examples: add an example of using DefaultLoadBalancer

servicetalk-examples/docs/modules/ROOT/pages/_partials/nav-versioned.adoc

@@ -12,6 +12,7 @@
 ** xref:{page-version}@servicetalk-examples::http/index.adoc#HTTP2[HTTP/2]
 ** xref:{page-version}@servicetalk-examples::http/index.adoc#Mutual-TLS[Mutual TLS]
 ** xref:{page-version}@servicetalk-examples::http/index.adoc#Observer[Observer]
+** xref:{page-version}@servicetalk-examples::http/index.adoc#DefaultLoadBalancer[DefaultLoadBalancer]
 ** xref:{page-version}@servicetalk-examples::http/index.adoc#OpenTracing[OpenTracing]
 ** xref:{page-version}@servicetalk-examples::http/index.adoc#Redirects[Redirects]
 ** xref:{page-version}@servicetalk-examples::http/index.adoc#Retries[Retries]

servicetalk-examples/docs/modules/ROOT/pages/http/index.adoc

@@ -226,6 +226,20 @@ on via a client filter on the client builder.
 link:{source-root}/servicetalk-http-api/src/main/java/io/servicetalk/http/api/HttpLifecycleObserver.java[HttpLifecycleObserver]
 on via a client filter on the client builder.
 
+[#DefaultLoadBalancer]
+== DefaultLoadBalancer
+This example demonstrates how to use the experimental link:{source-root}/servicetalk-loadbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/DefaultLoadBalancer.java[DefaultLoadBalancer]:
+
+- by setting the load balancer to DefaultLoadBalancer for a HTTP client
+- configuring xDS failure detection for that client using default settings
+
+Using the following classes:
+
+- link:{source-root}/servicetalk-examples/http/defaultloadbalancer/src/main/java/io/servicetalk/examples/http/defaultloadbalancer/DefaultLoadBalancerClient.java[DefaultLoadBalancerClient] - A client that uses the DefaultLoadBalancer.
+- link:{source-root}/servicetalk-examples/http/defaultloadbalancer/src/main/java/io/servicetalk/examples/http/defaultloadbalancer/HelloWorldServer.java[HelloWorldServer] - A simple server implementation.
+
+NOTE: DefaultLoadBalancer is currently considered experimental and therefore the API is subject to change.
+
 [#OpenTracing]
 == OpenTracing
 

servicetalk-examples/http/defaultloadbalancer/README.adoc

@@ -0,0 +1,4 @@
+== ServiceTalk DefaultLoadBalancer Example
+
+A simple hello-world style application that uses a client configured with the DefaultLoadBalancer and xDS style outlier
+detection.

servicetalk-examples/http/defaultloadbalancer/build.gradle

@@ -0,0 +1,25 @@
+/*
+ * Copyright © 2019 Apple Inc. and the ServiceTalk project authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+apply plugin: "java"
+apply from: "../../gradle/idea.gradle"
+
+dependencies {
+  implementation project(":servicetalk-annotations")
+  implementation project(":servicetalk-http-netty")
+  implementation project(":servicetalk-loadbalancer-experimental")
+
+  runtimeOnly "org.apache.logging.log4j:log4j-slf4j-impl:$log4jVersion"
+}

servicetalk-examples/http/defaultloadbalancer/src/main/java/io/servicetalk/examples/http/defaultloadbalancer/DefaultLoadBalancerClient.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright © 2024 Apple Inc. and the ServiceTalk project authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.servicetalk.examples.http.defaultloadbalancer;
+
+import io.servicetalk.client.api.LoadBalancerFactory;
+import io.servicetalk.http.api.BlockingHttpClient;
+import io.servicetalk.http.api.FilterableStreamingHttpLoadBalancedConnection;
+import io.servicetalk.http.api.HttpResponse;
+import io.servicetalk.http.api.SingleAddressHttpClientBuilder;
+import io.servicetalk.http.netty.DefaultHttpLoadBalancerFactory;
+import io.servicetalk.http.netty.HttpClients;
+import io.servicetalk.loadbalancer.LoadBalancers;
+import io.servicetalk.loadbalancer.OutlierDetectorConfig;
+import io.servicetalk.loadbalancer.XdsHealthCheckerFactory;
+import io.servicetalk.transport.api.HostAndPort;
+
+import java.net.InetSocketAddress;
+
+import static io.servicetalk.http.api.HttpSerializers.textSerializerUtf8;
+
+public final class DefaultLoadBalancerClient {
+
+    public static void main(String[] args) throws Exception {
+        SingleAddressHttpClientBuilder<HostAndPort, InetSocketAddress> builder =
+                HttpClients.forSingleAddress("localhost", 8080)
+                .loadBalancerFactory(DefaultHttpLoadBalancerFactory.Builder.from(
+                        loadBalancer("localhost-defaultloadbalancer")).build());
+        try (BlockingHttpClient client = builder.buildBlocking()) {
+            HttpResponse response = client.request(client.get("/sayHello"));
+            System.out.println(response.toString((name, value) -> value));
+            System.out.println(response.payloadBody(textSerializerUtf8()));
+        }
+    }
+
+    private static LoadBalancerFactory<InetSocketAddress, FilterableStreamingHttpLoadBalancedConnection> loadBalancer(
+            String id) {
+        return LoadBalancers.<InetSocketAddress, FilterableStreamingHttpLoadBalancedConnection>
+                builder(id)
+                .healthCheckerFactory(new XdsHealthCheckerFactory<>(
+                        new OutlierDetectorConfig.Builder().build()
+                    )).build();
+    }
+}

servicetalk-examples/http/defaultloadbalancer/src/main/java/io/servicetalk/examples/http/defaultloadbalancer/HelloWorldServer.java

@@ -0,0 +1,30 @@
+/*
+ * Copyright © 2024 Apple Inc. and the ServiceTalk project authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.servicetalk.examples.http.defaultloadbalancer;
+
+import io.servicetalk.http.netty.HttpServers;
+
+import static io.servicetalk.http.api.HttpSerializers.textSerializerUtf8;
+
+public final class HelloWorldServer {
+
+    public static void main(String[] args) throws Exception {
+        HttpServers.forPort(8080)
+                .listenBlockingAndAwait((ctx, request, responseFactory) ->
+                        responseFactory.ok().payloadBody("Hello World!", textSerializerUtf8()))
+                .awaitShutdown();
+    }
+}

servicetalk-examples/http/defaultloadbalancer/src/main/java/io/servicetalk/examples/http/defaultloadbalancer/package-info.java

@@ -0,0 +1,19 @@
+/*
+ * Copyright © 2024 Apple Inc. and the ServiceTalk project authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+@ElementsAreNonnullByDefault
+package io.servicetalk.examples.http.defaultloadbalancer;
+
+import io.servicetalk.annotations.ElementsAreNonnullByDefault;

servicetalk-examples/http/defaultloadbalancer/src/main/resources/log4j2.xml

@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ~ Copyright © 2018 Apple Inc. and the ServiceTalk project authors
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~   http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" BASIS,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License.
+  -->
+<Configuration status="info">
+  <Appenders>
+    <Console name="Console" target="SYSTEM_OUT">
+      <PatternLayout pattern="%d %30t [%-5level] %-30logger{1} - %msg%n"/>
+    </Console>
+  </Appenders>
+  <Loggers>
+    <!-- Prints server start and shutdown -->
+    <Logger name="io.servicetalk.http.netty.NettyHttpServer" level="DEBUG"/>
+
+    <!-- Prints default subscriber errors-->
+    <Logger name="io.servicetalk.concurrent.api" level="DEBUG"/>
+
+    <!-- Use `-Dservicetalk.logger.level=DEBUG` to change the root logger level via command line  -->
+    <Root level="${sys:servicetalk.logger.level:-INFO}">
+      <AppenderRef ref="Console"/>
+    </Root>
+  </Loggers>
+</Configuration>

settings.gradle

@@ -70,6 +70,7 @@ include "servicetalk-annotations",
         "servicetalk-examples:http:compression",
         "servicetalk-examples:http:debugging",
         "servicetalk-examples:http:timeout",
+        "servicetalk-examples:http:defaultloadbalancer",
         "servicetalk-gradle-plugin-internal",
         "servicetalk-grpc-api",
         "servicetalk-grpc-health",