spring 在@HystrixCommand 回退方法中获取失败异常
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Get failure exception in @HystrixCommand fallback method
提问by Andrew Serff
Is there a way to get the reason a HystrixCommandfailed when using the @HystrixCommandannotation within a Spring Boot application? It looks like if you implement your own HystrixCommand, you have access to the getFailedExecutionExceptionbut how can you get access to this when using the annotation? I would like to be able to do different things in the fallback method based on the type of exception that occurred. Is this possible?
在 Spring Boot 应用程序中HystrixCommand使用@HystrixCommand注释时，有没有办法找出失败的原因？看起来如果您实现自己的HystrixCommand，您可以访问 ，getFailedExecutionException但是在使用注释时如何访问它？我希望能够根据发生的异常类型在回退方法中做不同的事情。这可能吗？
I saw a noteabout HystrixRequestContext.initializeContext()but the HystrixRequestContextdoesn't give you access to anything, is there a different way to use that context to get access to the exceptions?
我看到了一条关于但没有让您访问任何内容的注释，是否有其他方法可以使用该上下文来访问异常？HystrixRequestContext.initializeContext()HystrixRequestContext
采纳答案by Andrew Serff
I haven't found a way to get the exception with Annotations either, but creating my own Command worked for me like so:
我也没有找到通过注释获取异常的方法，但是创建我自己的命令对我来说是这样的：
public static class DemoCommand extends HystrixCommand<String> {
protected DemoCommand() {
super(HystrixCommandGroupKey.Factory.asKey("Demo"));
}
@Override
protected String run() throws Exception {
throw new RuntimeException("failed!");
}
@Override
protected String getFallback() {
System.out.println("Events (so far) in Fallback: " + getExecutionEvents());
return getFailedExecutionException().getMessage();
}
}
Hopefully this helps someone else as well.
希望这对其他人也有帮助。
回答by MattJ
Simply add a Throwable parameter to the fallback method and it will receive the exception which the original command produced.
只需向回退方法添加一个 Throwable 参数，它就会收到原始命令产生的异常。
From https://github.com/Netflix/Hystrix/tree/master/hystrix-contrib/hystrix-javanica
来自https://github.com/Netflix/Hystrix/tree/master/hystrix-contrib/hystrix-javanica
@HystrixCommand(fallbackMethod = "fallback1")
User getUserById(String id) {
throw new RuntimeException("getUserById command failed");
}
@HystrixCommand(fallbackMethod = "fallback2")
User fallback1(String id, Throwable e) {
assert "getUserById command failed".equals(e.getMessage());
throw new RuntimeException("fallback1 failed");
}
回答by ákos Ratku
I couldn't find a way to obtain the exception with the annotations, but i found HystrixPlugins, with that you can register a HystrixCommandExecutionHookand you can get the exact exception in that like this :
我找不到通过注释获取异常的方法，但我发现HystrixPlugins，您可以注册 aHystrixCommandExecutionHook并且可以像这样获得确切的异常：
HystrixPlugins.getInstance().registerCommandExecutionHook(new HystrixCommandExecutionHook() {
@Override
public <T> void onFallbackStart(final HystrixInvokable<T> commandInstance) {
}
});
The command instance is a GenericCommand.
命令实例是一个GenericCommand.
回答by Seetharamani Tmr
Most of the time just using getFailedExecutionException().getMessage() gave me null values.
大多数时候只使用 getFailedExecutionException().getMessage() 给我空值。
Exception errorFromThrowable = getExceptionFromThrowable(getExecutionException());
String errMessage = (errorFromThrowable != null) ? errorFromThrowable.getMessage()
this gives me better results all the time.
这一直给我更好的结果。
回答by vicco
As said in the documentation Hystrix-documentationgetFallback()method will be thrown when:
如文档中所述，Hystrix-documentationgetFallback()方法将在以下情况下抛出：
- Whenever a command execution fails: when an exception is thrown by construct() or run()
- When the command is short-circuited because the circuit is open
- When the command's thread pool and queue or semaphore are at capacity
- When the command has exceeded its timeout length.
- 每当命令执行失败时：construct() 或 run() 抛出异常时
- 当指令因电路开路而短路时
- 当命令的线程池和队列或信号量已满时
- 当命令超过其超时长度时。
So you can easily get what raised your fallback method called by assigning the the execution exception to a Throwable object.
因此，您可以通过将执行异常分配给Throwable 对象来轻松获取引发回退方法调用的内容。
Assuming your HystrixCommand returns a String
假设你的 HystrixCommand 返回一个字符串
public class ExampleTask extends HystrixCommand<String> {
//Your class body
}
do as follows:
做如下：
@Override
protected ErrorCodes getFallback() {
Throwable t = getExecutionException();
if (circuitBreaker.isOpen()) {
// Log or something
} else if (t instanceof RejectedExecutionException) {
// Log and get the threadpool name, could be useful
} else {
// Maybe something else happened
}
return "A default String"; // Avoid using any HTTP request or ypu will need to wrap it also in HystrixCommand
}
More info here
更多信息在这里
