/**
* Copyright 2012 Netflix, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.netflix.hystrix.examples.basic;
import static org.junit.Assert.*;
import org.junit.Test;
import com.netflix.hystrix.HystrixCommand;
import com.netflix.hystrix.HystrixCommandGroupKey;
import com.netflix.hystrix.HystrixCommandKey;
import com.netflix.hystrix.HystrixEventType;
import com.netflix.hystrix.HystrixRequestLog;
import com.netflix.hystrix.HystrixThreadPoolKey;
import com.netflix.hystrix.strategy.concurrency.HystrixRequestContext;
/**
* Sample {@link HystrixCommand} that implements fallback logic that requires
* network traffic and thus executes another {@link HystrixCommand} from the {@link #getFallback()} method.
* <p>
* Note also that the fallback command uses a separate thread-pool as well even though
* it's in the same command group.
* <p>
* It needs to be on a separate thread-pool otherwise the first command could saturate it
* and the fallback command never have a chance to execute.
*/
public class CommandWithFallbackViaNetwork extends HystrixCommand<String> {
private final int id;
protected CommandWithFallbackViaNetwork(int id) {
super(Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("RemoteServiceX"))
.andCommandKey(HystrixCommandKey.Factory.asKey("GetValueCommand")));
this.id = id;
}
@Override
protected String run() {
// RemoteServiceXClient.getValue(id);
throw new RuntimeException("force failure for example");
}
@Override
protected String getFallback() {
return new FallbackViaNetwork(id).execute();
}
private static class FallbackViaNetwork extends HystrixCommand<String> {
private final int id;
public FallbackViaNetwork(int id) {
super(Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("RemoteServiceX"))
.andCommandKey(HystrixCommandKey.Factory.asKey("GetValueFallbackCommand"))
// use a different threadpool for the fallback command
// so saturating the RemoteServiceX pool won't prevent
// fallbacks from executing
.andThreadPoolKey(HystrixThreadPoolKey.Factory.asKey("RemoteServiceXFallback")));
this.id = id;
}
@Override
protected String run() {
// MemCacheClient.getValue(id);
throw new RuntimeException("the fallback also failed");
}
@Override
protected String getFallback() {
// the fallback also failed
// so this fallback-of-a-fallback will
// fail silently and return null
return null;
}
}
public static class UnitTest {
@Test
public void test() {
HystrixRequestContext context = HystrixRequestContext.initializeContext();
try {
assertEquals(null, new CommandWithFallbackViaNetwork(1).execute());
HystrixCommand<?> command1 = HystrixRequestLog.getCurrentRequest().getExecutedCommands().toArray(new HystrixCommand<?>[2])[0];
assertEquals("GetValueCommand", command1.getCommandKey().name());
assertTrue(command1.getExecutionEvents().contains(HystrixEventType.FAILURE));
HystrixCommand<?> command2 = HystrixRequestLog.getCurrentRequest().getExecutedCommands().toArray(new HystrixCommand<?>[2])[1];
assertEquals("GetValueFallbackCommand", command2.getCommandKey().name());
assertTrue(command2.getExecutionEvents().contains(HystrixEventType.FAILURE));
} finally {
context.shutdown();
}
}
}
}