Hystrix configuration for circuit breaker in Java

Question

I am writing an application and I want to implement circuit breaker pattern. This is the Hystrix Command class I have written:

public class HystrixCommandNextGen extends HystrixCommand<ScriptContext> {

    private ScriptContext scriptctx;
    private ScriptFactory scriptFactory;
    private ScriptContext responseContext = null;

    private Logger logger = LoggerFactory.getLogger(HystrixCommandNextGen.class);

    public HystrixCommandNextGen(ScriptContext scriptctx, ScriptFactory scriptFactory) {
        super(
            Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("Thread_Pool"))
            .andCommandKey(HystrixCommandKey.Factory.asKey(scriptctx.getExecutionData(ExecutionParam.SCRIPTNAME)))
        );
        this.scriptctx = scriptctx;
        this.scriptFactory = scriptFactory;

        HystrixCommandProperties.Setter().withCircuitBreakerEnabled(true);
        HystrixCommandProperties.Setter().withCircuitBreakerRequestVolumeThreshold(150);
    }

    @Override
    protected ScriptContext run() throws Exception {
        scriptFactory.execute(scriptctx);
        return scriptctx;
    }

    @Override
    protected ScriptContext getFallback() {
        logger.error("FI is not responding: Error occurred in the execution of " + getClass().getSimpleName());
        return scriptctx;
    }
}

I am not able to understand how to configure the number of threads, threshold time for circuit breaker and number of requests to handle.

Answer 1

Hystrix uses Archaius for configuration management. The Archaius library allows for dynamic reloading of property values at runtime. Documentation on how to configure Archaius is here: https://github.com/Netflix/archaius/wiki/Users-Guide

If you want to configure Hystrix in code, you can use the Archaius ConfigurationManager class like this:

ConfigurationManager.getConfigInstance().setProperty(
  "hystrix.command.HystrixCommandKey.execution.isolation.thread.timeoutInMilliseconds", 
  500);

Note that the HystrixCommandKey part of the property name string is actually the name of the circuit breaker you set with the .andCommandKey() method of the Setter. So if you set the command key to be "MyCommand", the property key for timeout would actually be "hystrix.command.MyCommand.execution.isolation.thread.timeoutInMilliseconds"