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@@ -157,15 +157,16 @@ $(addBlockSwitches);
<li><a href="#spring-cloud-loadbalancer">3. Spring Cloud LoadBalancer</a>
<ul class="sectlevel2">
<li><a href="#spring-cloud-loadbalancer-integrations">3.1. Spring Cloud LoadBalancer integrations</a></li>
<li><a href="#spring-cloud-loadbalancer-caching">3.2. Spring Cloud LoadBalancer Caching</a>
<li><a href="#loadbalancer-caching">3.2. Spring Cloud LoadBalancer Caching</a>
<ul class="sectlevel3">
<li><a href="#caffeine-backed-loadbalancer-cache-implementation">3.2.1. Caffeine-backed LoadBalancer Cache Implementation</a></li>
<li><a href="#default-loadbalancer-cache-implementation">3.2.2. Default LoadBalancer Cache Implementation</a></li>
<li><a href="#loadbalancer-cache-configuration">3.2.3. LoadBalancer Cache Configuration</a></li>
</ul>
</li>
<li><a href="#spring-cloud-loadbalancer-starter">3.3. Spring Cloud LoadBalancer Starter</a></li>
<li><a href="#passing-your-own-spring-cloud-loadbalancer-configuration">3.4. Passing Your Own Spring Cloud LoadBalancer Configuration</a></li>
<li><a href="#zone-based-load-balancing">3.3. Zone-Based Load-Balancing</a></li>
<li><a href="#spring-cloud-loadbalancer-starter">3.4. Spring Cloud LoadBalancer Starter</a></li>
<li><a href="#custom-loadbalancer-configuration">3.5. Passing Your Own Spring Cloud LoadBalancer Configuration</a></li>
</ul>
</li>
<li><a href="#spring-cloud-circuit-breaker">4. Spring Cloud Circuit Breaker</a>
@@ -1413,9 +1414,8 @@ that retrieves available instances from Service Discovery using a <a href="#disc
<div class="sect2">
<h3 id="spring-cloud-loadbalancer-integrations"><a class="anchor" href="#spring-cloud-loadbalancer-integrations"></a><a class="link" href="#spring-cloud-loadbalancer-integrations">3.1. Spring Cloud LoadBalancer integrations</a></h3>
<div class="paragraph">
<p>In order to make it easy to use Spring Cloud LoadBalancer, we provide <code>ReactorLoadBalancerExchangeFilterFunction</code> that can be used
with <code>WebClient</code> and <code>BlockingLoadBalancerClient</code> that works with <code>RestTemplate</code>. You can see more information and examples of usage
in the following sections:</p>
<p>In order to make it easy to use Spring Cloud LoadBalancer, we provide <code>ReactorLoadBalancerExchangeFilterFunction</code> that can be used with <code>WebClient</code> and <code>BlockingLoadBalancerClient</code> that works with <code>RestTemplate</code>.
You can see more information and examples of usage in the following sections:</p>
</div>
<div class="ulist">
<ul>
@@ -1432,7 +1432,7 @@ in the following sections:</p>
</div>
</div>
<div class="sect2">
<h3 id="spring-cloud-loadbalancer-caching"><a class="anchor" href="#spring-cloud-loadbalancer-caching"></a><a class="link" href="#spring-cloud-loadbalancer-caching">3.2. Spring Cloud LoadBalancer Caching</a></h3>
<h3 id="loadbalancer-caching"><a class="anchor" href="#loadbalancer-caching"></a><a class="link" href="#loadbalancer-caching">3.2. Spring Cloud LoadBalancer Caching</a></h3>
<div class="paragraph">
<p>Apart from the basic <code>ServiceInstanceListSupplier</code> implementation that retrieves instances via <code>DiscoveryClient</code> each time it has to choose an instance, we provide two caching implementations.</p>
</div>
@@ -1490,8 +1490,7 @@ to <code>false</code>.</p>
<i class="fa icon-warning" title="Warning"></i>
</td>
<td class="content">
Although the basic, non-cached, implementation is useful for prototyping and testing, it&#8217;s much less efficient
than the cached versions, so we recommend always using the cached version in production.
Although the basic, non-cached, implementation is useful for prototyping and testing, it&#8217;s much less efficient than the cached versions, so we recommend always using the cached version in production.
</td>
</tr>
</table>
@@ -1499,11 +1498,79 @@ than the cached versions, so we recommend always using the cached version in pro
</div>
</div>
<div class="sect2">
<h3 id="spring-cloud-loadbalancer-starter"><a class="anchor" href="#spring-cloud-loadbalancer-starter"></a><a class="link" href="#spring-cloud-loadbalancer-starter">3.3. Spring Cloud LoadBalancer Starter</a></h3>
<h3 id="zone-based-load-balancing"><a class="anchor" href="#zone-based-load-balancing"></a><a class="link" href="#zone-based-load-balancing">3.3. Zone-Based Load-Balancing</a></h3>
<div class="paragraph">
<p>To enable zone-based load-balancing, we provide the <code>ZonePreferenceServiceInstanceListSupplier</code>.
We use <code>DiscoveryClient</code>-specific <code>zone</code> configuration (for example, <code>eureka.instance.metadata-map.zone</code>) to pick the zone that the client tries to filter available service instances for.</p>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<i class="fa icon-note" title="Note"></i>
</td>
<td class="content">
You can also override <code>DiscoveryClient</code>-specific zone setup by setting the value of <code>spring.cloud.loadbalancer.zone</code> property.
</td>
</tr>
</table>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<i class="fa icon-note" title="Note"></i>
</td>
<td class="content">
To determine the zone of a retrieved <code>ServiceInstance</code>, we check the value under the <code>"zone"</code> key in its metadata map.
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p>The <code>ZonePreferenceServiceInstanceListSupplier</code> filters retrieved instances and only returns the ones within the same zone.
If the zone is <code>null</code> or there are no instances within the same zone, it returns all the retrieved instances.</p>
</div>
<div class="paragraph">
<p>In order to use the zone-based load-balancing approach, you will have to instantiate a <code>ZonePreferenceServiceInstanceListSupplier</code> bean in a <a href="#custom-loadbalancer-configuration">custom configuration</a>.</p>
</div>
<div class="paragraph">
<p>We use delegates to work with <code>ServiceInstanceListSupplier</code> beans.
We suggest passing a <code>DiscoveryClientServiceInstanceListSupplier</code> delegate in the constructor of <code>ZonePreferenceServiceInstanceListSupplier</code> and, in turn, wrapping the latter with a <code>CachingServiceInstanceListSupplier</code> to leverage <a href="#loadbalancer-caching">LoadBalancer caching mechanism</a>.</p>
</div>
<div class="paragraph">
<p>You could use this sample configuration to set it up:</p>
</div>
<div id="zoned-based-custom-loadbalancer-configuration" class="listingblock">
<div class="content">
<pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java">public class CustomLoadBalancerConfiguration {
@Bean
public ServiceInstanceListSupplier discoveryClientServiceInstanceListSupplier(
ReactiveDiscoveryClient discoveryClient, Environment environment,
ApplicationContext context) {
DiscoveryClientServiceInstanceListSupplier firstDelegate = new DiscoveryClientServiceInstanceListSupplier(
discoveryClient, environment);
ZonePreferenceServiceInstanceListSupplier delegate = new ZonePreferenceServiceInstanceListSupplier(firstDelegate,
environment);
ObjectProvider&lt;LoadBalancerCacheManager&gt; cacheManagerProvider = context
.getBeanProvider(LoadBalancerCacheManager.class);
if (cacheManagerProvider.getIfAvailable() != null) {
return new CachingServiceInstanceListSupplier(delegate,
cacheManagerProvider.getIfAvailable());
}
return delegate;
}
}</code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="spring-cloud-loadbalancer-starter"><a class="anchor" href="#spring-cloud-loadbalancer-starter"></a><a class="link" href="#spring-cloud-loadbalancer-starter">3.4. Spring Cloud LoadBalancer Starter</a></h3>
<div class="paragraph">
<p>We also provide a starter that allows you to easily add Spring Cloud LoadBalancer in a Spring Boot app.
In order to use it, just add <code>org.springframework.cloud:spring-cloud-starter-loadbalancer</code> to your Spring
Cloud dependencies in your build file.</p>
In order to use it, just add <code>org.springframework.cloud:spring-cloud-starter-loadbalancer</code> to your Spring Cloud dependencies in your build file.</p>
</div>
<div class="admonitionblock note">
<table>
@@ -1526,17 +1593,15 @@ and <a href="https://github.com/stoyanr">Evictor</a>.
<i class="fa icon-warning" title="Warning"></i>
</td>
<td class="content">
If you have both Ribbon and Spring Cloud LoadBalancer int the classpath, in order to maintain
backward compatibility, Ribbon-based implementations will be used by default. In order
to switch to using Spring Cloud LoadBalancer under the hood,
make sure you set the property <code>spring.cloud.loadbalancer.ribbon.enabled</code> to <code>false</code>.
If you have both Ribbon and Spring Cloud LoadBalancer int the classpath, in order to maintain backward compatibility, Ribbon-based implementations will be used by default.
In order to switch to using Spring Cloud LoadBalancer under the hood, make sure you set the property <code>spring.cloud.loadbalancer.ribbon.enabled</code> to <code>false</code>.
</td>
</tr>
</table>
</div>
</div>
<div class="sect2">
<h3 id="passing-your-own-spring-cloud-loadbalancer-configuration"><a class="anchor" href="#passing-your-own-spring-cloud-loadbalancer-configuration"></a><a class="link" href="#passing-your-own-spring-cloud-loadbalancer-configuration">3.4. Passing Your Own Spring Cloud LoadBalancer Configuration</a></h3>
<h3 id="custom-loadbalancer-configuration"><a class="anchor" href="#custom-loadbalancer-configuration"></a><a class="link" href="#custom-loadbalancer-configuration">3.5. Passing Your Own Spring Cloud LoadBalancer Configuration</a></h3>
<div class="paragraph">
<p>You can also use the <code>@LoadBalancerClient</code> annotation to pass your own load-balancer client configuration, passing the name of the load-balancer client and the configuration class, as follows:</p>
</div>
@@ -1545,7 +1610,7 @@ make sure you set the property <code>spring.cloud.loadbalancer.ribbon.enabled</c
<div class="listingblock">
<div class="content">
<pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java">@Configuration
@LoadBalancerClient(value = "stores", configuration = StoresLoadBalancerClientConfiguration.class)
@LoadBalancerClient(value = "stores", configuration = CustomLoadBalancerConfiguration.class)
public class MyConfiguration {
@Bean
@@ -1559,6 +1624,25 @@ public class MyConfiguration {
</div>
</div>
<div class="paragraph">
<p>You can use this feature to instantiate different implementations of <code>ServiceInstanceListSupplier</code> or <code>ReactorLoadBalancer</code>,
either written by you, or provided by us as alternatives (for example <code>ZonePreferenceServiceInstanceListSupplier</code>) to override the default setup.</p>
</div>
<div class="paragraph">
<p>You can see an example of a custom cofiguration <a href="#zoned-based-custom-loadbalancer-configuration">here</a>.</p>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<i class="fa icon-note" title="Note"></i>
</td>
<td class="content">
The annotation <code>value</code> arguments (<code>stores</code> in the example above) specifies the service id of the service that we should send the requests to with the given custom configuration.
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p>You can also pass multiple configurations (for more than one load-balancer client) through the <code>@LoadBalancerClients</code> annotation, as the following example shows:</p>
</div>
<div class="exampleblock">