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I am trying to implement hystrix for my application using hystrix-javanica.
I have configured hystrix-configuration.properties as below
hystrix.command.default.execution.isolation.strategy=SEMAPHORE
hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds=10000
hystrix.command.default.fallback.enabled=true
hystrix.command.default.circuitBreaker.enabled=true
hystrix.command.default.circuitBreaker.requestVolumeThreshold=3
hystrix.command.default.circuitBreaker.sleepWindowInMilliseconds=50000
hystrix.command.default.circuitBreaker.errorThresholdPercentage=50
short-circuit pattern is working fine but i have a doubt in this hystrix.command.default.circuitBreaker.requestVolumeThreshold=3
Gone through the documentation link
Can anybody answer?
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First, we need to add the Spring Cloud Starter Hystrix dependency in our build configuration file. Now, add the @EnableHystrix annotation into your main Spring Boot application class file. The @EnableHystrix annotation is used to enable the Hystrix functionalities into your Spring Boot application.
The @HystrixCommand is provided by a Netflix contrib library called “javanica”. Spring Cloud automatically wraps Spring beans with that annotation in a proxy that is connected to the Hystrix circuit breaker. The circuit breaker calculates when to open and close the circuit and what to do in case of a failure.
Hystrix is a library that controls the interaction between microservices to provide latency and fault tolerance. Additionally, it makes sense to modify the UI to let the user know that something might not have worked as expected or would take more time.
Hystrix helps by providing protection and control over latency and failure from dependencies, most commonly those accessed over network. It helps stop cascading failures and allows you to fail fast and rapidly recover, or fallback and gracefully degrade. Here's how it works.
How Hystrix Circuit-Breaker operates: Hystrix does not offer a circuit breaker which breaks after a given number of failures. The Hystrix circuit will break if:
within a timespan of duration
metrics.rollingStats.timeInMilliseconds, the percentage of actions resulting in a handled exception exceedserrorThresholdPercentage, provided also that the number of actions through the circuit in the timespan is at leastrequestVolumeThreshold
What is requestVolumeThreshold?
requestVolumeThreshold is a minimum threshold for the volume (number) of calls through the circuit that must be met (within the rolling window), before the circuit calculates a percentage failure rate at all. Only when this minimum volume (in each time window) has been met, will the circuit compare the failure proportion of your calls against the errorThresholdPercentage you have configured.
Imagine there was no such minimum-volume-through-the-circuit threshold. Imagine the first call in a time window errors. You would have 1 of 1 calls being an error, = 100% failure rate, which is higher than the 50% threshold you have set. So the circuit would break immediately.
The requestVolumeThreshold exists so that this does not happen. It's effectively saying, the error rate through your circuit isn't statistically significant (and won't be compared against errorThresholdPercentage) until at least requestVolumeThreshold calls have been received in each time window.
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