
                member {
                        memberaddr: node3
                }
         ringnumber: 0
                 bindnetaddr: current-node
                 mcastport: 5405
                 ttl: 1
        }
        transport: udpu
}

logging {
        fileline: off
        to_logfile: yes
        to_syslog: yes
        logfile: /var/log/cluster/corosync.log
        debug: off
        timestamp: on
        logger_subsys {
                subsys: AMF
                debug: off
        }
}

# this will start Pacemaker processes

service {
ver: 0
name: pacemaker
}

Please note in this example:

  • unicast UDP is used

  • bindnetaddr for corosync process is current-node, that has the right value on each node due to the alias added in /etc/hosts above

  • Pacemaker processes are started by the corosync daemon, so there is no need to launch it via /etc/init.d/pacemaker start

(7) copy configuration files and auth key on each of the other nodes

[root@node2 ~]# scp /etc/corosync/*  root@node1:/etc/corosync/
...
[root@node2 ~]# scp /etc/corosync/*  root@nodeN:/etc/corosync/

(8) Corosync needs port 5405 to be opened:

  • configure any firewall or iptables accordingly

For a quick start just disable iptables on each nodes:

[root@node2 ~]# service iptables stop
...
[root@nodeN ~]# service iptables stop

(9) Start Corosyn on each node:

[root@node2 ~] #/etc/init.d/corosync start
...
[root@nodeN ~] #/etc/init.d/corosync start

and check the corosync daemon is successfully bound to port 5405:

[root@node2 ~] #netstat -na | grep 5405
udp        0      0 10.228.103.72:5405        0.0.0.0:*

Check if other nodes are reachable with nc utility and option UDP (-u):

[root@node2 ~] #echo "check ..."  | nc -u node1 5405
[root@node2 ~] #echo "check ..."  | nc -u node3 5405
...
[root@node1 ~] #echo "check ..."  | nc -u node2 5405
[root@node1 ~] #echo "check ..."  | nc -u node3 5405

If the following message is displayed

nc: Write error: Connection refused

There is an issue with communication between the nodes, this is most likely to be an issue with the firewall configuration on your nodes. Check and resolve issues with your firewall configuration.

(10) Check the cluster status, from any node

[root@node3 ~]# crm status

After a while this will be the output:

[root@node3 ~]# crm status
Last updated: Mon Jun 30 12:47:53 2014
Last change: Mon Jun 30 12:47:39 2014 via crmd on node2
Stack: classic openais (with plugin)
Current DC: node2 - partition with quorum
Version: 1.1.10-14.el6_5.3-368c726

3 Nodes configured, 3 expected votes
0 Resources configured

Online: [ node1 node2 node3 ]

For the basic setup disable the following properties:

  • stonith

  • quorum policy

[root@node3 ~]# crm configure property 'stonith-enabled'='false'
[root@node3 ~]# crm configure property 'no-quorum-policy'='ignore'

For additional information see:

http://www.clusterlabs.org/doc/crm_fencing.html

http://clusterlabs.org/doc/

The configuration is automatically updated on every node:

Check it from another node, say node1

[root@node1 ~]# crm configure show
node node1
node node2
node node3
property cib-bootstrap-options: \
    dc-version=1.1.10-14.el6_5.3-368c726 \
    cluster-infrastructure="classic openais (with plugin)" \
    expected-quorum-votes=3 \
    stonith-enabled=false \
    no-quorum-policy=ignore \
    placement-strategy=balanced \
    default-resource-stickiness=infinity

The Corosync / Pacemaker cluster is ready to be configured to manage resources.

MariaDB MaxScale init script /etc/init.d/maxscale

The MariaDB MaxScale /etc/init.d./maxscale script allows to start/stop/restart and monitor MariaDB MaxScale process running in the system.

[root@node1 ~]# /etc/init.d/maxscale 
Usage: /etc/init.d/maxscale {start|stop|status|restart|condrestart|reload}
  • Start
[root@node1 ~]# /etc/init.d/maxscale start
Starting MaxScale: maxscale (pid 25892) is running...      [  OK  ]
  • Start again
[root@node1 ~]# /etc/init.d/maxscale start
Starting MaxScale:  found maxscale (pid  25892) is running.[  OK  ]
  • Stop
[root@node1 ~]# /etc/init.d/maxscale stop
Stopping MaxScale:                                         [  OK  ]
  • Stop again
[root@node1 ~]# /etc/init.d/maxscale stop
Stopping MaxScale:                                         [FAILED]
  • Status (MaxScale not running)
[root@node1 ~]# /etc/init.d/maxscale status
MaxScale is stopped                                        [FAILED]

The script exit code for "status" is 3

  • Status (MaxScale is running)
[root@node1 ~]# /etc/init.d/maxscale status
Checking MaxScale status: MaxScale (pid  25953) is running.[  OK  ]

The script exit code for "status" is 0

Note: the MariaDB MaxScale script is LSB compatible and returns the proper exit code for each action:

For additional information;

http://www.linux-ha.org/wiki/LSB_Resource_Agents

After checking MariaDB MaxScale is well managed by the /etc/init.d/script is possible to configure the MariaDB MaxScale HA via Pacemaker.

Configure MariaDB MaxScale for HA with Pacemaker

[root@node2 ~]# crm configure primitive MaxScale lsb:maxscale \
op monitor interval="10s” timeout=”15s” \
op start interval="0” timeout=”15s” \
op stop interval="0” timeout=”30s”

MaxScale resource will be started:

[root@node2 ~]# crm status
Last updated: Mon Jun 30 13:15:34 2014
Last change: Mon Jun 30 13:15:28 2014 via cibadmin on node2
Stack: classic openais (with plugin)
Current DC: node2 - partition with quorum
Version: 1.1.10-14.el6_5.3-368c726

3 Nodes configured, 3 expected votes
1 Resources configured

Online: [ node1 node2 node3 ]

 MaxScale   (lsb:maxscale): Started node1

Basic use cases:

1. Resource restarted after a failure:

In the example MariaDB MaxScale PID is 26114, kill the process immediately:

[root@node2 ~]# kill -9 26114
...
[root@node2 ~]# crm status
Last updated: Mon Jun 30 13:16:11 2014
Last change: Mon Jun 30 13:15:28 2014 via cibadmin on node2
Stack: classic openais (with plugin)
Current DC: node2 - partition with quorum
Version: 1.1.10-14.el6_5.3-368c726

3 Nodes configured, 3 expected votes
1 Resources configured

Online: [ node1 node2 node3 ]

Failed actions:

    MaxScale_monitor_15000 on node1 'not running' (7): call=19, status=complete, last-rc-change='Mon Jun 30 13:16:14 2014', queued=0ms, exec=0ms

Note the MaxScale_monitor failed action

After a few seconds it will be started again:

[root@node2 ~]# crm status
Last updated: Mon Jun 30 13:21:12 2014
Last change: Mon Jun 30 13:15:28 2014 via cibadmin on node1
Stack: classic openais (with plugin)
Current DC: node2 - partition with quorum
Version: 1.1.10-14.el6_5.3-368c726

3 Nodes configured, 3 expected votes
1 Resources configured

Online: [ node1 node2 node3 ]

 MaxScale   (lsb:maxscale): Started node1 

2. The resource cannot be migrated to node1 for a failure:

First, migrate the the resource to another node, say node3

[root@node1 ~]# crm resource migrate MaxScale node3
...

Online: [ node1 node2 node3 ]

Failed actions:

    MaxScale_start_0 on node1 'not running' (7): call=76, status=complete, last-rc-change='Mon Jun 30 13:31:17 2014', queued=2015ms, exec=0ms

Note the MaxScale_start failed action on node1, and after a few seconds

[root@node3 ~]# crm status
Last updated: Mon Jun 30 13:35:00 2014
Last change: Mon Jun 30 13:31:13 2014 via crm_resource on node3
Stack: classic openais (with plugin)
Current DC: node2 - partition with quorum
Version: 1.1.10-14.el6_5.3-368c726

3 Nodes configured, 3 expected votes
1 Resources configured

Online: [ node1 node2 node3 ]

 MaxScale   (lsb:maxscale): Started node2 

Failed actions:

    MaxScale_start_0 on node1 'not running' (7): call=76, status=complete, last-rc-change='Mon Jun 30 13:31:17 2014', queued=2015ms, exec=0ms

Successfully, MaxScale has been started on a new node: node2.

Note: Failed actions remain in the output of crm status.

With "crm resource cleanup MaxScale" is possible to cleanup the messages:
[root@node1 ~]# crm resource cleanup MaxScale
Cleaning up MaxScale on node1
Cleaning up MaxScale on node2
Cleaning up MaxScale on node3

The cleaned status is visible from other nodes as well:

[root@node2 ~]# crm status
Last updated: Mon Jun 30 13:38:18 2014
Last change: Mon Jun 30 13:38:17 2014 via crmd on node3
Stack: classic openais (with plugin)
Current DC: node2 - partition with quorum
Version: 1.1.10-14.el6_5.3-368c726

3 Nodes configured, 3 expected votes
1 Resources configured

Online: [ node1 node2 node3 ]

 MaxScale   (lsb:maxscale): Started node2

Add a Virtual IP (VIP) to the cluster

It’s possible to add a virtual IP to the cluster:

MariaDB MaxScale process will be only contacted with this IP, that mat move across nodes with maxscale process as well.

Setup is very easy:

assuming an addition IP address is available and can be added to one of the nodes, this i the new configuration to add:

[root@node2 ~]# crm configure primitive maxscale_vip ocf:heartbeat:IPaddr2 params ip=192.168.122.125 op monitor interval=10s

MariaDB MaxScale process and the VIP must be run in the same node, so it’s mandatory to add to the configuration the group ‘maxscale_service’.

[root@node2 ~]# crm configure group maxscale_service maxscale_vip MaxScale

The final configuration is, from another node:

[root@node3 ~]# crm configure show
node node1
node node2
node node3
primitive MaxScale lsb:maxscale \
    op monitor interval=15s timeout=10s \
    op start interval=0 timeout=15s \
    op stop interval=0 timeout=30s
primitive maxscale_vip IPaddr2 \
    params ip=192.168.122.125 \
    op monitor interval=10s
group maxscale_service maxscale_vip MaxScale \
    meta target-role=Started
property cib-bootstrap-options: \
    dc-version=1.1.10-14.el6_5.3-368c726 \
    cluster-infrastructure="classic openais (with plugin)" \
    expected-quorum-votes=3 \
    stonith-enabled=false \
    no-quorum-policy=ignore \
    placement-strategy=balanced \
    last-lrm-refresh=1404125486

Check the resource status:

[root@node1 ~]# crm status
Last updated: Mon Jun 30 13:51:29 2014
Last change: Mon Jun 30 13:51:27 2014 via crmd on node1
Stack: classic openais (with plugin)
Current DC: node2 - partition with quorum
Version: 1.1.10-14.el6_5.3-368c726

3 Nodes configured, 3 expected votes
2 Resources configured

Online: [ node1 node2 node3 ]

 Resource Group: maxscale_service

     maxscale_vip   (ocf::heartbeat:IPaddr2):   Started node2 

     MaxScale   (lsb:maxscale): Started node2 

With both resources on node2, now MariaDB MaxScale service will be reachable via the configured VIP address 192.168.122.125