Source Code Cross Referenced for BackendWorkerThread.java in  » Database-JDBC-Connection-Pool » sequoia-2.10.9 » org » continuent » sequoia » controller » loadbalancer » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Database JDBC Connection Pool » sequoia 2.10.9 » org.continuent.sequoia.controller.loadbalancer 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /**
002:         * Sequoia: Database clustering technology.
003:         * Copyright (C) 2002-2004 French National Institute For Research In Computer
004:         * Science And Control (INRIA).
005:         * Contact: sequoia@continuent.org
006:         *
007:         * Licensed under the Apache License, Version 2.0 (the "License");
008:         * you may not use this file except in compliance with the License.
009:         * You may obtain a copy of the License at
010:         *
011:         * http://www.apache.org/licenses/LICENSE-2.0
012:         *
013:         * Unless required by applicable law or agreed to in writing, software
014:         * distributed under the License is distributed on an "AS IS" BASIS,
015:         * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
016:         * See the License for the specific language governing permissions and
017:         * limitations under the License.
018:         *
019:         * Initial developer(s): Emmanuel Cecchet.
020:         * Contributor(s):
021:         */package org.continuent.sequoia.controller.loadbalancer;
022:
023:        import java.sql.SQLException;
024:        import java.sql.Statement;
025:
026:        import org.continuent.sequoia.common.i18n.Translate;
027:        import org.continuent.sequoia.common.log.Trace;
028:        import org.continuent.sequoia.controller.backend.DatabaseBackend;
029:        import org.continuent.sequoia.controller.loadbalancer.tasks.KillThreadTask;
030:        import org.continuent.sequoia.controller.loadbalancer.tasks.RollbackTask;
031:        import org.continuent.sequoia.controller.virtualdatabase.activity.ActivityService;
032:
033:        /**
034:         * Process sequentially a set of tasks and send them to a backend.
035:         *
036:         * @author <a href="mailto:Emmanuel.Cecchet@inria.fr">Emmanuel Cecchet </a>
037:         * @version 1.0
038:         */
039:        public class BackendWorkerThread extends Thread {
040:            //
041:            // How the code is organized ?
042:            // 1. Member variables
043:            // 2. Constructor(s)
044:            // 3. Task management
045:            // 4. Getter/Setters
046:            //
047:
048:            private AbstractLoadBalancer loadBalancer;
049:            private DatabaseBackend backend;
050:            private boolean isKilled = false;
051:
052:            private Trace logger = null;
053:            private BackendTaskQueues queues;
054:            private Statement currentStatement;
055:
056:            /** True if this thread only plays commit/rollback tasks */
057:            private boolean playingCommitRollbackOnly = false;
058:
059:            /*
060:             * Constructor
061:             */
062:
063:            /**
064:             * Creates a new <code>BackendWorkerThread</code>.
065:             *
066:             * @param backend the backend this thread is associated to.
067:             * @param loadBalancer the load balancer instanciating this thread
068:             */
069:            public BackendWorkerThread(DatabaseBackend backend,
070:                    AbstractLoadBalancer loadBalancer) {
071:                this (loadBalancer.vdb.getVirtualDatabaseName()
072:                        + " - BackendWorkerThread for backend '"
073:                        + backend.getName() + "' with RAIDb level:"
074:                        + loadBalancer.getRAIDbLevel(), backend, loadBalancer);
075:            }
076:
077:            /**
078:             * Creates a new <code>BackendWorkerThread</code>.
079:             *
080:             * @param name the name to give to the thread
081:             * @param backend the backend this thread is associated to.
082:             * @param loadBalancer the load balancer instanciating this thread
083:             */
084:            public BackendWorkerThread(String name, DatabaseBackend backend,
085:                    AbstractLoadBalancer loadBalancer) {
086:                super (name);
087:                // Sanity checks
088:                if (backend == null) {
089:                    String msg = Translate
090:                            .get("backendworkerthread.null.backend");
091:                    logger = Trace
092:                            .getLogger("org.continuent.sequoia.controller.backend.DatabaseBackend");
093:                    logger.error(msg);
094:                    throw new NullPointerException(msg);
095:                }
096:
097:                logger = Trace
098:                        .getLogger("org.continuent.sequoia.controller.backend.DatabaseBackend."
099:                                + backend.getName());
100:
101:                if (loadBalancer == null) {
102:                    String msg = Translate
103:                            .get("backendworkerthread.null.loadbalancer");
104:                    logger.error(msg);
105:                    throw new NullPointerException(msg);
106:                }
107:
108:                this .backend = backend;
109:                this .loadBalancer = loadBalancer;
110:                this .queues = backend.getTaskQueues();
111:            }
112:
113:            /**
114:             * Kills this thread after the next task processing and forces the load
115:             * balancer to disable the backend. It also marks all remaining tasks in the
116:             * task list as failed.
117:             */
118:            public void killAndForceDisable() {
119:                kill(true);
120:            }
121:
122:            /**
123:             * Kills this thread after the next task processing. It also disables the
124:             * backend.
125:             */
126:            public void killWithoutDisablingBackend() {
127:                kill(false);
128:            }
129:
130:            /**
131:             * Kills this thread after the next task processing. It also marks all
132:             * remaining tasks in the task list as failed.
133:             *
134:             * @param forceDisable true if the task must call the load balancer to disable
135:             *          the backend
136:             */
137:            private void kill(boolean forceDisable) {
138:                synchronized (this ) {
139:                    if (logger.isDebugEnabled())
140:                        logger.debug(this .getName() + " is shutting down");
141:
142:                    isKilled = true;
143:                    notify(); // Wake up thread
144:                }
145:                if (forceDisable) {
146:                    try {
147:                        // This ensure that all worker threads get removed from the load
148:                        // balancer list and that the backend state is set to disable.
149:                        loadBalancer.disableBackend(backend, true);
150:                    } catch (SQLException ignore) {
151:                    }
152:                }
153:            }
154:
155:            /**
156:             * Process the tasklist and call <code>wait()</code> (on itself) when the
157:             * tasklist becomes empty.
158:             */
159:            public void run() {
160:                BackendTaskQueueEntry currentlyProcessingEntry = null;
161:
162:                while (!isKilled) {
163:                    try {
164:                        // Take the next available task
165:                        if (isPlayingCommitRollbackOnly())
166:                            currentlyProcessingEntry = queues
167:                                    .getNextCommitRollbackToExecute(this );
168:                        else
169:                            currentlyProcessingEntry = queues
170:                                    .getNextEntryToExecute(this );
171:
172:                        if (currentlyProcessingEntry == null) {
173:                            logger.warn("Null task in BackendWorkerThread");
174:                            continue;
175:                        }
176:
177:                        // Execute the tasks
178:                        if (logger.isDebugEnabled())
179:                            logger.debug(Translate.get(
180:                                    "backendworkerthread.execute.task",
181:                                    currentlyProcessingEntry.getTask()
182:                                            .toString()));
183:                        currentlyProcessingEntry.getTask().execute(this );
184:                    } catch (SQLException e) {
185:                        // Task should have notified of failure
186:                        logger.warn(Translate.get(
187:                                "backendworkerthread.task.failed", e));
188:                    } catch (Throwable re) {
189:                        logger
190:                                .fatal(
191:                                        Translate
192:                                                .get(
193:                                                        "backendworkerthread.task.unexpected.throwable",
194:                                                        currentlyProcessingEntry == null ? "null task"
195:                                                                : currentlyProcessingEntry
196:                                                                        .toString()),
197:                                        re);
198:
199:                        // We can't know for sure if the task has notified the failure or not.
200:                        // To prevent a deadlock, we force the failure notification here.
201:                        try {
202:                            currentlyProcessingEntry.getTask().notifyFailure(
203:                                    this , 1, new SQLException(re.getMessage()));
204:                        } catch (SQLException e1) {
205:                            // just notify
206:                        }
207:                    } finally {
208:                        // do not treat "rollback" or "kill thread" tasks
209:                        // as activity reaching the backend
210:                        if (currentlyProcessingEntry != null
211:                                && !(currentlyProcessingEntry.getTask() instanceof  RollbackTask)
212:                                && !(currentlyProcessingEntry.getTask() instanceof  KillThreadTask)) {
213:                            ActivityService.getInstance().notifyActivityFor(
214:                                    backend.getVirtualDatabaseName());
215:                        }
216:                        setCurrentStatement(null);
217:                        try {
218:                            if (currentlyProcessingEntry != null) {
219:                                queues
220:                                        .completedEntryExecution(currentlyProcessingEntry);
221:                                if (logger.isDebugEnabled())
222:                                    logger
223:                                            .debug(Translate
224:                                                    .get(
225:                                                            "backendworkerthread.execute.task.completed",
226:                                                            currentlyProcessingEntry
227:                                                                    .getTask()
228:                                                                    .toString()));
229:                            }
230:                        } catch (RuntimeException e) {
231:                            logger
232:                                    .warn(
233:                                            Translate
234:                                                    .get(
235:                                                            "backendworkerthread.remove.task.error",
236:                                                            e), e);
237:                        }
238:                        // Trying to speed-up GC on potentially large request objects
239:                        // referenced by this task (think BLOBs).
240:                        currentlyProcessingEntry = null;
241:                    }
242:                } // end while (!isKilled)
243:            }
244:
245:            /*
246:             * Getter/Setter
247:             */
248:
249:            /**
250:             * Returns the backend.
251:             *
252:             * @return a <code>DatabaseBackend</code> instance
253:             */
254:            public DatabaseBackend getBackend() {
255:                return backend;
256:            }
257:
258:            /**
259:             * Returns the currentStatement value.
260:             *
261:             * @return Returns the currentStatement.
262:             */
263:            public final Statement getCurrentStatement() {
264:                return currentStatement;
265:            }
266:
267:            /**
268:             * Sets the currentStatement value.
269:             *
270:             * @param currentStatement The currentStatement to set.
271:             */
272:            public final void setCurrentStatement(Statement currentStatement) {
273:                this .currentStatement = currentStatement;
274:            }
275:
276:            /**
277:             * Returns the loadBalancer value.
278:             *
279:             * @return Returns the loadBalancer.
280:             */
281:            public final AbstractLoadBalancer getLoadBalancer() {
282:                return loadBalancer;
283:            }
284:
285:            /**
286:             * Returns the logger for tracing.
287:             *
288:             * @return a <code>Trace</code> instance
289:             */
290:            public Trace getLogger() {
291:                return logger;
292:            }
293:
294:            /**
295:             * Returns the playCommitRollbackOnly value.
296:             *
297:             * @return Returns the playCommitRollbackOnly.
298:             */
299:            public boolean isPlayingCommitRollbackOnly() {
300:                return playingCommitRollbackOnly;
301:            }
302:
303:            /**
304:             * Sets the playCommitRollbackOnly value.
305:             *
306:             * @param playCommitRollbackOnly The playCommitRollbackOnly to set.
307:             */
308:            public void setPlayCommitRollbackOnly(boolean playCommitRollbackOnly) {
309:                this .playingCommitRollbackOnly = playCommitRollbackOnly;
310:            }
311:
312:            /**
313:             * @see java.lang.Object#equals(java.lang.Object)
314:             */
315:            public boolean equals(Object obj) {
316:                if (obj instanceof  BackendWorkerThread) {
317:                    return backend.equals(((BackendWorkerThread) obj)
318:                            .getBackend());
319:                }
320:                return false;
321:            }
322:
323:            /**
324:             * @see java.lang.Object#hashCode()
325:             */
326:            public int hashCode() {
327:                return backend.hashCode();
328:            }
329:
330:        }
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