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Gh 1300 backport sc loadbalancer support (#1414)

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* Gh 1294 add reactive sc loadbalancer support (#1295)

* Initial ReactiveLoadBalancer support

# Conflicts:
#	spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/LoadBalancerClientFilter.java

* Optimise imports. Minor refactoring.

* Use `LoadBalancerUriTools` for reconstructing uris.
Handle 404 exceptions. Add more tests and javadocs.

* Finish autoConfiguration and dependencies setup.

* Rename to `ReactorLoadBalancerClientFilter`. Fix test. Add docs.

* Fix after review.

* Fix dependencies, docs and formatting after backporting changes.
This commit is contained in:
Olga Maciaszek-Sharma
2019-11-15 20:53:03 +01:00
committed by GitHub
parent 25f28f1f55
commit 64879c32f7
9 changed files with 645 additions and 59 deletions
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docs/src/main/asciidoc/spring-cloud-gateway.adoc
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@@ -1263,6 +1263,45 @@ but the `ServiceInstance` indicates it is not secure, then the downstream reques
route in the Gateway configuration, the prefix will be stripped and the resulting scheme from the
route URL will override the `ServiceInstance` configuration.
WARNING: `LoadBalancerClientFilter` uses a blocking Ribbon `LoadBalancerClient` under the hood.
We suggest you use <<reactive-loadbalancer-client-filter,`ReactiveLoadBalancerClientFilter` instead>>.
You can switch to using it by adding `org.springframework.cloud:spring-cloud-loadbalancer` dependency to your project
and setting the value of the `spring.cloud.loadbalancer.ribbon.enabled` to `false`.
[[reactive-loadbalancer-client-filter]]
=== ReactiveLoadBalancerClientFilter
The `ReactiveLoadBalancerClientFilter` looks for a URI in the exchange attribute
`ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR`. If the url has a `lb` scheme (ie `lb://myservice`),
it will use the Spring Cloud `ReactorLoadBalancer` to resolve the name (`myservice` in the previous example)
to an actual host and port and replace the URI in the same attribute. The unmodified
original url is appended to the list in the `ServerWebExchangeUtils.GATEWAY_ORIGINAL_REQUEST_URL_ATTR` attribute.
The filter will also look in the `ServerWebExchangeUtils.GATEWAY_SCHEME_PREFIX_ATTR` attribute to see if it equals
`lb` and then the same rules apply.
.application.yml
[source,yaml]
----
spring:
cloud:
gateway:
routes:
- id: myRoute
uri: lb://service
predicates:
- Path=/service/**
----
NOTE: By default when a service instance cannot be found by the `ReactorLoadBalancer`, a `503` will be returned.
You can configure the Gateway to return a `404` by setting `spring.cloud.gateway.loadbalancer.use404=true`.
NOTE: The `isSecure` value of the `ServiceInstance` returned from the `ReactiveLoadBalancerClientFilter` will override
the scheme specified in the request made to the Gateway. For example, if the request comes into the Gateway over `HTTPS`
but the `ServiceInstance` indicates it is not secure, then the downstream request will be made over
`HTTP`. The opposite situation can also apply. However if `GATEWAY_SCHEME_PREFIX_ATTR` is specified for the
route in the Gateway configuration, the prefix will be stripped and the resulting scheme from the
route URL will override the `ServiceInstance` configuration.
=== Netty Routing Filter
The Netty Routing Filter runs if the url located in the `ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR` exchange attribute has a `http` or `https` scheme. It uses the Netty `HttpClient` to make the downstream proxy request. The response is put in the `ServerWebExchangeUtils.CLIENT_RESPONSE_ATTR` exchange attribute for use in a later filter. (There is an experimental `WebClientHttpRoutingFilter` that performs the same function, but does not require netty)