org.apache.ratis.thirdparty.io.grpc.ServerRegistry Maven / Gradle / Ivy
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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 org.apache.ratis.thirdparty.io.grpc;
import org.apache.ratis.thirdparty.com.google.common.annotations.VisibleForTesting;
import org.apache.ratis.thirdparty.com.google.common.base.Preconditions;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.logging.Logger;
import javax.annotation.concurrent.GuardedBy;
import javax.annotation.concurrent.ThreadSafe;
/**
* Registry of {@link ServerProvider}s. The {@link #getDefaultRegistry default instance} loads
* providers at runtime through the Java service provider mechanism.
*/
@Internal
@ThreadSafe
public final class ServerRegistry {
private static final Logger logger = Logger.getLogger(ServerRegistry.class.getName());
private static ServerRegistry instance;
@GuardedBy("this")
private final LinkedHashSet allProviders = new LinkedHashSet<>();
/** Immutable, sorted version of {@code allProviders}. Is replaced instead of mutating. */
@GuardedBy("this")
private List effectiveProviders = Collections.emptyList();
/**
* Register a provider.
*
* If the provider's {@link ServerProvider#isAvailable isAvailable()} returns
* {@code false}, this method will throw {@link IllegalArgumentException}.
*
*
Providers will be used in priority order. In case of ties, providers are used in
* registration order.
*/
public synchronized void register(ServerProvider provider) {
addProvider(provider);
refreshProviders();
}
private synchronized void addProvider(ServerProvider provider) {
Preconditions.checkArgument(provider.isAvailable(), "isAvailable() returned false");
allProviders.add(provider);
}
/**
* Deregisters a provider. No-op if the provider is not in the registry.
*
* @param provider the provider that was added to the register via {@link #register}.
*/
public synchronized void deregister(ServerProvider provider) {
allProviders.remove(provider);
refreshProviders();
}
private synchronized void refreshProviders() {
List providers = new ArrayList<>(allProviders);
// Sort descending based on priority.
// sort() must be stable, as we prefer first-registered providers
Collections.sort(providers, Collections.reverseOrder(new Comparator() {
@Override
public int compare(ServerProvider o1, ServerProvider o2) {
return o1.priority() - o2.priority();
}
}));
effectiveProviders = Collections.unmodifiableList(providers);
}
/**
* Returns the default registry that loads providers via the Java service loader mechanism.
*/
public static synchronized ServerRegistry getDefaultRegistry() {
if (instance == null) {
List providerList = ServiceProviders.loadAll(
ServerProvider.class,
Collections.>emptyList(),
ServerProvider.class.getClassLoader(),
new ServerPriorityAccessor());
instance = new ServerRegistry();
for (ServerProvider provider : providerList) {
logger.fine("Service loader found " + provider);
if (provider.isAvailable()) {
instance.addProvider(provider);
}
}
instance.refreshProviders();
}
return instance;
}
/**
* Returns effective providers, in priority order.
*/
@VisibleForTesting
synchronized List providers() {
return effectiveProviders;
}
// For emulating ServerProvider.provider()
ServerProvider provider() {
List providers = providers();
return providers.isEmpty() ? null : providers.get(0);
}
ServerBuilder newServerBuilderForPort(int port, ServerCredentials creds) {
List providers = providers();
if (providers.isEmpty()) {
throw new ProviderNotFoundException("No functional server found. "
+ "Try adding a dependency on the grpc-netty or grpc-netty-shaded artifact");
}
StringBuilder error = new StringBuilder();
for (ServerProvider provider : providers()) {
ServerProvider.NewServerBuilderResult result
= provider.newServerBuilderForPort(port, creds);
if (result.getServerBuilder() != null) {
return result.getServerBuilder();
}
error.append("; ");
error.append(provider.getClass().getName());
error.append(": ");
error.append(result.getError());
}
throw new ProviderNotFoundException(error.substring(2));
}
private static final class ServerPriorityAccessor
implements ServiceProviders.PriorityAccessor {
@Override
public boolean isAvailable(ServerProvider provider) {
return provider.isAvailable();
}
@Override
public int getPriority(ServerProvider provider) {
return provider.priority();
}
}
/** Thrown when no suitable {@link ServerProvider} objects can be found. */
public static final class ProviderNotFoundException extends RuntimeException {
private static final long serialVersionUID = 1;
public ProviderNotFoundException(String msg) {
super(msg);
}
}
}