Distributed Foundation

1. What is distributed

Use the physical architecture to form multiple autonomous processing elements , Don't share main memory , But by Send a message cooperation .——Leslie Lamport

2. The role of distributed

Pain points in actual work ： Bloated Engineering ; test 、 Cumbersome Online ; Low development efficiency .

Problems of monomer application ： Application code coupling is serious , It's hard to expand ; The interaction cycle of new requirements development is long , The test work is heavy ; It will take a long time for new developers to get familiar with the system ; Upgrading maintenance is also very difficult ( If you change anything, you have to upgrade the whole system ); It's hard to improve the system performance , Low availability , unstable .

The benefits of distributed ： Increase system capacity ; Enhanced system available ; Because of modularity , So the system module reuse degree is higher . Because the software service module is split , Development and publishing can be done in parallel and faster ; The system is more scalable ; The teamwork process will also be improved ; Technology upgrade .

3. Comparison of distributed and single structure

4.CAP Theorem

1. CAP Importance
2. CAP What is the theory ?
   C ( Consistency , Uniformity ）: Whether the read operation always reads the result of the previous write operation ;
   A( Availability, Usability ): The non fault node should make a reasonable response within a reasonable time ;
   P( Partition tolerance, Partition tolerance ): When network partition occurs , The system can continue to run .
   
3. Partition fault tolerance
   
4. Uniformity
   
   
   
5. Usability
   
6. CAP How to choose ?
   CP perhaps AP; On what occasion , Usability is better than consistency ?
   What suits is the best .
   If it is a bank transfer or payment business scenario , Priority is given to consistency , choice CP;
   If it is a large portal , Priority is given to availability , choice AP;

5. colony 、 Distributed 、 The difference between microservices

The difference between clustering and distribution
Distributed : A business is divided into several sub businesses , Deployed on different servers ;
colony : The same business , Deployed on multiple servers ;

The difference between cluster and microservice
colony : Dispersion pressure ;
Microservices ∶ The ability to disperse ;

Difference between microservices and distributed
Microservices are the way of architecture design ;
Distributed is the way of system deployment ;