What is fuse:
Service A calls a certain function of service B. The function time is too long due to the instability of the network or the card machine of service B. If this happens too many times, we can directly disconnect B. (A is not requesting the B interface ) Any call to the service of B will directly return degraded data without waiting for the timeout execution of B. In this way, the failure of B will not affect A in cascade.
What is downgrade:
The entire website is in a peak traffic period and server pressure increases sharply. According to the current business conditions and traffic, some services and pages are strategically downgraded/stopped. All calls directly return the downgraded data to relieve the pressure on server resources to ensure The normal operation of the core business also kept customers and most customers waiting for the correct response.
Same point
1. In order to ensure the availability and reliability of most services in the cluster, prevent crashes, sacrifice the individual
2. Users eventually experience that a certain function is unavailable
difference:
1. Fuse is a failure of the callee and triggers the active rules of the system
2. Downgrade is based on global considerations to stop some normal services and release resources
What is current limiting:
Control the request flow of incoming services so that the service can bear the flow pressure that does not exceed its own capacity