SpringCloud/spring-cloud-zookeeper
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Switch from Ribbon to SC LoadBalancer (#240)

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* WIP

* Remove repeated dependency.

* Gitignore fix.

* Implement Spring Cloud LoadBalancer-based DependencyFeignClientAutoConfiguration and DependencyLoadBalancerAutoConfiguration.

* Fix dependency-based configurations.
Add ZookeeperServiceInstanceListSupplier.
Add LoadBalancerZookeeperAutoConfiguration.

* Adjust tests to changes in code.

* Adjust tests to changes in code. Add missing license Strings. Refactor.

* Add BlockingDependencyLoadBalancerConfiguration. Remove condition from ZookeeperDependenciesAutoConfiguration.

* Switch EmptyResponse to chooseDefault(). Fix DependencyRestTemplateAutoConfiguration. Change return type for BlockingDependencyLoadBalancerConfiguration.

* Fix zookeeper-specific BlockingLoadBalancerClient implementation.

* Remove zookeeper-specific LoadBalancerClient and ReactorExchangeFilterFunction implementations following a team discussion. Remove Ribbon-specific entries from docs. Add javadocs.

Co-authored-by: Marcin Grzejszczak <marcin@grzejszczak.pl>
This commit is contained in:
Olga Maciaszek-Sharma
2020-02-22 14:40:17 +01:00
committed by GitHub
parent fe4a48c5ec
commit 59c0010be3
37 changed files with 468 additions and 639 deletions
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11
docs/src/main/asciidoc/README.adoc
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@@ -6,17 +6,16 @@ include::_attributes.adoc[]
== Zookeeper overview
ZooKeeper is a centralized service for maintaining configuration information, naming,
providing distributed synchronization, and providing group services. See the
https://zookeeper.apache.org[Zookeeper site] for more information. Spring Cloud Zookeeper
also builds on the https://curator.apache.org[Apache Curator] project, which started life
at Netflix.
ZooKeeper is a centralized service for maintaining configuration information, naming, providing distributed synchronization, and providing group services.
See the
https://zookeeper.apache.org[Zookeeper site] for more information.
Spring Cloud Zookeeper also builds on the https://curator.apache.org[Apache Curator] project, which started life at Netflix.
== Spring Cloud Zookeeper Features
Spring Cloud Zookeeper includes the following features:
* Spring Cloud `DiscoveryClient` implementation (supports Ribbon and Zuul)
* Spring Cloud `DiscoveryClient` implementation (supports Spring Cloud LoadBalancer)
* Zookeeper-based `PropertySource` loaded during the 'bootstrap' phase
== Running the Sample

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docs/src/main/asciidoc/_configprops.adoc
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@@ -5,8 +5,7 @@
|spring.cloud.zookeeper.block-until-connected-unit | | The unit of time related to blocking on connection to Zookeeper.
|spring.cloud.zookeeper.block-until-connected-wait | 10 | Wait time to block on connection to Zookeeper.
|spring.cloud.zookeeper.connect-string | localhost:2181 | Connection string to the Zookeeper cluster.
|spring.cloud.zookeeper.default-health-endpoint | | Default health endpoint that will be checked to verify that a dependency is alive.
|spring.cloud.zookeeper.dependencies | | Mapping of alias to ZookeeperDependency. From Ribbon perspective the alias is actually serviceID since Ribbon can't accept nested structures in serviceID.
|spring.cloud.zookeeper.dependencies | | Mapping of alias to ZookeeperDependency. From LoadBalancer perspective the alias is actually serviceID since SC LoadBalancer can't accept nested structures in serviceID.
|spring.cloud.zookeeper.dependency-configurations | |
|spring.cloud.zookeeper.dependency-names | |
|spring.cloud.zookeeper.discovery.enabled | true |

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docs/src/main/asciidoc/intro.adoc
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@@ -5,6 +5,5 @@ This project provides Zookeeper integrations for Spring Boot applications throug
autoconfiguration and binding to the Spring Environment and other Spring programming model
idioms. With a few annotations, you can quickly enable and configure the common patterns
inside your application and build large distributed systems with Zookeeper based
components. The provided patterns include Service Discovery and Configuration. Integration
with Spring Cloud Netflix provides Intelligent Routing (Zuul), Client Side Load Balancing
(Ribbon), and Circuit Breaker (Hystrix).
components. The provided patterns include Service Discovery and Configuration. The project
also provides client-side load-balancing via integration with Spring Cloud LoadBalancer.

4
docs/src/main/asciidoc/sagan-index.adoc
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@@ -6,8 +6,8 @@ Spring Cloud Zookeeper provides http://zookeeper.apache.org/[Apache Zookeeper] i
## Features
* Service Discovery: instances can be registered with Zookeeper and clients can discover the instances using Spring-managed beans
* Supports Ribbon, the client side load-balancer via Spring Cloud Netflix
* Supports Zuul, a dynamic router and filter via Spring Cloud Netflix
* Supports Spring Cloud LoadBalancer - client-side load-balancing solution
* Supports Spring Cloud OpenFeign
* Distributed Configuration: using Zookeeper as a data store
## Quick Start

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docs/src/main/asciidoc/spring-cloud-zookeeper.adoc
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@@ -164,14 +164,14 @@ public String serviceUrl() {
== Using Spring Cloud Zookeeper with Spring Cloud Netflix Components
Spring Cloud Netflix supplies useful tools that work regardless of which `DiscoveryClient`
implementation you use. Feign, Turbine, Ribbon, and Zuul all work with Spring Cloud
Zookeeper.
implementation you use.
Feign and Spring Cloud LoadBalancer also work with Spring Cloud Zookeeper.
=== Ribbon with Zookeeper
=== Spring Cloud LoadBalancer with Zookeeper
Spring Cloud Zookeeper provides an implementation of Ribbon's `ServerList`. When you use
the `spring-cloud-starter-zookeeper-discovery`, Ribbon is autoconfigured to use the
`ZookeeperServerList` by default.
Spring Cloud Zookeeper provides an implementation of Spring Cloud LoadBalancer `ServiceInstanceListSupplier`.
When you use the `spring-cloud-starter-zookeeper-discovery`, Spring Cloud LoadBalancer is autoconfigured to use the
`ZookeeperServiceInstanceListSupplier` by default.
[[spring-cloud-zookeeper-service-registry]]
== Spring Cloud Zookeeper and Service Registry
@@ -201,15 +201,13 @@ public void registerThings() {
=== Instance Status
Netflix Eureka supports having instances that are `OUT_OF_SERVICE` registered with the
server. These instances are not returned as active service instances. This is useful for
behaviors such as blue/green deployments. (Note that the Curator Service Discovery recipe
does not support this behavior.) Taking advantage of the flexible payload has let Spring
Cloud Zookeeper implement `OUT_OF_SERVICE` by updating some specific metadata and then
filtering on that metadata in the Ribbon `ZookeeperServerList`. The `ZookeeperServerList`
filters out all non-null instance statuses that do not equal `UP`. If the instance status
field is empty, it is considered to be `UP` for backwards compatibility. To change the
status of an instance, make a `POST` with `OUT_OF_SERVICE` to the `ServiceRegistry`
Netflix Eureka supports having instances that are `OUT_OF_SERVICE` registered with the server.
These instances are not returned as active service instances.
This is useful for behaviors such as blue/green deployments.
(Note that the Curator Service Discovery recipe does not support this behavior.) Taking advantage of the flexible payload has let Spring Cloud Zookeeper implement `OUT_OF_SERVICE` by updating some specific metadata and then filtering on that metadata in the Spring Cloud LoadBalancer `ZookeeperServiceInstanceListSupplier`.
The `ZookeeperServiceInstanceListSupplier` filters out all non-null instance statuses that do not equal `UP`.
If the instance status field is empty, it is considered to be `UP` for backwards compatibility.
To change the status of an instance, make a `POST` with `OUT_OF_SERVICE` to the `ServiceRegistry`
instance status actuator endpoint, as shown in the following example:
[source,sh,indent=0]
@@ -290,14 +288,14 @@ name is `spring.cloud.zookeeper.dependencies`.
[[spring-cloud-zookeeper-dependencies-setting-up-aliases]]
==== Aliases
Below the root property you have to represent each dependency as an alias. This is due to
the constraints of Ribbon, which requires that the application ID be placed in the URL.
Consequently, you cannot pass any complex path, suchas `/myApp/myRoute/name`). The alias
is the name you use instead of the `serviceId` for `DiscoveryClient`, `Feign`, or
Below the root property you have to represent each dependency as an alias.
This is due to the constraints of Spring Cloud LoadBalancer, which requires that the application ID be placed in the URL.
Consequently, you cannot pass any complex path, suchas `/myApp/myRoute/name`).
The alias is the name you use instead of the `serviceId` for `DiscoveryClient`, `Feign`, or
`RestTemplate`.
In the previous examples, the aliases are `newsletter` and `mailing`. The following
example shows Feign usage with a `newsletter` alias:
In the previous examples, the aliases are `newsletter` and `mailing`.
The following example shows Feign usage with a `newsletter` alias:
[source,java,indent=0]
----
@@ -310,19 +308,18 @@ public interface NewsletterService {
==== Path
The path is represented by the `path` YAML property and is the path under which the
dependency is registered under Zookeeper. As described in the
<<spring-cloud-zookeeper-dependencies-setting-up-aliases,previous section>>, Ribbon
operates on URLs. As a result, this path is not compliant with its requirement.
The path is represented by the `path` YAML property and is the path under which the dependency is registered under Zookeeper.
As described in the
<<spring-cloud-zookeeper-dependencies-setting-up-aliases,previous section>>, Spring Cloud LoadBalancer operates on URLs.
As a result, this path is not compliant with its requirement.
That is why Spring Cloud Zookeeper maps the alias to the proper path.
==== Load Balancer Type
The load balancer type is represented by `loadBalancerType` YAML property.
If you know what kind of load-balancing strategy has to be applied when calling this
particular dependency, you can provide it in the YAML file, and it is automatically
applied. You can choose one of the following load balancing strategies:
If you know what kind of load-balancing strategy has to be applied when calling this particular dependency, you can provide it in the YAML file, and it is automatically applied.
You can choose one of the following load balancing strategies:
* STICKY: Once chosen, the instance is always called.
* RANDOM: Picks an instance randomly.
@@ -412,29 +409,15 @@ example:
[[spring-cloud-zookeeper-dependencies-configuring]]
=== Configuring Spring Cloud Zookeeper Dependencies
You can set the following properties to enable or disable parts of Zookeeper Dependencies
functionalities:
You can set the following properties to enable or disable parts of Zookeeper Dependencies functionalities:
* `spring.cloud.zookeeper.dependencies`: If you do not set this property, you cannot use
Zookeeper Dependencies.
* `spring.cloud.zookeeper.dependency.ribbon.enabled` (enabled by default): Ribbon requires
either explicit global configuration or a particular one for a dependency. By turning on
this property, runtime load balancing strategy resolution is possible, and you can use the
`loadBalancerType` section of the Zookeeper Dependencies. The configuration that needs
this property has an implementation of `LoadBalancerClient` that delegates to the
`ILoadBalancer` presented in the next bullet.
* `spring.cloud.zookeeper.dependency.ribbon.loadbalancer` (enabled by default): Thanks to
this property, the custom `ILoadBalancer` knows that the part of the URI passed to Ribbon
might actually be the alias that has to be resolved to a proper path in Zookeeper. Without
this property, you cannot register applications under nested paths.
* `spring.cloud.zookeeper.dependency.headers.enabled` (enabled by default): This property
registers a `RibbonClient` that automatically appends appropriate headers and content
types with their versions, as presented in the Dependency configuration. Without this
setting, those two parameters do not work.
* `spring.cloud.zookeeper.dependency.resttemplate.enabled` (enabled by default): When
enabled, this property modifies the request headers of a `@LoadBalanced`-annotated
`RestTemplate` such that it passes headers and content type with the version set in
dependency configuration. Without this setting, those two parameters do not work.
* `spring.cloud.zookeeper.dependencies`: If you do not set this property, you cannot use Zookeeper Dependencies.
* `spring.cloud.zookeeper.dependency.loadbalancer.enabled` (enabled by default): Turns on Zookeeper-specific custom load-balancing strategies, including `ZookeeperServiceInstanceListSupplier` and dependency-based load-balanced `RestTemplate` setup.
* `spring.cloud.zookeeper.dependency.headers.enabled` (enabled by default): This property registers a `FeignBlockingLoadBalancerClient` that automatically appends appropriate headers and content types with their versions, as presented in the Dependency configuration.
Without this setting, those two parameters do not work.
* `spring.cloud.zookeeper.dependency.resttemplate.enabled` (enabled by default): When enabled, this property modifies the request headers of a `@LoadBalanced`-annotated
`RestTemplate` such that it passes headers and content type with the version set in dependency configuration.
Without this setting, those two parameters do not work.
[[spring-cloud-zookeeper-dependency-watcher]]
== Spring Cloud Zookeeper Dependency Watcher