IllegalStateException with Hystrix

Question

I am new to Hystrix. I am trying to use it with Spring AOP. The following details what I am trying to achieve.

There is a "ServiceClass", into which some RestClient class is injected. I am using Spring. Now, I want to use Hystrix together with Spring AOP so that method calls to the RestClient from the ServiceClass could be made synchronously or asynchronously.

What I have done so far is as follows.

created a class "MyCommand" that extends HystrixCommand implements MethodInterceptor

implemented a method "execute(MethodInvocation m, String mode) in it as follows:

                      protected Object execute(MethodInvocation m, String mode){
                      this.mode = mode;
                      this.method = m;
                      return execute();}

in the (overridden method) "invoke"

                       public Object invoke(MethodInvocation m) throws throwable{
                         try{
                              execute(m,"Sync");
                         } catch(Exception e){
                             e.printStackTrace();
                         }
                        }

This "MyCommand" is being set as the AOP Interceptor for the "ServiceClass" in the spring-config file.

Now, the issue is; in my "Main" application when I retrieve the "ServiceClass" from the ClassPathXmlApplicationContext and invoke one method, it works fine. But if I try to invoke two of the methods of the "ServiceClass" it throws the following exception:

              *java.lang.IllegalStateException: This instance can only be executed once. Please instantiate a new instance.*

Code snippet:

              ServiceClass srvc = (ServiceClass) ctx.getBean("proxy");
              srvc.getRequest();
              srvc.postRequest();

I have spent almost three days trying to figure it out the cause and solution for this exception but without any good. Please help me get this right. What am I missing?

As always, Thanks in advance

Ok, looks like one cannot call execute() multiple times on the same instance of a Hystrix command (not really sure why though). So have modified the code to use a new instance of the Hystrix command every time. And it works. — 5122014009

harperska harperska · Accepted Answer · 2015-07-22T19:05:38

A HystrixCommand object can only be used once, because it contains useful state information after it is executed that can be used for further processing. For example, if you wanted to do special handling after the fact if the call to run() timed out, you could do the following:

public class MyHystrixCommand extends HystrixCommand<Object> { ... }

MyHystrixCommand command = new MyHystrixCommand();

command.execute();

if(command.isResponseTimedOut()){
    //do post processing
}

If you could invoke execute() multiple times, especially from multiple threads as would happen if you had multiple consumers of your REST endpoint, you would have no way of knowing which invocation was the one that timed out when you queried the command for its state.

IllegalStateException with Hystrix

1 Answers