Large Web site Technical Architecture Transcript (2): Mode

Large Web site architecture mode
Since it is a pattern, it is the way of experience, something that can be reused.

1) layering
Consider the 7-layer or 4-layer network model, where each layer is responsible for a relatively single function, and the upper and lower layers are called.
The site is generally divided into three levels: the application layer, the service layer, and the data tier. Specifically, you can continue to refine the layering.
Application layer: Specific business, view display, homepage, search results, etc.
Service Layer: Service support for the application layer, such as shopping cart, user management
Data tier: Provides data storage access, such as databases, caches, files
Layered independence, maintaining interface, reasonable planning of layered boundaries and interfaces, prohibit cross-layer calls and reverse calls

2) Split
Vertical segmentation, the different functions and services cut open, such as shopping business can be split into household appliances business, clothing business.
Cohesion Poly, low coupling.

3) distributed
Resolve high concurrency issues.
Network delay, consistency issues and so on.

4) Cluster
Multiple servers deploy the same application to form a cluster that provides services externally through load balancing devices. When a server fails, the load Balancer device or the system's failover mechanism forwards the request to the other servers in the cluster, improving the system's availability, known as HA (High availability).

5) Caching
As mentioned earlier, CDN, reverse proxy (site frontend, general cache static resources), local and distributed cache (hotspot data)
Cache Prerequisites:
1) Access hotspot uneven, cache hotspot data
2) cached data does not expire quickly

6) asynchronous
Another means of reducing system coupling is that the business is not synchronous between calls, but instead splits into multiple phases, each of which asynchronously executes through shared data, asynchronous Message Queuing.
Producer consumer model, does not exist this direct call, expansion convenient
Improve system availability, consumers

7) Redundancy
What if the server goes down?
Of course, there are data redundancy backups so that when a server goes down, it can transfer services and data access to other machines.
Database in addition to regular backup archive saving to achieve cold backup, in order to ensure the high availability of online services, but also need to master-slave separation of the database, real-time synchronous implementation of hot backup.
8) Automation
In the case of unattended, the site can run normally, everything can be automated is the ideal state of the site. At present, the automation architecture design of large-scale Web sites is mainly focused on publishing operations.
① release deployment process automation;
② Automation code management;
③ automated testing;
④ Automatic safety monitoring;

9) Safety
It's not much to say.

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Large Web site Technical Architecture Transcript (2): Mode