Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, * software distributed under the License is distributed on an * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY * KIND, either express or implied. See the License for the * specific language governing permissions and limitations * under the License. */ package org.apache.axis2.clustering.tribes; import org.apache.axis2.clustering.ClusteringConstants; import org.apache.axis2.clustering.MembershipListener; import org.apache.axis2.clustering.control.wka.MemberJoinedCommand; import org.apache.axis2.clustering.control.wka.MemberListCommand; import org.apache.axis2.clustering.management.GroupManagementAgent; import org.apache.axis2.context.ConfigurationContext; import org.apache.catalina.tribes.Channel; import org.apache.catalina.tribes.Member; import org.apache.catalina.tribes.RemoteProcessException; import org.apache.catalina.tribes.group.GroupChannel; import org.apache.catalina.tribes.group.Response; import org.apache.catalina.tribes.group.RpcChannel; import org.apache.catalina.tribes.group.interceptors.StaticMembershipInterceptor; import org.apache.catalina.tribes.membership.MemberImpl; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import java.util.ArrayList; import java.util.List; import java.util.Random; import java.util.Set; import java.util.concurrent.CopyOnWriteArraySet; import java.util.concurrent.Executors; import java.util.concurrent.ScheduledExecutorService; import java.util.concurrent.TimeUnit; /** * Responsible for managing the membership. Handles membership changes. */ public class MembershipManager { private static final Log log = LogFactory.getLog(MembershipManager.class); private RpcChannel rpcMembershipChannel; private StaticMembershipInterceptor staticMembershipInterceptor; /** * The domain corresponding to the membership handled by this MembershipManager */ private byte[] domain; private GroupManagementAgent groupManagementAgent; private ConfigurationContext configContext; /** * List of current members in the cluster. Only the members who are alive will be in this * list */ private final List<Member> members = new ArrayList<Member>(); /** * List of Well-Known members. These members may or may not be alive at a given moment. */ private final List<Member> wkaMembers = new ArrayList<Member>(); /** * Set of Well-Known members which have not responded to the MEMBER_LIST message. * We need to retry sending the MEMBER_LIST message to these members until they respond, * otherwise, we cannot be sure whether these WKA members added the members in the MEMBER_LIST */ private final Set<Member> nonRespondingWkaMembers = new CopyOnWriteArraySet<Member>(); private List<MembershipListener> membershipListeners = new ArrayList<MembershipListener>(); /** * The member representing this node */ private Member localMember; /** * */ private boolean isMemberListResponseReceived; public MembershipManager(ConfigurationContext configContext) { this.configContext = configContext; } public MembershipManager() { } public void setMembershipListeners(List<MembershipListener> membershipListeners) { this.membershipListeners = membershipListeners; } public void setRpcMembershipChannel(RpcChannel rpcMembershipChannel) { this.rpcMembershipChannel = rpcMembershipChannel; } public RpcChannel getRpcMembershipChannel() { return rpcMembershipChannel; } public void setupStaticMembershipManagement(StaticMembershipInterceptor staticMembershipInterceptor) { this.staticMembershipInterceptor = staticMembershipInterceptor; ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1); scheduler.scheduleWithFixedDelay(new MemberListSenderTask(), 5, 5, TimeUnit.SECONDS); } public void setGroupManagementAgent(GroupManagementAgent groupManagementAgent) { this.groupManagementAgent = groupManagementAgent; } public void setDomain(byte[] domain) { this.domain = domain; } public byte[] getDomain() { return domain; } public Member getLocalMember() { return localMember; } public void setLocalMember(Member localMember) { this.localMember = localMember; } public void addWellKnownMember(Member wkaMember) { if (!wkaMembers.contains(wkaMember)) wkaMembers.add(wkaMember); } public void removeWellKnownMember(Member wkaMember) { wkaMembers.remove(wkaMember); } /** * A new member is added * * @param member The new member that joined the cluster * @return true If the member was added to the <code>members</code> array; false, otherwise. */ public boolean memberAdded(Member member) { if (log.isDebugEnabled()) { log.debug("members.contains(member) =" + members.contains(member)); log.debug("Is in my domain: " + TribesUtil.isInDomain(member, domain)); } // If this member already exists or if the member belongs to another domain, // there is no need to add it if (members.contains(member) || !TribesUtil.isInDomain(member, domain)) { return false; } if (staticMembershipInterceptor != null) { // this interceptor is null when multicast based scheme is used staticMembershipInterceptor.addStaticMember(member); if (log.isDebugEnabled()) { log.debug("Added static member " + TribesUtil.getName(member)); } } boolean shouldAddMember = localMember == null || TribesUtil.areInSameDomain(localMember, member); // If this member is a load balancer, notify the respective load balance event handler? if (groupManagementAgent != null) { synchronized (groupManagementAgent) { int memberCount = groupManagementAgent.getMembers().size(); groupManagementAgent.applicationMemberAdded(TribesUtil.toAxis2Member(member)); if (memberCount == groupManagementAgent.getMembers().size()) { // we shouldn't add the member, if the GroupManagementAgent // refuses to add it. shouldAddMember = false; } else { log.info("Application member " + TribesUtil.getName(member) + " joined group " + new String(member.getDomain())); } } } if (shouldAddMember) { boolean wkaMemberBelongsToLocalDomain = true; if (rpcMembershipChannel != null && isLocalMemberInitialized() && wkaMembers.contains(member)) { // if it is a well-known member log.info("A WKA member " + TribesUtil.getName(member) + " just joined the group. Sending MEMBER_LIST message."); wkaMemberBelongsToLocalDomain = sendMemberListToWellKnownMember(member); } if (wkaMemberBelongsToLocalDomain) { members.add(member); if (rpcMembershipChannel != null) { GroupChannel channel = (GroupChannel) rpcMembershipChannel.getChannel(); channel.memberAdded(member); log.debug("Member added to the channel: " + member); } for (MembershipListener membershipListener : membershipListeners) { membershipListener.memberAdded(TribesUtil.toAxis2Member(member), false); } if (log.isDebugEnabled()) { log.debug("Added group member " + TribesUtil.getName(member) + " to domain " + new String(member.getDomain())); } return true; } } return false; } /** * Task which send MEMBER_LIST messages to WKA members which have not yet responded to the * MEMBER_LIST message */ private class MemberListSenderTask implements Runnable { public void run() { try { if (nonRespondingWkaMembers != null && !nonRespondingWkaMembers.isEmpty()) { for (Member wkaMember : nonRespondingWkaMembers) { if (wkaMember != null) { sendMemberListToWellKnownMember(wkaMember); } } } } catch (Throwable e) { log.error("Could not send MemberList to WKA Members", e); } } } /** * Send MEMBER_LIST message to WKA member * * @param wkaMember The WKA member to whom the MEMBER_LIST has to be sent * @return true - if the WKA member belongs to the domain of this local member */ private boolean sendMemberListToWellKnownMember(Member wkaMember) { /*if (wkaMember.isFailing() || wkaMember.isSuspect()) { return false; }*/ // send the member list to it MemberListCommand memListCmd; try { memListCmd = new MemberListCommand(); List<Member> members = new ArrayList<Member>(this.members); members.add(localMember); // Need to set the local member too memListCmd.setMembers(members.toArray(new Member[members.size()])); Response[] responses = rpcMembershipChannel.send(new Member[] { wkaMember }, memListCmd, RpcChannel.ALL_REPLY, Channel.SEND_OPTIONS_ASYNCHRONOUS | TribesConstants.MEMBERSHIP_MSG_OPTION, 10000); // Once a response is received from the WKA member to the MEMBER_LIST message, // if it does not belong to this domain, simply remove it from the members if (responses != null && responses.length > 0 && responses[0] != null) { nonRespondingWkaMembers.remove(wkaMember); Member source = responses[0].getSource(); if (!TribesUtil.areInSameDomain(source, wkaMember)) { if (log.isDebugEnabled()) { log.debug("WKA Member " + TribesUtil.getName(source) + " does not belong to local domain " + new String(domain) + ". Hence removing it from the list."); } return false; } } else { // No response from WKA member if (nonRespondingWkaMembers.add(wkaMember)) { log.debug("No response from WKA member added to the list of non-responsive members : " + wkaMember); } // we still don't know the details of this WKA member, hence should return false return false; } } catch (Exception e) { String errMsg = "Could not send MEMBER_LIST to well-known member " + TribesUtil.getName(wkaMember); log.error(errMsg, e); throw new RemoteProcessException(errMsg, e); } return true; } /** * Send the list of members to the <code>member</code> * * @param member The member to whom the member list has to be sent */ public void sendMemberList(Member member) { try { MemberListCommand memListCmd = new MemberListCommand(); List<Member> members = new ArrayList<Member>(this.members); memListCmd.setMembers(members.toArray(new Member[members.size()])); rpcMembershipChannel.send(new Member[] { member }, memListCmd, RpcChannel.ALL_REPLY, Channel.SEND_OPTIONS_ASYNCHRONOUS | TribesConstants.MEMBERSHIP_MSG_OPTION, 10000); if (log.isDebugEnabled()) { log.debug("Sent MEMBER_LIST to " + TribesUtil.getName(member)); } } catch (Exception e) { String errMsg = "Could not send MEMBER_LIST to member " + TribesUtil.getName(member); log.error(errMsg, e); throw new RemoteProcessException(errMsg, e); } } /** * Inform all members that a particular member just joined * * @param member The member who just joined */ public void sendMemberJoinedToAll(Member member) { try { MemberJoinedCommand cmd = new MemberJoinedCommand(); cmd.setMember(member); ArrayList<Member> membersToSend = (ArrayList<Member>) (((ArrayList) members).clone()); membersToSend.remove(member); // Do not send MEMBER_JOINED to the new member who just joined if (membersToSend.size() > 0) { rpcMembershipChannel.send(membersToSend.toArray(new Member[membersToSend.size()]), cmd, RpcChannel.ALL_REPLY, Channel.SEND_OPTIONS_ASYNCHRONOUS | TribesConstants.MEMBERSHIP_MSG_OPTION, 10000); if (log.isDebugEnabled()) { log.debug("Sent MEMBER_JOINED[" + TribesUtil.getName(member) + "] to all members in domain " + new String(domain)); } } } catch (Exception e) { String errMsg = "Could not send MEMBER_JOINED[" + TribesUtil.getName(member) + "] to all members "; log.error(errMsg, e); throw new RemoteProcessException(errMsg, e); } } private boolean isLocalMemberInitialized() { if (configContext == null) { return false; } Object clusterInitialized = configContext.getPropertyNonReplicable(ClusteringConstants.CLUSTER_INITIALIZED); return clusterInitialized != null && clusterInitialized.equals("true"); } /** * A member disappeared * * @param member The member that left the cluster */ public void memberDisappeared(Member member) { members.remove(member); nonRespondingWkaMembers.remove(member); if (member != null && localMember != null) { if (TribesUtil.areInSameDomain(member, this.localMember)) { for (MembershipListener membershipListener : membershipListeners) { membershipListener.memberDisappeared(TribesUtil.toAxis2Member(member), false); } } } // Is this an application domain member? if (groupManagementAgent != null) { groupManagementAgent.applicationMemberRemoved(TribesUtil.toAxis2Member(member)); } } /** * Get the list of current members * * @return list of current members */ public Member[] getMembers() { return members.toArray(new Member[members.size()]); } public void removeAllMembers() { members.clear(); } /** * Get the member that has been alive for the longest time * * @return The member that has been alive for the longest time */ public Member getLongestLivingMember() { Member longestLivingMember = null; if (members.size() > 0) { Member member0 = members.get(0); long longestAliveTime = member0.getMemberAliveTime(); longestLivingMember = member0; for (Member member : members) { if (longestAliveTime < member.getMemberAliveTime()) { longestAliveTime = member.getMemberAliveTime(); longestLivingMember = member; } } } return longestLivingMember; } /** * Get a random member from the list of current members * * @return A random member from the list of current members */ public Member getRandomMember() { if (members.size() == 0) { return null; } int memberIndex = new Random().nextInt(members.size()); return members.get(memberIndex); } /** * Check whether there are any members * * @return true if there are other members, false otherwise */ public boolean hasMembers() { return members.size() > 0; } /** * Get a member * * @param member The member to be found * @return The member, if it is found */ public Member getMember(Member member) { if (hasMembers()) { MemberImpl result = null; for (int i = 0; i < this.members.size() && result == null; i++) { if (members.get(i).equals(member)) { result = (MemberImpl) members.get(i); } } return result; } return null; } }