/**
* 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.HystrixRequestCache;
import com.netflix.hystrix.strategy.concurrency.HystrixConcurrencyStrategyDefault;
import com.netflix.hystrix.strategy.concurrency.HystrixRequestContext;
/**
* Example {@link HystrixCommand} implementation for handling the get-set-get use case within
* a single request context so that the "set" can invalidate the cached "get".
*/
public class CommandUsingRequestCacheInvalidation {
/* represents a remote data store */
private static volatile String prefixStoredOnRemoteDataStore = "ValueBeforeSet_";
public static class GetterCommand extends HystrixCommand<String> {
private static final HystrixCommandKey GETTER_KEY = HystrixCommandKey.Factory.asKey("GetterCommand");
private final int id;
public GetterCommand(int id) {
super(Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("GetSetGet"))
.andCommandKey(GETTER_KEY));
this.id = id;
}
@Override
protected String run() {
return prefixStoredOnRemoteDataStore + id;
}
@Override
protected String getCacheKey() {
return String.valueOf(id);
}
/**
* Allow the cache to be flushed for this object.
*
* @param id
* argument that would normally be passed to the command
*/
public static void flushCache(int id) {
HystrixRequestCache.getInstance(GETTER_KEY,
HystrixConcurrencyStrategyDefault.getInstance()).clear(String.valueOf(id));
}
}
public static class SetterCommand extends HystrixCommand<Void> {
private final int id;
private final String prefix;
public SetterCommand(int id, String prefix) {
super(HystrixCommandGroupKey.Factory.asKey("GetSetGet"));
this.id = id;
this.prefix = prefix;
}
@Override
protected Void run() {
// persist the value against the datastore
prefixStoredOnRemoteDataStore = prefix;
// flush the cache
GetterCommand.flushCache(id);
// no return value
return null;
}
}
public static class UnitTest {
@Test
public void getGetSetGet() {
HystrixRequestContext context = HystrixRequestContext.initializeContext();
try {
assertEquals("ValueBeforeSet_1", new GetterCommand(1).execute());
GetterCommand commandAgainstCache = new GetterCommand(1);
assertEquals("ValueBeforeSet_1", commandAgainstCache.execute());
// confirm it executed against cache the second time
assertTrue(commandAgainstCache.isResponseFromCache());
// set the new value
new SetterCommand(1, "ValueAfterSet_").execute();
// fetch it again
GetterCommand commandAfterSet = new GetterCommand(1);
// the getter should return with the new prefix, not the value from cache
assertFalse(commandAfterSet.isResponseFromCache());
assertEquals("ValueAfterSet_1", commandAfterSet.execute());
} finally {
context.shutdown();
}
}
}
}