loadbalancer: move DefaultLoadBalancer out of experimental (#3136)

Motivation:

We've had DefaultLoadBalancer running in place of round-robin for
some time and it looks good. It's time to move it into the main
package and prepare to remove RoundRobinLoadBalancer.

Modifications:

Move most of the contents of servicetalk-loadbalancer-experimental
to the servicetalk-loadbalancer package.

servicetalk-loadbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/RequestTracker.java → servicetalk-client-api/src/main/java/io/servicetalk/client/api/RequestTracker.java

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package io.servicetalk.loadbalancer;
+package io.servicetalk.client.api;
 
 import io.servicetalk.context.api.ContextMap;
 

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

@@ -236,20 +236,18 @@ on via a client filter on the client builder.
 
 [#LoadBalancer]
 == LoadBalancer
-This example demonstrates how to use and configure the experimental link:{source-root}/servicetalk-loadbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/LoadBalancers.java[LoadBalancers]:
+This example demonstrates how to use and configure link:{source-root}/servicetalk-loadbalancer/src/main/java/io/servicetalk/loadbalancer/LoadBalancers.java[LoadBalancers]:
 
-- by using link:{source-root}/servicetalk-loadbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/LoadBalancerBuilder.java[LoadBalancerBuilder] to customize its setting:
-  * configuring a different link:{source-root}/servicetalk-loadbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/LoadBalancingPolicy.java[LoadBalancingPolicy]
-  * configuring xDS failure detection using link:{source-root}/servicetalk-loadbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/OutlierDetectorConfig.java[OutlierDetectorConfig]
+- by using link:{source-root}/servicetalk-loadbalancer/src/main/java/io/servicetalk/loadbalancer/LoadBalancerBuilder.java[LoadBalancerBuilder] to customize its setting:
+  * configuring a different link:{source-root}/servicetalk-loadbalancer/src/main/java/io/servicetalk/loadbalancer/LoadBalancingPolicy.java[LoadBalancingPolicy]
+  * configuring xDS failure detection using link:{source-root}/servicetalk-loadbalancer/src/main/java/io/servicetalk/loadbalancer/OutlierDetectorConfig.java[OutlierDetectorConfig]
 - by using link:{source-root}/servicetalk-http-api/src/main/java/io/servicetalk/http/api/DefaultHttpLoadBalancerFactory.java[DefaultHttpLoadBalancerFactory] to adapt a LoadBalancer to HTTP and configure it via client builder
 
 Using the following classes:
 
 - link:{source-root}/servicetalk-examples/http/loadbalancer/src/main/java/io/servicetalk/examples/http/loadbalancer/CustomLoadBalancerClient.java[CustomLoadBalancerClient] - A client that configures custom settings for its LoadBalancer.
 - link:{source-root}/servicetalk-examples/http/loadbalancer/src/main/java/io/servicetalk/examples/http/loadbalancer/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/loadbalancer/build.gradle

@@ -19,7 +19,7 @@ apply from: "../../gradle/idea.gradle"
 dependencies {
   implementation project(":servicetalk-annotations")
   implementation project(":servicetalk-http-netty")
-  implementation project(":servicetalk-loadbalancer-experimental")
+  implementation project(":servicetalk-loadbalancer")
 
   runtimeOnly "org.apache.logging.log4j:log4j-slf4j-impl:$log4jVersion"
 }

servicetalk-grpc-netty/build.gradle

@@ -36,7 +36,6 @@ dependencies {
   implementation project(":servicetalk-transport-netty-internal")
   implementation project(":servicetalk-utils-internal")
   implementation project(":servicetalk-concurrent-internal")
-  implementation project(":servicetalk-loadbalancer-experimental")
   implementation "org.slf4j:slf4j-api:$slf4jVersion"
   implementation "com.google.protobuf:protobuf-java"
 

servicetalk-grpc-netty/src/main/java/io/servicetalk/grpc/netty/GrpcRequestTracker.java

@@ -19,6 +19,7 @@
 import io.servicetalk.client.api.ConnectionFactory;
 import io.servicetalk.client.api.ConnectionFactoryFilter;
 import io.servicetalk.client.api.DelegatingConnectionFactory;
+import io.servicetalk.client.api.RequestTracker;
 import io.servicetalk.concurrent.api.Single;
 import io.servicetalk.context.api.ContextMap;
 import io.servicetalk.grpc.api.GrpcLifecycleObserver;
@@ -28,7 +29,6 @@
 import io.servicetalk.http.api.HttpRequestMetaData;
 import io.servicetalk.http.api.HttpResponseMetaData;
 import io.servicetalk.http.netty.HttpLifecycleObserverRequesterFilter;
-import io.servicetalk.loadbalancer.RequestTracker;
 import io.servicetalk.transport.api.ConnectionInfo;
 import io.servicetalk.transport.api.ExecutionStrategy;
 import io.servicetalk.transport.api.TransportObserver;
@@ -40,7 +40,7 @@
 import java.util.function.Function;
 import javax.annotation.Nullable;
 
-import static io.servicetalk.loadbalancer.RequestTracker.REQUEST_TRACKER_KEY;
+import static io.servicetalk.client.api.RequestTracker.REQUEST_TRACKER_KEY;
 
 final class GrpcRequestTracker {
 

servicetalk-grpc-netty/src/test/java/io/servicetalk/grpc/netty/GrpcRequestTrackerTest.java

@@ -16,6 +16,7 @@
 package io.servicetalk.grpc.netty;
 
 import io.servicetalk.client.api.DelegatingConnectionFactory;
+import io.servicetalk.client.api.RequestTracker;
 import io.servicetalk.concurrent.api.Publisher;
 import io.servicetalk.concurrent.api.Single;
 import io.servicetalk.context.api.ContextMap;
@@ -25,7 +26,6 @@
 import io.servicetalk.grpc.api.GrpcStatusCode;
 import io.servicetalk.grpc.api.GrpcStatusException;
 import io.servicetalk.http.api.FilterableStreamingHttpConnection;
-import io.servicetalk.loadbalancer.RequestTracker;
 import io.servicetalk.transport.api.HostAndPort;
 import io.servicetalk.transport.api.ServerContext;
 import io.servicetalk.transport.api.TransportObserver;
@@ -40,7 +40,7 @@
 import java.util.concurrent.atomic.AtomicInteger;
 import javax.annotation.Nullable;
 
-import static io.servicetalk.loadbalancer.RequestTracker.REQUEST_TRACKER_KEY;
+import static io.servicetalk.client.api.RequestTracker.REQUEST_TRACKER_KEY;
 import static io.servicetalk.transport.netty.internal.AddressUtils.localAddress;
 import static io.servicetalk.transport.netty.internal.AddressUtils.serverHostAndPort;
 import static org.hamcrest.MatcherAssert.assertThat;

servicetalk-http-netty/build.gradle

@@ -29,7 +29,6 @@ dependencies {
   implementation project(":servicetalk-dns-discovery-netty")
   implementation project(":servicetalk-http-utils")
   implementation project(":servicetalk-loadbalancer")
-  implementation project(":servicetalk-loadbalancer-experimental")
   implementation project(":servicetalk-loadbalancer-experimental-provider")
   implementation project(":servicetalk-logging-slf4j-internal")
   implementation project(":servicetalk-tcp-netty-internal")

servicetalk-http-netty/src/main/java/io/servicetalk/http/netty/HttpRequestTracker.java

@@ -19,14 +19,14 @@
 import io.servicetalk.client.api.ConnectionFactory;
 import io.servicetalk.client.api.ConnectionFactoryFilter;
 import io.servicetalk.client.api.DelegatingConnectionFactory;
+import io.servicetalk.client.api.RequestTracker;
 import io.servicetalk.concurrent.api.Single;
 import io.servicetalk.context.api.ContextMap;
 import io.servicetalk.http.api.FilterableStreamingHttpConnection;
 import io.servicetalk.http.api.HttpHeaders;
 import io.servicetalk.http.api.HttpLifecycleObserver;
 import io.servicetalk.http.api.HttpRequestMetaData;
 import io.servicetalk.http.api.HttpResponseMetaData;
-import io.servicetalk.loadbalancer.RequestTracker;
 import io.servicetalk.transport.api.ConnectionInfo;
 import io.servicetalk.transport.api.ExecutionStrategy;
 import io.servicetalk.transport.api.TransportObserver;
@@ -38,11 +38,11 @@
 import java.util.concurrent.atomic.AtomicLongFieldUpdater;
 import javax.annotation.Nullable;
 
+import static io.servicetalk.client.api.RequestTracker.ErrorClass.EXT_ORIGIN_TIMEOUT;
+import static io.servicetalk.client.api.RequestTracker.ErrorClass.LOCAL_ORIGIN_REQUEST_FAILED;
+import static io.servicetalk.client.api.RequestTracker.REQUEST_TRACKER_KEY;
 import static io.servicetalk.http.api.HttpResponseStatus.StatusClass.SERVER_ERROR_5XX;
 import static io.servicetalk.http.api.HttpResponseStatus.TOO_MANY_REQUESTS;
-import static io.servicetalk.loadbalancer.RequestTracker.ErrorClass.EXT_ORIGIN_TIMEOUT;
-import static io.servicetalk.loadbalancer.RequestTracker.ErrorClass.LOCAL_ORIGIN_REQUEST_FAILED;
-import static io.servicetalk.loadbalancer.RequestTracker.REQUEST_TRACKER_KEY;
 
 final class HttpRequestTracker {
 

servicetalk-http-netty/src/test/java/io/servicetalk/http/netty/HttpRequestTrackerTest.java

@@ -16,14 +16,14 @@
 package io.servicetalk.http.netty;
 
 import io.servicetalk.client.api.DelegatingConnectionFactory;
+import io.servicetalk.client.api.RequestTracker;
 import io.servicetalk.concurrent.api.Single;
 import io.servicetalk.context.api.ContextMap;
 import io.servicetalk.http.api.FilterableStreamingHttpConnection;
 import io.servicetalk.http.api.HttpClient;
 import io.servicetalk.http.api.HttpResponse;
 import io.servicetalk.http.api.HttpService;
 import io.servicetalk.http.api.SingleAddressHttpClientBuilder;
-import io.servicetalk.loadbalancer.RequestTracker;
 import io.servicetalk.transport.api.HostAndPort;
 import io.servicetalk.transport.api.ServerContext;
 import io.servicetalk.transport.api.TransportObserver;
@@ -39,7 +39,7 @@
 
 import static io.netty.handler.codec.http.HttpStatusClass.SERVER_ERROR;
 import static io.netty.handler.codec.http.HttpStatusClass.SUCCESS;
-import static io.servicetalk.loadbalancer.RequestTracker.REQUEST_TRACKER_KEY;
+import static io.servicetalk.client.api.RequestTracker.REQUEST_TRACKER_KEY;
 import static io.servicetalk.transport.netty.internal.AddressUtils.localAddress;
 import static io.servicetalk.transport.netty.internal.AddressUtils.serverHostAndPort;
 import static org.hamcrest.MatcherAssert.assertThat;

servicetalk-loadbalancer-experimental-provider/build.gradle

@@ -21,6 +21,5 @@ dependencies {
 
   implementation project(":servicetalk-annotations")
   implementation project(":servicetalk-loadbalancer")
-  implementation project(":servicetalk-loadbalancer-experimental")
   implementation "org.slf4j:slf4j-api:$slf4jVersion"
 }

servicetalk-loadbalancer-experimental/build.gradle

@@ -16,24 +16,9 @@
 
 apply plugin: "io.servicetalk.servicetalk-gradle-plugin-internal-library"
 
-dependencies {
-  api project(":servicetalk-client-api")
-  api project(":servicetalk-concurrent-api")
-
-  implementation project(":servicetalk-annotations")
-  implementation project(":servicetalk-concurrent-api-internal")
-  implementation project(":servicetalk-concurrent-internal")
-  implementation project(":servicetalk-loadbalancer")
-  implementation project(":servicetalk-utils-internal")
-  implementation "org.slf4j:slf4j-api:$slf4jVersion"
+tasks.named("javadoc").configure {
+    enabled = false
+}
 
-  testImplementation enforcedPlatform("org.junit:junit-bom:$junit5Version")
-  testImplementation testFixtures(project(":servicetalk-concurrent-api"))
-  testImplementation testFixtures(project(":servicetalk-concurrent-internal"))
-  testImplementation project(":servicetalk-concurrent-test-internal")
-  testImplementation project(":servicetalk-test-resources")
-  testImplementation "org.junit.jupiter:junit-jupiter-api"
-  testImplementation "org.junit.jupiter:junit-jupiter-params"
-  testImplementation "org.hamcrest:hamcrest:$hamcrestVersion"
-  testImplementation "org.mockito:mockito-core:$mockitoCoreVersion"
+dependencies {
 }

servicetalk-loadbalancer-experimental/gradle.lockfile

@@ -1,7 +1,4 @@
 # This is a Gradle generated file for dependency locking.
 # Manual edits can break the build and are not advised.
 # This file is expected to be part of source control.
-com.google.code.findbugs:jsr305:3.0.2=compileClasspath,runtimeClasspath
-org.jctools:jctools-core:4.0.3=runtimeClasspath
-org.slf4j:slf4j-api:1.7.36=compileClasspath,runtimeClasspath
-empty=annotationProcessor,spotbugsPlugins,testAnnotationProcessor
+empty=annotationProcessor,compileClasspath,runtimeClasspath

servicetalk-loadbalancer-experimental/gradle/checkstyle/suppressions.xml

@@ -21,8 +21,4 @@
 <suppressions>
     <!-- No need for package-info.java file because we reuse the package where this file already exists -->
     <suppress checks="JavadocPackage" files=".*[\\/]src[\\/]main[\\/]java[\\/]io[\\/]servicetalk[\\/]loadbalancer.*"/>
-    <suppress id="MissedElementsAreNonnullByDefault"
-              files="io[\\/]servicetalk[\\/]loadbalancer[\\/]package-info.java"/>
-    <suppress checks="LineLength"
-              files="io[\\/]servicetalk[\\/]loadbalancer[\\/]OutlierDetectorConfig.java"/>
 </suppressions>

servicetalk-loadbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/PlaceHolder.java

@@ -0,0 +1,23 @@
+/*
+ * 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.loadbalancer;
+
+// FIXME: 0.43: TL;DR: Remove this module. This package existed to support the DefaultLoadBalancer development which
+//  has since been merged into the servicetalk-loadbalancer module.
+final class PlaceHolder {
+    private PlaceHolder() {
+    }
+}

servicetalk-loadbalancer-experimental/README.adoc → servicetalk-loadbalancer/DEFAULTLOADBALANCER.adoc

@@ -2,7 +2,7 @@
 
 == What is DefaultLoadBalancer?
 
-https://github.com/apple/servicetalk/blob/main/servicetalk-loadbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/DefaultLoadBalancer.java[DefaultLoadBalancer]
+https://github.com/apple/servicetalk/blob/main/servicetalk-loadbalancer/src/main/java/io/servicetalk/loadbalancer/DefaultLoadBalancer.java[DefaultLoadBalancer]
 is a refactor of the ServiceTalk
 https://github.com/apple/servicetalk/blob/main/servicetalk-loadbalancer/src/main/java/io/servicetalk/loadbalancer/RoundRobinLoadBalancer.java[RoundRobinLoadBalancer]
 that is intended to provide a more flexible foundation for building load balancers. It also serves as the basis for new
@@ -11,7 +11,7 @@ outlier detectors.
 
 === Relationship Between the LoadBalancer and Connections
 
-The load balancer is structured as a series of https://github.com/apple/servicetalk/blob/main/servicetalk-loadbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/Host.java[Host]'s
+The load balancer is structured as a series of https://github.com/apple/servicetalk/blob/main/servicetalk-loadbalancer/src/main/java/io/servicetalk/loadbalancer/Host.java[Host]'s
 and those hosts can have many connections. The number of connections to each Host is driven by the number of connections
 required to satisfy the request load. Usage of the HTTP/2 protocol will dramatically shrink the necessary number of
 connections to each backend, often to 1, and is strongly encouraged.

servicetalk-loadbalancer/gradle/checkstyle/suppressions.xml

@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ~ 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.
+  -->
+<!DOCTYPE suppressions PUBLIC
+        "-//Checkstyle//DTD SuppressionFilter Configuration 1.2//EN"
+        "https://checkstyle.org/dtds/suppressions_1_2.dtd">
+
+<suppressions>
+    <suppress checks="LineLength"
+              files="io[\\/]servicetalk[\\/]loadbalancer[\\/]OutlierDetectorConfig.java"/>
+</suppressions>

servicetalk-loadbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/ConnectTracker.java → servicetalk-loadbalancer/src/main/java/io/servicetalk/loadbalancer/ConnectTracker.java

@@ -15,6 +15,8 @@
  */
 package io.servicetalk.loadbalancer;
 
+import io.servicetalk.client.api.RequestTracker;
+
 /**
  * An interface for tracking connection establishment measurements.
  * This has an intended usage similar to the {@link RequestTracker} but with a focus on connection establishment

servicetalk-loadbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/DefaultHost.java → servicetalk-loadbalancer/src/main/java/io/servicetalk/loadbalancer/DefaultHost.java

@@ -42,6 +42,7 @@
 import java.util.function.Predicate;
 import javax.annotation.Nullable;
 
+import static io.servicetalk.client.api.RequestTracker.REQUEST_TRACKER_KEY;
 import static io.servicetalk.concurrent.api.AsyncCloseables.toAsyncCloseable;
 import static io.servicetalk.concurrent.api.Completable.completed;
 import static io.servicetalk.concurrent.api.Publisher.fromIterable;
@@ -52,7 +53,6 @@
 import static io.servicetalk.loadbalancer.ConnectTracker.ErrorClass.CANCELLED;
 import static io.servicetalk.loadbalancer.ConnectTracker.ErrorClass.CONNECT_ERROR;
 import static io.servicetalk.loadbalancer.ConnectTracker.ErrorClass.CONNECT_TIMEOUT;
-import static io.servicetalk.loadbalancer.RequestTracker.REQUEST_TRACKER_KEY;
 import static java.util.Collections.emptyList;
 import static java.util.Objects.requireNonNull;
 import static java.util.concurrent.atomic.AtomicReferenceFieldUpdater.newUpdater;

servicetalk-loadbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/DefaultRequestTracker.java → servicetalk-loadbalancer/src/main/java/io/servicetalk/loadbalancer/DefaultRequestTracker.java

@@ -15,6 +15,7 @@
  */
 package io.servicetalk.loadbalancer;
 
+import io.servicetalk.client.api.RequestTracker;
 import io.servicetalk.client.api.ScoreSupplier;
 
 import java.util.concurrent.locks.StampedLock;

servicetalk-loadbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/HealthIndicator.java → servicetalk-loadbalancer/src/main/java/io/servicetalk/loadbalancer/HealthIndicator.java

@@ -16,6 +16,7 @@
 package io.servicetalk.loadbalancer;
 
 import io.servicetalk.client.api.LoadBalancedConnection;
+import io.servicetalk.client.api.RequestTracker;
 import io.servicetalk.client.api.ScoreSupplier;
 import io.servicetalk.concurrent.Cancellable;
 

servicetalk-loadbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/XdsHealthIndicator.java → servicetalk-loadbalancer/src/main/java/io/servicetalk/loadbalancer/XdsHealthIndicator.java

@@ -16,6 +16,7 @@
 package io.servicetalk.loadbalancer;
 
 import io.servicetalk.client.api.LoadBalancedConnection;
+import io.servicetalk.client.api.RequestTracker;
 import io.servicetalk.concurrent.api.Executor;
 import io.servicetalk.loadbalancer.LoadBalancerObserver.HostObserver;
 

servicetalk-loadbalancer-experimental/src/test/java/io/servicetalk/loadbalancer/DefaultLoadBalancerTest.java → servicetalk-loadbalancer/src/test/java/io/servicetalk/loadbalancer/DefaultLoadBalancerTest.java

@@ -15,6 +15,7 @@
  */
 package io.servicetalk.loadbalancer;
 
+import io.servicetalk.client.api.RequestTracker;
 import io.servicetalk.client.api.ServiceDiscovererEvent;
 import io.servicetalk.concurrent.PublisherSource;
 import io.servicetalk.concurrent.api.Processors;

servicetalk-loadbalancer-experimental/src/test/java/io/servicetalk/loadbalancer/DefaultRequestTrackerTest.java → servicetalk-loadbalancer/src/test/java/io/servicetalk/loadbalancer/DefaultRequestTrackerTest.java

@@ -15,6 +15,8 @@
  */
 package io.servicetalk.loadbalancer;
 
+import io.servicetalk.client.api.RequestTracker;
+
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;