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xds: implement WeightedTargetLoadBalancer
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221
xds/src/main/java/io/grpc/xds/WeightedTargetLoadBalancer.java
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| /* | ||
| * Copyright 2020 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.xds; | ||
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| import static com.google.common.base.Preconditions.checkNotNull; | ||
| import static io.grpc.ConnectivityState.CONNECTING; | ||
| import static io.grpc.ConnectivityState.IDLE; | ||
| import static io.grpc.ConnectivityState.READY; | ||
| import static io.grpc.ConnectivityState.TRANSIENT_FAILURE; | ||
| import static io.grpc.xds.XdsSubchannelPickers.BUFFER_PICKER; | ||
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|
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| import com.google.common.annotations.VisibleForTesting; | ||
| import com.google.common.collect.ImmutableMap; | ||
| import io.grpc.ChannelLogger; | ||
| import io.grpc.ChannelLogger.ChannelLogLevel; | ||
| import io.grpc.ConnectivityState; | ||
| import io.grpc.LoadBalancer; | ||
| import io.grpc.LoadBalancerRegistry; | ||
| import io.grpc.Status; | ||
| import io.grpc.util.ForwardingLoadBalancerHelper; | ||
| import io.grpc.util.GracefulSwitchLoadBalancer; | ||
| import io.grpc.xds.RandomWeightedPicker.WeightedChildPicker; | ||
| import io.grpc.xds.RandomWeightedPicker.WeightedPickerFactory; | ||
| import io.grpc.xds.WeightedTargetLoadBalancerProvider.WeightedChildLbConfig; | ||
| import io.grpc.xds.WeightedTargetLoadBalancerProvider.WeightedTargetConfig; | ||
| import io.grpc.xds.XdsSubchannelPickers.ErrorPicker; | ||
| import java.util.ArrayList; | ||
| import java.util.HashMap; | ||
| import java.util.List; | ||
| import java.util.Map; | ||
| import javax.annotation.Nullable; | ||
|
|
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| /** Load balancer for weighted_target policy. */ | ||
| final class WeightedTargetLoadBalancer extends LoadBalancer { | ||
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| private final ChannelLogger channelLogger; | ||
| private final LoadBalancerRegistry lbRegistry; | ||
| private final Map<String, GracefulSwitchLoadBalancer> childBalancers = new HashMap<>(); | ||
| private final Map<String, ChildHelper> childHelpers = new HashMap<>(); | ||
| private final Helper helper; | ||
| private final WeightedPickerFactory weightedPickerFactory; | ||
|
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| private Map<String, WeightedChildLbConfig> targets = ImmutableMap.of(); | ||
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| /** | ||
| * Constructs a WeightedTargetLoadBalancer with the given weighted list of child balancer configs. | ||
| * The list must not be empty and must not contain duplicate lb configs. | ||
| */ | ||
| WeightedTargetLoadBalancer(Helper helper, LoadBalancerRegistry lbRegistry) { | ||
| this( | ||
| checkNotNull(helper, "helper"), | ||
| checkNotNull(lbRegistry, "lbRegistry"), | ||
| WeightedPickerFactory.RANDOM_PICKER_FACTORY); | ||
| } | ||
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| @VisibleForTesting | ||
| WeightedTargetLoadBalancer( | ||
| Helper helper, LoadBalancerRegistry lbRegistry, WeightedPickerFactory weightedPickerFactory) { | ||
| this.helper = helper; | ||
| this.lbRegistry = lbRegistry; | ||
| this.weightedPickerFactory = weightedPickerFactory; | ||
| channelLogger = helper.getChannelLogger(); | ||
| } | ||
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| @Override | ||
| public void handleResolvedAddresses(ResolvedAddresses resolvedAddresses) { | ||
| channelLogger.log(ChannelLogLevel.DEBUG, "Received ResolvedAddresses {0}", resolvedAddresses); | ||
| Object lbConfig = resolvedAddresses.getLoadBalancingPolicyConfig(); | ||
| if (!(lbConfig instanceof WeightedTargetConfig)) { | ||
| helper.updateBalancingState( | ||
| TRANSIENT_FAILURE, | ||
| new ErrorPicker(Status.UNAVAILABLE.withDescription( | ||
| "Load balancing config '" + lbConfig + "' is not a CdsConfig"))); | ||
| return; | ||
| } | ||
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| WeightedTargetConfig weightedTargetConfig = (WeightedTargetConfig) lbConfig; | ||
| Map<String, WeightedChildLbConfig> newTargets = weightedTargetConfig.targets; | ||
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| for (String targetName : newTargets.keySet()) { | ||
| WeightedChildLbConfig weightedChildLbConfig = newTargets.get(targetName); | ||
| if (!targets.containsKey(targetName)) { | ||
| // Create child balancers for new names. | ||
| ChildHelper childHelper = new ChildHelper(); | ||
| GracefulSwitchLoadBalancer childBalancer = new GracefulSwitchLoadBalancer(childHelper); | ||
| childBalancer.switchTo(lbRegistry.getProvider(weightedChildLbConfig.policyName)); | ||
| childHelpers.put(targetName, childHelper); | ||
| childBalancers.put(targetName, childBalancer); | ||
| } else if (!weightedChildLbConfig.policyName.equals(targets.get(targetName).policyName)) { | ||
| // Policy name change for the same target is not a typical usecase, but we should support | ||
| // it. Switch child policy. | ||
| childBalancers.get(targetName) | ||
| .switchTo(lbRegistry.getProvider(weightedChildLbConfig.policyName)); | ||
| } | ||
| } | ||
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| // Update new config map. | ||
| targets = newTargets; | ||
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| // Call handleResolvedAddresses() for each child balancer. | ||
| for (String targetName : targets.keySet()) { | ||
| childBalancers.get(targetName).handleResolvedAddresses( | ||
| resolvedAddresses.toBuilder() | ||
| .setLoadBalancingPolicyConfig(targets.get(targetName).config) | ||
| .build()); | ||
| } | ||
|
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| // Cleanup removed targets. | ||
| // TODO(zdapeng): cache removed target for 15 minutes. | ||
| for (String targetName : childBalancers.keySet()) { | ||
| if (!targets.containsKey(targetName)) { | ||
| childBalancers.get(targetName).shutdown(); | ||
| } | ||
| } | ||
| childBalancers.keySet().retainAll(targets.keySet()); | ||
| childHelpers.keySet().retainAll(targets.keySet()); | ||
| } | ||
|
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| @Override | ||
| public void handleNameResolutionError(Status error) { | ||
| channelLogger.log(ChannelLogLevel.ERROR, "Name resolution error: {0}", error); | ||
| if (childBalancers.isEmpty()) { | ||
| helper.updateBalancingState(TRANSIENT_FAILURE, new ErrorPicker(error)); | ||
| } | ||
| for (LoadBalancer childBalancer : childBalancers.values()) { | ||
| childBalancer.handleNameResolutionError(error); | ||
| } | ||
| } | ||
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| @Override | ||
| public boolean canHandleEmptyAddressListFromNameResolution() { | ||
| return true; | ||
| } | ||
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| @Override | ||
| public void shutdown() { | ||
| channelLogger.log(ChannelLogLevel.DEBUG, "weighted_target load balancer is shutting down"); | ||
| for (LoadBalancer childBalancer : childBalancers.values()) { | ||
| childBalancer.shutdown(); | ||
| } | ||
| } | ||
|
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| private void updateBalancingState() { | ||
| List<WeightedChildPicker> childPickers = new ArrayList<>(); | ||
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| ConnectivityState overallState = null; | ||
| for (String name : targets.keySet()) { | ||
| ChildHelper childHelper = childHelpers.get(name); | ||
| ConnectivityState childState = childHelper.currentState; | ||
| overallState = aggregateState(overallState, childState); | ||
| if (READY == childState) { | ||
| int weight = targets.get(name).weight; | ||
| childPickers.add(new WeightedChildPicker(weight, childHelper.currentPicker)); | ||
| } | ||
| } | ||
|
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| SubchannelPicker picker; | ||
| if (childPickers.isEmpty()) { | ||
| if (overallState == TRANSIENT_FAILURE) { | ||
| picker = new ErrorPicker(Status.UNAVAILABLE); // TODO: more details in status | ||
| } else { | ||
| picker = XdsSubchannelPickers.BUFFER_PICKER; | ||
| } | ||
| } else { | ||
| picker = weightedPickerFactory.picker(childPickers); | ||
| } | ||
|
|
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| if (overallState != null) { | ||
| helper.updateBalancingState(overallState, picker); | ||
| } | ||
| } | ||
|
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| @Nullable | ||
| private ConnectivityState aggregateState( | ||
| @Nullable ConnectivityState overallState, ConnectivityState childState) { | ||
| if (overallState == null) { | ||
| return childState; | ||
| } | ||
| if (overallState == READY || childState == READY) { | ||
| return READY; | ||
| } | ||
| if (overallState == CONNECTING || childState == CONNECTING) { | ||
| return CONNECTING; | ||
| } | ||
| if (overallState == IDLE || childState == IDLE) { | ||
| return IDLE; | ||
| } | ||
| return overallState; | ||
| } | ||
|
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| private final class ChildHelper extends ForwardingLoadBalancerHelper { | ||
| ConnectivityState currentState = CONNECTING; | ||
| SubchannelPicker currentPicker = BUFFER_PICKER; | ||
|
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| @Override | ||
| public void updateBalancingState(ConnectivityState newState, SubchannelPicker newPicker) { | ||
| currentState = newState; | ||
| currentPicker = newPicker; | ||
| WeightedTargetLoadBalancer.this.updateBalancingState(); | ||
| } | ||
|
|
||
| @Override | ||
| protected Helper delegate() { | ||
| return helper; | ||
| } | ||
| } | ||
| } |
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