io.grpc.internal.AutoConfiguredLoadBalancerFactory Maven / Gradle / Ivy
/*
* Copyright 2018 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.internal;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.MoreObjects;
import io.grpc.ChannelLogger.ChannelLogLevel;
import io.grpc.ConnectivityState;
import io.grpc.ConnectivityStateInfo;
import io.grpc.LoadBalancer;
import io.grpc.LoadBalancer.Helper;
import io.grpc.LoadBalancer.PickResult;
import io.grpc.LoadBalancer.PickSubchannelArgs;
import io.grpc.LoadBalancer.ResolvedAddresses;
import io.grpc.LoadBalancer.Subchannel;
import io.grpc.LoadBalancer.SubchannelPicker;
import io.grpc.LoadBalancerProvider;
import io.grpc.LoadBalancerRegistry;
import io.grpc.NameResolver.ConfigOrError;
import io.grpc.Status;
import io.grpc.internal.ServiceConfigUtil.LbConfig;
import io.grpc.internal.ServiceConfigUtil.PolicySelection;
import java.util.List;
import java.util.Map;
import javax.annotation.Nullable;
// TODO(creamsoup) fully deprecate LoadBalancer.ATTR_LOAD_BALANCING_CONFIG
@SuppressWarnings("deprecation")
public final class AutoConfiguredLoadBalancerFactory {
private final LoadBalancerRegistry registry;
private final String defaultPolicy;
public AutoConfiguredLoadBalancerFactory(String defaultPolicy) {
this(LoadBalancerRegistry.getDefaultRegistry(), defaultPolicy);
}
@VisibleForTesting
AutoConfiguredLoadBalancerFactory(LoadBalancerRegistry registry, String defaultPolicy) {
this.registry = checkNotNull(registry, "registry");
this.defaultPolicy = checkNotNull(defaultPolicy, "defaultPolicy");
}
public AutoConfiguredLoadBalancer newLoadBalancer(Helper helper) {
return new AutoConfiguredLoadBalancer(helper);
}
private static final class NoopLoadBalancer extends LoadBalancer {
@Override
@Deprecated
@SuppressWarnings("InlineMeSuggester")
public void handleResolvedAddresses(ResolvedAddresses resolvedAddresses) {
}
@Override
public Status acceptResolvedAddresses(ResolvedAddresses resolvedAddresses) {
return Status.OK;
}
@Override
public void handleNameResolutionError(Status error) {}
@Override
public void shutdown() {}
}
@VisibleForTesting
public final class AutoConfiguredLoadBalancer {
private final Helper helper;
private LoadBalancer delegate;
private LoadBalancerProvider delegateProvider;
AutoConfiguredLoadBalancer(Helper helper) {
this.helper = helper;
delegateProvider = registry.getProvider(defaultPolicy);
if (delegateProvider == null) {
throw new IllegalStateException("Could not find policy '" + defaultPolicy
+ "'. Make sure its implementation is either registered to LoadBalancerRegistry or"
+ " included in META-INF/services/io.grpc.LoadBalancerProvider from your jar files.");
}
delegate = delegateProvider.newLoadBalancer(helper);
}
/**
* Returns non-OK status if the delegate rejects the resolvedAddresses (e.g. if it does not
* support an empty list).
*/
Status tryAcceptResolvedAddresses(ResolvedAddresses resolvedAddresses) {
PolicySelection policySelection =
(PolicySelection) resolvedAddresses.getLoadBalancingPolicyConfig();
if (policySelection == null) {
LoadBalancerProvider defaultProvider;
try {
defaultProvider = getProviderOrThrow(defaultPolicy, "using default policy");
} catch (PolicyException e) {
Status s = Status.INTERNAL.withDescription(e.getMessage());
helper.updateBalancingState(ConnectivityState.TRANSIENT_FAILURE, new FailingPicker(s));
delegate.shutdown();
delegateProvider = null;
delegate = new NoopLoadBalancer();
return Status.OK;
}
policySelection =
new PolicySelection(defaultProvider, /* config= */ null);
}
if (delegateProvider == null
|| !policySelection.provider.getPolicyName().equals(delegateProvider.getPolicyName())) {
helper.updateBalancingState(ConnectivityState.CONNECTING, new EmptyPicker());
delegate.shutdown();
delegateProvider = policySelection.provider;
LoadBalancer old = delegate;
delegate = delegateProvider.newLoadBalancer(helper);
helper.getChannelLogger().log(
ChannelLogLevel.INFO, "Load balancer changed from {0} to {1}",
old.getClass().getSimpleName(), delegate.getClass().getSimpleName());
}
Object lbConfig = policySelection.config;
if (lbConfig != null) {
helper.getChannelLogger().log(
ChannelLogLevel.DEBUG, "Load-balancing config: {0}", policySelection.config);
}
return getDelegate().acceptResolvedAddresses(
ResolvedAddresses.newBuilder()
.setAddresses(resolvedAddresses.getAddresses())
.setAttributes(resolvedAddresses.getAttributes())
.setLoadBalancingPolicyConfig(lbConfig)
.build());
}
void handleNameResolutionError(Status error) {
getDelegate().handleNameResolutionError(error);
}
@Deprecated
void handleSubchannelState(Subchannel subchannel, ConnectivityStateInfo stateInfo) {
getDelegate().handleSubchannelState(subchannel, stateInfo);
}
void requestConnection() {
getDelegate().requestConnection();
}
void shutdown() {
delegate.shutdown();
delegate = null;
}
@VisibleForTesting
public LoadBalancer getDelegate() {
return delegate;
}
@VisibleForTesting
void setDelegate(LoadBalancer lb) {
delegate = lb;
}
@VisibleForTesting
LoadBalancerProvider getDelegateProvider() {
return delegateProvider;
}
}
private LoadBalancerProvider getProviderOrThrow(String policy, String choiceReason)
throws PolicyException {
LoadBalancerProvider provider = registry.getProvider(policy);
if (provider == null) {
throw new PolicyException(
"Trying to load '" + policy + "' because " + choiceReason + ", but it's unavailable");
}
return provider;
}
/**
* Parses first available LoadBalancer policy from service config. Available LoadBalancer should
* be registered to {@link LoadBalancerRegistry}. If the first available LoadBalancer policy is
* invalid, it doesn't fall-back to next available policy, instead it returns error. This also
* means, it ignores LoadBalancer policies after the first available one even if any of them are
* invalid.
*
* Order of policy preference:
*
*
* - Policy from "loadBalancingConfig" if present
* - The policy from deprecated "loadBalancingPolicy" if present
*
*
*
* Unlike a normal {@link LoadBalancer.Factory}, this accepts a full service config rather than
* the LoadBalancingConfig.
*
* @return the parsed {@link PolicySelection}, or {@code null} if no selection could be made.
*/
@Nullable
ConfigOrError parseLoadBalancerPolicy(Map serviceConfig) {
try {
List loadBalancerConfigs = null;
if (serviceConfig != null) {
List> rawLbConfigs =
ServiceConfigUtil.getLoadBalancingConfigsFromServiceConfig(serviceConfig);
loadBalancerConfigs = ServiceConfigUtil.unwrapLoadBalancingConfigList(rawLbConfigs);
}
if (loadBalancerConfigs != null && !loadBalancerConfigs.isEmpty()) {
return ServiceConfigUtil.selectLbPolicyFromList(loadBalancerConfigs, registry);
}
return null;
} catch (RuntimeException e) {
return ConfigOrError.fromError(
Status.UNKNOWN.withDescription("can't parse load balancer configuration").withCause(e));
}
}
@VisibleForTesting
static final class PolicyException extends Exception {
private static final long serialVersionUID = 1L;
private PolicyException(String msg) {
super(msg);
}
}
private static final class EmptyPicker extends SubchannelPicker {
@Override
public PickResult pickSubchannel(PickSubchannelArgs args) {
return PickResult.withNoResult();
}
@Override
public String toString() {
return MoreObjects.toStringHelper(EmptyPicker.class).toString();
}
}
private static final class FailingPicker extends SubchannelPicker {
private final Status failure;
FailingPicker(Status failure) {
this.failure = failure;
}
@Override
public PickResult pickSubchannel(PickSubchannelArgs args) {
return PickResult.withError(failure);
}
}
}