preface

I’ve been looking at distributed and highly available cluster architectures and deploying highly available clusters lately, so I want to summarize these experiences.

As we all know, when the business of the company starts to develop, the traffic we bear will increase accordingly. From the beginning, a single Nginx server as a proxy request forwarding is not enough to cope with our daily traffic, so we need to carry more traffic.

Although some people will say, now are on the cloud products, which also need to build their own server cluster, or loadbalance but still that sentence, development is definitely to make the technology more and more easy to use, master difficult, maybe you will click a few buttons can set up the entrance of the whole cluster, when others asked its principle how to do?

Keepalived

To bind THE VRRP protocol to VIP, you are advised to disable the iptables serviceCopy the code

Keepalived is what? Keepalived is a server health check tool that can be used to kick a server out of the cluster if it crashes/malfunctions, and to add it back to the cluster when it recovers. That’s what Keepalived is all about, leaving it all to the machine.

The concepts of layer 4 and layer 7 of load balancing are not outlined here. Because this time it’s all about summary deployment.

There are two options for Keepalived: master/slave mode the difference between the two modes is that the former standby machine does not work and the latter standby machine works together.

Before configuring KeepAlived, let’s prepare 2 Linux virtual machines as an example

• 192.168.1.100 master
• 192.168.1.101 salve

Configure Keepalived – master slave mode

First we need to install Keepalived, here I use the simplest way to install, compile and install you can refer to other ways. I just want to be convenient

yum install keepalived
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Remember that both hosts need to be installed and then entered into the configuration file

vim /etc/keepalived/keepalive.conf
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So if you go into configuration, you’ll see a lot of configuration, and I have a lot of features here that I don’t need to use like health detection email and so on. So just skip this part right here, and we can get rid of all that stuff and keep this stuff.

global_defs {
    # Route ID, the identifier of the host where the keepalived node is currently installed
   router_id keep_100
}

# Computer node
vrrp_instance VI_1 {
    # status, current
    state MASTER
    # Network card bound to the current instance
    interface eth0
    # Ensure that the active and standby nodes are consistent
    virtual_router_id 51
    # Priority/weight
    When the master dies, it becomes master
    The current master node is therefore the highest
    priority 100
    # Interval for checking synchronization between the active and standby nodes
    advert_int 1
    # Authentication and authorization password to prevent the entry of illegal nodes
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        # VIP192.168.1.161}}Copy the code

Now that you’ve basically done the configuration of the master node, let’s do the configuration of the Salve, which is basically the same

global_defs {
    # Route ID, the identifier of the host where the keepalived node is currently installed
   router_id keep_101
}

# Computer node
vrrp_instance VI_1 {
    BACKUP is required
    state BACKUP
    # Network card bound to the current instance
    interface eth0
    # Ensure that the active and standby nodes are consistent
    virtual_router_id 51
    # Priority/weight
    Set this side to 50 because it's salve
    priority 50
    # Interval for checking synchronization between the active and standby nodes
    advert_int 1
    # Authentication and authorization password to prevent the entry of illegal nodes
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        # VIP192.168.1.161}}Copy the code

Don’t forget to reboot when you’re done

systemctl restart keepalived.service
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And then we type on the master node

ip addr
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At this point we should see that our configured network adapter has 192.168.1.161 bound to this network adapter. Easy, right?

Configure service heartbeat detection

Next we need to configure the check nginx server state, write a simple script to help us check nginx

#! /bin/bash
A=`ps -C nginx --no-header |wc -l`
# Determine if nginx is down and try to restart it
if [ $A -eq 0 ];then
    /usr/local/nginx/sbin/nginx
    sleep 3
    # Wait and check again. If not, close Keepalive and let it start the standby machine
    if [ `ps -C nginx --no-header |wc -l` -eq 0 ];then
        killall keepalived
    fi
fi
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We saved it in /etc/keepalived/check_nginx_alive.sh, remember to set executable permissions for the file once it is saved

chmod +x check_nginx_alive.sh
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Then go back to the keepalive. conf file on the master node to configure the script to execute periodically and open the configuration file to add

// Add script to master keepalive.conf vrrp_script check_nginx_alive {script"/etc/keepalived/check_nginx_alive.sh"Interval 2 // Weight 10 is executed every two secondsIf the script runs successfully, the weight of the current node is +10

}
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Then configure the script into our instance

vrrp_instance VI_1 {
    state MASTER
    interface eth0
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    Add heartbeat detection script
    track_script {
        The name here needs to be handled by the name above the rootCheck_nginx_alive} virtual_ipaddress {192.168.1.161}}Copy the code

After the configuration is complete, we can also try to stop all the master nodes by keepalived. Then go back to the IP addr on the salve machine and you will find that the IP address 192.168.1.161 is bound to the network card of the Salve machine. This is also known as IP drift

This completes the master-slave configuration. However, you will find that all requests will only be made to the master node, and salve is completely a backup machine. How can we allow such waste? Therefore, the standby machine should also join in the service of users can ah

Configuration Keepalived – Master mode (dual Master hot Backup)

After configuring the master/slave mode, it is very easy to configure the dual master mode. It literally means dual master mode is basically two machines, both master and salve at the same time what does that mean? Let’s configure it and you’ll get the idea pretty quickly

Let’s open the master configuration file and add the standby configuration file below

Change instance to vi_2
vrrp_instance VI_2 {
    state BACKUP
    interface eth0
    # to 52
    virtual_router_id 52
    priority 50
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        # VIP192.168.1.161}}Copy the code

Then we will go to the Salve node to configure a master CONF

# change the instance name
vrrp_instance VI_2 {
    state MASTER
    interface eth0
    # to 52
    virtual_router_id 52
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        # VIP192.168.1.161}}Copy the code

That completes the configuration. It’s very simple to configure the salve on the master, configure the master on the salve so that it becomes a bidirectional node. Master each other, and also successfully applied salve machine.

Keepalived +LVS is usually used together with keepalived. Let me write a separate summary of keepalived+LVS.