Distributed systems background
He said distributed system must say that the centralized system, centralized system in the whole project is a stand-alone application, the entire application is the entire project, everything in one application inside.
As shown below
As a website is an application, and finally increased more multiple servers or multiple containers to achieve load balancing purposes to avoid single point of failure, of course, it is a database that can be deployed separately.
It is clear that the development of the advantages of centralized operation and maintenance of the test would be more convenient, not to consider the complex distributed environments.
Centralized obvious drawbacks is difficult to expand, each update must update all applications. Moreover, there is a problem means that all applications have problems. When the system is growing, centralized system will be the biggest bottleneck.
What is a distributed system?
Distributed system is a collection of several stand-alone computer, which is like a single computer user related systems.
<< above definition is taken from the principles of distributed systems and paradigms >> a book.
That is behind a distributed system is composed of a series of computer components, but the user can not perceive the logic behind it, like access to a single computer.
Said a little around, we can simply look at a distributed system of FIG.
Pros and cons of Distributed Systems
In a distributed system:
1, the application may split into a plurality of applications according to the service type, then the interface layer into the structure, the service layer; we can also click access entry points, such as a mobile terminal, PC terminal and so define different application interfaces;
2, the database can be split into several instances by business type, the sub-library may also be a single sub-table of the table;
3, increased distributed caching, search, file, message queues, and other non-relational database middleware;
Obviously, centralized distributed system can solve the inconvenience of extended defects, we can easily extend the application at any link, even if an application problem will not affect other applications.
With the rebirth of the hot micro-services Spring Cloud & Docker's, and domestic open-source framework for distributed Dubbo, distributed technology is developing rapidly.
Distributed system is good, it also brings the problem of complexity of the system, such as distributed transactions, distributed lock, distributed session, data consistency, etc. are now distributed systems need to be addressed, although there have been many mature program, but not perfect. Distributed systems development and testing also increased operation and maintenance costs, increased workload, the distributed system management but will not become a burden.
If you have a better view of distributed technology, or objection to this article are welcome to leave a comment below.
