This tutorial is based on Falko Timme’s tutorial for MySQL Cluster 5.0. It shows how to configure a MySQL 5.1 cluster with five nodes: 1 x management, 2 x storage nodes and 2 x balancer nodes. This cluster is load-balanced by an Ultra Monkey package which provides heartbeat (for checking if the other node is still alive) and ldirectord (to split up the requests to the nodes of the MySQL cluster).

In this document I use Debian Etch 4.0 for all nodes. Therefore the setup might differ a bit for other distributions. The two data nodes were x64 to use all of the 8GB RAM. Servers were compiled from source so you should be able to make it running on any platform. The MySQL version I use in this setup is 5.1.24-rc. It’s a release candidate, but I wanted to use 5.1 to take advantage of Memory-Disk Based tables.

Beginning with MySQL 5.1.6, it is possible to store the non-indexed columns of NDB tables on disk, rather than in RAM as with previous versions of MySQL Cluster.[More here]

This howto is just a scratch to make it running, for many of you I am suggesting to read some off docs from MySQL page to be prepared to how manage the whole cluster and always know whats going on.

This document comes without warranty of any kind! Bare in mind you need to make tests and prepare your databases before using it in production mode.

1 My Servers

I will use the following Debian servers that are all in the same network (10.0.1.x in this example):

  • mysql-mngt.example.com:10.0.1.30 [ MySQL cluster management server ]
  • lb1.example.com: 10.0.1.31 [ Load Balancer 1 ]
  • lb2.example.com: 10.0.1.32 [ Load Balancer 2 ]
  • mysql-data1.example.com: 10.0.1.33 [ MySQL cluster node 1 ]
  • mysql-data2.example.com: 10.0.1.34 [ MySQL cluster node 2 ]

In addition to that we need a virtual IP address : 10.0.1.10. It will be assigned to the MySQL cluster by the load balancer so that applications have a single IP address to access the cluster.

Although we want to have two MySQL cluster nodes in our MySQL cluster, we still need a third node, the MySQL cluster management server, for mainly one reason: if one of the two MySQL cluster nodes fails, and the management server is not running, then the data on the two cluster nodes will become inconsistent (“split brain”). We also need it for configuring the MySQL cluster.

2 MySQL data nodes + 1 cluster management server + 2 Load Balancers = 5

Here is my hardware configuration:

MySQL Data : DELL R300 Intel(R) Quad Core Xeon(R) CPU X3353 @ 2.66GHz, 2x SAS 146GB Drives (Raid 1), 8GB RAM

MySQL LoadBalancer : DELL R200 Intel(R) Xeon(R) CPU 3065 @ 2.33GHz, 2x SATA 250 GB Drives (Raid 1), 1GB RAM

MySQL Management : DELL R200 Intel(R) Celeron(R) CPU 430 @ 1.80GHz, 1x SATA 160 GB Drives (Raid 1), 1GB RAM

As the MySQL cluster management server does not use many resources, you can put additional load balancer on this machine or you can use it for monitoring the whole cluster by Nagios or Cacti.

2 Set Up The MySQL Cluster Management Server

First we have to download MySQL 5.1.24 (the sources version) and install the cluster management server (ndb_mgmd) and the cluster management client (ndb_mgm – it can be used to monitor what’s going on in the cluster). The following steps are carried out on mysql-mngt.example.com (10.0.1.30):

mysql-mngt.example.com:

cd /usr/src
wget http://mysql.mirrors.pair.com/Downloads/MySQL-5.1/mysql-5.1.24-rc.tar.gz
tar xvzf mysql-5.1.24-rc.tar.gz
#Lets add proper user and group
groupadd mysql
useradd -g mysql mysql
./configure --prefix=/usr/local/mysql --enable-community-features \
--with-mysqld-user=mysql --with-mysqlmanager --with-plugins=ndbcluster
make
make install

This way we are wasting about 124MB space since we do not need all the actual MySQL files, but believe me it’s way easier to make any cleanup/upgrade in just one dir /usr/local/mysql instead of searching for all files in /usr/bin and so on. After compiling we have two directories we are interested in /usr/local/mysql/bin and /usr/local/mysql/libexec [last one contains the ndb management exec].

Just to make life easier let’s add this below to your PATH environment, to do so we have to edit file /root/.bash_profile:

mysql-mngt.example.com:

echo "PATH=$PATH:/usr/local/mysql/bin:/usr/local/mysql/libexec" >>/root/.bash_profile
echo "export PATH" >>/root/.bash_profile

Next, we must create the cluster configuration file, /usr/local/mysql/var/mysql-cluster/config.ini: [Hints here]

mysql-mngt.example.com:

mkdir /usr/local/mysql/var/mysql-cluster
cd /usr/local/mysql/var/mysql-cluster
vi config.ini

[NDBD DEFAULT]
NoOfReplicas=2
DataMemory=80M # How much memory to allocate for data storage
IndexMemory=18M # How much memory to allocate for index storage
# For DataMemory and IndexMemory, we have used the
# default values. Since the “world” database takes up
# only about 500KB, this should be more than enough for
# this example Cluster setup.
[MYSQLD DEFAULT]
[NDB_MGMD DEFAULT]
[TCP DEFAULT]
# Section for the cluster management node
[NDB_MGMD]
# IP address of the management node (this system)
HostName=10.0.1.30
# Section for the storage nodes
[NDBD]
# IP address of the first storage node
HostName=10.0.1.33
DataDir=/usr/local/mysql/var/mysql-cluster
BackupDataDir=/usr/local/mysql/var/mysql-cluster/backup
DataMemory=2048M
[NDBD]
# IP address of the second storage node
HostName=10.0.1.34
DataDir=/usr/local/mysql/var/mysql-cluster
BackupDataDir=/usr/local/mysql/var/mysql-cluster/backup
DataMemory=2048M

# one [MYSQLD] per storage node
[MYSQLD]
[MYSQLD]

Please replace the IP addresses in the file appropriately to your setup.

Then we proceed to DataSQL nodes to make necessary dirs and files setup.

mysql-mngt.example.com:

ndb_mgmd -f /usr/local/mysql/var/mysql-cluster/config.ini

It makes sense to automatically start the management server at system boot time, so we create a very simple init script and the appropriate startup links:

mysql-mngt.example.com:

echo '/usr/local/mysql/libexec/ndb_mgmd -f /usr/local/mysql/var/mysql-cluster/config.ini' > /etc/init.d/ndb_mgmd
chmod 755 /etc/init.d/ndb_mgmd
update-rc.d ndb_mgmd defaults

3 Set Up The MySQL Cluster Nodes (Storage Nodes)

Now we install mysql-5.1.14-rc on both mysql-data1.example.com and mysql-data2.example.com:

mysql-data1.example.com / mysql-data2.example.com:

cd /usr/src
wget http://mysql.mirrors.pair.com/Downloads/MySQL-5.1/mysql-5.1.24-rc.tar.gz
tar xvzf mysql-5.1.24-rc.tar.gz
groupadd mysql
useradd -g mysql mysql
cd /usr/src/mysql-5.1.24-rc
./configure --prefix=/usr/local/mysql --enable-community-features --with-mysqld-user=mysql --with-plugins=ndbcluster
make
make install
/usr/src/mysql-5.1.24-rc/scripts/mysql_install_db --user=mysql
cd /usr/local/mysql
chown -R root:mysql .
chown -R mysql.mysql /usr/local/mysql/var

cd /usr/src/mysql-5.1.24-rc
cp support-files/mysql.server /etc/init.d/
chmod 755 /etc/init.d/mysql.server
cd /etc/init.d
update-rc.d mysql.server defaults

Then we create the MySQL configuration file /etc/my.cnf on both nodes:

mysql-data1.example.com / mysql-data2.example.com:

vi /etc/my.cnf

[client]
port=3306
socket=/tmp/mysql.sock
[mysqld]
ndbcluster
# IP address of the cluster management node
ndb-connectstring=10.0.1.30
default-storage-engine=NDBCLUSTER

#Those are for future tuning
#max_connections=341
#query_cache_size=16M
#thread_concurrency = 4
[mysql_cluster]
# IP address of the cluster management node
ndb-connectstring=10.0.1.30

Make sure to fill in the correct IP address of the MySQL cluster management server.

Lets add PATH env. to data nodes also:

mysql-data1.example.com / mysql-data2.example.com:

echo "PATH=$PATH:/usr/local/mysql/bin:/usr/local/mysql/libexec" >>/root/.bash_profile
echo "export PATH" >>/root/.bash_profile

Next we create the data and backup directories and start the MySQL server on both cluster nodes:

mysql-data1.example.com / mysql-data2.example.com:

mkdir /usr/local/mysql/var/mysql-cluster
mkdir /usr/local/mysql/var/mysql-cluster/backup
cd /var/lib/mysql-cluster
ndbd --initial
/etc/init.d/mysql.server start

(Please note: we have to run ndbd –initial only when we start MySQL for the first time, and if /usr/local/mysql/mysql-cluster/config.ini on mysql-mngt.example.com changes.)

Now is a good time to set a password for the MySQL root user:

mysql-data1.example.com / mysql-data2.example.com:

mysqladmin -u root password yourrootsqlpassword

We want to start the cluster nodes at boot time, so we create an ndbd init script and the appropriate system startup links:

mysql-data1.example.com / mysql-data2.example.com:

echo '/usr/local/mysql/libexec/ndbd' > /etc/init.d/ndbd
chmod 755 /etc/init.d/ndbd
update-rc.d ndbd defaults

4 Test The MySQL Cluster

Our MySQL cluster configuration is already finished, now it’s time to test it. On the cluster management server (loadb1.example.com), run the cluster management client ndb_mgm to check if the cluster nodes are connected:

mysql-mngt.example.com:

ndb_mgm

You should see this:

– NDB Cluster — Management Client –
ndb_mgm>

Now type show; at the command prompt:

show;

The output should be like this:

ndb_mgm> show;
Connected to Management Server at: localhost:1186
Cluster Configuration
———————
[ndbd(NDB)] 2 node(s)
id=2 @10.0.1.33 (Version: 5.1.24, Nodegroup: 0, Master)
id=3 @10.0.1.34 (Version: 5.1.24, Nodegroup: 0)

[ndb_mgmd(MGM)] 1 node(s)
id=1 @10.0.1.30 (Version: 5.1.24)

[mysqld(API)] 2 node(s)
id=4 @10.0.1.34 (Version: 5.1.24)
id=5 @10.0.1.33 (Version: 5.1.24)

ndb_mgm>

If you see that your nodes are connected, then everything’s ok!

Type

quit;

to leave the ndb_mgm client console.

Now we have to create a test database with a test table and some data on mysql-data1.example.com:

mysql-data1.example.com:

mysql -u root -p
CREATE DATABASE mysqlclustertest;
USE mysqlclustertest;
CREATE TABLE testtable (I INT) ENGINE=NDBCLUSTER;
INSERT INTO testtable () VALUES (1);
SELECT * FROM testtable;
quit;

(Have a look at the CREATE statement: We must use ENGINE=NDBCLUSTER for all database tables that we want to get clustered! If you use another engine, then clustering will not work!)

The result of the SELECT statement should be:

mysql> SELECT * FROM testtable;
+——+
| I |
+——+
| 1 |
+——+
1 row in set (0.03 sec)

Now we have to create the same database on sql2.example.com (yes, we still have to create it, but afterwards testtable and its data should be replicated to mysql-data2.example.com because testtable uses ENGINE=NDBCLUSTER):

mysql-data2.example.com:

mysql -u root -p
CREATE DATABASE mysqlclustertest;
USE mysqlclustertest;
SELECT * FROM testtable;

The SELECT statement should deliver you the same result as before on mysql-data1.example.com: [The CREATE statement should fail due to NDBCLUSTER Engine]

mysql> SELECT * FROM testtable;
+——+
| I |
+——+
| 1 |
+——+
1 row in set (0.04 sec)

So the data was replicated from mysql-data1.example.com to mysql-data2.example.com. Now we insert another row into testtable:

mysql-data2.example.com:

INSERT INTO testtable () VALUES (2);
quit;

Now let’s go back to mysql-data1.example.com and check if we see the new row there:

mysql-data1.example.com:

mysql -u root -p
USE mysqlclustertest;
SELECT * FROM testtable;
quit;

You should see something like this:

mysql> SELECT * FROM testtable;
+——+
| I |
+——+
| 1 |
| 2 |
+——+
2 rows in set (0.05 sec)

So both MySQL cluster nodes always have the same data!

Now let’s see what happens if we stop node 1 (mysql-data1.example.com): Run

mysql-data1.example.com:

killall ndbd

and check with

ps aux | grep ndbd | grep -iv grep

that all ndbd processes have terminated. If you still see ndbd processes, run another

killall ndbd

until all ndbd processes are gone.

Now let’s check the cluster status on our management server (mysql-mngt.example.com):

mysql-mngt.example.com:

ndb_mgm

On the ndb_mgm console, issue

show;

and you should see this:

ndb_mgm> show;
Connected to Management Server at: localhost:1186
Cluster Configuration
———————
[ndbd(NDB)] 2 node(s)
id=2 (not connected, accepting connect from 10.0.1.33)
id=3 @10.0.1.34 (Version: 5.1.24, Nodegroup: 0, Master)

[ndb_mgmd(MGM)] 1 node(s)
id=1 @10.0.1.30 (Version: 5.1.24)

[mysqld(API)] 2 node(s)
id=4 @10.0.1.34 (Version: 5.1.24)
id=5 @10.0.1.33 (Version: 5.1.24)

ndb_mgm>

You see, mysql-data1.example.com is not connected anymore.

Type

quit;

to leave the ndb_mgm console.

Let’s check mysql-data2.example.com:

mysql-data2.example.com:

mysql -u root -p
USE mysqlclustertest;
SELECT * FROM testtable;
quit;

The result of the SELECT query should still be

mysql> SELECT * FROM testtable;
+——+
| I |
+——+
| 1 |
| 2 |
+——+
2 rows in set (0.17 sec)

Ok, all tests went fine, so let’s start our mysql-data1.example.com node again:

mysql-data1.example.com:

ndbd

5 How To Restart The Cluster

Now let’s asume you want to restart the MySQL cluster, for example because you have changed /usr/local/mysql/var/mysql-cluster/config.ini on mysql-mngt.example.com or for some other reason. To do this, you use the ndb_mgm cluster management client on mysql-mngt.example.com:

mysql-mngt.example.com:

ndb_mgm

On the ndb_mgm console, you type

shutdown;

You will then see something like this:

ndb_mgm> shutdown;
Node 3: Cluster shutdown initiated
Node 2: Node shutdown completed.
2 NDB Cluster node(s) have shutdown.
NDB Cluster management server shutdown.
ndb_mgm>

This means that the cluster data nodes mysql-data1.example.com and mysql-data2.example.com and also the cluster management server have shut down.

Run

quit;

to leave the ndb_mgm console.

To start the cluster management server, do this on mysql-mngt.example.com:

mysql-mngt.example.com:

ndb_mgmd -f /usr/local/mysql/mysql-cluster/config.ini

and on mysql-data1.example.com and mysql-data2.example.com you can run

mysql-data1.example.com / mysql-data2.example.com:

ndbd

or, if you have changed /usr/local/mysql/var/mysql-cluster/config.ini on mysql-mngt.example.com:

ndbd --initial

Afterwards, you can check on mysql-mngt.example.com if the cluster has restarted:

mysql-mngt.example.com:

ndb_mgm

On the ndb_mgm console, type

show;

to see the current status of the cluster. It might take a few seconds after a restart until all nodes are reported as connected.

Type

quit;

to leave the ndb_mgm console.

6 Configure The Load Balancers

Our MySQL cluster is finished now, and you could start using it now. However, we don’t have a single IP address that we can use to access the cluster, which means you must configure your applications in a way that a part of it uses the MySQL cluster node 1 (mysql-data1.example.com), and the rest uses the other node (mysql-data2.example.com). Of course, all your applications could just use one node, but what’s the point then in having a cluster if you do not split up the load between the cluster nodes? Another problem is, what happens if one of the cluster nodes fails? Then the applications that use this cluster node cannot work anymore.

The solution is to have a load balancer in front of the MySQL cluster which (as its name suggests) balances the load between the MySQL cluster nodes. The load blanacer configures a virtual IP address that is shared between the cluster nodes, and all your applications use this virtual IP address to access the cluster. If one of the nodes fails, then your applications will still work, because the load balancer redirects the requests to the working node.

Now in this scenario the load balancer becomes the bottleneck. What happens if the load balancer fails? Therefore we will configure two load balancers (mysql-lb1.example.com and mysql-b2.example.com) in an active/passive setup, which means we have one active load balancer, and the other one is a hot-standby and becomes active if the active one fails. Both load balancers use heartbeat to check if the other load balancer is still alive, and both load balancers also use ldirectord, the actual load balancer the splits up the load onto the cluster nodes. heartbeat and ldirectord are provided by the Ultra Monkey package that we will install.

It is important that mysql-lb1.example.com and mysql-lb2.example.com have support for IPVS (IP Virtual Server) in their kernels. IPVS implements transport-layer load balancing inside the Linux kernel.

6.1 Install Ultra Monkey

Ok, let’s start: first we enable IPVS on mysql-lb1.example.com and mysql-lb2.example.com:

mysql-lb1.example.com / mysql-lb2.example.com:

modprobe ip_vs_dh
modprobe ip_vs_ftp
modprobe ip_vs
modprobe ip_vs_lblc
modprobe ip_vs_lblcr
modprobe ip_vs_lc
modprobe ip_vs_nq
modprobe ip_vs_rr
modprobe ip_vs_sed
modprobe ip_vs_sh
modprobe ip_vs_wlc
modprobe ip_vs_wrr

In order to load the IPVS kernel modules at boot time, we list the modules in /etc/modules:

mysql-lb1.example.com / mysql-lb2.example.com:

vi /etc/modules

ip_vs_dh
ip_vs_ftp
ip_vs
ip_vs_lblc
ip_vs_lblcr
ip_vs_lc
ip_vs_nq
ip_vs_rr
ip_vs_sed
ip_vs_sh
ip_vs_wlc
ip_vs_wrr

Now we edit /etc/apt/sources.list and add the Ultra Monkey repositories (don’t remove the other repositories), and then we install Ultra Monkey:

mysql-lb1.example.com / mysql-lb2.example.com:

vi /etc/apt/sources.list

deb http://www.ultramonkey.org/download/3/ sarge main
deb-src http://www.ultramonkey.org/download/3 sarge main

apt-get update
apt-get install ultramonkey libdbi-perl libdbd-mysql-perl libmysqlclient14-dev

Now Ultra Monkey is being installed. If you see this warning:

¦ libsensors3 not functional ¦
¦ ¦
¦ It appears that your kernel is not compiled with sensors support. As a ¦
¦ result, libsensors3 will not be functional on your system. ¦
¦ ¦
¦ If you want to enable it, have a look at “I2C Hardware Sensors Chip ¦
¦ support” in your kernel configuration. ¦

you can ignore it.

Answer the following questions:

Do you want to automatically load IPVS rules on boot?
<– No

Select a daemon method.
<– none

The libdbd-mysql-perl package we’ve just installed does not work with MySQL 5 (we use MySQL 5 on our MySQL cluster…), so we install the newest DBD::mysql Perl package:

mysql-lb1.example.com / mysql-lb2.example.com:

cd /tmp
wget http://search.cpan.org/CPAN/authors/id/C/CA/CAPTTOFU/DBD-mysql-3.0002.tar.gz
tar xvfz DBD-mysql-3.0002.tar.gz
cd DBD-mysql-3.0002
perl Makefile.PL
make
make install

We must enable packet forwarding:

mysql-lb1.example.com / mysql-lb2.example.com:

vi /etc/sysctl.conf

# Enables packet forwarding
net.ipv4.ip_forward = 1

sysctl -p

6.2 Configure heartbeat

Next we configure heartbeat by creating three files (all three files must be identical on mysql-lb1.example.com and mysql-lb2.example.com):

mysql-lb1.example.com / mysql-lb2.example.com:

vi /etc/ha.d/ha.cf

logfacility local0
bcast eth0
mcast eth0 225.0.0.1 694 1 0
auto_failback off
node mysql-lb1
node mysql-lb2
respawn hacluster /usr/lib/heartbeat/ipfail
apiauth ipfail gid=haclient uid=hacluster

Please note: you must list the node names (in this case mysql-lb1 and lmysql-lb2) as shown by

uname -n

IP addresses does not work here, it is also good idea to add proper entries on both load balancers(mysql-lb1 and lmysql-lb2) in

vi /etc/hosts

127.0.0.1 localhost
10.0.1.31 mysql-lb1.example.com mysql-lb1
10.0.1.32 mysql-lb2.example.com mysql-lb2

Now let’s change here your Virtual MySQL IP:

vi /etc/ha.d/haresources

loadb1 \
ldirectord::ldirectord.cf \
LVSSyncDaemonSwap::master \
IPaddr2::10.0.1.10/24/eth0/10.0.1.255

You must list one of the load balancer node names (here: mysql-lb1) and list the virtual IP address (10.0.1.10) together with the correct netmask (24) and broadcast address (10.0.1.255). If you are unsure about the correct settings, http://www.subnetmask.info/ might help you.

vi /etc/ha.d/authkeys

auth 3
3 md5 somerandomstring

somerandomstring is a password which the two heartbeat daemons on loadb1 and loadb2 use to authenticate against each other. Use your own string here. You have the choice between three authentication mechanisms. I use md5 as it is the most secure one.

/etc/ha.d/authkeys should be readable by root only, therefore we do this:

mysql-lb1.example.com / mysql-lb2.example.com:

chmod 600 /etc/ha.d/authkeys

6.3 Configure ldirectord

Now we create the configuration file for ldirectord, the load balancer:

mysql-lb1.example.com / mysql-lb2.example.com:

vi /etc/ha.d/ldirectord.cf

# Global Directives
checktimeout=10
checkinterval=2
autoreload=no
logfile=”local0″
quiescent=yes
virtual = 10.0.1.10:3306
service = mysql
real = 10.0.1.33:3306 gate
real = 10.0.1.34:3306 gate
checktype = negotiate
login = “ldirector”
passwd = “ldirectorpassword”
database = “ldirectordb”
request = “SELECT * FROM connectioncheck”
scheduler = wrr

Please fill in the correct virtual IP address (10.0.1.10) and the correct IP addresses of your MySQL cluster nodes (10.0.1.33 and 10.0.1.34). 3306 is the port that MySQL runs on by default. We also specify a MySQL user (ldirector) and password (ldirectorpassword), a database (ldirectordb) and an SQL query. ldirectord uses this information to make test requests to the MySQL cluster nodes to check if they are still available. We are going to create the ldirector database with the ldirector user in the next step.

Now we create the necessary system startup links for heartbeat and remove those of ldirectord (bacause ldirectord will be started by heartbeat):

mysql-lb1.example.com / mysql-lb2.example.com:

update-rc.d -f heartbeat remove
update-rc.d heartbeat start 75 2 3 4 5 . stop 05 0 1 6 .
update-rc.d -f ldirectord remove

6.4 Create A Database Called ldirector

Next we create the ldirector database on our MySQL cluster nodes mysql-data1.example.com and mysql-data2.example.com. This database will be used by our load balancers to check the availability of the MySQL cluster nodes.

mysql-data1.example.com:

mysql -u root -p
GRANT ALL ON ldirectordb.* TO 'ldirector'@'%' IDENTIFIED BY 'ldirectorpassword';
FLUSH PRIVILEGES;
CREATE DATABASE ldirectordb;
USE ldirectordb;
CREATE TABLE connectioncheck (I INT) ENGINE=NDBCLUSTER;
INSERT INTO connectioncheck () VALUES (1);
quit;

mysql-data2.example.com:

mysql -u root -p
GRANT ALL ON ldirectordb.* TO 'ldirector'@'%' IDENTIFIED BY 'ldirectorpassword';
FLUSH PRIVILEGES;
CREATE DATABASE ldirectordb;
quit;

6.5 Prepare The MySQL Cluster Nodes For Load Balancing

Finally we must configure our MySQL cluster nodes mysql-data1.example.com and mysql-data2.example.com to accept requests on the virtual IP address 192.168.0.105.

mysql-data1.example.com / mysql-data2.example.com:

apt-get install iproute

Add the following to /etc/sysctl.conf:

mysql-data1.example.com / mysql-data2.example.com:

vi /etc/sysctl.conf

# Enable configuration of arp_ignore option
net.ipv4.conf.all.arp_ignore = 1

# When an arp request is received on eth0, only respond if that address is
# configured on eth0. In particular, do not respond if the address is
# configured on lo
net.ipv4.conf.eth0.arp_ignore = 1

# Ditto for eth1, add for all ARPing interfaces
#net.ipv4.conf.eth1.arp_ignore = 1

# Enable configuration of arp_announce option
net.ipv4.conf.all.arp_announce = 2

# When making an ARP request sent through eth0 Always use an address that
# is configured on eth0 as the source address of the ARP request. If this
# is not set, and packets are being sent out eth0 for an address that is on
# lo, and an arp request is required, then the address on lo will be used.
# As the source IP address of arp requests is entered into the ARP cache on
# the destination, it has the effect of announcing this address. This is
# not desirable in this case as adresses on lo on the real-servers should
# be announced only by the linux-director.
net.ipv4.conf.eth0.arp_announce = 2

# Ditto for eth1, add for all ARPing interfaces
#net.ipv4.conf.eth1.arp_announce = 2

sysctl -p

Add this section for the virtual IP address to /etc/network/interfaces:

mysql-data1.example.com / mysql-data2.example.com:

vi /etc/network/interfaces

auto lo:0
iface lo:0 inet static
address 10.0.1.10
netmask 255.255.255.255
pre-up sysctl -p > /dev/null

ifup lo:0

7 Start The Load Balancer And Do Some Testing

Now we can start our two load balancers for the first time:

mysql-lb1.example.com / mysql-lb2.example.com:

/etc/init.d/ldirectord stop
/etc/init.d/heartbeat start

If you don’t see errors, you should now reboot both load balancers.If you do see errors go to the end of this tutorial I might know whats the problem :) [Chapter 8]

mysql-lb1.example.com / mysql-lb2.example.com:

shutdown -r now

After the reboot we can check if both load balancers work as expected :

mysql-lb1.example.com / mysql-lb2.example.com:

ip addr sh eth0

The active load balancer should list the virtual IP address (10.0.1.10):

2: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
link/ether 00:16:3e:45:fc:f8 brd ff:ff:ff:ff:ff:ff
inet 10.0.1.31/24 brd 192.168.0.255 scope global eth0
inet 10.0.1.10/24 brd 192.168.0.255 scope global secondary eth0

The hot-standby should show this:

2: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
link/ether 00:16:3e:16:c1:4e brd ff:ff:ff:ff:ff:ff
inet 10.0.1.32/24 brd 192.168.0.255 scope global eth0

mysql-lb1.example.com / mysql-lb2.example.com:

ldirectord ldirectord.cf status

Output on the active load balancer:

ldirectord for /etc/ha.d/ldirectord.cf is running with pid: 1603

Output on the hot-standby:

ldirectord is stopped for /etc/ha.d/ldirectord.cf

mysql-lb1.example.com / mysql-lb2.example.com:

ipvsadm -L -n

Output on the active load balancer:

IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 10.0.1.10:3306 wrr
-> 10.0.1.33:3306 Route 1 0 0
-> 10.0.1.34:3306 Route 1 0 0

Output on the hot-standby:

IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn

mysql-lb1.example.com / mysql-lb2.example.com:

/etc/ha.d/resource.d/LVSSyncDaemonSwap master status

Output on the active load balancer:

master running
(ipvs_syncmaster pid: 1766)

Output on the hot-standby:

master stopped
(ipvs_syncbackup pid: 1440)

If your tests went fine, you can now try to access the MySQL database from a totally different server in the same network (10.0.1.x) using the virtual IP address 10.0.1.10:

mysql -h 10.0.1.10 -u ldirector -p

(Please note: your MySQL client must at least be of version 4.1; older versions do not work with MySQL 5.)

You can now switch off one of the MySQL cluster nodes for test purposes; you should then still be able to connect to the MySQL database.

8 Annotations and hints

Errors with ldirectord:

/etc/init.d/ldirectord stop
/etc/init.d/heartbeat start
Stopping ldirectord Error [] reading file /etc/ha.d/ldirectord.cf at line 8: >Unknown command service=mysql

This error is due to formatting, it took me some time to figure it out.
The serivce= mysql is probably connected to /etc/services which is correct.
If you have libmysqlclient15 or 14 installed, fixing right formatting will do the trick like here:

vi /etc/heartbeat/ldirectord.cf

# Global Directives
checktimeout=10
checkinterval=2
autoreload=no
logfile=”local0″
quiescent=yes
#after virtual=… make TABS (or double spaces) in every line
virtual = 10.0.1.10:3306
service = mysql
real = 10.0.1.33:3306 gate
real = 10.0.1.34:3306 gate
checktype = negotiate
login = “ldirector”
passwd = “ldirector”
database = “ldirectordb”
request = “SELECT * FROM connectioncheck”
scheduler = wrr

And that should be it.

There are some important things to keep in mind when running a MySQL cluster:

1.If you have your databases and you want to use them in MySQL cluster please read this as it will guide you through how to change ENGINE=MyISAM to NDBCLUSTER.

2. Adding user to mysql database and changing GRANTS must be done on all data nodes since mysql database is MyISAM/InoDB. You can of course convert it’s engine.

3.All data is stored in RAM! as a default, but Therefore you need lots of RAM on your cluster nodes. The formula how much RAM you need on each node goes like this:

(SizeofDatabase × NumberOfReplicas × 1.1 ) / NumberOfDataNodes

So if you have a database that is 1 GB of size, you would need 1.1 GB RAM on each node!

4.The cluster management node listens on port 1186, and anyone can connect. So that’s definitely not secure, and therefore you should run your cluster in an isolated private network! Since it would be harder to manage it may be a good idea to make changes to /etc/hosts.deny or prepare iptables based firewall.

5.It’s a good idea to have a look at the MySQL Cluster FAQ: http://dev.mysql.com/doc/refman/5.1/en/mysql-cluster-faq.html and also at the MySQL Cluster documentation: http://dev.mysql.com/doc/refman/5.1/en/ndbcluster.html

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