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This article introduces the relevant knowledge of "the principle, advantages and disadvantages of DNS server load balancing configuration". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Load balancing technology can balance the communication load between all the servers and requesting applications in the server cluster, judge according to the real-time response time, and leave the task to the server with the lightest load, in order to achieve real intelligent communication management and the best server farm performance, so that the website can always run and ensure its accessibility.

In order to make full use of the advantages of existing server software, load balancing is best done outside the server software. The earliest load balancing technology is realized by random name resolution in DNS service. This is commonly known as DNS load balancing technology.

The implementation principle of DNS load balancing technology is to configure multiple IP addresses for the same host name in the DNS server. When answering the DNS query, the DNS server will return different parsing results for each query according to the IP address recorded by the host in the DNS file, and guide the client access to different machines, so that different clients access different servers, so as to achieve the purpose of load balancing.

The basic principle of DNS load balancing

The 1.dns system itself is a distributed network, which is relatively reliable, at least much more reliable than your website itself.

The final interpretation of 2.dns can be under our own control.

With these two conclusions, the rest is simple, and we just need to focus on the final explained query results. To put it simply, all your server addresses will be returned to the user according to the frequency of your needs.

Take github.com as an example, we first get its SOA server (because the dns cache query server caches the results, and if you query the domain name directly, it will return the same result every time). There are also 13 dns domain name servers on .com, which are [aMum]. Gtld-servers.net, let's randomly choose one to find github.com 's SOA.

OK, we have obtained four SOA servers ns [1-4] .p16.dynect.net, and randomly pick one to ask the corresponding record of github.com, and try several times to see if the final ip address will change.

We have queried twice here, and notice that the ANSWER SECTION section returns two results, one is 192.30.252.129 and the other is 192.30.252.128.

This is the use of dns to achieve load balancing, your final access will reach a different ip address.

Which DNS service providers support load balancing?

This is a relatively advanced service, which is not supported by the dns server of domain name registrars. At present, I know that the service providers that support it are

1.AWS Route 53

2.NSONE

3.Dyn

4.dnspod

Among them, 1 and 4 are what we are already using, and the effect is ideal.

Until now, many websites still use DNS load balancing to ensure the operation and accessibility of the site. From the perspective of its implementation and effect, it mainly has the following advantages and disadvantages:

Main advantages

The main disadvantages of this technique are as follows:

First, the technical implementation is flexible, convenient, simple and low cost, so it is suitable for most TCP/IP applications. There is no need for a network expert to set it up or maintain it if something goes wrong.

Second, there is no need to make any changes to the code for Web applications. In fact, the Web application itself is not aware of the load balancing configuration, even in front of it.

Third, the Web server can be located anywhere on the Internet.

Main shortcoming

When DNS load balancing technology has the above advantages, its disadvantages are also very obvious, mainly as follows:

First, the load cannot be distributed according to the processing capacity of the Web server. DNS load balancing uses a simple round robin load algorithm, which can not distinguish the differences between servers and can not reflect the current running state of the server. So the DNS server distributes Http requests evenly to the Web servers in the background, regardless of the current load on each Web server. If the configuration and processing capacity of the Web server in the background are different, the slowest Web server will become the bottleneck of the system, and the server with strong processing capacity can not play a full role. It is not possible to allocate more requests to better-performing servers, and there may even be cases where customer requests are concentrated on one server.

Second, it does not support high reliability, and DNS load balancing technology does not consider fault tolerance. If a Web server in the background fails, the DNS server will still assign DNS requests to the failed server, causing it to fail to respond to the client.

Third, it may cause additional network problems. In order to make this DNS server and other DNS servers interact in time, to ensure that the DNS data is updated in time, and to assign addresses randomly, it is generally necessary to set the refresh time of DNS to be small, but too small will cause additional network problems due to the increase of DNS traffic.

Fourth, once a server fails, even if you modify the DNS settings in time, you still have to wait enough time (refresh time) to work, during which time, the client computer that saved the failed server address will not be able to access the server properly.

This is the end of the introduction of "the principle, advantages and disadvantages of DNS server load balancing configuration". Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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