org.jgroups.protocols.MERGE2 Maven / Gradle / Ivy
package org.jgroups.protocols;
import org.jgroups.*;
import org.jgroups.annotations.*;
import org.jgroups.stack.Protocol;
import org.jgroups.util.*;
import java.io.DataInput;
import java.io.DataOutput;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArraySet;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* Protocol to discover subgroups; e.g., existing due to a network partition (that healed). Example: group
* {p,q,r,s,t,u,v,w} is split into 3 subgroups {p,q}, {r,s,t,u} and {v,w}. This protocol will eventually send
* a MERGE event with the coordinators of each subgroup up the stack: {p,r,v}. Note that - depending on the time
* of subgroup discovery - there could also be 2 MERGE events, which first join 2 of the subgroups, and then the
* resulting group to the last subgroup. The real work of merging the subgroups into one larger group is done
* somewhere above this protocol (typically in the GMS protocol).
* This protocol works as follows:
*
* - If coordinator: periodically multicast a discovery message. Everyone (or (if configured) only the coords) reply
* with their current view. Based on the received views:
*
- If there is more than 1 coordinator:
*
* - Get all coordinators
*
- Create a MERGE event with the list of coordinators as argument
*
- Send the event up the stack
*
*
*
*
*
* Provides: sends MERGE event with list of coordinators up the stack
* @author Bela Ban, Oct 16 2001
* @deprecated Use {@link org.jgroups.protocols.MERGE3} instead, as it causes less traffic, especially for large clusters
*/
@MBean(description="Protocol to discover subgroups existing due to a network partition")
@Deprecated
public class MERGE2 extends Protocol {
/* ----------------------------------------- Properties -------------------------------------------------- */
@Property(description="Minimum time in ms between runs to discover other clusters")
protected long min_interval=5000;
@Property(description="Maximum time in ms between runs to discover other clusters")
protected long max_interval=20000;
@Property(description="Number of inconsistent views with only 1 coord after a MERGE event is sent up")
protected int inconsistent_view_threshold=1;
@Property(description="When receiving a multicast message, checks if the sender is member of the cluster. " +
"If not, initiates a merge. Generates a lot of traffic for large clusters when there is a lot of merging")
protected boolean merge_fast=true;
@Property(description="The delay (in milliseconds) after which a merge fast execution is started")
protected long merge_fast_delay=1000;
@Property(description="Always sends a discovery response, no matter what",writable=true)
protected boolean force_sending_discovery_rsps=true;
@Property(description="Time (in ms) to wait for all discovery responses")
protected long discovery_timeout=5000;
/* ---------------------------------------------- JMX -------------------------------------------------------- */
@ManagedAttribute(writable=false, description="whether or not a merge task is currently running " +
"(should be the case in a coordinator")
public boolean isMergeTaskRunning() {
return task.isRunning();
}
/* --------------------------------------------- Fields ------------------------------------------------------ */
protected Address local_addr;
protected volatile View view;
protected final Set
members=new HashSet<>();
protected final Set merge_candidates=new CopyOnWriteArraySet<>();
protected final FindSubgroupsTask task=new FindSubgroupsTask();
@ManagedAttribute(description="Whether this member is the current coordinator")
protected volatile boolean is_coord=false;
protected volatile Address current_coord;
protected TimeScheduler timer;
@ManagedAttribute(description="Number of inconsistent 1-coord views until a MERGE event is sent up the stack")
protected int num_inconsistent_views;
@ManagedAttribute(description="Number of times a MERGE event was sent up the stack")
protected int num_merge_events;
protected final Map views=new ConcurrentHashMap<>();
protected final Lock discovery_lock=new ReentrantLock();
protected final CondVar discovery_cond=new CondVar(discovery_lock);
protected volatile boolean fetching_done=false;
protected boolean transport_supports_multicasting=true;
protected String cluster_name;
public void init() throws Exception {
timer=getTransport().getTimer();
if(timer == null)
throw new Exception("timer cannot be retrieved");
if(min_interval <= 0 || max_interval <= 0)
throw new Exception("min_interval and max_interval have to be > 0");
if(max_interval <= min_interval)
throw new Exception ("max_interval has to be greater than min_interval");
transport_supports_multicasting=getTransport().supportsMulticasting();
}
public long getMinInterval() {
return min_interval;
}
public void setMinInterval(long i) {
min_interval=i;
}
public long getMaxInterval() {
return max_interval;
}
public void setMaxInterval(long l) {
max_interval=l;
}
protected boolean isMergeRunning() {
Object retval=up_prot.up(new Event(Event.IS_MERGE_IN_PROGRESS));
return retval instanceof Boolean && (Boolean)retval;
}
/** Discovers members and detects whether we have multiple coordinator. If so, kicks off a merge */
@ManagedOperation
public void sendMergeSolicitation() {
task.findAndNotify();
}
@ManagedAttribute(description="The address of the current coordinator")
public String getCurrentCoord() {return current_coord != null? current_coord.toString() : "n/a";}
@ManagedOperation public void startMergeTask() {task.start();}
@ManagedOperation public void stopMergeTask() {task.stop();}
@ManagedOperation(description="Fetches all views")
public String fetchAllViews() {
try {
task.fetchViews();
StringBuilder sb=new StringBuilder();
for(Map.Entry entry: views.entrySet())
sb.append(entry.getKey() + ": " + entry.getValue() + "\n");
return sb.toString();
}
catch(Throwable e) {
return null;
}
}
public void stop() {
is_coord=false;
merge_candidates.clear();
task.stop();
}
public Object down(Event evt) {
switch(evt.getType()) {
case Event.CONNECT:
case Event.CONNECT_USE_FLUSH:
case Event.CONNECT_WITH_STATE_TRANSFER:
case Event.CONNECT_WITH_STATE_TRANSFER_USE_FLUSH:
cluster_name=(String)evt.getArg();
return down_prot.down(evt);
case Event.VIEW_CHANGE:
Object ret=down_prot.down(evt);
view=(View)evt.getArg();
List mbrs=view.getMembers();
if(mbrs == null || mbrs.isEmpty() || local_addr == null) {
task.stop();
return ret;
}
members.clear();
members.addAll(mbrs);
merge_candidates.removeAll(members);
current_coord=mbrs.isEmpty()? null : mbrs.get(0);
if(current_coord != null && current_coord.equals(local_addr)) {
is_coord=true;
task.start(); // start task if we became coordinator (doesn't start if already running)
}
else {
// if we were coordinator, but are no longer, stop task. this happens e.g. when we merge and someone
// else becomes the new coordinator of the merged group
is_coord=false;
task.stop();
}
return ret;
case Event.SET_LOCAL_ADDRESS:
local_addr=(Address)evt.getArg();
return down_prot.down(evt);
default:
return down_prot.down(evt); // Pass on to the layer below us
}
}
public Object up(Event evt) {
switch(evt.getType()) {
case Event.MSG:
Message msg=(Message)evt.getArg();
MergeHeader hdr=(MergeHeader)msg.getHeader(id);
if(hdr == null) {
if(merge_fast)
mergeFast(msg.dest(), msg.src());
break;
}
else {
handle(hdr, msg.src());
return null;
}
}
return up_prot.up(evt);
}
public void up(MessageBatch batch) {
for(Message msg: batch) {
MergeHeader hdr=(MergeHeader)msg.getHeader(id);
if(hdr != null) {
batch.remove(msg);
handle(hdr, batch.sender());
}
}
if(!batch.isEmpty()) {
if(merge_fast)
mergeFast(batch.dest(), batch.sender());
up_prot.up(batch);
}
}
protected void mergeFast(final Address dest, final Address sender) {
if(dest == null) {
if(!members.contains(sender) && merge_candidates.add(sender)) {
timer.schedule(new Runnable() {
public void run() {
if(!members.contains(sender))
task.findAndNotify();
}
}, merge_fast_delay, TimeUnit.MILLISECONDS);
}
}
}
protected void handle(MergeHeader hdr, Address sender) {
switch(hdr.type) {
case 1: // request
boolean send_discovery_rsp=force_sending_discovery_rsps || is_coord
|| current_coord == null || current_coord.equals(sender);
if(!send_discovery_rsp) {
log.trace("%s: suppressing discovery response as I'm not a coordinator and the " +
"discovery request was not sent by a coordinator", local_addr);
return;
}
if(isMergeRunning()) {
log.trace("%s: suppressing discovery response as a merge is in progress", local_addr);
return;
}
if(view != null) {
Message msg=new Message(sender).putHeader(id,new MergeHeader(MergeHeader.RSP,view));
down_prot.down(new Event(Event.MSG, msg));
}
break;
case 2: // response
View rsp_view=hdr.view;
if(rsp_view != null && !fetching_done) {
views.put(sender,rsp_view);
List diff_views=Util.detectDifferentViews(views);
if(diff_views.size() > 1) {
discovery_lock.lock();
try {
fetching_done=true;
discovery_cond.signal(true);
}
finally {
discovery_lock.unlock();
}
}
}
break;
}
}
/**
* Task periodically executing (if role is coordinator). Gets the initial membership and determines
* whether there are subgroups (multiple coordinators for the same group). If yes, it sends a MERGE event
* with the list of the coordinators up the stack
*/
protected class FindSubgroupsTask implements Condition {
@GuardedBy("this")
protected Future future;
protected final Lock lock=new ReentrantLock();
public synchronized void start() {
if(future == null || future.isDone()) {
future=timer.scheduleWithDynamicInterval(new TimeScheduler.Task() {
public long nextInterval() {
return computeInterval();
}
public void run() {
findAndNotify();
}
public String toString() {
return MERGE2.class.getSimpleName() + ": " + getClass().getSimpleName();
}
});
}
}
public synchronized void stop() {
if(future != null) {
future.cancel(true);
future=null;
}
}
public synchronized boolean isRunning() {
return future != null && !future.isDone();
}
public boolean isMet() {return fetching_done;}
public void findAndNotify() {
if(isMergeRunning())
return;
if(lock.tryLock()) {
try {
_findAndNotify();
}
catch(InterruptedException iex) {
}
catch(Throwable t) {
log.error(Util.getMessage("FindSubgroupsTaskFailed"), t);
}
finally {
lock.unlock();
}
}
}
protected void _findAndNotify() throws InterruptedException {
fetchViews();
if(log.isTraceEnabled()) {
StringBuilder sb=new StringBuilder();
sb.append(local_addr + ": discovery results:\n");
for(Map.Entry entry: views.entrySet())
sb.append("[" + entry.getKey() + "]: " + entry.getValue().getViewId()).append("\n");
log.trace(sb);
}
// A list of different views
List different_views=Util.detectDifferentViews(views);
if(different_views.size() <= 1) {
num_inconsistent_views=0;
return;
}
Collection merge_participants=Util.determineMergeParticipants(views);
if(merge_participants.size() == 1) {
if(num_inconsistent_views < inconsistent_view_threshold) {
log.debug("%s: dropping MERGE for inconsistent views (%s) as inconsistent view threshold (%d) " +
"has not yet been reached (%d)",
local_addr, Util.printViews(different_views), inconsistent_view_threshold, num_inconsistent_views);
num_inconsistent_views++;
return;
}
else
num_inconsistent_views=0;
}
else
num_inconsistent_views=0;
if(log.isDebugEnabled()) {
StringBuilder sb=new StringBuilder();
sb.append(local_addr + " found different views : " + Util.printViews(different_views) +
"; sending up MERGE event with merge participants " + merge_participants + ".\n");
sb.append("Discovery results:\n");
for(Map.Entry entry: views.entrySet())
sb.append("[" + entry.getKey() + "]: coord=" + entry.getValue().getCreator()).append("\n");
log.debug(sb.toString());
}
Event evt=new Event(Event.MERGE, views);
try {
up_prot.up(evt);
num_merge_events++;
}
catch(Throwable t) {
log.error(Util.getMessage("FailedSendingUpMERGEEvent"), t);
}
}
/** Fetches views from members in the cluster. Returns when either discovery_timeout ms have elapsed or
* more than 1 different view has been found */
protected void fetchViews() throws InterruptedException {
views.clear();
View tmp_view=view;
if(tmp_view != null)
views.put(local_addr, tmp_view);
fetching_done=false;
if(transport_supports_multicasting) {
Message discovery_req=new Message(null).putHeader(id, new MergeHeader(MergeHeader.REQ, null))
.setTransientFlag(Message.TransientFlag.DONT_LOOPBACK);
down_prot.down(new Event(Event.MSG, discovery_req));
try {
discovery_cond.waitFor(this, discovery_timeout, TimeUnit.MILLISECONDS);
}
finally {
fetching_done=true;
}
return;
}
Responses rsps=(Responses)down_prot.down(Event.FIND_MBRS_EVT);
rsps.waitFor(discovery_timeout); // return immediately if done
if(rsps.isEmpty())
return;
log.trace("discovery protocol returned %d responses: %s", rsps.size(), rsps);
for(PingData rsp: rsps) {
PhysicalAddress addr=rsp.getPhysicalAddr();
if(addr == null) continue;
Message discovery_req=new Message(addr).putHeader(id, new MergeHeader(MergeHeader.REQ, null))
.setTransientFlag(Message.TransientFlag.DONT_LOOPBACK);
down_prot.down(new Event(Event.MSG, discovery_req));
}
try {
discovery_cond.waitFor(this, discovery_timeout, TimeUnit.MILLISECONDS);
}
finally {
fetching_done=true;
}
}
/**
* Returns a random value within [min_interval - max_interval]
*/
protected long computeInterval() {
return min_interval + Util.random(max_interval - min_interval);
}
}
protected static class MergeHeader extends Header {
protected byte type=1; // 1 == req, 2 == rsp
protected View view;
protected static final byte REQ=1;
protected static final byte RSP=2;
public MergeHeader() {
}
public MergeHeader(byte type, View view) {
this.type=type;
this.view=view;
}
public String toString() {
return (type==1? "req" : "rsp") + ", view=" + view;
}
public int size() {
return Global.BYTE_SIZE + Util.size(view);
}
public void writeTo(DataOutput out) throws Exception {
out.writeByte(type);
Util.writeView(view, out);
}
public void readFrom(DataInput in) throws Exception {
type=in.readByte();
view=Util.readView(in);
}
}
}
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