1, MHA concept

(1) MHA (MasterHigh Availability) is a set of excellent software for failover and master-slave replication in MySQL high availability environment.

(2) The emergence of MHA is to solve the problem of MySQL single point.

(3) During MySQL failover, MHA can automatically complete the failover operation within 0-30 seconds.

(4) MHA can ensure the consistency of data to the greatest extent in the process of failover, so as to achieve high availability in the real sense.

1. MHA composition

(1) MHA Node

The MHA Node runs on each MySQL server.

(2) MHA Manager (management node)

MHA Manager can be deployed on an independent machine to manage multiple master slave clusters; It can also be deployed on a slave node.

The MHA Manager will periodically probe the master node in the cluster. When the master fails, it can automatically promote the slave of the latest data to the new master, and then point all other slave to the new master again. The entire failover process is completely transparent to the application.

2. Characteristics of MHA

(1) In the process of automatic failover, MHA tries to save binary logs from the down main server to ensure no data loss to the greatest extent.

(2) Using semi synchronous replication can greatly reduce the risk of data loss. If only one slave has received the latest binary log, MHA can apply the latest binary log to all other slave servers, so it can ensure the data consistency of all nodes.

(3) At present, MHA supports a master-slave architecture with at least three services, i.e. one master and two slaves.

2, Build MySQL+MHA

host	operating system	IP address	Installation package / software / tools
MHAmanager	CentOS7-3	192.168.10.11	MHAnode component, MHAmanager component
master	CentOS7-3	192.168.10.12	mysql-boost-5.7.20.tar.gz, MHAnode components
Slave1	CentOS7-3	192.168.10.13	mysql-boost-5.7.20.tar.gz, MHAnode components
Slave2	CentOS7-3	192.168.10.14	mysql-boost-5.7.20.tar.gz, MHAnode components

Test three sets mysql Is the server service started
netstat -natp | grep 3306

1. All servers, turn off the system firewall and security mechanism

systemctl stop firewalld
systemctl disable firewalld
setenforce 0

2. Modify the host names of master (192.168.10.12), Slave1 (192.168.10.13) and Slave2 (192.168.10.14) nodes

hostnamectl set-hostname master
su -

hostnamectl set-hostname slave1
su -

hostnamectl set-hostname slave2
su -

3. Modify the main configuration file / etc / my. Of the three MySQL servers cnf

master: master(192.168.10.12)

vim /etc/my.cnf
[mysqld]
server-id = 1
log_bin = master-bin
log-slave-updates = true

systemctl restart mysqld

ln -s /usr/local/mysql/bin/mysql /usr/sbin/
ln -s /usr/local/mysql/bin/mysqlbinlog /usr/sbin/

slave: slave1(192.168.10.13),slave2(192.168.10.14)

vim /etc/my.cnf
server-id = 2  
#Server id = 3, slave2 is 3, and the server IDs of the three servers cannot be the same
log_bin = master-bin
relay-log = relay-log-bin
relay-log-index = slave-relay-bin.index

systemctl restart mysqld

ln -s /usr/local/mysql/bin/mysql /usr/sbin/
ln -s /usr/local/mysql/bin/mysqlbinlog /usr/sbin/

4. Configure MySQL with one master and two slaves

MySQL server for MySQL authorization

mysql -uroot -pqwe123

grant replication slave on *.* to 'myslave'@'192.168.10.%' identified by 'qwe123';
grant all privileges on *.* to 'mha'@'192.168.10.%' identified by 'manager';
grant all privileges on *.* to 'mha'@'master' identified by 'manager';
grant all privileges on *.* to 'mha'@'slave1' identified by 'manager';
grant all privileges on *.* to 'mha'@'slave2' identified by 'manager';

Slave1 and Slave2 nodes perform synchronization operations

stay Master Node view binaries and synchronization points
show master status;
stay Slave1,Slave2 The node performs synchronization operations
change master to master_host='192.168.10.12',master_user='myslave',master_password='qwe123',master_log_file='master-bin.000001',master_log_pos=1893;

start slave;
show slave status\G

Slave1 and Slave2 nodes are set to read-only mode

Slave1,Slave2 The node is set to read-only mode
set global read_only=1;

5. Master slave replication verification

6. Install MHA software

MHA dependent environments are installed on all servers

MHAmanager(192.168.10.11)

master(192.168.10.12)

slave1(192.168.10.13)

slave2(192.168.10.14)

First install the epel source, which needs to be installed online

Then install the node component on all servers

Here I use Alibaba source to download
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
yum list

yum install epel-release --nogpgcheck -y

yum install -y perl-DBD-MySQL \
perl-Config-Tiny \
perl-Log-Dispatch \
perl-Parallel-ForkManager \
perl-ExtUtils-CBuilder \
perl-ExtUtils-MakeMaker \
perl-CPAN

Package mha4mysql-node-0.57.tar.gz Put/opt Under the directory

cd /opt
tar zxvf mha4mysql-node-0.57.tar.gz
cd mha4mysql-node-0.57
perl Makefile.PL
make -j 2 && make install

Install the manager component on the MHA manager node

Package mha4mysql-manager-0.57.tar.gz Put/opt Under the directory	#Just drag it into xshell

cd /opt
tar zxvf mha4mysql-manager-0.57.tar.gz
cd mha4mysql-manager-0.57
perl Makefile.PL
make  -j 2 && make install

After the manager component is installed, several tools will be generated under / usr/local/bin, mainly including the following:

assembly	effect
masterha_check_ssh	Check the SSH configuration of MHA
masterha_check_repl	Check MySQL replication status
masterha_manger	Script to start manager
masterha_check_status	Detect the current MHA operation status
masterha_master_monitor	Check whether the master is down
masterha_master_switch	Control failover (automatic or manual)
masterha_conf_host	Add or delete configured server information
masterha_stop	Close manager

After installing node, several scripts will also be generated in / usr/local/bin directory, which need to be checked, mainly including the following:

script	effect
save_binary_logs	Save and copy binary logs of master
apply_diff_relay_logs	Identify the different relay log events and apply the different events to other slave s
filter_mysqlbinlog	Remove unnecessary ROLLBACK events (MHA no longer uses this tool)
purge_relay_logs	Clear relay log (does not block SQL thread)

7. Configure password less authentication on all servers

Configure password free authentication to all database nodes on manager

ssh-keygen -t rsa 				#Press enter all the way

ssh-copy-id 192.168.10.12
ssh-copy-id 192.168.10.13
ssh-copy-id 192.168.10.14

Configure password free authentication to slave1 and salve2 on the master

ssh-keygen -t rsa

ssh-copy-id 192.168.10.13
ssh-copy-id 192.168.10.14

Configure password free authentication to master and salve2 on slave1

ssh-keygen -t rsa

ssh-copy-id 192.168.10.12
ssh-copy-id 192.168.10.14

Configure password free authentication to master and salve1 on slave2

ssh-keygen -t rsa

ssh-copy-id 192.168.10.12
ssh-copy-id 192.168.10.14

8. Configure MHA on the manager node

(1) On the manager node, copy the relevant scripts to the / usr/local/bin directory

cp -rp /opt/mha4mysql-manager-0.57/samples/scripts /usr/local/bin

#After copying, there will be four execution files
ll /usr/local/bin/scripts/

file name	effect
master_ip_failover	Script of VIP management during automatic switching
master_ip_online_change	Management of vip during online switching
power_manager	Script to shut down the host after failure
send_report	Script for sending alarms after failover

(2) Copy the above master_ ip_ Failover (script for VIP management during automatic switching) to / usr/local/bin directory, where the script is used to manage VIP

cp /usr/local/bin/scripts/master_ip_failover /usr/local/bin

(3) Modify master_ip_failover content (delete the original content, copy directly, and configure failover in the following parts)

#!/usr/bin/env perl
use strict;
use warnings FATAL => 'all';

use Getopt::Long;

my (
$command, $ssh_user, $orig_master_host, $orig_master_ip,
$orig_master_port, $new_master_host, $new_master_ip, $new_master_port
);
my $vip = '192.168.172.200';
my $brdc = '192.168.172.255';
my $ifdev = 'ens33';
my $key = '1';
my $ssh_start_vip = "/sbin/ifconfig ens33:$key $vip";
my $ssh_stop_vip = "/sbin/ifconfig ens33:$key down";
my $exit_code = 0;
#my $ssh_start_vip = "/usr/sbin/ip addr add $vip/24 brd $brdc dev $ifdev label $ifdev:$key;/usr/sbin/arping -q -A -c 1 -I $ifdev $vip;iptables -F;";
#my $ssh_stop_vip = "/usr/sbin/ip addr del $vip/24 dev $ifdev label $ifdev:$key";
GetOptions(
'command=s' => \$command,
'ssh_user=s' => \$ssh_user,
'orig_master_host=s' => \$orig_master_host,
'orig_master_ip=s' => \$orig_master_ip,
'orig_master_port=i' => \$orig_master_port,
'new_master_host=s' => \$new_master_host,
'new_master_ip=s' => \$new_master_ip,
'new_master_port=i' => \$new_master_port,
);

exit &main();

sub main {

print "\n\nIN SCRIPT TEST====$ssh_stop_vip==$ssh_start_vip===\n\n";

if ( $command eq "stop" || $command eq "stopssh" ) {

my $exit_code = 1;
eval {
print "Disabling the VIP on old master: $orig_master_host \n";
&stop_vip();
$exit_code = 0;
};
if ($@) {
warn "Got Error: $@\n";
exit $exit_code;
}
exit $exit_code;
}
elsif ( $command eq "start" ) {

my $exit_code = 10;
eval {
print "Enabling the VIP - $vip on the new master - $new_master_host \n";
&start_vip();
$exit_code = 0;
};
if ($@) {
warn $@;
exit $exit_code;
}
exit $exit_code;
}
elsif ( $command eq "status" ) {
print "Checking the Status of the script.. OK \n";
exit 0;
}
else {
&usage();
exit 1;
}
}
sub start_vip() {
`ssh $ssh_user\@$new_master_host \" $ssh_start_vip \"`;
}
## A simple system call that disable the VIP on the old_master
sub stop_vip() {
`ssh $ssh_user\@$orig_master_host \" $ssh_stop_vip \"`;
}

sub usage {
print
"Usage: master_ip_failover --command=start|stop|stopssh|status --orig_master_host=host --orig_master_ip=ip --orig_master_port=port --new_master_host=host --new_master_ip=ip --new_master_port=port\n";
}

(4) Create MHA software directory and copy the configuration file, using app1 CNF configuration file is used to manage the mysql node server. The configuration file is generally placed in the / etc / directory

mkdir /etc/masterha
cp /opt/mha4mysql-manager-0.57/samples/conf/app1.cnf /etc/masterha/

Delete the original content, directly copy and modify the IP address of the node server

[server default]
manager_log=/var/log/masterha/app1/manager.log
manager_workdir=/var/log/masterha/app1
master_binlog_dir=/usr/local/mysql/data
master_ip_failover_script=/usr/local/bin/master_ip_failover
master_ip_online_change_script=/usr/local/bin/master_ip_online_change
password=manager
user=mha					
ping_interval=1
remote_workdir=/tmp
repl_password=qwe123
repl_user=myslave		
secondary_check_script=/usr/local/bin/masterha_secondary_check -s 192.168.10.13 -s 192.168.10.14
shutdown_script=""
ssh_user=root			

[server1]
hostname=192.168.10.12
port=3306

[server2]
candidate_master=1
check_repl_delay=0
hostname=192.168.10.13
port=3306

[server3]
hostname=192.168.10.14
port=3306

#manager working directory
manager_log=/var/log/masterha/app1/manager.log

#manager log
manager_workdir=/var/log/masterha/app1

#The location where the master saves binlog. The path here should be the same as the binlog configured in the master
master_binlog_dir=/usr/local/mysql/data

#Switch scripts when setting automatic failover, that is, the last configured script
master_ip_failover_script=/usr/local/bin/master_ip_failover

#Set the switching script for manual switching
master_ip_online_change_script=/usr/local/bin/master_ip_online_change

#The password here is the password of the previously created monitoring user
password=manager

#Set monitoring user
user=mha

#Set the event interval for monitoring the main database and sending ping packets. The default is 3 seconds. When there is no response for three attempts, the system will automatically perform a sexual failover
ping_interval=1

#Set the (temporary) save location of binlog in case of remote MySQL switching
remote_workdir=/tmp

#Set the password of the slave user
repl_password=qwe123

#Set the account of the copying user
repl_user=myslave

#Set the script of the alarm sent after switching
report_script=/usr/local/send_report

#Set the script to check from the server
secondary_check_script=/usr/local/bin/masterha_secondary_check -s 192.168.226.133 -s 192.168.226.134

#Set the script to close the failed host after the failure occurs
shutdown_script=""

#Set the login user name of ssh
ssh_user=root

[server2]
#Set the candidate master. If this parameter is set, this library will be promoted to the master library after the master-slave switch
candidate_master=1
#Replication check is supported. By default, if a slave lags behind the relay logs of the master by 100m,
MHA The will not be selected slave As new master，If set to 0, this rule will be ignored
check_repl_delay=0

hostname=192.168.226.131
port=3306

9. For the first configuration, you need to manually turn on the virtual IP on the master node

Master(192.168.10.12)

/sbin/ifconfig ens33:1 192.168.10.200/24

10. Test ssh password less authentication on the manager node

MHAmanager(192.168.10.11)

masterha_check_ssh -conf=/etc/masterha/app1.cnf
#If it is normal, it will finally output successfully;
#If it fails, you can go to the place where the server has no password authentication to see if there is a problem

11. Test master-slave replication

masterha_check_repl -conf=/etc/masterha/app1.cnf
#Finally, MySQL Replication Health is OK appears, indicating that it is normal;
#MySQL Replication Health is NOT OK appears! , you can check whether there are fewer soft links on the mysql server -- > location of this article:
2,Modify three sets MySQL Master profile of the server/etc/my.cnf，And create a command soft link

12. Start MHA on the manager node

nohup masterha_manager --conf=/etc/masterha/app1.cnf --remove_dead_master_conf --ignore_last_failover < /dev/null > /var/log/masterha/app1/manager.log 2>&1 &

nohup //option

masterha_manager //open

–conf=/etc/masterha/app1.cnf //Specify profile

–remove_dead_master_conf //When the master server fails, the old master ip will be deleted from the master configuration file after the master-slave switch

–ignore_last_failover //Ignore failover, ignore servers that are always down and unreliable

13. View relevant information

See who the current master node is
masterha_check_status --conf=/etc/masterha/app1.cnf

View current log information
cat /var/log/masterha/app1/manager.log | grep "current master"

Check whether the MySQL VIP address 192.168.172.200 exists. This VIP address will not disappear because the manager node stops MHA service
ifconfig

3, Fault simulation

1. Monitor observation log records on the manager node

MHAmanager(192.168.10.11)

tail -f /var/log/masterha/app1/manager.log

2. Stop MySQL service on Master node Mysql1

master(192.168.10.12)

systemctl stop mysqld
 or
pkill -9 mysql

3. Check whether salve1 takes over VIP

slave1(192.168.10.13)

4. Monitor observation log records on the manager node

4, Troubleshooting steps

1. Repair master

master(192.168.10.12)
systemctl restart mysqld

2. Repair master-slave

3. On the manager node, modify the configuration file app1 cnf

vim /etc/masterha/app1.cnf
......
secondary_check_script=/usr/local/bin/masterha_secondary_check -s 192.168.172.10 -s 192.168.172.30
......
[server1]
hostname=192.168.10.13
port=3306

[server2]
candidate_master=1
check_repl_delay=0
hostname=192.168.10.14
port=3306

[server3]
hostname=192.168.10.12
port=3306

4. Start MHA on the manager node