Why are these features needed?
To prevent link avalanche and ensure the stability and usability of the system;
please refer to the image explanation (he has a picture, I am too lazy to draw haha):
The drawn picture explains the link avalanche more vividly
What can these functions do?
Current limiting: Ensure that business modules can process response requests within an acceptable time for business (users) . However, in order to ensure that the system processing rate remains unchanged, it is followed by additional processing of requests that exceed the system's load (denial of service or joining the waiting queue and other degraded operations that will not affect the system load ). This effect ensures that a single business availability, but also had to reduce the experience of some requests.
Fuse: When a node in the downstream of the service link has a response timeout of a certain magnitude and takes up a lot of load on itself and the caller, it will be disconnected before causing a link avalanche (that is, the unavailability of the entire calling link service). Fuse with downstream calls (that is, no longer call downstream, downgrade (friendly prompts, join the waiting queue, etc.)) to ensure the availability of the remaining functions of the entire system.
The difference between current limiting and fusing is (visual explanation):
Current limit (chef): If you want me to cook well, the speed is the only thing I want to do, and I don’t want to do too much (downgrade and let the apprentice burn it or burn it after I’m busy).
Circuit breaker (restaurant front desk): After finding that the back kitchen is too busy to handle, the memorized menu will not be handed over to the back kitchen ( circuit breaker ), and the flyer will be issued after the back kitchen is a little free and someone can take orders. (Because at this time, going to the back kitchen with the flyer will only drag down the efficiency of the back kitchen even more, and because the efficiency of the back kitchen has decreased, the process of the flyer will be lengthened, resulting in insufficient manpower at the front desk, and the original work of recording the menu will not be completed well, and it will be downgraded After no more leaflets, appease the customer's emotions, arrange the notes in order and put them away, and then pass them on in sequence when the kitchen is free)