1 files changed, 233 insertions, 0 deletions
diff --git a/feature-distributed-locking/src/main/java/org/onap/policy/distributed/locking/TargetLock.java b/feature-distributed-locking/src/main/java/org/onap/policy/distributed/locking/TargetLock.java
new file mode 100644
index 00000000..ceaa849f
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+++ b/feature-distributed-locking/src/main/java/org/onap/policy/distributed/locking/TargetLock.java
@@ -0,0 +1,233 @@
+/*
+ * ============LICENSE_START=======================================================
+ * feature-distributed-locking
+ * ================================================================================
+ * Copyright (C) 2018 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * 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.
+ * ============LICENSE_END=========================================================
+ */
+package org.onap.policy.distributed.locking;
+
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.UUID;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class TargetLock {
+	
+	private static final Logger logger = LoggerFactory.getLogger(TargetLock.class);
+	
+	/**
+	 * The Target resource we want to lock
+	 */
+	private String resourceId;
+	
+	/**
+	 * Properties object containing properties needed by class
+	 */
+	private DistributedLockingProperties lockProps;
+
+	/**
+	 * UUID 
+	 */
+	private UUID uuid;
+	
+	/**
+	 * Owner
+	 */
+	private String owner;
+	
+	/**
+	 * Constructs a TargetLock object.
+	 * 
+	 * @param resourceId ID of the entity we want to lock
+	 * @param lockProps Properties object containing properties needed by class
+	 */
+	public TargetLock (String resourceId, UUID uuid, String owner, DistributedLockingProperties lockProps) {
+		this.resourceId = resourceId;
+		this.uuid = uuid;
+		this.owner = owner;
+		this.lockProps = lockProps;
+	}
+	
+	/**
+	 * obtain a lock
+	 */
+	public boolean lock() {
+		
+		return grabLock();
+	}
+	
+	/**
+	 * Unlock a resource by deleting it's associated record in the db
+	 */
+	public boolean unlock() {
+		return deleteLock();
+	}
+	
+	/**
+	 * "Grabs" lock by attempting to insert a new record in the db.
+	 *  If the insert fails due to duplicate key error resource is already locked
+	 *  so we call secondGrab. 
+	 */
+	private boolean grabLock() {
+
+		try (Connection conn = DriverManager.getConnection(lockProps.getDbUrl(), lockProps.getDbUser(),
+				lockProps.getDbPwd());
+
+				// try to insert a record into the table(thereby grabbing the lock)
+				PreparedStatement statement = conn
+						.prepareStatement("INSERT INTO pooling.locks (resourceId, host, owner, expirationTime) values (?, ?, ?, ?)");) {
+			statement.setString(1, this.resourceId);
+			statement.setString(2, this.uuid.toString());
+			statement.setString(3, this.owner);
+			statement.setLong(4, System.currentTimeMillis() + lockProps.getAgingProperty());
+
+			statement.executeUpdate();
+		}  catch (SQLException e) {
+			logger.error("error in TargetLock.grabLock()", e);
+			return secondGrab();
+		}
+
+		return true;
+	}
+
+	/**
+	 * A second attempt at grabbing a lock. It first attempts to update the lock in case it is expired.
+	 * If that fails, it attempts to insert a new record again
+	 */
+	private boolean secondGrab() {
+
+		try (Connection conn = DriverManager.getConnection(lockProps.getDbUrl(), lockProps.getDbUser(),
+				lockProps.getDbPwd());
+
+				PreparedStatement updateStatement = conn.prepareStatement("UPDATE pooling.locks SET host = ?, owner = ?, expirationTime = ? WHERE expirationTime <= ? AND resourceId = ?");
+				
+				PreparedStatement insertStatement = conn.prepareStatement("INSERT INTO pooling.locks (resourceId, host, owner, expirationTime) values (?, ?, ?, ?)");) {
+
+			updateStatement.setString(1, this.uuid.toString());
+			updateStatement.setString(2, this.owner);
+			updateStatement.setLong(3, System.currentTimeMillis() + lockProps.getAgingProperty());
+			updateStatement.setLong(4, System.currentTimeMillis());
+			updateStatement.setString(5, this.resourceId);
+
+			// The lock was expired and we grabbed it.
+			// return true
+			if (updateStatement.executeUpdate() == 1) {
+				return true;
+			}
+			// If our update does not return 1 row, the lock either has not expired
+			// or it was removed. Try one last grab
+			else {
+				insertStatement.setString(1, this.resourceId);
+				insertStatement.setString(2, this.uuid.toString());
+				insertStatement.setString(3, this.owner);
+				insertStatement.setLong(4, System.currentTimeMillis() + lockProps.getAgingProperty());
+
+					// If our insert returns 1 we successfully grabbed the lock
+				return (insertStatement.executeUpdate() == 1);
+			}
+
+		} catch (SQLException e) {
+			logger.error("error in TargetLock.secondGrab()", e);
+			return false;
+		}
+
+	}
+	
+	/**
+	 *To remove a lock we simply delete the record from the db 
+	 */
+	private boolean deleteLock() {
+
+		try (Connection conn = DriverManager.getConnection(lockProps.getDbUrl(), lockProps.getDbUser(),
+				lockProps.getDbPwd());
+
+				PreparedStatement deleteStatement = conn
+						.prepareStatement("DELETE FROM pooling.locks WHERE resourceId = ? AND owner = ? AND host = ?");) {
+
+			deleteStatement.setString(1, this.resourceId);
+			deleteStatement.setString(2, this.owner);
+			deleteStatement.setString(3, this.uuid.toString());
+			
+			return (deleteStatement.executeUpdate() == 1);
+
+		} catch (SQLException e) {
+			logger.error("error in TargetLock.deleteLock()", e);
+			return false;
+		}
+
+	}
+	
+	/**
+	 * Is the lock active
+	 */
+	public boolean isActive() {
+
+		try (Connection conn = DriverManager.getConnection(lockProps.getDbUrl(), lockProps.getDbUser(),
+				lockProps.getDbPwd());
+
+				PreparedStatement selectStatement = conn
+						.prepareStatement("SELECT * FROM pooling.locks WHERE resourceId = ? AND host = ? AND owner= ? AND expirationTime >= ?");) {
+			{
+				selectStatement.setString(1, this.resourceId);
+				selectStatement.setString(2, this.uuid.toString());
+				selectStatement.setString(3, this.owner);
+				selectStatement.setLong(4, System.currentTimeMillis());
+
+				ResultSet result = selectStatement.executeQuery();
+
+				// This will return true if the
+				// query returned at least one row
+				return result.first();
+
+			}
+		} catch (SQLException e) {
+			logger.error("error in TargetLock.isActive()", e);
+			return false;
+		}
+	}
+
+	/**
+	 * Is the resource locked
+	 */
+	public boolean isLocked() {
+
+		try (Connection conn = DriverManager.getConnection(lockProps.getDbUrl(), lockProps.getDbUser(),
+				lockProps.getDbPwd());
+
+				PreparedStatement selectStatement = conn
+						.prepareStatement("SELECT * FROM pooling.locks WHERE resourceId = ? AND expirationTime >= ?");) {
+			{
+				selectStatement.setString(1, this.resourceId);
+				selectStatement.setLong(2, System.currentTimeMillis());
+				ResultSet result = selectStatement.executeQuery();
+
+				// This will return true if the
+				// query returned at least one row
+				return result.first();
+
+			}
+		} catch (SQLException e) {
+			logger.error("error in TargetLock.isActive()", e);
+			return false;
+		}
+	}
+
+}