HystrixMetricsPublisherFactory does not respect HystrixPlugins.reset()

[mabn]

The problem is that HystrixMetricsPublisherFactory caches the reference to HystrixMetricsPublisher.

Also it's not possible to really reset it because HystrixMetricsPublisherFactory.INSTANCE must not be null and creating HystrixMetricsPublisherFactory instance calls HystrixPlugins.getMetricsPublisher() which sets metrics publisher to default implementation.

One way to fix it would be to remove HystrixMetricsPublisherFactory.strategy and always call HystrixPlugins.getInstance().getMetricsPublisher() instead.

Test case reproducing this issue:

package com.netflix.hystrix.strategy.metrics;

import static org.junit.Assert.assertNotSame;
import static org.junit.Assert.assertSame;

import org.junit.Test;

import com.netflix.hystrix.HystrixCircuitBreaker;
import com.netflix.hystrix.HystrixCommandGroupKey;
import com.netflix.hystrix.HystrixCommandKey;
import com.netflix.hystrix.HystrixCommandMetrics;
import com.netflix.hystrix.HystrixCommandProperties;
import com.netflix.hystrix.strategy.HystrixPlugins;

public class FactoryResetTest {
    static class CustomPublisher extends HystrixMetricsPublisher{
        private HystrixMetricsPublisherCommand commandToReturn;
        public CustomPublisher(HystrixMetricsPublisherCommand commandToReturn){
            this.commandToReturn = commandToReturn;
        }
        @Override
        public HystrixMetricsPublisherCommand getMetricsPublisherForCommand(HystrixCommandKey commandKey,
                        HystrixCommandGroupKey commandGroupKey, HystrixCommandMetrics metrics, HystrixCircuitBreaker circuitBreaker,
                        HystrixCommandProperties properties) {
            return commandToReturn;
        }
    }

    @Test
    public void testMetricsPublisherReset() {
        // precondition: HystrixMetricsPublisherFactory class is not loaded. Calling HystrixPlugins.reset() here should be good enough to run this with other tests. 

        // set first custom publisher
        HystrixCommandKey key = HystrixCommandKey.Factory.asKey("key");
        HystrixMetricsPublisherCommand firstCommand = new HystrixMetricsPublisherCommandDefault(key, null, null, null, null);
        HystrixPlugins.getInstance().registerMetricsPublisher(new CustomPublisher(firstCommand));

        // ensure that first custom publisher is used 
        HystrixMetricsPublisherCommand cmd = HystrixMetricsPublisherFactory.createOrRetrievePublisherForCommand(key, null, null, null, null);
        assertSame(firstCommand, cmd);

        // reset, then change to second custom publisher
        HystrixPlugins.reset();
        HystrixMetricsPublisherCommand secondCommand = new HystrixMetricsPublisherCommandDefault(key, null, null, null, null);
        HystrixPlugins.getInstance().registerMetricsPublisher(new CustomPublisher(secondCommand));

        // ensure that second custom publisher is used 
        cmd = HystrixMetricsPublisherFactory.createOrRetrievePublisherForCommand(key, null, null, null, null);
        assertNotSame(firstCommand, cmd);
        assertSame(secondCommand, cmd);
    }
}

[mattrjacobs]

Thanks for the report, @mabn, I'll take a look at this later today.

[mattrjacobs]

Thanks for the unit test and suggested fix, @mabn