Evolution of IT system architecture in internet companies

One day, chatting with a master in a teahouse. He asked: In the Shoe Factory sword faction These two years, can learn what advanced sword? I am not a leng, to think carefully, these two years of daily practice are simple chopping action and some concise routines. Did not go to practice what advanced sword. But the Shoe Factory sword faction in the lake is also a small fame war force is not bad, also took the big Hill, even the world three of the gate faction BB faction also on our hill eyeing. Why didn't the leaders of the gates let us practice the Advanced sword? Come to think of it, we're playing a bunch of racks, not heads-up. Put together each person who exercises simple moves, the simple moves are composed of powerful sword array. The sword array is a martial art. Sword array is not the beginning of the powerful, but also by a few people simple combination, experience life and death of the battle, only gradually developed. This sword is the big IT system of our internet company.    How do you calculate a large IT system? A system must have large concurrent user access, and a huge amount of data to calculate large IT systems.   The large IT systems we use today are all starting from small systems, one step at a time as users and data volumes increase dramatically.   is initially the simplest system architecture, where applications and databases are deployed on the same server, such as Web applications + database servers or app-oriented service+ database servers. This system architecture can support hundreds of to tens of thousands of people per day access. One, with the increase in user volume and data volume, the load of a single server gradually increased, this time you can split the database into a separate server. This will relieve the pressure on the system. Second, the application server load is too high, this time it is necessary to expand the application server as a cluster. Through 2 means: 1, the introduction of load balancer device, the request is evenly forwarded to the server in the cluster. 2, introduce session server to let the user feel that it is communicating with the same server. Thirdly, the pressure of the database becomes larger later. At this point, the database can be split vertically, and the database is decoupled according to the business unit. Each separate business data can be stored in a single database. There are also horizontal table, read-write separation and other measures. At this time the company can build a unified distributed data access layer framework within the company.   Four, with the rapid development of the business, the system of uncontrolled change of bloated huge, a large number of Web service calls to our system into a spider web. Quality is increasingly difficult to guarantee. Trouble-prone, inefficient, team outplayed.     This time can be introduced into the service framework, the system to remove small, pay attention to system layering, control the call relationship between the system.     uses messaging systems to solve strong coupling problems between business systems. Use of soft load center and centralized configuration management to support Service framework, message system, distributed data access layer, all applicationsManagement and so on. Other elements of building large-scale Internet IT systems: CDN, storage systems for large Web sites (Distributed file systems, NoSQL, Cache systems), search systems, data calculation support, release systems, application monitoring systems, dependency management systems, etc.   

Evolution of IT system architecture in internet companies