mirror of https://github.com/apache/activemq.git
AMQ-1618 Refine thread safety of pool access operations
git-svn-id: https://svn.apache.org/repos/asf/activemq/trunk@637218 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
David Jencks
parent
ceb7e1a86c
commit
8d28bbfdab
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@ -20,6 +20,8 @@ import java.util.ArrayList;
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import java.util.Iterator;
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import java.util.List;
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import java.util.concurrent.atomic.AtomicBoolean;
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import java.util.concurrent.locks.Lock;
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import java.util.concurrent.locks.ReentrantLock;
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import javax.jms.JMSException;
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import javax.jms.ServerSession;
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@ -45,9 +47,10 @@ public class ServerSessionPoolImpl implements ServerSessionPool {
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private final ActiveMQEndpointWorker activeMQAsfEndpointWorker;
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private final int maxSessions;
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private List<ServerSessionImpl> idleSessions = new ArrayList<ServerSessionImpl>();
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private List<ServerSessionImpl> activeSessions = new ArrayList<ServerSessionImpl>();
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private AtomicBoolean closing = new AtomicBoolean(false);
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private final List<ServerSessionImpl> idleSessions = new ArrayList<ServerSessionImpl>();
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private final List<ServerSessionImpl> activeSessions = new ArrayList<ServerSessionImpl>();
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private final Lock sessionLock = new ReentrantLock();
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private final AtomicBoolean closing = new AtomicBoolean(false);
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public ServerSessionPoolImpl(ActiveMQEndpointWorker activeMQAsfEndpointWorker, int maxSessions) {
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this.activeMQAsfEndpointWorker = activeMQAsfEndpointWorker;
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@ -100,48 +103,32 @@ public class ServerSessionPoolImpl implements ServerSessionPool {
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if (closing.get()) {
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throw new JMSException("Session Pool Shutting Down.");
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}
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ServerSessionImpl ss = null;
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synchronized (idleSessions) {
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if (idleSessions.size() > 0) {
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ss = idleSessions.remove(idleSessions.size() - 1);
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}
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sessionLock.lock();
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try {
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ss = getExistingServerSession(false);
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} finally {
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sessionLock.unlock();
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}
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if (ss != null) {
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synchronized (activeSessions) {
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activeSessions.add(ss);
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}
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if (LOG.isDebugEnabled()) {
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LOG.debug("Using idle session: " + ss);
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}
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return ss;
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}
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synchronized (activeSessions) {
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// Are we at the upper limit?
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if (activeSessions.size() >= maxSessions) {
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// then reuse the already created sessions..
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// This is going to queue up messages into a session for
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// processing.
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return getExistingServerSession();
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}
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}
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ss = createServerSessionImpl();
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// We may not be able to create a session due to the container
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// restricting us.
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if (ss == null) {
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synchronized (activeSessions) {
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if (activeSessions.isEmpty()) {
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throw new JMSException(
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"Endpoint factory did not allow creation any endpoints.");
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sessionLock.lock();
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try {
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// We may not be able to create a session due to the container
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// restricting us.
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if (ss == null) {
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if (activeSessions.isEmpty() && idleSessions.isEmpty()) {
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throw new JMSException("Endpoint factory did not allow creation of any endpoints.");
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}
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}
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return getExistingServerSession();
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}
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synchronized (activeSessions) {
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activeSessions.add(ss);
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ss = getExistingServerSession(true);
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} else {
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activeSessions.add(ss);
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}
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} finally {
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sessionLock.unlock();
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}
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if (LOG.isDebugEnabled()) {
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LOG.debug("Created a new session: " + ss);
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@ -150,6 +137,94 @@ public class ServerSessionPoolImpl implements ServerSessionPool {
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}
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/**
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* Must be called with sessionLock held.
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* Returns an idle session if one exists or an active session if no more
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* sessions can be created. Sessions can not be created if force is true
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* or activeSessions >= maxSessions.
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* @param force do not check activeSessions >= maxSessions, return an active connection anyway.
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* @return an already existing session.
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*/
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private ServerSessionImpl getExistingServerSession(boolean force) {
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ServerSessionImpl ss = null;
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if (idleSessions.size() > 0) {
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ss = idleSessions.remove(idleSessions.size() - 1);
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}
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if (ss != null) {
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activeSessions.add(ss);
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if (LOG.isDebugEnabled()) {
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LOG.debug("Using idle session: " + ss);
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}
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} else if (force || activeSessions.size() >= maxSessions) {
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// If we are at the upper limit
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// then reuse the already created sessions..
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// This is going to queue up messages into a session for
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// processing.
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ss = getExistingActiveServerSession();
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}
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return ss;
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}
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/**
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* Must be called with sessionLock held.
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* Returns the first session from activeSessions, shifting it to last.
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* @return session
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*/
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private ServerSessionImpl getExistingActiveServerSession() {
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ServerSessionImpl ss = null;
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if (!activeSessions.isEmpty()) {
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if (activeSessions.size() > 1) {
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// round robin
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ss = activeSessions.remove(0);
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activeSessions.add(ss);
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} else {
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ss = activeSessions.get(0);
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}
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}
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if (LOG.isDebugEnabled()) {
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LOG.debug("Reusing an active session: " + ss);
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}
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return ss;
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}
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public void returnToPool(ServerSessionImpl ss) {
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if (LOG.isDebugEnabled()) {
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LOG.debug("Session returned to pool: " + ss);
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}
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sessionLock.lock();
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try {
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activeSessions.remove(ss);
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idleSessions.add(ss);
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} finally {
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sessionLock.unlock();
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}
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synchronized (closing) {
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closing.notify();
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}
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}
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public void removeFromPool(ServerSessionImpl ss) {
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sessionLock.lock();
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try {
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activeSessions.remove(ss);
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} finally {
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sessionLock.unlock();
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}
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try {
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ActiveMQSession session = (ActiveMQSession)ss.getSession();
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List l = session.getUnconsumedMessages();
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for (Iterator i = l.iterator(); i.hasNext();) {
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dispatchToSession((MessageDispatch)i.next());
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}
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} catch (Throwable t) {
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LOG.error("Error redispatching unconsumed messages from stale session", t);
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}
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ss.close();
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synchronized (closing) {
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closing.notify();
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}
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}
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/**
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* @param messageDispatch
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* the message to dispatch
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@ -177,69 +252,15 @@ public class ServerSessionPoolImpl implements ServerSessionPool {
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serverSession.start();
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}
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/**
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* @return session
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*/
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private ServerSession getExistingServerSession() {
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ServerSessionImpl ss = null;
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if (!activeSessions.isEmpty()) {
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if (activeSessions.size() > 1) {
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// round robin
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ss = activeSessions.remove(0);
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activeSessions.add(ss);
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} else {
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ss = activeSessions.get(0);
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}
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}
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if (LOG.isDebugEnabled()) {
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LOG.debug("Reusing an active session: " + ss);
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}
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return ss;
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}
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public void returnToPool(ServerSessionImpl ss) {
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if (LOG.isDebugEnabled()) {
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LOG.debug("Session returned to pool: " + ss);
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}
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synchronized(activeSessions) {
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activeSessions.remove(ss);
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}
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synchronized(idleSessions) {
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idleSessions.add(ss);
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}
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synchronized (closing) {
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closing.notify();
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}
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}
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public void removeFromPool(ServerSessionImpl ss) {
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synchronized(activeSessions) {
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activeSessions.remove(ss);
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}
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try {
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ActiveMQSession session = (ActiveMQSession)ss.getSession();
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List l = session.getUnconsumedMessages();
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for (Iterator i = l.iterator(); i.hasNext();) {
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dispatchToSession((MessageDispatch)i.next());
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}
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} catch (Throwable t) {
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LOG.error("Error redispatching unconsumed messages from stale session", t);
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}
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ss.close();
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synchronized (closing) {
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closing.notify();
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}
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}
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public void close() {
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closing.set(true);
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closeIdleSessions();
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int activeCount = closeIdleSessions();
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// we may have to wait erroneously 250ms if an
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// active session is removed during our wait and we
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// are not notified
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while (getActiveSessionSize() > 0) {
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while (activeCount > 0) {
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if (LOG.isDebugEnabled()) {
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LOG.debug("Active Sessions = " + getActiveSessionSize());
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LOG.debug("Active Sessions = " + activeCount);
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}
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try {
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synchronized (closing) {
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@ -249,18 +270,21 @@ public class ServerSessionPoolImpl implements ServerSessionPool {
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Thread.currentThread().interrupt();
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return;
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}
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closeIdleSessions();
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activeCount = closeIdleSessions();
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}
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}
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private void closeIdleSessions() {
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synchronized(idleSessions) {
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for (Iterator<ServerSessionImpl> iter = idleSessions.iterator(); iter.hasNext();) {
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ServerSessionImpl ss = iter.next();
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private int closeIdleSessions() {
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sessionLock.lock();
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try {
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for (ServerSessionImpl ss : idleSessions) {
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ss.close();
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}
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idleSessions.clear();
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return activeSessions.size();
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} finally {
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sessionLock.unlock();
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}
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}
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@ -270,18 +294,12 @@ public class ServerSessionPoolImpl implements ServerSessionPool {
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public boolean isClosing() {
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return closing.get();
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}
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/**
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* @param closing The closing to set.
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*/
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public void setClosing(boolean closing) {
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this.closing.set(closing);
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}
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private int getActiveSessionSize() {
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synchronized(activeSessions) {
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return activeSessions.size();
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}
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}
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}
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