Java tutorial
// ================================================================================================= // Copyright 2011 Twitter, Inc. // ------------------------------------------------------------------------------------------------- // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this work except in compliance with the License. // You may obtain a copy of the License in the LICENSE file, or 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 com.twitter.common.application.modules; import java.net.InetSocketAddress; import java.net.UnknownHostException; import java.util.List; import java.util.Map; import java.util.Set; import com.google.common.base.Function; import com.google.common.base.Optional; import com.google.common.base.Preconditions; import com.google.common.base.Predicate; import com.google.common.base.Predicates; import com.google.common.collect.FluentIterable; import com.google.common.collect.ImmutableList; import com.google.common.collect.ImmutableMap; import com.google.common.collect.ImmutableSet; import com.google.common.collect.Iterables; import com.google.common.collect.Maps; import com.google.inject.Inject; import com.google.inject.Provider; import org.apache.commons.lang.builder.ToStringBuilder; import com.twitter.common.application.ShutdownRegistry; import com.twitter.common.application.modules.LifecycleModule.LaunchException; import com.twitter.common.application.modules.LifecycleModule.Service; import com.twitter.common.application.modules.LifecycleModule.ServiceRunner; import com.twitter.common.base.Command; import com.twitter.common.base.MorePreconditions; import com.twitter.common.net.InetSocketAddressHelper; /** * Registry for services that should be exported from the application. * * Example of announcing and registering a port: * <pre> * class MyLauncher implements Provider<LocalService> { * public LocalService get() { * // Launch service. * } * } * * class MyServiceModule extends AbstractModule { * public void configure() { * LifeCycleModule.bindServiceLauncher(binder(), MyLauncher.class); * } * } * </pre> */ public class LocalServiceRegistry { private static final Predicate<LocalService> IS_PRIMARY = new Predicate<LocalService>() { @Override public boolean apply(LocalService service) { return service.primary; } }; private static final Function<LocalService, InetSocketAddress> SERVICE_TO_SOCKET = new Function<LocalService, InetSocketAddress>() { @Override public InetSocketAddress apply(LocalService service) { try { return InetSocketAddressHelper.getLocalAddress(service.port); } catch (UnknownHostException e) { throw new RuntimeException("Failed to resolve local address for " + service, e); } } }; private static final Function<LocalService, String> GET_NAME = new Function<LocalService, String>() { @Override public String apply(LocalService service) { return Iterables.getOnlyElement(service.names); } }; private final ShutdownRegistry shutdownRegistry; private final Provider<Set<ServiceRunner>> runnerProvider; private Optional<InetSocketAddress> primarySocket = null; private Map<String, InetSocketAddress> auxiliarySockets = null; /** * Creates a new local service registry. * * @param runnerProvider provider of registered local services. * @param shutdownRegistry Shutdown registry to tear down launched services. */ @Inject public LocalServiceRegistry(@Service Provider<Set<ServiceRunner>> runnerProvider, ShutdownRegistry shutdownRegistry) { this.runnerProvider = Preconditions.checkNotNull(runnerProvider); this.shutdownRegistry = Preconditions.checkNotNull(shutdownRegistry); } private static final Function<LocalService, Iterable<LocalService>> AUX_NAME_BREAKOUT = new Function<LocalService, Iterable<LocalService>>() { @Override public Iterable<LocalService> apply(final LocalService service) { Preconditions.checkArgument(!service.primary); Function<String, LocalService> oneNameService = new Function<String, LocalService>() { @Override public LocalService apply(String name) { return LocalService.auxiliaryService(name, service.port, service.shutdownCommand); } }; return Iterables.transform(service.names, oneNameService); } }; /** * Launches the local services if not already launched, otherwise this is a no-op. */ void ensureLaunched() { if (primarySocket == null) { ImmutableList.Builder<LocalService> builder = ImmutableList.builder(); for (ServiceRunner runner : runnerProvider.get()) { try { LocalService service = runner.launch(); builder.add(service); shutdownRegistry.addAction(service.shutdownCommand); } catch (LaunchException e) { throw new IllegalStateException("Failed to launch " + runner, e); } } List<LocalService> localServices = builder.build(); Iterable<LocalService> primaries = Iterables.filter(localServices, IS_PRIMARY); switch (Iterables.size(primaries)) { case 0: primarySocket = Optional.absent(); break; case 1: primarySocket = Optional.of(SERVICE_TO_SOCKET.apply(Iterables.getOnlyElement(primaries))); break; default: throw new IllegalArgumentException("More than one primary local service: " + primaries); } Iterable<LocalService> auxSinglyNamed = Iterables.concat(FluentIterable.from(localServices) .filter(Predicates.not(IS_PRIMARY)).transform(AUX_NAME_BREAKOUT)); Map<String, LocalService> byName; try { byName = Maps.uniqueIndex(auxSinglyNamed, GET_NAME); } catch (IllegalArgumentException e) { throw new IllegalArgumentException("Auxiliary services with identical names.", e); } auxiliarySockets = ImmutableMap.copyOf(Maps.transformValues(byName, SERVICE_TO_SOCKET)); } } /** * Gets the mapping from auxiliary port name to socket. * * @return Auxiliary port mapping. */ public synchronized Map<String, InetSocketAddress> getAuxiliarySockets() { ensureLaunched(); return auxiliarySockets; } /** * Gets the optional primary socket address, and returns an unresolved local socket address * representing that port. * * @return Local socket address for the primary port. * @throws IllegalStateException If the primary port was not set. */ public synchronized Optional<InetSocketAddress> getPrimarySocket() { ensureLaunched(); return primarySocket; } /** * An individual local service. */ public static final class LocalService { private final boolean primary; private final Set<String> names; private final int port; private final Command shutdownCommand; private LocalService(boolean primary, Set<String> names, int port, Command shutdownCommand) { this.primary = primary; this.names = names; this.port = port; this.shutdownCommand = Preconditions.checkNotNull(shutdownCommand); } @Override public String toString() { return new ToStringBuilder(this).append("primary", primary).append("name", names).append("port", port) .toString(); } /** * Creates a primary local service. * * @param port Service port. * @param shutdownCommand A command that will shut down the service. * @return A new primary local service. */ public static LocalService primaryService(int port, Command shutdownCommand) { return new LocalService(true, ImmutableSet.<String>of(), port, shutdownCommand); } /** * Creates a named auxiliary service. * * @param name Service name. * @param port Service port. * @param shutdownCommand A command that will shut down the service. * @return A new auxiliary local service. */ public static LocalService auxiliaryService(String name, int port, Command shutdownCommand) { return auxiliaryService(ImmutableSet.of(name), port, shutdownCommand); } /** * Creates an auxiliary service identified by multiple names. * * @param names Service names. * @param port Service port. * @param shutdownCommand A command that will shut down the service. * @return A new auxiliary local service. */ public static LocalService auxiliaryService(Set<String> names, int port, Command shutdownCommand) { MorePreconditions.checkNotBlank(names); return new LocalService(false, names, port, shutdownCommand); } } }