Talk about the system architecture of large high-concurrency high-load Web sites (update)

Reprint please keep Source: June Lin Michael's blog (http://www.toplee.com/blog/?p=71)
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I have done in cernet dial-up access, in the yahoo&3721 to search the front-end, In MOP processed mop.com architecture upgrade, in the 6.cn video site engaged in development work, but also in many years of work to contact and develop a lot of large and medium-sized web site modules, so in large-scale web site to deal with high-load and concurrency of the solution has some accumulation and experience, and we hope to discuss with you.

A small website, such as personal website, can use the simplest HTML static page to achieve, with some pictures to achieve beautification effect, all the pages are stored in a directory, such a site on the system architecture, performance requirements are very simple, with the Internet business is constantly enriched, Website related technology After these years of development, has been subdivided into very fine aspects, especially for large sites, the use of technology is very wide, from hardware to software, programming languages, databases, WebServer, firewalls and other fields have a very high requirements, is not the original simple HTML static site can be compared.

Large Web sites, such as portals. In the face of a large number of user access, high concurrent requests, the basic solution is focused on a number of aspects: the use of high-performance servers, high-performance databases, high-efficiency programming language, as well as high-performance web containers. But in addition to these aspects, there is no way to solve the large-scale web site is facing high load and high concurrency problems.

The above offers a few solutions to a certain extent also means a greater input, and such a solution to the bottleneck, not very good extensibility, below I from the low cost, high performance and high expansion of the perspective of my experience.

1. Static HTML
In fact, we all know that the most efficient, the least expensive is the pure static HTML page, so we try to make the page on our site using static pages to achieve, the simplest method is actually the most effective method. But for a lot of content and frequently updated sites, we can not all manually to achieve, so we have a common information distribution system CMS, like we often visit the various portals of the news channel, and even their other channels, are through the information distribution system to manage and implement, Information Publishing system can achieve the simplest information input automatically generated static pages, but also with channel management, rights management, automatic capture and other functions, for a large web site, has a set of efficient, manageable CMS is essential.

In addition to the portal and the type of information publishing site, for the interactive requirements of the Community type site, as much as possible static is also to improve the performance of the necessary means, the community posts, articles in real-time static, there is a renewal of the time and re-static is a lot of use of the strategy, A hodgepodge like mop is the use of such strategies, such as the NetEase community. At present, many blogs have also been implemented static, I use this blog program WordPress has not been static, so if the face of high-load access, www.toplee.com must not bear

At the same time, HTML static is also the use of some caching policies, for the system frequently using database queries but the content of small updates, you can consider the use of HTML static, such as forum public settings information, This information is currently the mainstream forum can be managed in the background and stored in the database, which is actually a lot of the foreground program calls, but the update frequency is very small, you can consider this part of the background update the time to static, so as to avoid a large number of database access requests.

In the HTML static can use a compromise method, that is, the front-end use of dynamic implementation, under a certain strategy for the timing of static and timed call, this can achieve a lot of flexibility of operation, I developed the billiard site of the People (www.8zone.cn) is the use of such a method, I cache dynamic site content by setting some HTML static time intervals to share most of the stress on static pages, which can be applied to the architecture of small and medium-sized websites. Home Site Address: http://www.8zone.cn, by the way, there is a lot of friends like billiards support me this free site:)

2, Image server separation
You know, for the Web server, whether it is Apache, IIS or other containers, the picture is the most consumption of resources, so we have to separate the picture and the page, which is basically a large site will adopt the strategy, they have a separate picture server, and even many picture server. Such architectures can reduce the pressure on the server system that provides page access requests and ensure that the system does not crash due to picture problems.

In the application server and picture server, can be different configuration optimization, such as Apache in the configuration of contenttype can be as little as possible to support, as little as loadmodule, to ensure higher system consumption and execution efficiency.

My billiard site 8zone.cn also used the image server architecture on the separation, which is currently only architecturally separate, physically not separated, due to no money to buy more servers:), You can see the picture connection on the people's home is similar to img.9tmd.com or img1.9tmd.com URL.

In addition, in dealing with static pages or images, JS and other access, you can consider using LIGHTTPD instead of Apache, which provides a more lightweight and more efficient processing power.

3. Database cluster and library table hash
Large Web sites have complex applications, which must use databases, and in the face of a large number of accesses, the bottleneck of the database can soon be revealed, when a database will soon be unable to meet the application, so we need to use the database cluster or library table hash.

In the database cluster, many databases have their own solutions, Oracle, Sybase and so on have a good solution, the common MySQL provided by the Master/slave is a similar scenario, you use what kind of db, refer to the corresponding solutions to implement.

The database cluster mentioned above is constrained by the DB type used in architecture, cost, and extensibility, so we need to consider improving the system architecture from the perspective of the application, and the library table hashing is the most common and effective solution. We install the business and application in the application or function module to separate the database, different modules corresponding to different databases or tables, and then according to a certain policy on a page or function of a smaller database hash, such as the user table, according to user ID for the table hash, This makes it possible to improve the performance of the system at a low cost and has a good scalability. Sohu Forum is the use of such a framework, the Forum users, settings, posts and other information database separation, and then to the post, the user in accordance with the plate and ID hash database and table, finally can be configured in the configuration file simple configuration will allow the system at any time to add a low-cost database to supplement the system performance.

4. Cache
The word cache has been touched by technology, and caches are used in many places. Caching in the Web site architecture and Web development is also very important. Here we first describe the two most basic caches. The advanced and distributed caches are described later.

Architecture cache, people familiar with Apache can know that Apache provides its own Mod_proxy cache module, can also use additional squid for caching, both of which can effectively improve the access response of Apache.

Website program development Cache, Linux provides memcached is a common caching scheme, many Web programming languages provide memcache access interface, PHP, Perl, C and Java have, can be used in web development, can be in real-time or cron data, Objects and so on, the policy is very flexible. Some large communities have used such architectures.

In addition, in the use of web language development, all kinds of languages have their own cache modules and methods, PHP has pear cache module and eaccelerator acceleration and cache module, but also the well-known APC, XCache (developed by the Chinese, support!). PHP cache module, Java more,. NET is not very familiar, I believe there is certainly.

5. Mirror
Mirroring is often used by large web sites to improve performance and data security, the mirror technology can solve the different network access providers and geographical user access speed differences, such as the difference between chinanet and edunet prompted a lot of websites in the education network to build mirror site, Data is scheduled to be updated or updated in real time. In terms of mirror detail technology, this is not too deep, there are many professional ready-made solution architectures and products to choose from. There are also inexpensive ways to implement software, such as the tools of Rsync on Linux.

6. Load Balancing
Load balancing will be the ultimate solution for large web sites to address high-load access and a large number of concurrent requests.

Load balancing technology has developed for many years, there are many professional service providers and products can be selected, I personally contacted a number of solutions, including two architecture can give you a reference. In addition, the primary load balancer DNS round robin and the more professional CDN architecture is not much to say.

6.1 Hardware four-layer switching
The fourth layer Exchange uses the header information of the third layer and fourth layer packets, according to the application interval to identify the business flow, the entire interval segment of the business flow distribution to the appropriate application server for processing. The fourth layer switch function is like a virtual IP, pointing to the physical server. It transmits services that comply with a variety of protocols, such as HTTP, FTP, NFS, Telnet, or other protocols. These operations are based on physical servers and require complex load balancing algorithms. In the IP world, the business type is determined by the terminal TCP or UDP port address, and the application interval in layer fourth switching is determined by the source and endpoint IP addresses, TCP, and UDP ports.

In the hardware four-layer switching product area, there are some well-known products to choose from, such as Alteon, F5, etc., these products are expensive, but value for money, can provide very good performance and very flexible management capabilities. Yahoo China at the beginning of nearly 2000 servers using three or four alteon to be done.

6.2 Software four-layer switching
When you know the principle of hardware layer four switch, the software four layer exchange based on the OSI model comes into being, so the solution achieves the same principle, but the performance is slightly worse. But to meet a certain amount of pressure or comfortable, some people say that the software implementation is actually more flexible, the ability to handle the full look at your configuration of the familiar ability.

Software four-layer switching we can use the common LVS on Linux to solve, LVs is Linux Virtual Server, he provides a real-time disaster response based on the Heart Line heartbeat solution, improve the system robustness, At the same time, the flexible virtual VIP configuration and management functions can meet a variety of application requirements, which is necessary for distributed systems.

A typical use of load balancing strategy is to build a squid cluster on the basis of software or hardware four-layer switching, which is adopted on many large Web sites including search engines, which have low cost, high performance and strong extensibility, and it is easy to add or subtract nodes to the architecture at any time. Such a structure I am ready to empty a special detail and discuss with you.

6.3 Seven-layer switching
We all know that TCP/IP seven layer protocol, four layer exchange is based on the transport layer, in this layer can only handle the management of the connection, but can not be associated with the business, usually only for TCP, UDP connection to processing, and the real business logic needs to be processed by the following server group, with the development of technology, today , we have seven layers of switching in many advanced applications.

Layer Seven Exchange is based on the seventh layer of TCP/IP application layer to achieve, in this layer, we can first distinguish between specific applications, such as HTTP, TELNET, FTP, DNS, etc., but also according to the content of the application to carry out the management of the policy, such as we have so two of the path of the site a.com/music/... and a.com/photo/... Originally based on the four-layer exchange can only send these two URL requests to the subsequent set of servers, but the seven-tier exchange can determine whether to access the music/or photo/path, and then distributed to the non-reachable server farm, thus achieving a more flexible system architecture design.

Of course, the seven-layer exchange is also divided into hardware and software implementation, where I do not elaborate, the hardware has the famous F5, Nortel, etc., the software has haproxy, of course, seven layers of software is still in the performance of the hardware is far from the difference in the implementation, you know, these hardware are expensive

Summarize:
For large web sites, each of the previously mentioned methods may be used at the same time, Michael introduced here is relatively simple, the implementation of a lot of details of the process needs to be familiar with and experience, sometimes a very small squid parameter or Apache parameter settings, the impact on the system performance will be very large , we hope that we will discuss together to achieve the effect.

Reprint please keep Source: June Lin Michael's blog (http://www.toplee.com/blog/?p=71)
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Talk about the system architecture of large high-concurrency high-load Web sites (update)