Outlier detection load balancer (#9447)

New outlier detection load balancer.

Tracks all RPC results to the addresses it is configured with and periodically attempts
to detect outlier. It wraps a child load balancer from which it hides any addresses that
are deemed outliers.

As specified in gRFC A50: gRPC xDS Outlier Detection Support:
https://github.com/grpc/proposal/blob/master/A50-xds-outlier-detection.md

api/src/main/java/io/grpc/SynchronizationContext.java

@@ -163,6 +163,38 @@ public final class SynchronizationContext implements Executor {
     return new ScheduledHandle(runnable, future);
   }
 
+  /**
+   * Schedules a task to be added and run via {@link #execute} after an inital delay and then
+   * repeated after the delay until cancelled.
+   *
+   * @param task the task being scheduled
+   * @param initialDelay the delay before the first run
+   * @param delay the delay after the first run.
+   * @param unit the time unit for the delay
+   * @param timerService the {@code ScheduledExecutorService} that provides delayed execution
+   *
+   * @return an object for checking the status and/or cancel the scheduled task
+   */
+  public final ScheduledHandle scheduleWithFixedDelay(
+      final Runnable task, long initialDelay, long delay, TimeUnit unit,
+      ScheduledExecutorService timerService) {
+    final ManagedRunnable runnable = new ManagedRunnable(task);
+    ScheduledFuture<?> future = timerService.scheduleWithFixedDelay(new Runnable() {
+      @Override
+      public void run() {
+        execute(runnable);
+      }
+
+      @Override
+      public String toString() {
+        return task.toString() + "(scheduled in SynchronizationContext with delay of " + delay
+            + ")";
+      }
+    }, initialDelay, delay, unit);
+    return new ScheduledHandle(runnable, future);
+  }
+
+
   private static class ManagedRunnable implements Runnable {
     final Runnable task;
     boolean isCancelled;

api/src/test/java/io/grpc/LoadBalancerRegistryTest.java

@@ -41,7 +41,7 @@ public class LoadBalancerRegistryTest {
   @Test
   public void stockProviders() {
     LoadBalancerRegistry defaultRegistry = LoadBalancerRegistry.getDefaultRegistry();
-    assertThat(defaultRegistry.providers()).hasSize(3);
+    assertThat(defaultRegistry.providers()).hasSize(4);
 
     LoadBalancerProvider pickFirst = defaultRegistry.getProvider("pick_first");
     assertThat(pickFirst).isInstanceOf(PickFirstLoadBalancerProvider.class);
@@ -52,6 +52,12 @@ public class LoadBalancerRegistryTest {
         "io.grpc.util.SecretRoundRobinLoadBalancerProvider$Provider");
     assertThat(roundRobin.getPriority()).isEqualTo(5);
 
+    LoadBalancerProvider outlierDetection = defaultRegistry.getProvider(
+        "outlier_detection_experimental");
+    assertThat(outlierDetection.getClass().getName()).isEqualTo(
+        "io.grpc.util.OutlierDetectionLoadBalancerProvider");
+    assertThat(roundRobin.getPriority()).isEqualTo(5);
+
     LoadBalancerProvider grpclb = defaultRegistry.getProvider("grpclb");
     assertThat(grpclb).isInstanceOf(GrpclbLoadBalancerProvider.class);
     assertThat(grpclb.getPriority()).isEqualTo(5);

core/src/main/java/io/grpc/util/OutlierDetectionLoadBalancerProvider.java

@@ -0,0 +1,158 @@
+/*
+ * Copyright 2022 The gRPC 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.grpc.util;
+
+import io.grpc.LoadBalancer;
+import io.grpc.LoadBalancer.Helper;
+import io.grpc.LoadBalancerProvider;
+import io.grpc.LoadBalancerRegistry;
+import io.grpc.NameResolver.ConfigOrError;
+import io.grpc.Status;
+import io.grpc.internal.JsonUtil;
+import io.grpc.internal.ServiceConfigUtil;
+import io.grpc.internal.ServiceConfigUtil.LbConfig;
+import io.grpc.internal.ServiceConfigUtil.PolicySelection;
+import io.grpc.internal.TimeProvider;
+import io.grpc.util.OutlierDetectionLoadBalancer.OutlierDetectionLoadBalancerConfig;
+import io.grpc.util.OutlierDetectionLoadBalancer.OutlierDetectionLoadBalancerConfig.FailurePercentageEjection;
+import io.grpc.util.OutlierDetectionLoadBalancer.OutlierDetectionLoadBalancerConfig.SuccessRateEjection;
+import java.util.List;
+import java.util.Map;
+
+public final class OutlierDetectionLoadBalancerProvider extends LoadBalancerProvider {
+
+  @Override
+  public LoadBalancer newLoadBalancer(Helper helper) {
+    return new OutlierDetectionLoadBalancer(helper, TimeProvider.SYSTEM_TIME_PROVIDER);
+  }
+
+  @Override
+  public boolean isAvailable() {
+    return true;
+  }
+
+  @Override
+  public int getPriority() {
+    return 5;
+  }
+
+  @Override
+  public String getPolicyName() {
+    return "outlier_detection_experimental";
+  }
+
+  @Override
+  public ConfigOrError parseLoadBalancingPolicyConfig(Map<String, ?> rawConfig) {
+    // Common configuration.
+    Long intervalNanos = JsonUtil.getStringAsDuration(rawConfig, "interval");
+    Long baseEjectionTimeNanos = JsonUtil.getStringAsDuration(rawConfig, "baseEjectionTime");
+    Long maxEjectionTimeNanos = JsonUtil.getStringAsDuration(rawConfig, "maxEjectionTime");
+    Integer maxEjectionPercentage = JsonUtil.getNumberAsInteger(rawConfig,
+        "maxEjectionPercentage");
+
+    OutlierDetectionLoadBalancerConfig.Builder configBuilder
+        = new OutlierDetectionLoadBalancerConfig.Builder();
+    if (intervalNanos != null) {
+      configBuilder.setIntervalNanos(intervalNanos);
+    }
+    if (baseEjectionTimeNanos != null) {
+      configBuilder.setBaseEjectionTimeNanos(baseEjectionTimeNanos);
+    }
+    if (maxEjectionTimeNanos != null) {
+      configBuilder.setMaxEjectionTimeNanos(maxEjectionTimeNanos);
+    }
+    if (maxEjectionPercentage != null) {
+      configBuilder.setMaxEjectionPercent(maxEjectionPercentage);
+    }
+
+    // Success rate ejection specific configuration.
+    Map<String, ?> rawSuccessRateEjection = JsonUtil.getObject(rawConfig, "successRateEjection");
+    if (rawSuccessRateEjection != null) {
+      SuccessRateEjection.Builder successRateEjectionBuilder = new SuccessRateEjection.Builder();
+
+      Integer stdevFactor = JsonUtil.getNumberAsInteger(rawSuccessRateEjection, "stdevFactor");
+      Integer enforcementPercentage = JsonUtil.getNumberAsInteger(rawSuccessRateEjection,
+          "enforcementPercentage");
+      Integer minimumHosts = JsonUtil.getNumberAsInteger(rawSuccessRateEjection, "minimumHosts");
+      Integer requestVolume = JsonUtil.getNumberAsInteger(rawSuccessRateEjection, "requestVolume");
+
+      if (stdevFactor != null) {
+        successRateEjectionBuilder.setStdevFactor(stdevFactor);
+      }
+      if (enforcementPercentage != null) {
+        successRateEjectionBuilder.setEnforcementPercentage(enforcementPercentage);
+      }
+      if (minimumHosts != null) {
+        successRateEjectionBuilder.setMinimumHosts(minimumHosts);
+      }
+      if (requestVolume != null) {
+        successRateEjectionBuilder.setRequestVolume(requestVolume);
+      }
+
+      configBuilder.setSuccessRateEjection(successRateEjectionBuilder.build());
+    }
+
+    // Failure percentage ejection specific configuration.
+    Map<String, ?> rawFailurePercentageEjection = JsonUtil.getObject(rawConfig,
+        "failurePercentageEjection");
+    if (rawFailurePercentageEjection != null) {
+      FailurePercentageEjection.Builder failurePercentageEjectionBuilder
+          = new FailurePercentageEjection.Builder();
+
+      Integer threshold = JsonUtil.getNumberAsInteger(rawFailurePercentageEjection, "threshold");
+      Integer enforcementPercentage = JsonUtil.getNumberAsInteger(rawFailurePercentageEjection,
+          "enforcementPercentage");
+      Integer minimumHosts = JsonUtil.getNumberAsInteger(rawFailurePercentageEjection,
+          "minimumHosts");
+      Integer requestVolume = JsonUtil.getNumberAsInteger(rawFailurePercentageEjection,
+          "requestVolume");
+
+      if (threshold != null) {
+        failurePercentageEjectionBuilder.setThreshold(threshold);
+      }
+      if (enforcementPercentage != null) {
+        failurePercentageEjectionBuilder.setEnforcementPercentage(enforcementPercentage);
+      }
+      if (minimumHosts != null) {
+        failurePercentageEjectionBuilder.setMinimumHosts(minimumHosts);
+      }
+      if (requestVolume != null) {
+        failurePercentageEjectionBuilder.setRequestVolume(requestVolume);
+      }
+
+      configBuilder.setFailurePercentageEjection(failurePercentageEjectionBuilder.build());
+    }
+
+    // Child load balancer configuration.
+    List<LbConfig> childConfigCandidates = ServiceConfigUtil.unwrapLoadBalancingConfigList(
+        JsonUtil.getListOfObjects(rawConfig, "childPolicy"));
+    if (childConfigCandidates == null || childConfigCandidates.isEmpty()) {
+      return ConfigOrError.fromError(Status.INTERNAL.withDescription(
+          "No child policy in outlier_detection_experimental LB policy: "
+              + rawConfig));
+    }
+    ConfigOrError selectedConfig =
+        ServiceConfigUtil.selectLbPolicyFromList(childConfigCandidates,
+            LoadBalancerRegistry.getDefaultRegistry());
+    if (selectedConfig.getError() != null) {
+      return selectedConfig;
+    }
+    configBuilder.setChildPolicy((PolicySelection) selectedConfig.getConfig());
+
+    return ConfigOrError.fromConfig(configBuilder.build());
+  }
+}

core/src/main/resources/META-INF/services/io.grpc.LoadBalancerProvider

@@ -1,2 +1,3 @@
 io.grpc.internal.PickFirstLoadBalancerProvider
 io.grpc.util.SecretRoundRobinLoadBalancerProvider$Provider
+io.grpc.util.OutlierDetectionLoadBalancerProvider

core/src/test/java/io/grpc/internal/FakeClock.java

@@ -159,8 +159,10 @@ public final class FakeClock {
     }
 
     @Override public ScheduledFuture<?> scheduleWithFixedDelay(
-        Runnable command, long initialDelay, long delay, TimeUnit unit) {
-      throw new UnsupportedOperationException();
+        Runnable cmd, long initialDelay, long delay, TimeUnit unit) {
+      ScheduledTask task = new ScheduleWithFixedDelayTask(cmd, delay, unit);
+      schedule(task, initialDelay, unit);
+      return task;
     }
 
     @Override public boolean awaitTermination(long timeout, TimeUnit unit) {
@@ -234,6 +236,24 @@ public final class FakeClock {
         }
       }
     }
+
+    class ScheduleWithFixedDelayTask extends ScheduledTask {
+
+      final long delayNanos;
+
+      ScheduleWithFixedDelayTask(Runnable command, long delay, TimeUnit unit) {
+        super(command);
+        this.delayNanos = unit.toNanos(delay);
+      }
+
+      @Override
+      void run() {
+        command.run();
+        if (!isCancelled()) {
+          schedule(this, delayNanos, TimeUnit.NANOSECONDS);
+        }
+      }
+    }
   }
 
   /**

core/src/test/java/io/grpc/util/OutlierDetectionLoadBalancerProviderTest.java

@@ -0,0 +1,141 @@
+/*
+ * Copyright 2022 The gRPC 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.grpc.util;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.fail;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import io.grpc.InternalServiceProviders;
+import io.grpc.LoadBalancer.Helper;
+import io.grpc.LoadBalancerProvider;
+import io.grpc.NameResolver.ConfigOrError;
+import io.grpc.SynchronizationContext;
+import io.grpc.internal.JsonParser;
+import io.grpc.util.OutlierDetectionLoadBalancer.OutlierDetectionLoadBalancerConfig;
+import java.io.IOException;
+import java.lang.Thread.UncaughtExceptionHandler;
+import java.util.Map;
+import java.util.concurrent.ScheduledExecutorService;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/**
+ * Unit tests for {@link OutlierDetectionLoadBalancerProvider}.
+ */
+@RunWith(JUnit4.class)
+public class OutlierDetectionLoadBalancerProviderTest {
+
+  private final SynchronizationContext syncContext = new SynchronizationContext(
+      new UncaughtExceptionHandler() {
+        @Override
+        public void uncaughtException(Thread t, Throwable e) {
+          throw new AssertionError(e);
+        }
+      });
+  private final OutlierDetectionLoadBalancerProvider provider
+      = new OutlierDetectionLoadBalancerProvider();
+
+  @Test
+  public void provided() {
+    for (LoadBalancerProvider current : InternalServiceProviders.getCandidatesViaServiceLoader(
+        LoadBalancerProvider.class, getClass().getClassLoader())) {
+      if (current instanceof OutlierDetectionLoadBalancerProvider) {
+        return;
+      }
+    }
+    fail("OutlierDetectionLoadBalancerProvider not registered");
+  }
+
+  @Test
+  public void providesLoadBalancer() {
+    Helper helper = mock(Helper.class);
+    when(helper.getSynchronizationContext()).thenReturn(syncContext);
+    when(helper.getScheduledExecutorService()).thenReturn(mock(ScheduledExecutorService.class));
+    assertThat(provider.newLoadBalancer(helper))
+        .isInstanceOf(OutlierDetectionLoadBalancer.class);
+  }
+
+  @Test
+  public void parseLoadBalancingConfig_defaults() throws IOException {
+    String lbConfig =
+        "{ \"successRateEjection\" : {}, "
+        + "\"failurePercentageEjection\" : {}, "
+        + "\"childPolicy\" : [{\"round_robin\" : {}}]}";
+    ConfigOrError configOrError =
+        provider.parseLoadBalancingPolicyConfig(parseJsonObject(lbConfig));
+    assertThat(configOrError.getConfig()).isNotNull();
+    OutlierDetectionLoadBalancerConfig config
+        = (OutlierDetectionLoadBalancerConfig) configOrError.getConfig();
+    assertThat(config.successRateEjection).isNotNull();
+    assertThat(config.failurePercentageEjection).isNotNull();
+    assertThat(config.childPolicy.getProvider().getPolicyName()).isEqualTo("round_robin");
+  }
+
+  @Test
+  public void parseLoadBalancingConfig_valuesSet() throws IOException {
+    String lbConfig =
+        "{\"interval\" : \"100s\","
+        + " \"baseEjectionTime\" : \"100s\","
+        + " \"maxEjectionTime\" : \"100s\","
+        + " \"maxEjectionPercentage\" : 100,"
+        + " \"successRateEjection\" : {"
+        + "     \"stdevFactor\" : 100,"
+        + "     \"enforcementPercentage\" : 100,"
+        + "     \"minimumHosts\" : 100,"
+        + "     \"requestVolume\" : 100"
+        + "   },"
+        + " \"failurePercentageEjection\" : {"
+        + "     \"threshold\" : 100,"
+        + "     \"enforcementPercentage\" : 100,"
+        + "     \"minimumHosts\" : 100,"
+        + "     \"requestVolume\" : 100"
+        + "   },"
+        + "\"childPolicy\" : [{\"round_robin\" : {}}]}";
+    ConfigOrError configOrError =
+        provider.parseLoadBalancingPolicyConfig(parseJsonObject(lbConfig));
+    assertThat(configOrError.getConfig()).isNotNull();
+    OutlierDetectionLoadBalancerConfig config
+        = (OutlierDetectionLoadBalancerConfig) configOrError.getConfig();
+
+    assertThat(config.intervalNanos).isEqualTo(100_000_000_000L);
+    assertThat(config.baseEjectionTimeNanos).isEqualTo(100_000_000_000L);
+    assertThat(config.maxEjectionTimeNanos).isEqualTo(100_000_000_000L);
+    assertThat(config.maxEjectionPercent).isEqualTo(100);
+
+    assertThat(config.successRateEjection).isNotNull();
+    assertThat(config.successRateEjection.stdevFactor).isEqualTo(100);
+    assertThat(config.successRateEjection.enforcementPercentage).isEqualTo(100);
+    assertThat(config.successRateEjection.minimumHosts).isEqualTo(100);
+    assertThat(config.successRateEjection.requestVolume).isEqualTo(100);
+
+    assertThat(config.failurePercentageEjection).isNotNull();
+    assertThat(config.failurePercentageEjection.threshold).isEqualTo(100);
+    assertThat(config.failurePercentageEjection.enforcementPercentage).isEqualTo(100);
+    assertThat(config.failurePercentageEjection.minimumHosts).isEqualTo(100);
+    assertThat(config.failurePercentageEjection.requestVolume).isEqualTo(100);
+
+    assertThat(config.childPolicy.getProvider().getPolicyName()).isEqualTo("round_robin");
+  }
+
+  @SuppressWarnings("unchecked")
+  private static Map<String, ?> parseJsonObject(String json) throws IOException {
+    return (Map<String, ?>) JsonParser.parse(json);
+  }
+}