diff options
author | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
---|---|---|
committer | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
commit | 554fd8c5195424bdbcabf5de30fdc183aba391bd (patch) | |
tree | 976dc5ab7fddf506dadce60ae936f43f58787092 /libjava/classpath/gnu/java/rmi/dgc/LeaseRenewingTask.java | |
download | cbb-gcc-4.6.4-554fd8c5195424bdbcabf5de30fdc183aba391bd.tar.bz2 cbb-gcc-4.6.4-554fd8c5195424bdbcabf5de30fdc183aba391bd.tar.xz |
obtained gcc-4.6.4.tar.bz2 from upstream website;upstream
verified gcc-4.6.4.tar.bz2.sig;
imported gcc-4.6.4 source tree from verified upstream tarball.
downloading a git-generated archive based on the 'upstream' tag
should provide you with a source tree that is binary identical
to the one extracted from the above tarball.
if you have obtained the source via the command 'git clone',
however, do note that line-endings of files in your working
directory might differ from line-endings of the respective
files in the upstream repository.
Diffstat (limited to 'libjava/classpath/gnu/java/rmi/dgc/LeaseRenewingTask.java')
-rw-r--r-- | libjava/classpath/gnu/java/rmi/dgc/LeaseRenewingTask.java | 234 |
1 files changed, 234 insertions, 0 deletions
diff --git a/libjava/classpath/gnu/java/rmi/dgc/LeaseRenewingTask.java b/libjava/classpath/gnu/java/rmi/dgc/LeaseRenewingTask.java new file mode 100644 index 000000000..7995af744 --- /dev/null +++ b/libjava/classpath/gnu/java/rmi/dgc/LeaseRenewingTask.java @@ -0,0 +1,234 @@ +/* LeaseRenewingTask.java -- The task to renew the lease. + Copyright (C) 2006 Free Software Foundation, Inc. + +This file is part of GNU Classpath. + +GNU Classpath is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2, or (at your option) +any later version. + +GNU Classpath 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 for more details. + +You should have received a copy of the GNU General Public License +along with GNU Classpath; see the file COPYING. If not, write to the +Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA +02110-1301 USA. + +Linking this library statically or dynamically with other modules is +making a combined work based on this library. Thus, the terms and +conditions of the GNU General Public License cover the whole +combination. + +As a special exception, the copyright holders of this library give you +permission to link this library with independent modules to produce an +executable, regardless of the license terms of these independent +modules, and to copy and distribute the resulting executable under +terms of your choice, provided that you also meet, for each linked +independent module, the terms and conditions of the license of that +module. An independent module is a module which is not derived from +or based on this library. If you modify this library, you may extend +this exception to your version of the library, but you are not +obligated to do so. If you do not wish to do so, delete this +exception statement from your version. */ + + +package gnu.java.rmi.dgc; + +import gnu.java.rmi.server.UnicastRef; + +import java.lang.ref.WeakReference; +import java.rmi.dgc.Lease; +import java.util.Iterator; +import java.util.LinkedList; +import java.util.Timer; +import java.util.TimerTask; +import java.util.WeakHashMap; + +/** + * The task to renew the lease to some object reference. The UnicastRef + * being renewed is stored as a weak reference. So the presence of the + * sheduled task does not prevent it from being garbage collected. If the + * reference has not been garbage collected, the task is resheduled after + * the lease is renewed. + * + * @author Audrius Meskauskas (Audriusa@Bioinformatics.org) + */ +public class LeaseRenewingTask +{ + /** + * The sheduled timer task to call the renew() method. + */ + class LeaseTimerTask extends TimerTask + { + public void run() + { + renew(); + } + } + + /** + * The default requested lease duration time (one minute by default). + */ + public static long REQUEST_LEASE_DURATION = 60000; + + /** + * The reference to the UnicastRef that must renew its lease until not + * garbage collected. The different members of this list may point to the + * different instances of the UnicastRef's, but these references are + * pointing to the same remote object (they .equals() returns + * true when comparing with each other). Using LinkedList to make + * frequent deletions from the middle easy. + */ + LinkedList ref = new LinkedList(); + + /** + * The granted (or supposed) lease. + */ + Lease lease = new Lease(null, REQUEST_LEASE_DURATION); + + /** + * The timer, shared by all lease renewing tasks. The same instance is also + * used for the reference protector discarding in DGCImpl. + */ + static Timer timer = new Timer(true); + + /** + * Maps the UnicastRef to its renewing task. + */ + static WeakHashMap existingTasks = new WeakHashMap(); + + /** + * Creates the lease renewing task that renews the lease of the given + * UnicastRef until it is not collected. This constructor requests the lease + * value from the server and schedules the lease renewal action. + * + * @param renewIt the reference that must be renewed. + */ + public LeaseRenewingTask(UnicastRef renewIt) + { + lease = notifyDGC(renewIt); + if (lease != null) + { + schedule(lease); + ref.add(new WeakReference(renewIt)); + } + } + + /** + * Schedule periodic leases for the given UnicastRef reference. + * + * @param renewIt the reference, for that the leases must be scheduled. + */ + public static void scheduleLeases(UnicastRef renewIt) + { + // No need to schedule leases for null. + if (renewIt == null) + return; + try { + synchronized (existingTasks) + { + // Check maybe the task for refreshing this remote object already + // exists. + LeaseRenewingTask task = (LeaseRenewingTask) existingTasks.get(renewIt); + + if (task != null) + { + // Extend the reference list only. The scheduling must be + // alredy done with the previous lease. + synchronized (task.ref) + { + task.ref.add(new WeakReference(renewIt)); + } + } + else + existingTasks.put(renewIt, new LeaseRenewingTask(renewIt)); + } + } + catch (Exception ex) + { + InternalError ierr = new InternalError("Lease for "+renewIt); + ierr.initCause(ex); + throw ierr; + } + } + + /** + * Shedule the renewing call, taking into consideration that the following + * lease was granted. + * + * @param lease the lease that was granted. + */ + public void schedule(Lease lease) + { + long value = lease.getValue(); + + // Shedule a 10 % earlier because some time is needed for the message + // to reach the server. + long reduced = (value * 90)/100; + if (reduced == 0) + reduced = value; + + timer.schedule(new LeaseTimerTask(), reduced); + } + + /** + * Renew the lease. + */ + public void renew() + { + Object renewIt = null; + // Iterate throw the list of associated references. If all are + // discarded, there is no need to renew. + synchronized (ref) + { + Iterator iter = ref.iterator(); + WeakReference w; + while (iter.hasNext() && renewIt == null) + { + w = (WeakReference) iter.next(); + renewIt = w.get(); + if (renewIt == null) + // Discard the weak reference if its target has been garbage + // collected. + iter.remove(); + } + } + + if (renewIt!=null) + { + Lease lease = notifyDGC( (UnicastRef) renewIt); + + // Schedule the next renewing session. + if (lease!=null) + schedule(lease); + } + { + // All references collected - discard this entry. + } + } + + /** + * Notify DGC that we still hold this reference. + * + * @param renewIt the reference we still have (must not be null). + */ + public Lease notifyDGC(UnicastRef renewIt) + { + try + { + return renewIt.notifyDGC(lease); + } + catch (Exception e) + { + // Failed to notify. + // TODO Take some relevant action in the case if we failed + // to notify the remote object owner. + return null; + } + } + +} |