请求缓存 Request-Cache
请求缓存可以让(CommandKey/CommandGroup)相同的情况下,直接共享结果，降低依赖调用次数，在高并发和CacheKey碰撞率高场景下可以提升性能.
使用demo
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| package com.fuyi.hystrix.command;
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.HystrixConcurrencyStrategy;
import com.netflix.hystrix.strategy.concurrency.HystrixConcurrencyStrategyDefault;
import com.netflix.hystrix.strategy.concurrency.HystrixRequestContext;
public class CacheCommand extends HystrixCommand<String> {
private static int id;
private static final HystrixCommandKey COMMAND_KEY = HystrixCommandKey.Factory.asKey("getUserById");
public CacheCommand(int id) {
super(Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("userServiceGroup"))
.andCommandKey(COMMAND_KEY));
this.id = id;
}
@Override
protected String run() throws Exception {
System.out.println("thread: " + Thread.currentThread().getName());
return "executed = " + id;
}
/**
* 重写该方法，实现区分不同请求的逻辑
*/
@Override
protected String getCacheKey() {
return String.valueOf(id);
}
// 清理缓存
public static void clearCache() {
// 从默认的Hystrix并发策略中，根据COMMAND_KEY获取到该命令的请求缓存对象HystrixRequestCache的实例
HystrixRequestCache instance = HystrixRequestCache.getInstance(COMMAND_KEY, HystrixConcurrencyStrategyDefault.getInstance());
// 调用请求缓存对象实例的clear方法，对Key为id的缓存值进行清理
instance.clear(String.valueOf(id));
}
public static void main(String[] args) {
HystrixRequestContext ctx = HystrixRequestContext.initializeContext();
try {
CacheCommand ca = new CacheCommand(2);
CacheCommand cb = new CacheCommand(2);
// isResponseFromCache判定是否是在缓存中获取结果
String result = ca.execute();
System.out.println(ca.isResponseFromCache()); //false
System.out.println("result : " + result);
// 清理缓存代码，使用场景：getUserById配置了缓存，在UpdateUserById中要清理缓存
// CacheCommand.clearCache();
result = cb.execute();
System.out.println(cb.isResponseFromCache()); //true
System.out.println("result : " + result);
} finally {
ctx.shutdown();
}
// 在不同context中的缓存是不共享的，还有这个request内部一个ThreadLocal，所以request只能限于当前线程。
ctx = HystrixRequestContext.initializeContext();
try {
CacheCommand cc = new CacheCommand(2);
String result = cc.execute();
System.out.println(cc.isResponseFromCache()); // false
System.out.println("result : " + result);
} finally {
ctx.shutdown();
}
}
}
|
运行结果
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| thread: hystrix-userServiceGroup-1
false
result : executed = 2
true
result : executed = 2
thread: hystrix-userServiceGroup-2
false
result : executed = 2
|