Shulou(Shulou.com)06/02 Report--

Today, the editor will share with you the relevant knowledge points of Linux cluster. The content is detailed and the logic is clear. I believe most people still know too much about this knowledge, so share this article for your reference. I hope you can get something after reading this article. Let's take a look at it.

1. At present, the website architecture is generally divided into load balancing layer, web layer and database layer. In fact, I usually add one more layer, that is, the file server layer, because now with more and more PV of the website, the pressure on the file server becomes greater and greater. However, with the increasing maturity of moosefs and DRDB+Heartbeat+NFS, this problem is not serious. The front-end load balancing layer of the website is called Director, which plays the role of sharing requests, the most common of which is polling.

Second, F5 implements load balancing through hardware. It is widely used in CDN systems and is used for load balancing in squid reverse acceleration clusters. It is a professional hardware load balancing device, especially suitable for scenarios with high number of new and concurrent connections per second. LVS and Nginx are implemented by software, but they are also very stable and perform well when dealing with high concurrency.

Third, Nginx is less dependent on the network. In theory, as long as ping is accessible and web page access is normal, nginx can be connected. Nginx can also distinguish between internal and external networks. If you have nodes of both internal and external networks, it is equivalent to having a backup line on a stand-alone machine. Lvs is more dependent on the network environment. Currently, the server is in the same network segment and lvs uses direct streaming, the effect can be more guaranteed.

4. At present, the more mature high-availability technologies of load balancing are LVS+Keepalived and Nginx+Keepalived. In the past, Nginx did not have a mature dual-computer backup scheme, but it can be realized through shell script monitoring. If you are interested, you can refer to my project implementation plan on 51cto. In addition, if you consider the high availability of Nginx load balancing, you can also achieve it through DNS polling. If you are interested, you can refer to Zhang Yan's relevant articles. However, since our current business website has to take into account googel inclusion, domain name filing and other factors, we can only use a single domain name for the time being, so we only use the previous scheme. Nginx+keepalived has been running steadily in our computer room for a year and a half, so I would like to introduce this architecture to you.

5. Cluster refers to web cluster or tomcat cluster behind load balancer, but the current meaning of cluster generally refers to the entire system architecture, including load balancer and back-end application server cluster. Now many people like to refer to Linux cluster as LVS, but I think it should be distinguished in a strict sense.

6. The high availability of load balancer refers to the HA that implements the load balancer, that is, when one load balancer breaks down, the other can use the

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