On the process of Web request

1,B/S Network Architecture Description

b/S network architecture is based on the Unified Application layer protocol HTTP to interact with the data, the HTTP protocol uses a non-state short link communication mode, one request to complete the data interaction

This way you can serve more users at the same time.

When the user enters the URL, DNS resolves the domain name to the corresponding IP address, then accesses the server corresponding to the IP address, sends a GET request to the server, and the server returns the default data resource, which can be stored in the CDN Server for distributed, general static resources.

CDN (Content Delivery Network): It is built on the existing Internet, an advanced traffic distribution networks, it can publish the content of the site to the closest users to the edge of the network, so that users get the required content nearby. cdn= Mirror + cache + Overall load balancing

2, initiating the request

The difference between initiating an HTTP request and establishing a socket connection is that it is essentially a socket connection, a Java-based package that initiates an HTTP request: HttpClient

3,http Protocol resolution

Common request headers, response headers, status codes:

4, Domain name resolution

The user initiates the request, first looking for the results of DNS resolution in the system cache, the cache file path for Windows: c:\windows\system32\drivers\etc\hosts,linux:/etc/named.conf, If you do not have access to the local DNS server (the DNS server is provided by the network provider), if you still miss the request resolution directly to the root server domain name server, the root name server returns the primary Domain name server (GTLD server) to the domain name server

gTLD is the international top-level domain name server, the gTLD returns a name server, and then accesses the server to obtain the IP value and TTL value of the domain name (domain name resolution cache time is controlled by TTL) (name server may have multiple levels, or a GTM to load balance control)

5,CDN Architecture

　　

The company's own DNS server will re-alias the request to the DNS Load Balancer server in the CDN Global, and the GTM's final allocation returns the node closest to the user.

6, Load Balancing

Common load Balancing: Link load balancing, cluster load balancing, operating system load balancing

(PS: Content from the book "in-depth analysis of Java Web Technology Insider", summed up the memo)

On the process of Web request