Implementation of distributed locking feature

This feature is a very basic implementation of a distributed locking
system.

Issue-ID: POLICY-699
Change-Id: I012fd37926ccbbdd87a3e4acb2788b53680115f0
Signed-off-by: Magnusen, Drew (dm741q) <dm741q@att.com>

5 files changed, 630 insertions, 0 deletions

diff --git a/feature-distributed-locking/src/main/java/org/onap/policy/distributed/locking/DistributedLockingFeature.java b/feature-distributed-locking/src/main/java/org/onap/policy/distributed/locking/DistributedLockingFeature.java
new file mode 100644
index 00000000..cc7a7a12
--- /dev/null
+++ b/feature-distributed-locking/src/main/java/org/onap/policy/distributed/locking/DistributedLockingFeature.java
@@ -0,0 +1,158 @@
+/*
+ * ============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.SQLException;
+import java.util.UUID;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+import org.onap.policy.common.utils.properties.exception.PropertyException;
+import org.onap.policy.drools.core.lock.LockRequestFuture;
+import org.onap.policy.drools.core.lock.PolicyResourceLockFeatureAPI;
+import org.onap.policy.drools.features.PolicyEngineFeatureAPI;
+import org.onap.policy.drools.persistence.SystemPersistence;
+import org.onap.policy.drools.system.PolicyEngine;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class DistributedLockingFeature implements PolicyEngineFeatureAPI, PolicyResourceLockFeatureAPI {
+	
+	/**
+	 * Logger instance
+	 */
+	private static final Logger logger = LoggerFactory.getLogger(DistributedLockingFeature.class);
+	
+	/**
+	 * Properties Configuration Name
+	 */
+	public static final String CONFIGURATION_PROPERTIES_NAME = "feature-distributed-locking";
+	
+	/**
+	 * Properties for locking feature
+	 */
+	private DistributedLockingProperties lockProps;
+	
+	/**
+	 *ScheduledExecutorService for LockHeartbeat 
+	 */
+	private ScheduledExecutorService scheduledExecutorService;
+	
+	/**
+	 * UUID 
+	 */
+	private static final UUID uuid = UUID.randomUUID();
+	
+	/**
+	 * Config directory
+	 */
+	@Override
+	public int getSequenceNumber() {
+        return 1000;
+	}
+	
+	@Override
+	public Future<Boolean> beforeLock(String resourceId, String owner, Callback callback) {
+		
+		TargetLock tLock = new TargetLock(resourceId, this.uuid, owner, lockProps);
+		
+		return new LockRequestFuture(resourceId, owner, tLock.lock());
+				
+	}
+
+	@Override
+	public Boolean beforeUnlock(String resourceId, String owner) {
+		TargetLock tLock = new TargetLock(resourceId, this.uuid, owner, lockProps);
+		
+		return tLock.unlock();
+	}
+	
+	@Override
+	public Boolean beforeIsLockedBy(String resourceId, String owner) {
+		TargetLock tLock = new TargetLock(resourceId, this.uuid, owner, lockProps);
+		
+		return tLock.isActive();
+	}
+	
+	@Override
+	public Boolean beforeIsLocked(String resourceId) {
+		TargetLock tLock = new TargetLock(resourceId, this.uuid, "dummyOwner", lockProps);
+		
+		return tLock.isLocked();
+	}
+	
+	@Override
+	public boolean afterStart(PolicyEngine engine) {
+
+		try {
+			this.lockProps = new DistributedLockingProperties(SystemPersistence.manager.getProperties(DistributedLockingFeature.CONFIGURATION_PROPERTIES_NAME));
+		} catch (PropertyException e) {
+			logger.error("DistributedLockingFeature feature properies have not been loaded", e);
+			throw new DistributedLockingFeatureException(e);
+		}
+		
+		long heartbeatInterval = this.lockProps.getHeartBeatIntervalProperty();
+		
+		cleanLockTable();
+		Heartbeat heartbeat = new Heartbeat(this.uuid, lockProps);
+		
+		this.scheduledExecutorService = Executors.newScheduledThreadPool(1);
+		this.scheduledExecutorService.scheduleAtFixedRate(heartbeat, heartbeatInterval, heartbeatInterval, TimeUnit.MILLISECONDS);
+		return false;
+	}
+	
+	/**
+	 * This method kills the heartbeat thread and calls refreshLockTable which removes
+	 * any records from the db where the current host is the owner.
+	 */
+	@Override
+	public boolean beforeShutdown(PolicyEngine engine) {
+		scheduledExecutorService.shutdown();
+		cleanLockTable();
+		return false;
+	}
+
+	/**
+	 * This method removes all records owned by the current host from the db.
+	 */
+	private void cleanLockTable() {
+		
+	    try (Connection conn = DriverManager.getConnection(lockProps.getDbUrl(), 
+			lockProps.getDbUser(),
+			lockProps.getDbPwd());
+	    	PreparedStatement statement = conn.prepareStatement("DELETE FROM pooling.locks WHERE host = ? OR expirationTime < ?");
+	    	){
+			
+				statement.setString(1, this.uuid.toString());
+				statement.setLong(2, System.currentTimeMillis());
+				statement.executeUpdate();
+			
+		} catch (SQLException e) {
+			logger.error("error in refreshLockTable()", e);
+		}
+		
+	}
+	
+}
diff --git a/feature-distributed-locking/src/main/java/org/onap/policy/distributed/locking/DistributedLockingFeatureException.java b/feature-distributed-locking/src/main/java/org/onap/policy/distributed/locking/DistributedLockingFeatureException.java
new file mode 100644
index 00000000..f28ccbc9
--- /dev/null
+++ b/feature-distributed-locking/src/main/java/org/onap/policy/distributed/locking/DistributedLockingFeatureException.java
@@ -0,0 +1,34 @@
+/*
+ * ============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;
+
+public class DistributedLockingFeatureException extends RuntimeException {
+	private static final long serialVersionUID = 1L;
+
+	/**
+	 * 
+	 * @param e
+	 *            exception to be wrapped
+	 */
+	public DistributedLockingFeatureException(Exception e) {
+		super(e);
+	}
+}
diff --git a/feature-distributed-locking/src/main/java/org/onap/policy/distributed/locking/DistributedLockingProperties.java b/feature-distributed-locking/src/main/java/org/onap/policy/distributed/locking/DistributedLockingProperties.java
new file mode 100644
index 00000000..139bfb7b
--- /dev/null
+++ b/feature-distributed-locking/src/main/java/org/onap/policy/distributed/locking/DistributedLockingProperties.java
@@ -0,0 +1,127 @@
+/*
+ * ============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.util.Properties;
+
+import org.onap.policy.common.utils.properties.PropertyConfiguration;
+import org.onap.policy.common.utils.properties.exception.PropertyException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+
+public class DistributedLockingProperties extends PropertyConfiguration{
+	
+	private static final Logger  logger = LoggerFactory.getLogger(DistributedLockingProperties.class);
+	
+	/**
+     * Feature properties all begin with this prefix.
+     */
+    public static final String PREFIX = "distributed.locking.";
+    
+	public static final String DB_DRIVER = "javax.persistence.jdbc.driver";
+	public static final String DB_URL = "javax.persistence.jdbc.url";
+	public static final String DB_USER = "javax.persistence.jdbc.user";
+	public static final String DB_PWD = "javax.persistence.jdbc.password";
+	public static final String AGING_PROPERTY = PREFIX + "lock.aging";
+	public static final String HEARTBEAT_INTERVAL_PROPERTY = PREFIX + "heartbeat.interval";
+	
+	/**
+     * Properties from which this was constructed.
+     */
+    private Properties source;
+
+    /**
+     * Database driver
+     */
+    @Property(name = DB_DRIVER)
+    private String dbDriver;
+    
+    /**
+     * Database url
+     */
+    @Property(name = DB_URL)
+    private String dbUrl;
+    
+    /**
+     * Database user
+     */
+    @Property(name = DB_USER)
+    private String dbUser;
+    
+    /**
+     * Database password
+     */
+    @Property(name = DB_PWD)
+    private String dbPwd;
+    
+    /**
+     * Used to set expiration time for lock.
+     */
+    @Property(name = AGING_PROPERTY, defaultValue = "300000")
+    private long agingProperty;
+    
+    /**
+     * Indicates intervals at which we refresh locks.
+     */
+    @Property(name = HEARTBEAT_INTERVAL_PROPERTY, defaultValue = "60000")
+    private long heartBeatIntervalProperty;
+
+    public DistributedLockingProperties(Properties props) throws PropertyException {
+    	super(props);
+    	source = props;
+    }
+
+
+	public Properties getSource() {
+		return source;
+	}
+
+
+	public String getDbDriver() {
+		return dbDriver;
+	}
+
+
+	public String getDbUrl() {
+		return dbUrl;
+	}
+
+
+	public String getDbUser() {
+		return dbUser;
+	}
+
+
+	public String getDbPwd() {
+		return dbPwd;
+	}
+
+
+	public long getAgingProperty() {
+		return agingProperty;
+	}
+
+
+	public long getHeartBeatIntervalProperty() {
+		return heartBeatIntervalProperty;
+	}
+
+}
diff --git a/feature-distributed-locking/src/main/java/org/onap/policy/distributed/locking/Heartbeat.java b/feature-distributed-locking/src/main/java/org/onap/policy/distributed/locking/Heartbeat.java
new file mode 100644
index 00000000..c753dba9
--- /dev/null
+++ b/feature-distributed-locking/src/main/java/org/onap/policy/distributed/locking/Heartbeat.java
@@ -0,0 +1,78 @@
+/*
+ * ============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.SQLException;
+import java.util.Properties;
+import java.util.UUID;
+
+import org.onap.policy.drools.utils.NetworkUtil;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * 
+ * This runnable class scans the locks table for all locks owned by this host.
+ * It refreshes the expiration time of each lock using the locking.distributed.aging
+ * property
+ *
+ */
+public class Heartbeat implements Runnable{
+
+	private static final Logger logger = LoggerFactory.getLogger(Heartbeat.class);
+
+	/**
+	 * Properties object containing properties needed by class
+	 */
+	private DistributedLockingProperties lockProps;
+
+	/**
+	 * UUID 
+	 */
+	private UUID uuid;
+	
+	public Heartbeat(UUID uuid, DistributedLockingProperties lockProps) {
+		this.lockProps = lockProps;
+		this.uuid = uuid;
+	}
+	
+	@Override
+	public void run() {
+
+		long expirationAge = lockProps.getAgingProperty();
+
+		try (Connection conn = DriverManager.getConnection(lockProps.getDbUrl(), lockProps.getDbUser(),
+				lockProps.getDbPwd());
+			PreparedStatement statement = conn
+						.prepareStatement("UPDATE pooling.locks SET expirationTime = ? WHERE host = ?");) {
+
+			statement.setLong(1, System.currentTimeMillis() + expirationAge);
+			statement.setString(2, this.uuid.toString());
+			statement.executeUpdate();
+		} catch (SQLException e) {
+			logger.error("error in Heartbeat.run()", e);
+		}
+
+	}
+}
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
--- /dev/null
+++ 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;
+		}
+	}
+
+}