/* * Copyright (c) 1996, 2008, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */package sun.rmi.transport; import java.lang.ref.PhantomReference;import java.lang.ref.ReferenceQueue;import java.security.AccessController;import java.security.PrivilegedAction;import java.util.HashMap;import java.util.HashSet;import java.util.Iterator;import java.util.List;import java.util.Map;import java.util.Set;import java.rmi.ConnectException;import java.rmi.RemoteException;import java.rmi.dgc.DGC;import java.rmi.dgc.Lease;import java.rmi.dgc.VMID;import java.rmi.server.ObjID;import sun.misc.GC;import sun.rmi.runtime.NewThreadAction;import sun.rmi.server.UnicastRef;import sun.rmi.server.Util;import sun.security.action.GetLongAction; /** * DGCClient implements the client-side of the RMI distributed garbage * collection system. * * The external interface to DGCClient is the "registerRefs" method. * When a LiveRef to a remote object enters the VM, it needs to be * registered with the DGCClient to participate in distributed garbage * collection. * * When the first LiveRef to a particular remote object is registered, * a "dirty" call is made to the server-side distributed garbage * collector for the remote object, which returns a lease guaranteeing * that the server-side DGC will not collect the remote object for a * certain period of time. While LiveRef instances to remote objects * on a particular server exist, the DGCClient periodically sends more * "dirty" calls to renew its lease. * * The DGCClient tracks the local reachability of registered LiveRef * instances (using phantom references). When the LiveRef instance * for a particular remote object becomes garbage collected locally, * a "clean" call is made to the server-side distributed garbage * collector, indicating that the server no longer needs to keep the * remote object alive for this client. * * @see java.rmi.dgc.DGC, sun.rmi.transport.DGCImpl * * @author Ann Wollrath * @author Peter Jones */final class DGCClient { /** next sequence number for DGC calls (access synchronized on class) */ private static long nextSequenceNum = Long.MIN_VALUE; /** unique identifier for this VM as a client of DGC */ private static VMID vmid = new VMID(); /** lease duration to request (usually ignored by server) */ private static final long leaseValue = // default 10 minutes AccessController.doPrivileged( new GetLongAction("java.rmi.dgc.leaseValue", 600000)).longValue(); /** maximum interval between retries of failed clean calls */ private static final long cleanInterval = // default 3 minutes AccessController.doPrivileged( new GetLongAction("sun.rmi.dgc.cleanInterval", 180000)).longValue(); /** maximum interval between complete garbage collections of local heap */ private static final long gcInterval = // default 1 hour AccessController.doPrivileged( new GetLongAction("sun.rmi.dgc.client.gcInterval", 3600000)).longValue(); /** minimum retry count for dirty calls that fail */ private static final int dirtyFailureRetries = 5; /** retry count for clean calls that fail with ConnectException */ private static final int cleanFailureRetries = 5; /** constant empty ObjID array for lease renewal optimization */ private static final ObjID[] emptyObjIDArray = new ObjID[0]; /** ObjID for server-side DGC object */ private static final ObjID dgcID = new ObjID(ObjID.DGC_ID); /* * Disallow anyone from creating one of these. */ private DGCClient() {} /** * Register the LiveRef instances in the supplied list to participate * in distributed garbage collection. * * All of the LiveRefs in the list must be for remote objects at the * given endpoint. */ static void registerRefs(Endpoint ep, List refs) { /* * Look up the given endpoint and register the refs with it. * The retrieved entry may get removed from the global endpoint * table before EndpointEntry.registerRefs() is able to acquire * its lock; in this event, it returns false, and we loop and * try again. */ EndpointEntry epEntry; do { epEntry = EndpointEntry.lookup(ep); } while (!epEntry.registerRefs(refs)); } /** * Get the next sequence number to be used for a dirty or clean * operation from this VM. This method should only be called while * synchronized on the EndpointEntry whose data structures the * operation affects. */ private static synchronized long getNextSequenceNum() { return nextSequenceNum++; } /** * Given the length of a lease and the time that it was granted, * compute the absolute time at which it should be renewed, giving * room for reasonable computational and communication delays. */ private static long computeRenewTime(long grantTime, long duration) { /* * REMIND: This algorithm should be more sophisticated, waiting * a longer fraction of the lease duration for longer leases. */ return grantTime + (duration / 2); } /** * EndpointEntry encapsulates the client-side DGC information specific * to a particular Endpoint. Of most significance is the table that * maps LiveRef value to RefEntry objects and the renew/clean thread * that handles asynchronous client-side DGC operations. */ private static class EndpointEntry { /** the endpoint that this entry is for */ private Endpoint endpoint; /** synthesized reference to the remote server-side DGC */ private DGC dgc; /** table of refs held for endpoint: maps LiveRef to RefEntry */ private Map refTable = new HashMap(5); /** set of RefEntry instances from last (failed) dirty call */ private Set invalidRefs = new HashSet(5); /** true if this entry has been removed from the global table */ private boolean removed = false; /** absolute time to renew current lease to this endpoint */ private long renewTime = Long.MAX_VALUE; /** absolute time current lease to this endpoint will expire */ private long expirationTime = Long.MIN_VALUE; /** count of recent dirty calls that have failed */ private int dirtyFailures = 0; /** absolute time of first recent failed dirty call */ private long dirtyFailureStartTime; /** (average) elapsed time for recent failed dirty calls */ private long dirtyFailureDuration; /** renew/clean thread for handling lease renewals and clean calls */ private Thread renewCleanThread; /** true if renew/clean thread may be interrupted */ private boolean interruptible = false; /** reference queue for phantom references */ private ReferenceQueue refQueue = new ReferenceQueue(); /** set of clean calls that need to be made */ private Set pendingCleans = new HashSet(5); /** global endpoint table: maps Endpoint to EndpointEntry */ private static Map endpointTable = new HashMap(5); /** handle for GC latency request (for future cancellation) */ private static GC.LatencyRequest gcLatencyRequest = null; /** * Look up the EndpointEntry for the given Endpoint. An entry is * created if one does not already exist. */ public static EndpointEntry lookup(Endpoint ep) { synchronized (endpointTable) { EndpointEntry entry = (EndpointEntry) endpointTable.get(ep); if (entry == null) { entry = new EndpointEntry(ep); endpointTable.put(ep, entry); /* * While we are tracking live remote references registered * in this VM, request a maximum latency for inspecting the * entire heap from the local garbage collector, to place * an upper bound on the time to discover remote references * that have become unreachable (see bugid 4171278). */ if (gcLatencyRequest == null) { gcLatencyRequest = GC.requestLatency(gcInterval); } } return entry; } } private EndpointEntry(final Endpoint endpoint) { this.endpoint = endpoint; try { LiveRef dgcRef = new LiveRef(dgcID, endpoint, false); dgc = (DGC) Util.createProxy(DGCImpl.class, new UnicastRef(dgcRef), true); } catch (RemoteException e) { throw new Error("internal error creating DGC stub"); } renewCleanThread = AccessController.doPrivileged( new NewThreadAction(new RenewCleanThread(), "RenewClean-" + endpoint, true)); renewCleanThread.start(); } /** * Register the LiveRef instances in the supplied list to participate * in distributed garbage collection. * * This method returns false if this entry was removed from the * global endpoint table (because it was empty) before these refs * could be registered. In that case, a new EndpointEntry needs * to be looked up. * * This method must NOT be called while synchronized on this entry. */ public boolean registerRefs(List refs) { assert !Thread.holdsLock(this); Set refsToDirty = null; // entries for refs needing dirty long sequenceNum; // sequence number for dirty call synchronized (this) { if (removed) { return false; } Iterator iter = refs.iterator(); while (iter.hasNext()) { LiveRef ref = (LiveRef) iter.next(); assert ref.getEndpoint().equals(endpoint); RefEntry refEntry = (RefEntry) refTable.get(ref); if (refEntry == null) { LiveRef refClone = (LiveRef) ref.clone(); refEntry = new RefEntry(refClone); refTable.put(refClone, refEntry); if (refsToDirty == null) { refsToDirty = new HashSet(5); } refsToDirty.add(refEntry); } refEntry.addInstanceToRefSet(ref); } if (refsToDirty == null) { return true; } refsToDirty.addAll(invalidRefs); invalidRefs.clear(); sequenceNum = getNextSequenceNum(); } makeDirtyCall(refsToDirty, sequenceNum); return true; } /** * Remove the given RefEntry from the ref table. If that makes * the ref table empty, remove this entry from the global endpoint * table. * * This method must ONLY be called while synchronized on this entry. */ private void removeRefEntry(RefEntry refEntry) { assert Thread.holdsLock(this); assert !removed; assert refTable.containsKey(refEntry.getRef()); refTable.remove(refEntry.getRef()); invalidRefs.remove(refEntry); if (refTable.isEmpty()) { synchronized (endpointTable) { endpointTable.remove(endpoint); Transport transport = endpoint.getOutboundTransport(); transport.free(endpoint); /* * If there are no longer any live remote references * registered, we are no longer concerned with the * latency of local garbage collection here. */ if (endpointTable.isEmpty()) { assert gcLatencyRequest != null; gcLatencyRequest.cancel(); gcLatencyRequest = null; } removed = true; } } } /** * Make a DGC dirty call to this entry's endpoint, for the ObjIDs * corresponding to the given set of refs and with the given * sequence number. * * This method must NOT be called while synchronized on this entry. */ private void makeDirtyCall(Set refEntries, long sequenceNum) { assert !Thread.holdsLock(this); ObjID[] ids; if (refEntries != null) { ids = createObjIDArray(refEntries); } else { ids = emptyObjIDArray; } long startTime = System.currentTimeMillis(); try { Lease lease = dgc.dirty(ids, sequenceNum, new Lease(vmid, leaseValue)); long duration = lease.getValue(); long newRenewTime = computeRenewTime(startTime, duration); long newExpirationTime = startTime + duration; synchronized (this) { dirtyFailures = 0; setRenewTime(newRenewTime); expirationTime = newExpirationTime; } } catch (Exception e) { long endTime = System.currentTimeMillis(); synchronized (this) { dirtyFailures++; if (dirtyFailures == 1) { /* * If this was the first recent failed dirty call, * reschedule another one immediately, in case there * was just a transient network problem, and remember * the start time and duration of this attempt for * future calculations of the delays between retries. */ dirtyFailureStartTime = startTime; dirtyFailureDuration = endTime - startTime; setRenewTime(endTime); } else { /* * For each successive failed dirty call, wait for a * (binary) exponentially increasing delay before * retrying, to avoid network congestion. */ int n = dirtyFailures - 2; if (n == 0) { /* * Calculate the initial retry delay from the * average time elapsed for each of the first * two failed dirty calls. The result must be * at least 1000ms, to prevent a tight loop. */ dirtyFailureDuration = Math.max((dirtyFailureDuration + (endTime - startTime)) >> 1, 1000); } long newRenewTime = endTime + (dirtyFailureDuration << n); /* * Continue if the last known held lease has not * expired, or else at least a fixed number of times, * or at least until we've tried for a fixed amount * of time (the default lease value we request). */ if (newRenewTime < expirationTime || dirtyFailures < dirtyFailureRetries || newRenewTime < dirtyFailureStartTime + leaseValue) { setRenewTime(newRenewTime); } else { /* * Give up: postpone lease renewals until next * ref is registered for this endpoint. */ setRenewTime(Long.MAX_VALUE); } } if (refEntries != null) { /* * Add all of these refs to the set of refs for this * endpoint that may be invalid (this VM may not be in * the server's referenced set), so that we will * attempt to explicitly dirty them again in the * future. */ invalidRefs.addAll(refEntries); /* * Record that a dirty call has failed for all of these * refs, so that clean calls for them in the future * will be strong. */ Iterator iter = refEntries.iterator(); while (iter.hasNext()) { RefEntry refEntry = (RefEntry) iter.next(); refEntry.markDirtyFailed(); } } /* * If the last known held lease will have expired before * the next renewal, all refs might be invalid. */ if (renewTime >= expirationTime) { invalidRefs.addAll(refTable.values()); } } } } /** * Set the absolute time at which the lease for this entry should * be renewed. * * This method must ONLY be called while synchronized on this entry. */ private void setRenewTime(long newRenewTime) { assert Thread.holdsLock(this); if (newRenewTime < renewTime) { renewTime = newRenewTime; if (interruptible) { AccessController.doPrivileged( new PrivilegedAction<Void>() { public Void run() { renewCleanThread.interrupt(); return null; } }); } } else { renewTime = newRenewTime; } } /** * RenewCleanThread handles the asynchronous client-side DGC activity * for this entry: renewing the leases and making clean calls. */ private class RenewCleanThread implements Runnable { public void run() { do { long timeToWait; RefEntry.PhantomLiveRef phantom = null; boolean needRenewal = false; Set refsToDirty = null;Lines 1–500 of 807. 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/* * Copyright (c) 1996, 2008, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package sun.rmi.transport; import java.lang.ref.PhantomReference; import java.lang.ref.ReferenceQueue; import java.security.AccessController; import java.security.PrivilegedAction; import java.util.HashMap; import java.util.HashSet; import java.util.Iterator; import java.util.List; import java.util.Map; import java.util.Set; import java.rmi.ConnectException; import java.rmi.RemoteException; import java.rmi.dgc.DGC; import java.rmi.dgc.Lease; import java.rmi.dgc.VMID; import java.rmi.server.ObjID; import sun.misc.GC; import sun.rmi.runtime.NewThreadAction; import sun.rmi.server.UnicastRef; import sun.rmi.server.Util; import sun.security.action.GetLongAction; /** * DGCClient implements the client-side of the RMI distributed garbage * collection system. * * The external interface to DGCClient is the "registerRefs" method. * When a LiveRef to a remote object enters the VM, it needs to be * registered with the DGCClient to participate in distributed garbage * collection. * * When the first LiveRef to a particular remote object is registered, * a "dirty" call is made to the server-side distributed garbage * collector for the remote object, which returns a lease guaranteeing * that the server-side DGC will not collect the remote object for a * certain period of time. While LiveRef instances to remote objects * on a particular server exist, the DGCClient periodically sends more * "dirty" calls to renew its lease. * * The DGCClient tracks the local reachability of registered LiveRef * instances (using phantom references). When the LiveRef instance * for a particular remote object becomes garbage collected locally, * a "clean" call is made to the server-side distributed garbage * collector, indicating that the server no longer needs to keep the * remote object alive for this client. * * @see java.rmi.dgc.DGC, sun.rmi.transport.DGCImpl * * @author Ann Wollrath * @author Peter Jones */ final class DGCClient { /** next sequence number for DGC calls (access synchronized on class) */ private static long nextSequenceNum = Long.MIN_VALUE; /** unique identifier for this VM as a client of DGC */ private static VMID vmid = new VMID(); /** lease duration to request (usually ignored by server) */ private static final long leaseValue = // default 10 minutes AccessController.doPrivileged( new GetLongAction("java.rmi.dgc.leaseValue", 600000)).longValue(); /** maximum interval between retries of failed clean calls */ private static final long cleanInterval = // default 3 minutes AccessController.doPrivileged( new GetLongAction("sun.rmi.dgc.cleanInterval", 180000)).longValue(); /** maximum interval between complete garbage collections of local heap */ private static final long gcInterval = // default 1 hour AccessController.doPrivileged( new GetLongAction("sun.rmi.dgc.client.gcInterval", 3600000)).longValue(); /** minimum retry count for dirty calls that fail */ private static final int dirtyFailureRetries = 5; /** retry count for clean calls that fail with ConnectException */ private static final int cleanFailureRetries = 5; /** constant empty ObjID array for lease renewal optimization */ private static final ObjID[] emptyObjIDArray = new ObjID[0]; /** ObjID for server-side DGC object */ private static final ObjID dgcID = new ObjID(ObjID.DGC_ID); /* * Disallow anyone from creating one of these. */ private DGCClient() {} /** * Register the LiveRef instances in the supplied list to participate * in distributed garbage collection. * * All of the LiveRefs in the list must be for remote objects at the * given endpoint. */ static void registerRefs(Endpoint ep, List refs) { /* * Look up the given endpoint and register the refs with it. * The retrieved entry may get removed from the global endpoint * table before EndpointEntry.registerRefs() is able to acquire * its lock; in this event, it returns false, and we loop and * try again. */ EndpointEntry epEntry; do { epEntry = EndpointEntry.lookup(ep); } while (!epEntry.registerRefs(refs)); } /** * Get the next sequence number to be used for a dirty or clean * operation from this VM. This method should only be called while * synchronized on the EndpointEntry whose data structures the * operation affects. */ private static synchronized long getNextSequenceNum() { return nextSequenceNum++; } /** * Given the length of a lease and the time that it was granted, * compute the absolute time at which it should be renewed, giving * room for reasonable computational and communication delays. */ private static long computeRenewTime(long grantTime, long duration) { /* * REMIND: This algorithm should be more sophisticated, waiting * a longer fraction of the lease duration for longer leases. */ return grantTime + (duration / 2); } /** * EndpointEntry encapsulates the client-side DGC information specific * to a particular Endpoint. Of most significance is the table that * maps LiveRef value to RefEntry objects and the renew/clean thread * that handles asynchronous client-side DGC operations. */ private static class EndpointEntry { /** the endpoint that this entry is for */ private Endpoint endpoint; /** synthesized reference to the remote server-side DGC */ private DGC dgc; /** table of refs held for endpoint: maps LiveRef to RefEntry */ private Map refTable = new HashMap(5); /** set of RefEntry instances from last (failed) dirty call */ private Set invalidRefs = new HashSet(5); /** true if this entry has been removed from the global table */ private boolean removed = false; /** absolute time to renew current lease to this endpoint */ private long renewTime = Long.MAX_VALUE; /** absolute time current lease to this endpoint will expire */ private long expirationTime = Long.MIN_VALUE; /** count of recent dirty calls that have failed */ private int dirtyFailures = 0; /** absolute time of first recent failed dirty call */ private long dirtyFailureStartTime; /** (average) elapsed time for recent failed dirty calls */ private long dirtyFailureDuration; /** renew/clean thread for handling lease renewals and clean calls */ private Thread renewCleanThread; /** true if renew/clean thread may be interrupted */ private boolean interruptible = false; /** reference queue for phantom references */ private ReferenceQueue refQueue = new ReferenceQueue(); /** set of clean calls that need to be made */ private Set pendingCleans = new HashSet(5); /** global endpoint table: maps Endpoint to EndpointEntry */ private static Map endpointTable = new HashMap(5); /** handle for GC latency request (for future cancellation) */ private static GC.LatencyRequest gcLatencyRequest = null; /** * Look up the EndpointEntry for the given Endpoint. An entry is * created if one does not already exist. */ public static EndpointEntry lookup(Endpoint ep) { synchronized (endpointTable) { EndpointEntry entry = (EndpointEntry) endpointTable.get(ep); if (entry == null) { entry = new EndpointEntry(ep); endpointTable.put(ep, entry); /* * While we are tracking live remote references registered * in this VM, request a maximum latency for inspecting the * entire heap from the local garbage collector, to place * an upper bound on the time to discover remote references * that have become unreachable (see bugid 4171278). */ if (gcLatencyRequest == null) { gcLatencyRequest = GC.requestLatency(gcInterval); } } return entry; } } private EndpointEntry(final Endpoint endpoint) { this.endpoint = endpoint; try { LiveRef dgcRef = new LiveRef(dgcID, endpoint, false); dgc = (DGC) Util.createProxy(DGCImpl.class, new UnicastRef(dgcRef), true); } catch (RemoteException e) { throw new Error("internal error creating DGC stub"); } renewCleanThread = AccessController.doPrivileged( new NewThreadAction(new RenewCleanThread(), "RenewClean-" + endpoint, true)); renewCleanThread.start(); } /** * Register the LiveRef instances in the supplied list to participate * in distributed garbage collection. * * This method returns false if this entry was removed from the * global endpoint table (because it was empty) before these refs * could be registered. In that case, a new EndpointEntry needs * to be looked up. * * This method must NOT be called while synchronized on this entry. */ public boolean registerRefs(List refs) { assert !Thread.holdsLock(this); Set refsToDirty = null; // entries for refs needing dirty long sequenceNum; // sequence number for dirty call synchronized (this) { if (removed) { return false; } Iterator iter = refs.iterator(); while (iter.hasNext()) { LiveRef ref = (LiveRef) iter.next(); assert ref.getEndpoint().equals(endpoint); RefEntry refEntry = (RefEntry) refTable.get(ref); if (refEntry == null) { LiveRef refClone = (LiveRef) ref.clone(); refEntry = new RefEntry(refClone); refTable.put(refClone, refEntry); if (refsToDirty == null) { refsToDirty = new HashSet(5); } refsToDirty.add(refEntry); } refEntry.addInstanceToRefSet(ref); } if (refsToDirty == null) { return true; } refsToDirty.addAll(invalidRefs); invalidRefs.clear(); sequenceNum = getNextSequenceNum(); } makeDirtyCall(refsToDirty, sequenceNum); return true; } /** * Remove the given RefEntry from the ref table. If that makes * the ref table empty, remove this entry from the global endpoint * table. * * This method must ONLY be called while synchronized on this entry. */ private void removeRefEntry(RefEntry refEntry) { assert Thread.holdsLock(this); assert !removed; assert refTable.containsKey(refEntry.getRef()); refTable.remove(refEntry.getRef()); invalidRefs.remove(refEntry); if (refTable.isEmpty()) { synchronized (endpointTable) { endpointTable.remove(endpoint); Transport transport = endpoint.getOutboundTransport(); transport.free(endpoint); /* * If there are no longer any live remote references * registered, we are no longer concerned with the * latency of local garbage collection here. */ if (endpointTable.isEmpty()) { assert gcLatencyRequest != null; gcLatencyRequest.cancel(); gcLatencyRequest = null; } removed = true; } } } /** * Make a DGC dirty call to this entry's endpoint, for the ObjIDs * corresponding to the given set of refs and with the given * sequence number. * * This method must NOT be called while synchronized on this entry. */ private void makeDirtyCall(Set refEntries, long sequenceNum) { assert !Thread.holdsLock(this); ObjID[] ids; if (refEntries != null) { ids = createObjIDArray(refEntries); } else { ids = emptyObjIDArray; } long startTime = System.currentTimeMillis(); try { Lease lease = dgc.dirty(ids, sequenceNum, new Lease(vmid, leaseValue)); long duration = lease.getValue(); long newRenewTime = computeRenewTime(startTime, duration); long newExpirationTime = startTime + duration; synchronized (this) { dirtyFailures = 0; setRenewTime(newRenewTime); expirationTime = newExpirationTime; } } catch (Exception e) { long endTime = System.currentTimeMillis(); synchronized (this) { dirtyFailures++; if (dirtyFailures == 1) { /* * If this was the first recent failed dirty call, * reschedule another one immediately, in case there * was just a transient network problem, and remember * the start time and duration of this attempt for * future calculations of the delays between retries. */ dirtyFailureStartTime = startTime; dirtyFailureDuration = endTime - startTime; setRenewTime(endTime); } else { /* * For each successive failed dirty call, wait for a * (binary) exponentially increasing delay before * retrying, to avoid network congestion. */ int n = dirtyFailures - 2; if (n == 0) { /* * Calculate the initial retry delay from the * average time elapsed for each of the first * two failed dirty calls. The result must be * at least 1000ms, to prevent a tight loop. */ dirtyFailureDuration = Math.max((dirtyFailureDuration + (endTime - startTime)) >> 1, 1000); } long newRenewTime = endTime + (dirtyFailureDuration << n); /* * Continue if the last known held lease has not * expired, or else at least a fixed number of times, * or at least until we've tried for a fixed amount * of time (the default lease value we request). */ if (newRenewTime < expirationTime || dirtyFailures < dirtyFailureRetries || newRenewTime < dirtyFailureStartTime + leaseValue) { setRenewTime(newRenewTime); } else { /* * Give up: postpone lease renewals until next * ref is registered for this endpoint. */ setRenewTime(Long.MAX_VALUE); } } if (refEntries != null) { /* * Add all of these refs to the set of refs for this * endpoint that may be invalid (this VM may not be in * the server's referenced set), so that we will * attempt to explicitly dirty them again in the * future. */ invalidRefs.addAll(refEntries); /* * Record that a dirty call has failed for all of these * refs, so that clean calls for them in the future * will be strong. */ Iterator iter = refEntries.iterator(); while (iter.hasNext()) { RefEntry refEntry = (RefEntry) iter.next(); refEntry.markDirtyFailed(); } } /* * If the last known held lease will have expired before * the next renewal, all refs might be invalid. */ if (renewTime >= expirationTime) { invalidRefs.addAll(refTable.values()); } } } } /** * Set the absolute time at which the lease for this entry should * be renewed. * * This method must ONLY be called while synchronized on this entry. */ private void setRenewTime(long newRenewTime) { assert Thread.holdsLock(this); if (newRenewTime < renewTime) { renewTime = newRenewTime; if (interruptible) { AccessController.doPrivileged( new PrivilegedAction<Void>() { public Void run() { renewCleanThread.interrupt(); return null; } }); } } else { renewTime = newRenewTime; } } /** * RenewCleanThread handles the asynchronous client-side DGC activity * for this entry: renewing the leases and making clean calls. */ private class RenewCleanThread implements Runnable { public void run() { do { long timeToWait; RefEntry.PhantomLiveRef phantom = null; boolean needRenewal = false; Set refsToDirty = null;