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/*
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* Copyright (c) 1996, 2005, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package sun.rmi.transport;
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import java.rmi.Remote;
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import java.rmi.RemoteException;
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import java.rmi.dgc.DGC;
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import java.rmi.dgc.Lease;
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import java.rmi.dgc.VMID;
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import java.rmi.server.LogStream;
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import java.rmi.server.ObjID;
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import java.rmi.server.RemoteServer;
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import java.rmi.server.ServerNotActiveException;
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import java.security.AccessController;
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import java.security.PrivilegedAction;
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import java.util.ArrayList;
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import java.util.HashSet;
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import java.util.HashMap;
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import java.util.Iterator;
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import java.util.List;
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import java.util.Map;
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import java.util.Set;
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import java.util.concurrent.Future;
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import java.util.concurrent.ScheduledExecutorService;
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import java.util.concurrent.TimeUnit;
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import sun.rmi.runtime.Log;
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import sun.rmi.runtime.RuntimeUtil;
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import sun.rmi.server.UnicastRef;
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import sun.rmi.server.UnicastServerRef;
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import sun.rmi.server.Util;
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import sun.security.action.GetLongAction;
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import sun.security.action.GetPropertyAction;
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/**
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* This class implements the guts of the server-side distributed GC
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* algorithm
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*
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* @author Ann Wollrath
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*/
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final class DGCImpl implements DGC {
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/* dgc system log */
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static final Log dgcLog = Log.getLog("sun.rmi.dgc", "dgc",
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LogStream.parseLevel(AccessController.doPrivileged(
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new GetPropertyAction("sun.rmi.dgc.logLevel"))));
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/** lease duration to grant to clients */
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private static final long leaseValue = // default 10 minutes
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AccessController.doPrivileged(
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new GetLongAction("java.rmi.dgc.leaseValue", 600000));
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/** lease check interval; default is half of lease grant duration */
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private static final long leaseCheckInterval =
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AccessController.doPrivileged(
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new GetLongAction("sun.rmi.dgc.checkInterval", leaseValue / 2));
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/** thread pool for scheduling delayed tasks */
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private static final ScheduledExecutorService scheduler =
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AccessController.doPrivileged(
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new RuntimeUtil.GetInstanceAction()).getScheduler();
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/** remote implementation of DGC interface for this VM */
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private static DGCImpl dgc;
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/** table that maps VMID to LeaseInfo */
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private Map<VMID,LeaseInfo> leaseTable = new HashMap<VMID,LeaseInfo>();
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/** checks for lease expiration */
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private Future<?> checker = null;
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/**
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* Return the remote implementation of the DGC interface for
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* this VM.
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*/
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static DGCImpl getDGCImpl() {
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return dgc;
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}
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/**
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* Construct a new server-side remote object collector at
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* a particular port. Disallow construction from outside.
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*/
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private DGCImpl() {}
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/**
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* The dirty call adds the VMID "vmid" to the set of clients
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* that hold references to the object associated with the ObjID
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* id. The long "sequenceNum" is used to detect late dirty calls. If
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* the VMID "vmid" is null, a VMID will be generated on the
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* server (for use by the client in subsequent calls) and
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* returned.
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*
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* The client must call the "dirty" method to renew the lease
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* before the "lease" time expires or all references to remote
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* objects in this VM that the client holds are considered
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* "unreferenced".
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*/
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public Lease dirty(ObjID[] ids, long sequenceNum, Lease lease) {
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VMID vmid = lease.getVMID();
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/*
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* The server specifies the lease value; the client has
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* no say in the matter.
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*/
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long duration = leaseValue;
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if (dgcLog.isLoggable(Log.VERBOSE)) {
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dgcLog.log(Log.VERBOSE, "vmid = " + vmid);
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}
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// create a VMID if one wasn't supplied
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if (vmid == null) {
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vmid = new VMID();
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if (dgcLog.isLoggable(Log.BRIEF)) {
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String clientHost;
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try {
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clientHost = RemoteServer.getClientHost();
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} catch (ServerNotActiveException e) {
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clientHost = "<unknown host>";
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}
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dgcLog.log(Log.BRIEF, " assigning vmid " + vmid +
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" to client " + clientHost);
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}
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}
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lease = new Lease(vmid, duration);
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// record lease information
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synchronized (leaseTable) {
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LeaseInfo info = leaseTable.get(vmid);
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if (info == null) {
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leaseTable.put(vmid, new LeaseInfo(vmid, duration));
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if (checker == null) {
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checker = scheduler.scheduleWithFixedDelay(
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new Runnable() {
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public void run() {
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checkLeases();
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}
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},
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leaseCheckInterval,
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leaseCheckInterval, TimeUnit.MILLISECONDS);
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}
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} else {
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info.renew(duration);
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}
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}
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for (ObjID id : ids) {
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if (dgcLog.isLoggable(Log.VERBOSE)) {
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dgcLog.log(Log.VERBOSE, "id = " + id +
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", vmid = " + vmid + ", duration = " + duration);
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}
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ObjectTable.referenced(id, sequenceNum, vmid);
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}
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// return the VMID used
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return lease;
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}
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/**
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* The clean call removes the VMID from the set of clients
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* that hold references to the object associated with the LiveRef
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* ref. The sequence number is used to detect late clean calls. If the
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* argument "strong" is true, then the clean call is a result of a
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* failed "dirty" call, thus the sequence number for the VMID needs
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* to be remembered until the client goes away.
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*/
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public void clean(ObjID[] ids, long sequenceNum, VMID vmid, boolean strong)
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{
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for (ObjID id : ids) {
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if (dgcLog.isLoggable(Log.VERBOSE)) {
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dgcLog.log(Log.VERBOSE, "id = " + id +
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", vmid = " + vmid + ", strong = " + strong);
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}
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ObjectTable.unreferenced(id, sequenceNum, vmid, strong);
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}
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}
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/**
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* Register interest in receiving a callback when this VMID
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* becomes inaccessible.
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*/
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void registerTarget(VMID vmid, Target target) {
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synchronized (leaseTable) {
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LeaseInfo info = leaseTable.get(vmid);
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if (info == null) {
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target.vmidDead(vmid);
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} else {
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info.notifySet.add(target);
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}
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}
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}
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/**
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* Remove notification request.
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*/
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void unregisterTarget(VMID vmid, Target target) {
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synchronized (leaseTable) {
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LeaseInfo info = leaseTable.get(vmid);
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if (info != null) {
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info.notifySet.remove(target);
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}
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}
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}
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/**
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* Check if leases have expired. If a lease has expired, remove
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* it from the table and notify all interested parties that the
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* VMID is essentially "dead".
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*
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* @return if true, there are leases outstanding; otherwise leases
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* no longer need to be checked
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*/
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private void checkLeases() {
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long time = System.currentTimeMillis();
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/* List of vmids that need to be removed from the leaseTable */
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List<LeaseInfo> toUnregister = new ArrayList<LeaseInfo>();
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/* Build a list of leaseInfo objects that need to have
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* targets removed from their notifySet. Remove expired
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* leases from leaseTable.
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*/
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synchronized (leaseTable) {
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Iterator<LeaseInfo> iter = leaseTable.values().iterator();
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while (iter.hasNext()) {
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LeaseInfo info = iter.next();
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if (info.expired(time)) {
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toUnregister.add(info);
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iter.remove();
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}
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}
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if (leaseTable.isEmpty()) {
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checker.cancel(false);
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checker = null;
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}
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}
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/* Notify and unegister targets without holding the lock on
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* the leaseTable so we avoid deadlock.
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*/
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for (LeaseInfo info : toUnregister) {
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for (Target target : info.notifySet) {
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target.vmidDead(info.vmid);
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}
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}
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}
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static {
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/*
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* "Export" the singleton DGCImpl in a context isolated from
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* the arbitrary current thread context.
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*/
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AccessController.doPrivileged(new PrivilegedAction<Void>() {
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public Void run() {
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ClassLoader savedCcl =
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Thread.currentThread().getContextClassLoader();
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try {
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Thread.currentThread().setContextClassLoader(
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ClassLoader.getSystemClassLoader());
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/*
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* Put remote collector object in table by hand to prevent
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* listen on port. (UnicastServerRef.exportObject would
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* cause transport to listen.)
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*/
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try {
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dgc = new DGCImpl();
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ObjID dgcID = new ObjID(ObjID.DGC_ID);
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LiveRef ref = new LiveRef(dgcID, 0);
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UnicastServerRef disp = new UnicastServerRef(ref);
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Remote stub =
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Util.createProxy(DGCImpl.class,
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new UnicastRef(ref), true);
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disp.setSkeleton(dgc);
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Target target =
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new Target(dgc, disp, stub, dgcID, true);
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ObjectTable.putTarget(target);
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} catch (RemoteException e) {
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throw new Error(
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"exception initializing server-side DGC", e);
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}
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} finally {
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Thread.currentThread().setContextClassLoader(savedCcl);
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}
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return null;
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}
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});
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}
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private static class LeaseInfo {
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VMID vmid;
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long expiration;
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Set<Target> notifySet = new HashSet<Target>();
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LeaseInfo(VMID vmid, long lease) {
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this.vmid = vmid;
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expiration = System.currentTimeMillis() + lease;
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}
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synchronized void renew(long lease) {
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long newExpiration = System.currentTimeMillis() + lease;
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if (newExpiration > expiration)
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expiration = newExpiration;
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}
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boolean expired(long time) {
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if (expiration < time) {
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if (dgcLog.isLoggable(Log.BRIEF)) {
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dgcLog.log(Log.BRIEF, vmid.toString());
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}
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return true;
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} else {
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return false;
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}
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}
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}
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}
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