Mercurial > hg > release > thermostat-0.7
view storage/core/src/main/java/com/redhat/thermostat/storage/internal/DbServiceImpl.java @ 1035:e7725b744e57
Make DbService.connect/disconnect synchronous.
Reviewed-by: vanaltj
Review-thread: http://icedtea.classpath.org/pipermail/thermostat/2013-March/006005.html
author | Severin Gehwolf <sgehwolf@redhat.com> |
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date | Thu, 07 Mar 2013 15:37:35 +0100 |
parents | 121a6919baf5 |
children |
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/* * Copyright 2012, 2013 Red Hat, Inc. * * This file is part of Thermostat. * * Thermostat is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published * by the Free Software Foundation; either version 2, or (at your * option) any later version. * * Thermostat is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * * You should have received a copy of the GNU General Public License * along with Thermostat; see the file COPYING. If not see * <http://www.gnu.org/licenses/>. * * Linking this code with other modules is making a combined work * based on this code. Thus, the terms and conditions of the GNU * General Public License cover the whole combination. * * As a special exception, the copyright holders of this code give * you permission to link this code with independent modules to * produce an executable, regardless of the license terms of these * independent modules, and to copy and distribute the resulting * executable under terms of your choice, provided that you also * meet, for each linked independent module, the terms and conditions * of the license of that module. An independent module is a module * which is not derived from or based on this code. If you modify * this code, you may extend this exception to your version of the * library, but you are not obligated to do so. If you do not wish * to do so, delete this exception statement from your version. */ package com.redhat.thermostat.storage.internal; import java.util.concurrent.CountDownLatch; import java.util.logging.Level; import java.util.logging.Logger; import org.osgi.framework.BundleContext; import org.osgi.framework.FrameworkUtil; import org.osgi.framework.InvalidSyntaxException; import org.osgi.framework.ServiceReference; import org.osgi.framework.ServiceRegistration; import com.redhat.thermostat.common.utils.LoggingUtils; import com.redhat.thermostat.storage.config.ConnectionConfiguration; import com.redhat.thermostat.storage.config.StartupConfiguration; import com.redhat.thermostat.storage.core.Connection.ConnectionListener; import com.redhat.thermostat.storage.core.Connection.ConnectionStatus; import com.redhat.thermostat.storage.core.ConnectionException; import com.redhat.thermostat.storage.core.DbService; import com.redhat.thermostat.storage.core.Storage; import com.redhat.thermostat.storage.core.StorageException; import com.redhat.thermostat.storage.core.StorageProvider; public class DbServiceImpl implements DbService { private static Logger logger = LoggingUtils.getLogger(DbServiceImpl.class); @SuppressWarnings("rawtypes") private ServiceRegistration dbServiceReg; @SuppressWarnings("rawtypes") private ServiceRegistration storageReg; private Storage storage; private BundleContext context; private String dbUrl; DbServiceImpl(String username, String password, String dbUrl) throws StorageException { BundleContext context = FrameworkUtil.getBundle(DbService.class).getBundleContext(); init(context, username, password, dbUrl); } // for testing DbServiceImpl(BundleContext context, String username, String password, String dbUrl) { init(context, username, password, dbUrl); } // For testing. Injects custom storage. DbServiceImpl(BundleContext context, Storage storage) { this.context = context; this.storage = storage; } private void init(BundleContext context, String username, String password, String dbUrl) { Storage storage = createStorage(context, username, password, dbUrl); this.storage = storage; this.context = context; this.dbUrl = dbUrl; } public void connect() throws ConnectionException { // Storage and DbService must not be registered // as service ensureConnectPreCondition(); try { // connection needs to be synchronous, otherwise there is no // way to guarantee the postcondition if there's a delayed exception // during connection handling. doSynchronousConnect(); } catch (Exception cause) { throw new ConnectionException(cause); } // Connection didn't throw an exception. Now it is safe to register // services. dbServiceReg = context.registerService(DbService.class, this, null); storageReg = context.registerService(Storage.class.getName(), this.storage, null); } private void doSynchronousConnect() throws ConnectionException { CountDownLatch latch = new CountDownLatch(1); SynchronousConnectionListener listener = new SynchronousConnectionListener( latch, ConnectionStatus.CONNECTED); // Install listener in order to ensure connection is synchronous. addConnectionListener(listener); this.storage.getConnection().connect(); try { // Wait for connection to finish. // The synchronous connection listener gets removed once connection // has finished. latch.await(); } catch (InterruptedException e) { logger.log(Level.WARNING, e.getMessage(), e); } if (!listener.successful) { throw new ConnectionException(); } } public void disconnect() throws ConnectionException { // DbService and Storage must be registered as service at this point ensureDisconnectPrecondition(); try { doSyncronousDisconnect(); } catch (Exception cause) { throw new ConnectionException(cause); } storageReg.unregister(); dbServiceReg.unregister(); } private void doSyncronousDisconnect() { CountDownLatch latch = new CountDownLatch(1); SynchronousConnectionListener listener = new SynchronousConnectionListener( latch, ConnectionStatus.DISCONNECTED); // Install listener in order to ensure connection is synchronous. addConnectionListener(listener); this.storage.getConnection().disconnect(); try { // Wait for disconnect to finish. // The synchronous connection listener gets removed once connection // has finished. latch.await(); } catch (InterruptedException e) { logger.log(Level.WARNING, e.getMessage(), e); } if (!listener.successful) { throw new ConnectionException(); } } @Override public String getConnectionUrl() { return dbUrl; } /** * Factory method for creating a DbService instance. * * @param username * @param password * @param dbUrl * @return a DbService instance * @throws StorageException if no storage provider exists for the given {@code dbUrl}. */ public static DbService create(String username, String password, String dbUrl) throws StorageException { return new DbServiceImpl(username, password, dbUrl); } @SuppressWarnings("rawtypes") private void ensureDisconnectPrecondition() { ServiceReference dbServiceReference = context .getServiceReference(DbService.class); ServiceReference storageReference = context .getServiceReference(Storage.class); if (dbServiceReference == null || storageReference == null) { throw new IllegalStateException( "DbService or Storage not registered as service when " + "trying to disconnect"); } } @SuppressWarnings("rawtypes") private void ensureConnectPreCondition() { ServiceReference dbServiceReference = context .getServiceReference(DbService.class); ServiceReference storageReference = context .getServiceReference(Storage.class); if (dbServiceReference != null || storageReference != null) { throw new IllegalStateException( "DbService or Storage already registered as service when " + "trying to connect"); } } private static Storage createStorage(BundleContext context, String username, String password, String dbUrl) throws StorageException { StartupConfiguration config = new ConnectionConfiguration(dbUrl, username, password); StorageProvider prov = getStorageProvider(context, config); if (prov == null) { // no suitable provider found throw new StorageException("No storage found for URL " + dbUrl); } return prov.createStorage(); } @SuppressWarnings({ "rawtypes", "unchecked" }) private static StorageProvider getStorageProvider(BundleContext context, StartupConfiguration config) { try { ServiceReference[] refs = context.getServiceReferences(StorageProvider.class.getName(), null); if (refs == null) { throw new StorageException("No storage provider available"); } for (int i = 0; i < refs.length; i++) { StorageProvider prov = (StorageProvider) context.getService(refs[i]); prov.setConfig(config); if (prov.canHandleProtocol()) { return prov; } else { context.ungetService(refs[i]); } } } catch (InvalidSyntaxException e) { throw new AssertionError("Bad filter used to get StorageProviders", e); } return null; } @Override public void addConnectionListener(ConnectionListener listener) { storage.getConnection().addListener(listener); } @Override public void removeConnectionListener(ConnectionListener listener) { storage.getConnection().removeListener(listener); } class SynchronousConnectionListener implements ConnectionListener { CountDownLatch latch; boolean successful = false; ConnectionStatus expectedType; public SynchronousConnectionListener(CountDownLatch latch, ConnectionStatus expectedType) { this.latch = latch; this.expectedType = expectedType; } @Override public void changed(ConnectionStatus newStatus) { switch (newStatus) { case CONNECTED: { successful = (expectedType == ConnectionStatus.CONNECTED); latch.countDown(); removeConnectionListener(this); break; } case FAILED_TO_CONNECT: { latch.countDown(); removeConnectionListener(this); break; } case DISCONNECTED: { successful = (expectedType == ConnectionStatus.DISCONNECTED); latch.countDown(); removeConnectionListener(this); } default: { // nothing } } } } }