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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. | ||
*/ | ||
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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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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(); | ||
} | ||
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@Override | ||
protected Helper delegate() { | ||
return helper; | ||
} | ||
} | ||
} |
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