Reactive Feign client Spring auto-configuration is patterned after regular Feign client auto-configuration. If you already familiar with blocking/sync Feign client you will find that both auto-configurations has may things in common. In any case if this documentation looks very brief you can check first Spring documentation regarding auto-conf of regular Feign client.

To enable auto-configuration of reactive feign clients you need to add @EnableReactiveFeignClients annotation to your Spring Boot configuration class. Thus all interfaces annotated with @ReactiveFeignClient annotation will be instantiated and configured as Spring beans

You should specify name attribute in this annotation. Feign client bean will be registered with the name of name + "ReactiveFeignClient" if you had not specified qualifier attribute.

In cloud mode name attribute will be used as eureka application name. If you need several feign clients for one eureka application you should specify eureka application manually in application.yml for feign client with name that differs from eureka application name. See example in sample project

In cloudless mode you need to specify url attribute.

To configure you feign client as cloud ready (Hystrix + Ribbon) you need to add feign-reactor-cloud module to your classpath.

This may be useful in case of tests:

• set reactive.feign.cloud.enabled to false to disable cloud configuration for all clients
• set reactive.feign.ribbon.enabled to false to disable loadbalancer configuration for all clients
• set reactive.feign.hystrix.enabled to false to disable hystrix configuration for all clients
• set reactive.feign.logger.enabled to true to enable default logger
• set reactive.feign.metrics.enabled to true to enable default Micrometer logger. Also make sure that you added actual Micrometer implementation module into your project dependency

There are to ways to configure specific settings for feign clients: via application.properties file and configuration class. In both approaches it's possible specify default settings and override them for specific clients.

Each property should be prefixed with reactive.feign.client.config.<client-name>

All reactive feign client specific properties Spring read by ReactiveFeignClientProperties class.

Here is the list of available properties:

• options : reactive http client specific options. Check implementation of ReactiveOptions.Builder for each client.
• retry : retry configuration (check ReactiveFeignClientProperties.RetryConfiguration for details)
• statusHandler : class that implements ReactiveStatusHandler. Is a replacement of regular feign ErrorDecoder.
• errorMapper : class that implements ReactiveErrorMapper.
• requestInterceptors : classes of ReactiveHttpRequestInterceptor. May be used to setup specific headers to request
• logger : class of ReactiveLoggerListener
• metricsLogger : class of MicrometerReactiveLogger
• decode404 : the same as in regular feign

@EnableReactiveFeignClients annotation has defaultConfiguration attribute to specify default configuration class that will be used for all clients.

@ReactiveFeignClient annotation has configuration attribute for client specific configuration.

Here is the list of bean classes that will be used by reactive feign client if they declared in configuration class: ReactiveOptions.Builder, ReactiveRetryPolicies, List<Class<ReactiveHttpRequestInterceptor>>, ReactiveStatusHandler, feign.codec.ErrorDecoder, ReactiveErrorMapper, ReactiveLoggerListener, MicrometerReactiveLogger

ReactiveLoadBalancer.Factory or ReactiveRetryPolicies beans defined in configuration will used to configure loadbalancer for corresponding client

CloudReactiveFeign.SetterFactory bean defined in configuration will be used to configure hystrix for client

Use ReactiveRetryPolicy or ReactiveRetryPolicy.Builder as part of Reactive Feign configuration if you need to specify backoff period between retries. You can't anymore use Spring's RetryPolicy as part of Ribbon configuration if you need to configure backoff.

reactive.feign.client.config.<client-name>.retry.builder=reactivefeign.retry.BasicReactiveRetryPolicy.Builder
reactive.feign.client.config.<client-name>.retry.args.maxRetries=2
reactive.feign.client.config.<client-name>.retry.args.backoffInMs=10

Use ReactiveOptions.Builder as part of Reactive Feign configuration if you need to specify connect and read timeout. Each reactive http client has it's own set of properties that describes request timeouts. Ribbon request timeouts properties are ignored.

In Spring Cloud 2.2.0 more generic abstraction vere introduced for cloud environment. CircuitBreaker is the replacement of Hystrix (now is one of implementations) LoadBalancer is use instead of Ribbon

So below are the differences with old cloud module.

To configure you feign client as cloud ready (CircuitBreaker + LoadBalancer) you need to add feign-reactor-cloud module to your classpath and exclude feign-reactor-cloud.

This may be useful in case of tests:

• set reactive.feign.loadbalancer.enabled to false to disable loadbalancer configuration for all clients
• set reactive.feign.circuit.breaker.enabled to false to disable hystrix configuration for all clients

As for now LoadBalance doesnt have it's retry configuration so here is the list of new properties:

• retryOnSame : configure number of retries for the same server (check ReactiveFeignClientProperties.RetryConfiguration for details)
• retryOnNext : configure number of retries for the next server (check ReactiveFeignClientProperties.RetryConfiguration for details)

To configure LoadBalancer define your own ReactiveLoadBalancer.Factory bean in feign client configuration.

To configure CircuitBreaker you may use ReactiveFeignCircuitBreakerFactory bean or ReactiveCircuitBreakerFactory with ReactiveFeignCircuitBreakerCustomizer bean defined in feign client configuration.

Note: It's highly recommended to switch to cloud2 module as we'll stop support of cloud module in some time. There is an option to switch to cloud2 with well known Ribbon and Hystrix implementations.