The cause of the fallback is now logged by default to FINE level. You can programmatically inspect
the cause by making your own `FallbackFactory`. In many cases, the cause will be a `FeignException`,
which includes the http status.
Here's an example of using `FallbackFactory`:
```java
// This instance will be invoked if there are errors of any kind.
FallbackFactory<GitHub> fallbackFactory = cause -> (owner, repo) -> {
if (cause instanceof FeignException && ((FeignException) cause).status() == 403) {
return Collections.emptyList();
} else {
return Arrays.asList("yogi");
}
};
GitHub github = HystrixFeign.builder()
...
.target(GitHub.class, "https://api.github.com", fallbackFactory);
```
This exposes means to customize group and command keys, for example to
use non-default conventions from configuration or custom annotation
processing.
Ex.
```java
SetterFactory commandKeyIsRequestLine = (target, method) -> {
String groupKey = target.name();
String commandKey = method.getAnnotation(RequestLine.class).value();
return HystrixCommand.Setter
.withGroupKey(HystrixCommandGroupKey.Factory.asKey(groupKey))
.andCommandKey(HystrixCommandKey.Factory.asKey(commandKey));
};
api = HystrixFeign.builder()
.setterFactory(commandKeyIsRequestLine)
...
```
This also makes the default's more unique to avoid clashing in Hystrix's
cache.
This copies missing logic from `FeignInvocationHandler` to
`HystrixInvocationHandler`, preventing NPEs when calling methods defined
on `java.lang.Object`.
For interfaces with package-private access, hystrix fallback calls would
fail. This sets these methods accessible, caching to reduce reflection.
Fixes#353
Uses covariant overrides so that those collecting Feign configuration
via `Feign.Builder` can cast into `HystrixFeign.builder` to target an
api.
Closes#313
Fallbacks are known values, which you return when there's an error invoking an http method.
For example, you can return a cached result as opposed to raising an error to the caller. To use
this feature, pass a safe implementation of your target interface as the last parameter to `HystrixFeign.Builder.target`.
Here's an example:
```java
// When dealing with fallbacks, it is less tedious to keep interfaces small.
interface GitHub {
@RequestLine("GET /repos/{owner}/{repo}/contributors")
List<String> contributors(@Param("owner") String owner, @Param("repo") String repo);
}
// This instance will be invoked if there are errors of any kind.
GitHub fallback = (owner, repo) -> {
if (owner.equals("Netflix") && repo.equals("feign")) {
return Arrays.asList("stuarthendren"); // inspired this approach!
} else {
return Collections.emptyList();
}
};
GitHub github = HystrixFeign.builder()
...
.target(GitHub.class, "https://api.github.com", fallback);
```
Credit to the idea goes to @stuarthendren!
adriancole
Adrian Cole
bjsousa@wisc.edu
Pablo Diaz
liuzhengyang
Javier Campanini
Jimmy Lu
Spencer Gibb
Christopher Lakey