Java tutorial
/* * Copyright (C) 2010 University of Washington * * 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.opendatakit.common.persistence.engine.pgres; import java.sql.Connection; import java.sql.SQLException; import java.sql.Statement; import java.util.ArrayList; import java.util.Date; import java.util.List; import org.apache.commons.logging.LogFactory; import org.opendatakit.common.persistence.CommonFieldsBase; import org.opendatakit.common.persistence.DataField; import org.opendatakit.common.persistence.Datastore; import org.opendatakit.common.persistence.EntityKey; import org.opendatakit.common.persistence.ITaskLockType; import org.opendatakit.common.persistence.TaskLock; import org.opendatakit.common.persistence.engine.DatastoreAccessMetrics; import org.opendatakit.common.persistence.exception.ODKDatastoreException; import org.opendatakit.common.persistence.exception.ODKEntityNotFoundException; import org.opendatakit.common.persistence.exception.ODKTaskLockException; import org.opendatakit.common.security.User; import org.springframework.dao.DataAccessException; import org.springframework.jdbc.core.ConnectionCallback; import org.springframework.jdbc.core.JdbcTemplate; /** * * @author wbrunette@gmail.com * @author mitchellsundt@gmail.com * */ public class TaskLockImpl implements TaskLock { private static final String PERSISTENCE_LAYER_PROBLEM = "Persistence layer failure"; final DatastoreAccessMetrics dam; final DatastoreImpl datastore; final User user; TaskLockImpl(DatastoreImpl datastore, DatastoreAccessMetrics dam, User user) { this.datastore = datastore; this.dam = dam; this.user = user; } private static final String K_BQ = "\""; private TaskLockTable doTransaction(TaskLockTable entity, long l) throws ODKEntityNotFoundException, ODKTaskLockException { boolean first; final List<String> stmts = new ArrayList<String>(); String uri = entity.getUri(); StringBuilder b = new StringBuilder(); String tableName = K_BQ + datastore.getDefaultSchemaName() + K_BQ + "." + K_BQ + TaskLockTable.TABLE_NAME + K_BQ; b.append("'").append(user.getUriUser().replaceAll("'", "''")).append("'"); String uriUserInline = b.toString(); b.setLength(0); b.append("'").append(uri.replaceAll("'", "''")).append("'"); String uriLockInline = b.toString(); b.setLength(0); b.append("'").append(entity.getFormId().replaceAll("'", "''")).append("'"); String formIdInline = b.toString(); b.setLength(0); b.append("'").append(entity.getTaskType().replaceAll("'", "''")).append("'"); String taskTypeInline = b.toString(); b.setLength(0); b.append("interval '").append(l).append(" milliseconds'"); String lifetimeIntervalMilliseconds = b.toString(); b.setLength(0); b.append("LOCK TABLE ").append(tableName).append(" IN ACCESS EXCLUSIVE MODE"); stmts.add(b.toString()); b.setLength(0); dam.recordPutUsage(TaskLockTable.TABLE_NAME); if (!entity.isFromDatabase()) { // insert a new record (prospective lock) b.append("INSERT INTO "); b.append(tableName); b.append(" ("); first = true; for (DataField f : entity.getFieldList()) { if (!first) { b.append(","); } first = false; b.append(K_BQ); b.append(f.getName()); b.append(K_BQ); } first = true; b.append(") VALUES ( "); for (DataField f : entity.getFieldList()) { if (!first) { b.append(","); } first = false; if (f.equals(entity.creationDate) || f.equals(entity.lastUpdateDate)) { b.append("NOW()"); } else if (f.equals(entity.creatorUriUser) || f.equals(entity.lastUpdateUriUser)) { b.append(uriUserInline); } else if (f.equals(entity.formId)) { b.append(formIdInline); } else if (f.equals(entity.taskType)) { b.append(taskTypeInline); } else if (f.equals(entity.primaryKey)) { b.append(uriLockInline); } else if (f.equals(entity.expirationDateTime)) { b.append(" NOW() + "); b.append(lifetimeIntervalMilliseconds); } else { throw new IllegalStateException("unexpected case " + f.getName()); } } b.append(")"); stmts.add(b.toString()); b.setLength(0); } else { // update existing record (prospective lock) b.append("UPDATE "); b.append(tableName); b.append(" SET "); first = true; for (DataField f : entity.getFieldList()) { if (f == entity.primaryKey) continue; if (!first) { b.append(","); } first = false; b.append(K_BQ); b.append(f.getName()); b.append(K_BQ); b.append(" = "); if (f.equals(entity.creationDate) || f.equals(entity.lastUpdateDate)) { b.append("NOW()"); } else if (f.equals(entity.creatorUriUser) || f.equals(entity.lastUpdateUriUser)) { b.append(uriUserInline); } else if (f.equals(entity.formId)) { b.append(formIdInline); } else if (f.equals(entity.taskType)) { b.append(taskTypeInline); } else if (f.equals(entity.primaryKey)) { b.append(uriLockInline); } else if (f.equals(entity.expirationDateTime)) { b.append(" NOW() + "); b.append(lifetimeIntervalMilliseconds); } else { throw new IllegalStateException("unexpected case " + f.getName()); } } b.append(" WHERE "); b.append(K_BQ); b.append(entity.primaryKey.getName()); b.append(K_BQ); b.append(" = "); b.append(uriLockInline); stmts.add(b.toString()); b.setLength(0); } // delete stale locks (don't care who's) dam.recordDeleteUsage(TaskLockTable.TABLE_NAME); b.append("DELETE FROM ").append(tableName).append(" WHERE "); b.append(K_BQ).append(entity.expirationDateTime.getName()).append(K_BQ).append(" <= NOW()"); stmts.add(b.toString()); b.setLength(0); // delete prospective locks which are not the oldest for that resource and // task type dam.recordDeleteUsage(TaskLockTable.TABLE_NAME); b.append("DELETE FROM ").append(tableName).append(" WHERE "); b.append(K_BQ).append(entity.formId.getName()).append(K_BQ).append(" = ").append(formIdInline) .append(" AND "); b.append(K_BQ).append(entity.taskType.getName()).append(K_BQ).append(" = ").append(taskTypeInline) .append(" AND "); b.append(K_BQ).append(entity.expirationDateTime.getName()).append(K_BQ); b.append(" > (SELECT MIN(t3.").append(K_BQ).append(entity.expirationDateTime.getName()).append(K_BQ); b.append(") FROM ").append(tableName).append(" AS t3 WHERE t3."); b.append(K_BQ).append(entity.formId.getName()).append(K_BQ).append(" = ").append(formIdInline) .append(" AND t3."); b.append(K_BQ).append(entity.taskType.getName()).append(K_BQ).append(" = ").append(taskTypeInline) .append(")"); stmts.add(b.toString()); b.setLength(0); // delete our entry if it collides with another entry with exactly // this time. b.append("DELETE FROM ").append(tableName).append(" WHERE "); b.append(K_BQ).append(entity.formId.getName()).append(K_BQ).append(" = ").append(formIdInline) .append(" AND "); b.append(K_BQ).append(entity.taskType.getName()).append(K_BQ).append(" = ").append(taskTypeInline) .append(" AND "); b.append(K_BQ).append(entity.primaryKey.getName()).append(K_BQ).append(" = ").append(uriLockInline) .append(" AND "); b.append("1 < (SELECT COUNT(t3.").append(K_BQ).append(entity.expirationDateTime.getName()).append(K_BQ); b.append(") FROM ").append(tableName).append(" AS t3 WHERE t3."); b.append(K_BQ).append(entity.formId.getName()).append(K_BQ).append(" = ").append(formIdInline) .append(" AND t3."); b.append(K_BQ).append(entity.taskType.getName()).append(K_BQ).append(" = ").append(taskTypeInline) .append(")"); stmts.add(b.toString()); b.setLength(0); // assert: only the lock that holds the resource for that task type appears // in the task lock table TaskLockTable relation; try { JdbcTemplate jdbc = datastore.getJdbcConnection(); jdbc.execute(new ConnectionCallback<Object>() { @Override public Object doInConnection(Connection conn) throws SQLException, DataAccessException { boolean oldAutoCommitValue = conn.getAutoCommit(); int oldTransactionValue = conn.getTransactionIsolation(); try { conn.setAutoCommit(false); conn.setTransactionIsolation(Connection.TRANSACTION_SERIALIZABLE); Statement stmt = conn.createStatement(); for (String s : stmts) { // for debugging: LogFactory.getLog(TaskLockImpl.class).info(s); stmt.execute(s); } conn.commit(); } catch (Exception e) { e.printStackTrace(); conn.rollback(); } conn.setTransactionIsolation(oldTransactionValue); conn.setAutoCommit(oldAutoCommitValue); return null; } }); relation = TaskLockTable.assertRelation(datastore, user); } catch (Exception e) { throw new ODKTaskLockException(PERSISTENCE_LAYER_PROBLEM, e); } return (TaskLockTable) datastore.getEntity(relation, entity.getUri(), user); } @Override public boolean obtainLock(String lockId, String formId, ITaskLockType taskType) { boolean result = false; try { TaskLockTable relation = TaskLockTable.assertRelation(datastore, user); TaskLockTable entity = datastore.createEntityUsingRelation(relation, user); entity.setStringField(entity.primaryKey, lockId); entity.setFormId(formId); entity.setTaskType(taskType.getName()); entity = doTransaction(entity, taskType.getLockExpirationTimeout()); result = true; } catch (ODKEntityNotFoundException e) { // didn't gain the lock... } catch (ODKTaskLockException e) { // unexpected failure... e.printStackTrace(); } catch (ODKDatastoreException e) { // unexpected failure... e.printStackTrace(); } return result; } @Override public boolean renewLock(String lockId, String formId, ITaskLockType taskType) { boolean result = false; try { TaskLockTable relation = TaskLockTable.assertRelation(datastore, user); TaskLockTable entity = datastore.getEntity(relation, lockId, user); if (!(entity.getFormId().equals(formId) && entity.getTaskType().equals(taskType.getName()))) { throw new IllegalArgumentException("formId or taskType don't match datastore values"); } entity = doTransaction(entity, taskType.getLockExpirationTimeout()); result = true; } catch (IllegalArgumentException e) { // unexpected failure... e.printStackTrace(); } catch (ODKEntityNotFoundException e) { // unexpected failure... e.printStackTrace(); } catch (ODKDatastoreException e) { // unexpected failure... e.printStackTrace(); } catch (ODKTaskLockException e) { // unexpected failure... e.printStackTrace(); } return result; } @Override public boolean releaseLock(String lockId, String formId, ITaskLockType taskType) { boolean result = false; try { TaskLockTable relation = TaskLockTable.assertRelation(datastore, user); // we don't have the record that we want to delete; construct // the entity key from the relation and the URI for the record. datastore.deleteEntity(new EntityKey(relation, lockId), user); result = true; } catch (ODKDatastoreException e) { // if we see a lot of these, we are running too long between renewals LogFactory.getLog(TaskLockImpl.class).info("delete of taskLock threw exception!"); e.printStackTrace(); } return result; } private static class TaskLockTable extends CommonFieldsBase { static final String TABLE_NAME = "_task_lock"; private static final DataField FORM_ID = new DataField("FORM_ID", DataField.DataType.STRING, false, 4096L); private static final DataField TASK_TYPE = new DataField("TASK_TYPE", DataField.DataType.STRING, false, 80L); private static final DataField EXPIRATION_DATETIME = new DataField("EXPIRATION_DATETIME", DataField.DataType.DATETIME, true); DataField formId; DataField taskType; DataField expirationDateTime; TaskLockTable(String schema) { super(schema, TABLE_NAME); fieldList.add(formId = new DataField(FORM_ID)); fieldList.add(taskType = new DataField(TASK_TYPE)); fieldList.add(expirationDateTime = new DataField(EXPIRATION_DATETIME)); } TaskLockTable(TaskLockTable ref, User user) { super(ref, user); formId = ref.formId; taskType = ref.taskType; expirationDateTime = ref.expirationDateTime; } String getFormId() { return getStringField(formId); } void setFormId(String value) { if (!setStringField(formId, value)) { throw new IllegalStateException("overflow formId"); } } String getTaskType() { return getStringField(taskType); } void setTaskType(String value) { if (!setStringField(taskType, value)) { throw new IllegalStateException("overflow taskType"); } } @SuppressWarnings("unused") Date getExpirationDateTime() { return getDateField(expirationDateTime); } @SuppressWarnings("unused") void setExpirationDateTime(Date value) { setDateField(expirationDateTime, value); } @Override public CommonFieldsBase getEmptyRow(User user) { return new TaskLockTable(this, user); } static TaskLockTable relation = null; static synchronized final TaskLockTable assertRelation(Datastore datastore, User user) throws ODKDatastoreException { if (relation == null) { TaskLockTable relationPrototype; relationPrototype = new TaskLockTable(datastore.getDefaultSchemaName()); datastore.assertRelation(relationPrototype, user); relation = relationPrototype; } return relation; } } }