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* Copyright 1999,2004 The Apache Software Foundation.
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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package org.apache.catalina.tribes.membership;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.HashMap;
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import java.util.Iterator;
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import org.apache.catalina.tribes.Member;
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* A <b>membership</b> implementation using simple multicast.
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* This is the representation of a multicast membership.
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* This class is responsible for maintaining a list of active cluster nodes in the cluster.
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* If a node fails to send out a heartbeat, the node will be dismissed.
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* @author Peter Rossbach
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* @version $Revision: 356540 $, $Date: 2005-12-13 10:53:40 -0600 (Tue, 13 Dec 2005) $
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public class McastMembership
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protected static final MemberImpl[] EMPTY_MEMBERS = new MemberImpl[0];
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* The name of this membership, has to be the same as the name for the local
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protected MemberImpl local;
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* A map of all the members in the cluster.
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protected Map map = new HashMap();
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* A list of all the members in the cluster.
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protected MemberImpl[] members = EMPTY_MEMBERS;
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* sort members by alive time
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protected MemberComparator memberComparator = new MemberComparator();
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* Constructs a new membership
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* @param name - has to be the name of the local member. Used to filter the local member from the cluster membership
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public McastMembership(MemberImpl local) {
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* Reset the membership and start over fresh.
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* Ie, delete all the members and wait for them to ping again and join this membership
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public synchronized void reset() {
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members = EMPTY_MEMBERS ;
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* Notify the membership that this member has announced itself.
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* @param member - the member that just pinged us
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* @return - true if this member is new to the cluster, false otherwise.
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* @return - false if this member is the local member or updated.
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public synchronized boolean memberAlive(MemberImpl member) {
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boolean result = false;
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if ( member.equals(local) ) return result;
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//return true if the membership has changed
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MbrEntry entry = (MbrEntry)map.get(member);
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if ( entry == null ) {
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entry = new MbrEntry(member);
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map.put(member,entry);
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addMcastMember(member);
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//update the member alive time
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MemberImpl updateMember = entry.getMember() ;
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if(updateMember.getMemberAliveTime() != member.getMemberAliveTime()) {
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updateMember.setMemberAliveTime(member.getMemberAliveTime());
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Arrays.sort(members, memberComparator);
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* Add a member to this component and sort array with memberComparator
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* @param member The member to add
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protected void addMcastMember(MemberImpl member) {
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synchronized (members) {
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MemberImpl results[] =
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new MemberImpl[members.length + 1];
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for (int i = 0; i < members.length; i++)
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results[i] = members[i];
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results[members.length] = member;
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Arrays.sort(members, memberComparator);
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* Remove a member from this component.
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* @param member The member to remove
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protected void removeMcastMember(MemberImpl member) {
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synchronized (members) {
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for (int i = 0; i < members.length; i++) {
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if (members[i] == member) {
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MemberImpl results[] =
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new MemberImpl[members.length - 1];
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for (int i = 0; i < members.length; i++) {
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results[j++] = members[i];
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* Runs a refresh cycle and returns a list of members that has expired.
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* This also removes the members from the membership, in such a way that
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* getMembers() = getMembers() - expire()
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* @param maxtime - the max time a member can remain unannounced before it is considered dead.
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* @return the list of expired members
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public synchronized MemberImpl[] expire(long maxtime) {
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return EMPTY_MEMBERS;
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ArrayList list = null;
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Iterator i = map.values().iterator();
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MbrEntry entry = (MbrEntry)i.next();
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if( entry.hasExpired(maxtime) ) {
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if(list == null) // only need a list when members are expired (smaller gc)
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list = new java.util.ArrayList();
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list.add(entry.getMember());
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MemberImpl[] result = new MemberImpl[list.size()];
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list.toArray(result);
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for( int j=0; j<result.length; j++) {
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map.remove(result[j]);
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removeMcastMember(result[j]);
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return EMPTY_MEMBERS ;
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* Returning that service has members or not
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public synchronized boolean hasMembers() {
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return members.length > 0 ;
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public synchronized MemberImpl getMember(Member mbr) {
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MemberImpl result = null;
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for ( int i=0; i<this.members.length && result==null; i++ ) {
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if ( members[i].equals(mbr) ) result = members[i];
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* Returning a list of all the members in the membership
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* We not need a copy: add and remove generate new arrays.
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public synchronized MemberImpl[] getMembers() {
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return EMPTY_MEMBERS;
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* get a copy from all member entries
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protected synchronized MbrEntry[] getMemberEntries()
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MbrEntry[] result = new MbrEntry[map.size()];
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java.util.Iterator i = map.entrySet().iterator();
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while ( i.hasNext() )
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result[pos++] = ((MbrEntry)((java.util.Map.Entry)i.next()).getValue());
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// --------------------------------------------- Inner Class
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private class MemberComparator implements java.util.Comparator {
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public int compare(Object o1, Object o2) {
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return compare((MemberImpl) o1, (MemberImpl) o2);
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} catch (ClassCastException x) {
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public int compare(MemberImpl m1, MemberImpl m2) {
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//longer alive time, means sort first
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long result = m2.getMemberAliveTime() - m1.getMemberAliveTime();
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else if (result == 0)
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* Inner class that represents a member entry
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protected static class MbrEntry
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protected MemberImpl mbr;
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protected long lastHeardFrom;
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public MbrEntry(MemberImpl mbr) {
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* Indicate that this member has been accessed.
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public void accessed(){
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lastHeardFrom = System.currentTimeMillis();
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* Return the actual McastMember object
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public MemberImpl getMember() {
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* Check if this dude has expired
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* @param maxtime The time threshold
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public boolean hasExpired(long maxtime) {
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long delta = System.currentTimeMillis() - lastHeardFrom;
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return delta > maxtime;