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@@ -165,8 +165,9 @@ $(addBlockSwitches);
</ul>
</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>
<li><a href="#instance-health-check-for-loadbalancer">3.4. Instance Health-Check for LoadBalancer</a></li>
<li><a href="#spring-cloud-loadbalancer-starter">3.5. Spring Cloud LoadBalancer Starter</a></li>
<li><a href="#custom-loadbalancer-configuration">3.6. Passing Your Own Spring Cloud LoadBalancer Configuration</a></li>
</ul>
</li>
<li><a href="#spring-cloud-circuit-breaker">4. Spring Cloud Circuit Breaker</a>
@@ -1564,12 +1565,12 @@ We suggest passing a <code>DiscoveryClientServiceInstanceListSupplier</code> del
@Bean
public ServiceInstanceListSupplier discoveryClientServiceInstanceListSupplier(
ReactiveDiscoveryClient discoveryClient, Environment environment,
LoadBalancerProperties loadBalancerProperties,
LoadBalancerZoneConfig zoneConfig,
ApplicationContext context) {
DiscoveryClientServiceInstanceListSupplier firstDelegate = new DiscoveryClientServiceInstanceListSupplier(
discoveryClient, environment);
ZonePreferenceServiceInstanceListSupplier delegate = new ZonePreferenceServiceInstanceListSupplier(firstDelegate,
loadBalancerProperties);
zoneConfig);
ObjectProvider&lt;LoadBalancerCacheManager&gt; cacheManagerProvider = context
.getBeanProvider(LoadBalancerCacheManager.class);
if (cacheManagerProvider.getIfAvailable() != null) {
@@ -1583,7 +1584,83 @@ We suggest passing a <code>DiscoveryClientServiceInstanceListSupplier</code> del
</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>
<h3 id="instance-health-check-for-loadbalancer"><a class="anchor" href="#instance-health-check-for-loadbalancer"></a><a class="link" href="#instance-health-check-for-loadbalancer">3.4. Instance Health-Check for LoadBalancer</a></h3>
<div class="paragraph">
<p>It is possible to enable a scheduled HealthCheck for the LoadBalancer. The <code>HealthCheckServiceInstanceListSupplier</code>
is provided for that. It regularly verifies if the instances provided by a delegate
<code>ServiceInstanceListSupplier</code> are still alive and only returns the healthy instances,
unless there are none - then it returns all the retrieved instances.</p>
</div>
<div class="admonitionblock tip">
<table>
<tr>
<td class="icon">
<i class="fa icon-tip" title="Tip"></i>
</td>
<td class="content">
This mechanism is particularly helpful while using the <code>SimpleDiscoveryClient</code>. For the
clients backed by an actual Service Registry, it&#8217;s not necessary to use, as we already get
healthy instances after querying the external ServiceDiscovery.
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p>The <code>HealthCheckServiceInstanceListSupplier</code> uses <code>InstanceHealthChecker</code> to verify if the instances are
alive. We provide a default <code>PingHealthChecker</code> instance. It uses <code>WebClient</code> to execute
requests against the <code>health</code> endpoint of the instance. You can also provide your own implementation
of <code>InstanceHealthChecker</code> instead.</p>
</div>
<div class="paragraph">
<p><code>HealthCheckServiceInstanceListSupplier</code> uses properties prefixed with
<code>spring.cloud.loadbalancer.healthcheck</code>. You can set the <code>initialDelay</code> and <code>interval</code>
for the scheduler.</p>
</div>
<div class="paragraph">
<p>For the <code>PingHealthChecker</code>, you can set the default path for the healthcheck URL by setting
the value of the <code>spring.cloud.loadbalancer.healthcheck.path.default</code>. You can also set a specific value
for any given service by setting the value of the <code>spring.cloud.loadbalancer.healthcheck.path.[SERVICE_ID]</code>,
substituting the <code>[SERVICE_ID]</code> with the correct ID of your service. If the path is not set,
<code>/actuator/health</code> is used by default.</p>
</div>
<div class="paragraph">
<p>In order to use the health-check scheduler approach, you will have to instantiate a <code>HealthCheckServiceInstanceListSupplier</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>HealthCheckServiceInstanceListSupplier</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,
LoadBalancerProperties loadBalancerProperties,
ApplicationContext context,
InstanceHealthChecker healthChecker) {
DiscoveryClientServiceInstanceListSupplier firstDelegate = new DiscoveryClientServiceInstanceListSupplier(
discoveryClient, environment);
HealthCheckServiceInstanceListSupplier delegate = new HealthCheckServiceInstanceListSupplier(firstDelegate,
loadBalancerProperties, healthChecker);
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">3.5. 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>
@@ -1617,7 +1694,7 @@ In order to switch to using Spring Cloud LoadBalancer under the hood, make sure
</div>
</div>
<div class="sect2">
<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>
<h3 id="custom-loadbalancer-configuration"><a class="anchor" href="#custom-loadbalancer-configuration"></a><a class="link" href="#custom-loadbalancer-configuration">3.6. 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>