Request Cache
您可以通過在HystrixCommand或HystrixObservableCommand對象上實作getCacheKey()方法來啟用請求緩存,如下所示:
public class CommandUsingRequestCache extends HystrixCommand<Boolean> {
private final int value;
protected CommandUsingRequestCache(int value) {
super(HystrixCommandGroupKey.Factory.asKey("ExampleGroup"));
this.value = value;
}
@Override
protected Boolean run() {
return value == 0 || value % 2 == 0;
}
@Override
protected String getCacheKey() {
return String.valueOf(value);
}
}
由于這取決于請求上下文,我們必須初始化HystrixRequestContext。
在簡單的單元測試中,您可以按如下方式執行此操作:
@Test
public void testWithoutCacheHits() {
HystrixRequestContext context = HystrixRequestContext.initializeContext();
try {
assertTrue(new CommandUsingRequestCache(2).execute());
assertFalse(new CommandUsingRequestCache(1).execute());
assertTrue(new CommandUsingRequestCache(0).execute());
assertTrue(new CommandUsingRequestCache(58672).execute());
} finally {
context.shutdown();
}
}
通常,此上下文将通過包裝使用者請求或其他生命周期鈎子的ServletFilter進行初始化和關閉。
以下示例顯示指令如何在請求上下文中從緩存中檢索其值(以及如何查詢對象以了解其值是否來自緩存):
@Test
public void testWithCacheHits() {
HystrixRequestContext context = HystrixRequestContext.initializeContext();
try {
CommandUsingRequestCache command2a = new CommandUsingRequestCache(2);
CommandUsingRequestCache command2b = new CommandUsingRequestCache(2);
assertTrue(command2a.execute());
// this is the first time we've executed this command with
// the value of "2" so it should not be from cache
assertFalse(command2a.isResponseFromCache());
assertTrue(command2b.execute());
// this is the second time we've executed this command with
// the same value so it should return from cache
assertTrue(command2b.isResponseFromCache());
} finally {
context.shutdown();
}
// start a new request context
context = HystrixRequestContext.initializeContext();
try {
CommandUsingRequestCache command3b = new CommandUsingRequestCache(2);
assertTrue(command3b.execute());
// this is a new request context so this
// should not come from cache
assertFalse(command3b.isResponseFromCache());
} finally {
context.shutdown();
}
}