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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;

import com.google.common.annotations.VisibleForTesting;
import 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.Level;
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, getHardCodedClasses(), ServerProvider.class.getClassLoader(), new ServerPriorityAccessor()); instance = new ServerRegistry(); for (ServerProvider provider : providerList) { logger.fine("Service loader found " + provider); 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); } @VisibleForTesting static List> getHardCodedClasses() { // Class.forName(String) is used to remove the need for ProGuard configuration. Note that // ProGuard does not detect usages of Class.forName(String, boolean, ClassLoader): // https://sourceforge.net/p/proguard/bugs/418/ List> list = new ArrayList<>(); try { list.add(Class.forName("io.grpc.okhttp.OkHttpServerProvider")); } catch (ClassNotFoundException e) { logger.log(Level.FINE, "Unable to find OkHttpServerProvider", e); } return Collections.unmodifiableList(list); } 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, grpc-netty-shaded, or grpc-okhttp " + "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); } } }





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