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package eu.dnetlib.dhp.common.lock;
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import java.security.InvalidParameterException;
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import java.util.Collections;
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import java.util.Map;
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import java.util.concurrent.Semaphore;
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import org.apache.commons.lang.StringUtils;
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import org.apache.hadoop.conf.Configuration;
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import org.apache.hadoop.ha.ZKFailoverController;
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import org.apache.log4j.Logger;
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import org.apache.zookeeper.CreateMode;
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import org.apache.zookeeper.KeeperException;
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import org.apache.zookeeper.Watcher.Event;
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import org.apache.zookeeper.ZooDefs;
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import org.apache.zookeeper.ZooKeeper;
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import com.google.common.base.Preconditions;
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import com.google.common.base.Stopwatch;
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import eu.dnetlib.dhp.common.java.PortBindings;
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import eu.dnetlib.dhp.common.java.porttype.PortType;
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/**
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* Zookeeper lock managing process. Blocks until lock is released.
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*
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* @author mhorst
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*
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*/
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public class LockManagingProcess implements eu.dnetlib.dhp.common.java.Process {
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public static final String DEFAULT_ROOT_NODE = "/cache";
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public static final String NODE_SEPARATOR = "/";
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public static final String PARAM_ZK_SESSION_TIMEOUT = "zk_session_timeout";
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public static final String PARAM_NODE_ID = "node_id";
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public static final String PARAM_LOCK_MODE = "mode";
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public static enum LockMode {
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obtain,
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release
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}
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public static final int DEFAULT_SESSION_TIMEOUT = 60000;
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public static final Logger log = Logger.getLogger(LockManagingProcess.class);
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@Override
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public Map<String, PortType> getInputPorts() {
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return Collections.emptyMap();
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}
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@Override
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public Map<String, PortType> getOutputPorts() {
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return Collections.emptyMap();
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}
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@Override
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public void run(PortBindings portBindings, Configuration conf,
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Map<String, String> parameters) throws Exception {
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Preconditions.checkArgument(parameters.containsKey(PARAM_NODE_ID), "node id not provided!");
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Preconditions.checkArgument(parameters.containsKey(PARAM_LOCK_MODE), "lock mode not provided!");
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String zkConnectionString = conf.get(ZKFailoverController.ZK_QUORUM_KEY);
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Preconditions.checkArgument(StringUtils.isNotBlank(zkConnectionString),
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"zookeeper quorum is unknown, invalid '%s' property value: %s", ZKFailoverController.ZK_QUORUM_KEY, zkConnectionString);
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int sessionTimeout = parameters.containsKey(PARAM_ZK_SESSION_TIMEOUT)?
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Integer.valueOf(parameters.get(PARAM_ZK_SESSION_TIMEOUT)) : DEFAULT_SESSION_TIMEOUT;
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final ZooKeeper zooKeeper = new ZooKeeper(zkConnectionString, sessionTimeout, (e) -> {
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// we are not interested in generic events
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});
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// initializing root node if does not exist
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if (zooKeeper.exists(DEFAULT_ROOT_NODE, false) == null) {
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log.info("initializing root node: " + DEFAULT_ROOT_NODE);
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zooKeeper.create(DEFAULT_ROOT_NODE, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
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log.info("root node initialized");
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}
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final String nodePath = generatePath(parameters.get(PARAM_NODE_ID), DEFAULT_ROOT_NODE);
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final Semaphore semaphore = new Semaphore(1);
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semaphore.acquire();
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switch(LockMode.valueOf(parameters.get(PARAM_LOCK_MODE))) {
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case obtain: {
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obtain(zooKeeper, nodePath, semaphore);
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break;
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}
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case release: {
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release(zooKeeper, nodePath);
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break;
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}
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default: {
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throw new InvalidParameterException("unsupported lock mode: " + parameters.get(PARAM_LOCK_MODE));
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}
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}
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}
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// ------------------------- PRIVATE --------------------------
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private void obtain(final ZooKeeper zooKeeper, final String nodePath, final Semaphore semaphore) throws KeeperException, InterruptedException {
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log.info("trying to obtain lock: " + nodePath);
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if (zooKeeper.exists(nodePath, (event) -> {
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if (Event.EventType.NodeDeleted == event.getType()) {
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try {
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log.info(nodePath + " lock release detected");
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log.info("creating new lock instance: " + nodePath + "...");
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zooKeeper.create(nodePath, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
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log.info("lock" + nodePath + " created");
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semaphore.release();
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} catch (KeeperException e) {
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throw new RuntimeException(e);
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} catch (InterruptedException e) {
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throw new RuntimeException(e);
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}
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}
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}) == null) {
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log.info("lock not found, creating new lock instance: " + nodePath);
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zooKeeper.create(nodePath, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
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log.info("lock" + nodePath + " created");
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semaphore.release();
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} else {
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// waiting until node is removed by other lock manager
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log.info("waiting until lock is released");
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Stopwatch timer = new Stopwatch().start();
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semaphore.acquire();
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log.info("lock released, waited for " + timer.elapsedMillis() + " ms");
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semaphore.release();
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}
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}
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private void release(final ZooKeeper zooKeeper, final String nodePath) throws InterruptedException, KeeperException {
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log.info("removing lock" + nodePath + "...");
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zooKeeper.delete(nodePath, -1);
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log.info("lock" + nodePath + " removed");
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}
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private static final String generatePath(String nodeId, String rootNode) {
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return rootNode + NODE_SEPARATOR + nodeId.replace('/', '_');
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}
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}
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