What is the link between a fuse, Netflix and the Cloud ?
What is a Fuse ?
Protects appliances and wiring by monitoring failures
- Breaks the circuit when current flow is too high
- Needs manual re-set to close the circuit back
What is the Circuit Breaker pattern ?
Protects applications from catastrophic cascade by monitoring for failures
- Trips the circuit when failures reach a certain threshold
- Implements an automated re wiring process using threshold and half open state
Electric circuit breaker
- Switch oven on
- Power overhead
- Max current limit reached
- Fuse breaks - no more current flowing
- You (pissed) go and change the fuse , or press the CB
- The circuit is closed
- Time to heat up that pizza, at last !
Software circuit breaker
- Web app making a request
- Response latency
- Max failures / timespan reached
- CB opens - no more request sent
- Time to try again - CB is half open
- Transient fault on the remote is resolved
- Request succeeds - CB is Closed
What is Netflix Hystrix ?
Latency and fault tolerance library
Stop cascading failures
Fallbacks and graceful degradation
Fail fast and rapid recovery