SpringCloud/spring-cloud-openfeign
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Added support for Spring Cloud CircuitBreaker

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fixes gh-279
This commit is contained in:
Marcin Grzejszczak
2020-12-15 15:52:14 +01:00
parent 9336c1d7c5
commit 63a524843d
23 changed files with 849 additions and 94 deletions
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2
docs/src/main/asciidoc/_attributes.adoc
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@@ -14,3 +14,5 @@
:sc-ext: java
:project-full-name: Spring Cloud OpenFeign
:all: {asterisk}{asterisk}
:core_path: {project-root}/spring-cloud-openfeign-core

2
docs/src/main/asciidoc/_configprops.adoc
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@@ -1,6 +1,7 @@
|===
|Name | Default | Description
|feign.circuitbreaker.enabled | `false` | If true, an OpenFeign client will be wrapped with a Spring Cloud CircuitBreaker circuit breaker.
|feign.client.config | |
|feign.client.decode-slash | `true` | Feign clients do not encode slash `/` characters by default. To change this behavior, set the `decodeSlash` to `false`.
|feign.client.default-config | `default` |
@@ -19,7 +20,6 @@
|feign.httpclient.max-connections-per-route | `50` |
|feign.httpclient.time-to-live | `900` |
|feign.httpclient.time-to-live-unit | |
|feign.hystrix.enabled | `false` | If true, an OpenFeign client will be wrapped with a Hystrix circuit breaker.
|feign.okhttp.enabled | `false` | Enables the use of the OK HTTP Client by Feign.
|===

76
docs/src/main/asciidoc/spring-cloud-openfeign.adoc
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@@ -114,7 +114,7 @@ Spring Cloud OpenFeign provides the following beans by default for feign (`BeanT
* `Encoder` feignEncoder: `SpringEncoder`
* `Logger` feignLogger: `Slf4jLogger`
* `Contract` feignContract: `SpringMvcContract`
* `Feign.Builder` feignBuilder: `HystrixFeign.Builder`
* `Feign.Builder` feignBuilder: `FeignCircuitBreaker.Builder`
* `Client` feignClient: if Spring Cloud LoadBalancer is in the classpath, `FeignBlockingLoadBalancerClient` is used.
If none of them is in the classpath, the default feign client is used.
@@ -206,26 +206,6 @@ If we create both `@Configuration` bean and configuration properties, configurat
It will override `@Configuration` values. But if you want to change the priority to `@Configuration`,
you can change `feign.client.default-to-properties` to `false`.
NOTE: If you need to use `ThreadLocal` bound variables in your `RequestInterceptor`s you will need to either set the
thread isolation strategy for Hystrix to `SEMAPHORE` or disable Hystrix in Feign.
application.yml
[source,yaml]
----
# To disable Hystrix in Feign
feign:
hystrix:
enabled: false
# To set thread isolation to SEMAPHORE
hystrix:
command:
default:
execution:
isolation:
strategy: SEMAPHORE
----
If we want to create multiple feign clients with the same name or url
so that they would point to the same server but each with a different custom configuration then
we have to use `contextId` attribute of the `@FeignClient` in order to avoid name
@@ -330,12 +310,12 @@ the default Feign native annotations.
You can also use the `Builder`to configure FeignClient not to inherit beans from the parent context.
You can do this by overriding calling `inheritParentContext(false)` on the `Builder`.
[[spring-cloud-feign-hystrix]]
=== Feign Hystrix Support
[[spring-cloud-feign-circuitbreaker]]
=== Feign Spring Cloud CircuitBreaker Support
If Hystrix is on the classpath and `feign.hystrix.enabled=true`, Feign will wrap all methods with a circuit breaker. Returning a `com.netflix.hystrix.HystrixCommand` is also available. This lets you use reactive patterns (with a call to `.toObservable()` or `.observe()` or asynchronous use (with a call to `.queue()`).
If Spring Cloud CircuitBreaker is on the classpath and `feign.circuitbreaker.enabled=true`, Feign will wrap all methods with a circuit breaker.
To disable Hystrix support on a per-client basis create a vanilla `Feign.Builder` with the "prototype" scope, e.g.:
To disable Spring Cloud CircuitBreaker support on a per-client basis create a vanilla `Feign.Builder` with the "prototype" scope, e.g.:
[source,java,indent=0]
----
@@ -349,60 +329,28 @@ public class FooConfiguration {
}
----
WARNING: Prior to the Spring Cloud Dalston release, if Hystrix was on the classpath Feign would have wrapped
all methods in a circuit breaker by default. This default behavior was changed in Spring Cloud Dalston in
favor for an opt-in approach.
The circuit breaker name follows this pattern `<feignClientName>_<calledMethod>`. When calling a `@FeignClient` with name `foo` and the called interface method is `bar` then the circuit breaker name will be `foo_bar`.
[[spring-cloud-feign-hystrix-fallback]]
=== Feign Hystrix Fallbacks
[[spring-cloud-feign-circuitbreaker-fallback]]
=== Feign Spring Cloud CircuitBreaker Fallbacks
Hystrix supports the notion of a fallback: a default code path that is executed when they circuit is open or there is an error. To enable fallbacks for a given `@FeignClient` set the `fallback` attribute to the class name that implements the fallback. You also need to declare your implementation as a Spring bean.
Spring Cloud CircuitBreaker supports the notion of a fallback: a default code path that is executed when they circuit is open or there is an error. To enable fallbacks for a given `@FeignClient` set the `fallback` attribute to the class name that implements the fallback. You also need to declare your implementation as a Spring bean.
[source,java,indent=0]
----
@FeignClient(name = "hello", fallback = HystrixClientFallback.class)
protected interface HystrixClient {
@RequestMapping(method = RequestMethod.GET, value = "/hello")
Hello iFailSometimes();
}
static class HystrixClientFallback implements HystrixClient {
@Override
public Hello iFailSometimes() {
return new Hello("fallback");
}
}
include::{core_path}/src/test/java/org/springframework/cloud/openfeign/circuitbreaker/CirciutBreakerTests.java[tags=client_with_fallback, indent=0]
----
If one needs access to the cause that made the fallback trigger, one can use the `fallbackFactory` attribute inside `@FeignClient`.
[source,java,indent=0]
----
@FeignClient(name = "hello", fallbackFactory = HystrixClientFallbackFactory.class)
protected interface HystrixClient {
@RequestMapping(method = RequestMethod.GET, value = "/hello")
Hello iFailSometimes();
}
@Component
static class HystrixClientFallbackFactory implements FallbackFactory<HystrixClient> {
@Override
public HystrixClient create(Throwable cause) {
return new HystrixClient() {
@Override
public Hello iFailSometimes() {
return new Hello("fallback; reason was: " + cause.getMessage());
}
};
}
}
include::{core_path}/src/test/java/org/springframework/cloud/openfeign/circuitbreaker/CirciutBreakerTests.java[tags=client_with_fallback_factory, indent=0]
----
WARNING: There is a limitation with the implementation of fallbacks in Feign and how Hystrix fallbacks work. Fallbacks are currently not supported for methods that return `com.netflix.hystrix.HystrixCommand` and `rx.Observable`.
=== Feign and `@Primary`
When using Feign with Hystrix fallbacks, there are multiple beans in the `ApplicationContext` of the same type. This will cause `@Autowired` to not work because there isn't exactly one bean, or one marked as primary. To work around this, Spring Cloud OpenFeign marks all Feign instances as `@Primary`, so Spring Framework will know which bean to inject. In some cases, this may not be desirable. To turn off this behavior set the `primary` attribute of `@FeignClient` to false.
When using Feign with Spring Cloud CircuitBreaker fallbacks, there are multiple beans in the `ApplicationContext` of the same type. This will cause `@Autowired` to not work because there isn't exactly one bean, or one marked as primary. To work around this, Spring Cloud OpenFeign marks all Feign instances as `@Primary`, so Spring Framework will know which bean to inject. In some cases, this may not be desirable. To turn off this behavior set the `primary` attribute of `@FeignClient` to false.
[source,java,indent=0]
----