/**
* Invoked upon receiving a MERGE event from the MERGE layer. Starts the merge protocol. See
* description of protocol in DESIGN.
*
* @param views A List of <em>different</em> views detected by the merge protocol
*/
public void merge(Map<Address, View> views) {
if (isMergeInProgress()) {
if (log.isTraceEnabled())
log.trace(gms.local_addr + ": merge is already running (merge_id=" + merge_id + ")");
return;
}
// we need the merge *coordinators* not merge participants because not everyone can lead a merge
// !
Collection<Address> coords = Util.determineMergeCoords(views);
Collection<Address> merge_participants = Util.determineMergeParticipants(views);
Membership tmp =
new Membership(coords); // establish a deterministic order, so that coords can elect leader
tmp.sort();
Address merge_leader = tmp.elementAt(0);
if (log.isDebugEnabled()) log.debug("determining merge leader from " + merge_participants);
if (merge_leader.equals(gms.local_addr)) {
if (log.isDebugEnabled())
log.debug(
"I ("
+ gms.local_addr
+ ") will be the leader. Starting the merge task for "
+ merge_participants);
merge_task.start(views);
} else {
if (log.isDebugEnabled())
log.debug(
"I ("
+ gms.local_addr
+ ") am not the merge leader, "
+ "waiting for merge leader ("
+ merge_leader
+ ") to initiate merge");
}
}
/** Checks whether the potential_new_coord would be the new coordinator (2nd in line) */
protected boolean wouldBeNewCoordinator(Address potential_new_coord) {
if (potential_new_coord == null) return false;
synchronized (members) {
if (members.size() < 2) return false;
Address new_coord = members.elementAt(1); // member at 2nd place
return new_coord != null && new_coord.equals(potential_new_coord);
}
}
/**
* Merge all MergeData. All MergeData elements should be disjunct (both views and digests).
* However, this method is prepared to resolve duplicate entries (for the same member).
* Resolution strategy for views is to merge only 1 of the duplicate members. Resolution
* strategy for digests is to take the higher seqnos for duplicate digests.
*
* <p>After merging all members into a Membership and subsequent sorting, the first member of
* the sorted membership will be the new coordinator. This method has a lock on merge_rsps.
*
* @param merge_rsps A list of MergeData items. Elements with merge_rejected=true were removed
* before. Is guaranteed not to be null and to contain at least 1 member.
*/
private MergeData consolidateMergeData(Vector<MergeData> merge_rsps) {
long logical_time = 0; // for new_vid
Membership new_mbrs = new Membership();
Vector<View> subgroups =
new Vector<View>(11); // contains a list of Views, each View is a subgroup
for (MergeData tmp_data : merge_rsps) {
View tmp_view = tmp_data.getView();
if (tmp_view != null) {
ViewId tmp_vid = tmp_view.getVid();
if (tmp_vid != null) {
// compute the new view id (max of all vids +1)
logical_time = Math.max(logical_time, tmp_vid.getId());
}
// merge all membership lists into one (prevent duplicates)
new_mbrs.add(tmp_view.getMembers());
subgroups.addElement((View) tmp_view.clone());
}
}
// the new coordinator is the first member of the consolidated & sorted membership list
new_mbrs.sort();
Address new_coord = new_mbrs.size() > 0 ? new_mbrs.elementAt(0) : null;
if (new_coord == null) {
if (log.isErrorEnabled()) log.error("new_coord == null");
return null;
}
// should be the highest view ID seen up to now plus 1
ViewId new_vid = new ViewId(new_coord, logical_time + 1);
// determine the new view
MergeView new_view = new MergeView(new_vid, new_mbrs.getMembers(), subgroups);
// determine the new digest
Digest new_digest = consolidateDigests(merge_rsps, new_mbrs.size());
if (new_digest == null) {
if (log.isErrorEnabled())
log.error("Merge leader " + gms.local_addr + ": could not consolidate digest for merge");
return null;
}
if (log.isDebugEnabled())
log.debug(
"Merge leader "
+ gms.local_addr
+ ": consolidated view="
+ new_view
+ "\nconsolidated digest="
+ new_digest);
return new MergeData(gms.local_addr, new_view, new_digest);
}
/**
* Computes the next view. Returns a copy that has <code>old_mbrs</code> and <code>suspected_mbrs
* </code> removed and <code>new_mbrs</code> added.
*/
public View getNextView(
Collection<Address> new_mbrs,
Collection<Address> old_mbrs,
Collection<Address> suspected_mbrs) {
synchronized (members) {
ViewId view_id = view != null ? view.getViewId() : null;
if (view_id == null) {
log.error("view_id is null");
return null; // this should *never* happen !
}
long vid = Math.max(view_id.getId(), ltime) + 1;
ltime = vid;
Membership tmp_mbrs = tmp_members.copy(); // always operate on the temporary membership
tmp_mbrs.remove(suspected_mbrs);
tmp_mbrs.remove(old_mbrs);
tmp_mbrs.add(new_mbrs);
List<Address> mbrs = tmp_mbrs.getMembers();
Address new_coord = local_addr;
if (!mbrs.isEmpty()) new_coord = mbrs.get(0);
View v = new View(new_coord, vid, mbrs);
// Update membership (see DESIGN for explanation):
tmp_members.set(mbrs);
// Update joining list (see DESIGN for explanation)
if (new_mbrs != null) {
for (Address tmp_mbr : new_mbrs) {
if (!joining.contains(tmp_mbr)) joining.add(tmp_mbr);
}
}
// Update leaving list (see DESIGN for explanations)
if (old_mbrs != null) {
for (Address addr : old_mbrs) {
if (!leaving.contains(addr)) leaving.add(addr);
}
}
if (suspected_mbrs != null) {
for (Address addr : suspected_mbrs) {
if (!leaving.contains(addr)) leaving.add(addr);
}
}
return v;
}
}
@SuppressWarnings("unchecked")
public Object up(Event evt) {
switch (evt.getType()) {
case Event.MSG:
Message msg = (Message) evt.getArg();
GmsHeader hdr = (GmsHeader) msg.getHeader(this.id);
if (hdr == null) break;
switch (hdr.type) {
case GmsHeader.JOIN_REQ:
view_handler.add(
new Request(Request.JOIN, hdr.mbr, false, null, hdr.useFlushIfPresent));
break;
case GmsHeader.JOIN_REQ_WITH_STATE_TRANSFER:
view_handler.add(
new Request(
Request.JOIN_WITH_STATE_TRANSFER, hdr.mbr, false, null, hdr.useFlushIfPresent));
break;
case GmsHeader.JOIN_RSP:
impl.handleJoinResponse(hdr.join_rsp);
break;
case GmsHeader.LEAVE_REQ:
if (hdr.mbr == null) return null;
view_handler.add(new Request(Request.LEAVE, hdr.mbr, false));
break;
case GmsHeader.LEAVE_RSP:
impl.handleLeaveResponse();
break;
case GmsHeader.VIEW:
View new_view = hdr.view;
if (new_view == null) return null;
Address coord = msg.getSrc();
if (!new_view.containsMember(coord)) {
sendViewAck(
coord); // we need to send the ack first, otherwise the connection is removed
impl.handleViewChange(new_view, hdr.my_digest);
} else {
impl.handleViewChange(new_view, hdr.my_digest);
sendViewAck(coord); // send VIEW_ACK to sender of view
}
break;
case GmsHeader.VIEW_ACK:
Address sender = msg.getSrc();
ack_collector.ack(sender);
return null; // don't pass further up
case GmsHeader.MERGE_REQ:
impl.handleMergeRequest(msg.getSrc(), hdr.merge_id, hdr.mbrs);
break;
case GmsHeader.MERGE_RSP:
MergeData merge_data =
new MergeData(msg.getSrc(), hdr.view, hdr.my_digest, hdr.merge_rejected);
if (log.isTraceEnabled()) {
log.trace(
local_addr
+ ": got merge response from "
+ msg.getSrc()
+ ", merge_id="
+ hdr.merge_id
+ ", merge data is "
+ merge_data);
}
impl.handleMergeResponse(merge_data, hdr.merge_id);
break;
case GmsHeader.INSTALL_MERGE_VIEW:
impl.handleMergeView(
new MergeData(msg.getSrc(), hdr.view, hdr.my_digest), hdr.merge_id);
break;
case GmsHeader.INSTALL_DIGEST:
Digest tmp = hdr.my_digest;
down_prot.down(new Event(Event.MERGE_DIGEST, tmp));
break;
case GmsHeader.INSTALL_MERGE_VIEW_OK:
// [JGRP-700] - FLUSH: flushing should span merge
merge_ack_collector.ack(msg.getSrc());
break;
case GmsHeader.CANCEL_MERGE:
// [JGRP-524] - FLUSH and merge: flush doesn't wrap entire merge process
impl.handleMergeCancelled(hdr.merge_id);
break;
case GmsHeader.GET_DIGEST_REQ:
// only handle this request if it was sent by the coordinator (or at least a member) of
// the current cluster
synchronized (members) {
if (!members.contains(msg.getSrc())) break;
}
// discard my own request:
if (msg.getSrc().equals(local_addr)) return null;
if (hdr.merge_id != null
&& !(merger.matchMergeId(hdr.merge_id) || merger.setMergeId(null, hdr.merge_id)))
return null;
// fetch only my own digest
Digest digest = (Digest) down_prot.down(new Event(Event.GET_DIGEST, local_addr));
if (digest != null) {
GmsHeader rsp_hdr = new GmsHeader(GmsHeader.GET_DIGEST_RSP);
rsp_hdr.my_digest = digest;
Message get_digest_rsp = new Message(msg.getSrc(), null, null);
get_digest_rsp.setFlag(Message.OOB);
get_digest_rsp.putHeader(this.id, rsp_hdr);
down_prot.down(new Event(Event.MSG, get_digest_rsp));
}
break;
case GmsHeader.GET_DIGEST_RSP:
Digest digest_rsp = hdr.my_digest;
impl.handleDigestResponse(msg.getSrc(), digest_rsp);
break;
default:
if (log.isErrorEnabled()) log.error("GmsHeader with type=" + hdr.type + " not known");
}
return null; // don't pass up
case Event.SUSPECT:
Object retval = up_prot.up(evt);
Address suspected = (Address) evt.getArg();
view_handler.add(new Request(Request.SUSPECT, suspected, true));
ack_collector.suspect(suspected);
merge_ack_collector.suspect(suspected);
return retval;
case Event.UNSUSPECT:
impl.unsuspect((Address) evt.getArg());
return null; // discard
case Event.MERGE:
view_handler.add(
new Request(Request.MERGE, null, false, (Map<Address, View>) evt.getArg()));
return null; // don't pass up
case Event.IS_MERGE_IN_PROGRESS:
return merger.isMergeInProgress();
}
return up_prot.up(evt);
}
protected Address determineCoordinator() {
synchronized (members) {
return members.size() > 0 ? members.elementAt(0) : null;
}
}
/**
* Sets the new view and sends a VIEW_CHANGE event up and down the stack. If the view is a
* MergeView (subclass of View), then digest will be non-null and has to be set before installing
* the view.
*/
public void installView(View new_view, Digest digest) {
ViewId vid = new_view.getVid();
List<Address> mbrs = new_view.getMembers();
ltime =
Math.max(
vid.getId(),
ltime); // compute the logical time, regardless of whether the view is accepted
// Discards view with id lower than or equal to our own. Will be installed without check if it
// is the first view
if (view != null) {
ViewId view_id = view.getViewId();
int rc = vid.compareToIDs(view_id);
if (rc <= 0) {
if (log.isWarnEnabled()
&& rc < 0
&& log_view_warnings) { // only scream if view is smaller, silently discard same views
log.warn(
local_addr
+ ": received view < current view;"
+ " discarding it (current vid: "
+ view_id
+ ", new vid: "
+ vid
+ ')');
}
return;
}
}
/* Check for self-inclusion: if I'm not part of the new membership, I just discard it.
This ensures that messages sent in view V1 are only received by members of V1 */
if (!mbrs.contains(local_addr)) {
if (log.isWarnEnabled() && log_view_warnings)
log.warn(local_addr + ": not member of view " + new_view.getViewId() + "; discarding it");
return;
}
if (digest != null) {
if (new_view instanceof MergeView) mergeDigest(digest);
else setDigest(digest);
}
if (log.isDebugEnabled()) log.debug(local_addr + ": installing view " + new_view);
Event view_event;
synchronized (members) {
view = new View(new_view.getVid(), new_view.getMembers());
view_event = new Event(Event.VIEW_CHANGE, new_view);
// Set the membership. Take into account joining members
if (!mbrs.isEmpty()) {
members.set(mbrs);
tmp_members.set(members);
joining.removeAll(mbrs); // remove all members in mbrs from joining
// remove all elements from 'leaving' that are not in 'mbrs'
leaving.retainAll(mbrs);
tmp_members.add(joining); // add members that haven't yet shown up in the membership
tmp_members.remove(
leaving); // remove members that haven't yet been removed from the membership
// add to prev_members
for (Address addr : mbrs) {
if (!prev_members.contains(addr)) prev_members.add(addr);
}
}
Address coord = determineCoordinator();
if (coord != null && coord.equals(local_addr) && !haveCoordinatorRole()) {
becomeCoordinator();
} else {
if (haveCoordinatorRole() && !local_addr.equals(coord)) {
becomeParticipant();
merge_ack_collector.reset(null); // we don't need this one anymore
}
}
}
// - Changed order of passing view up and down (http://jira.jboss.com/jira/browse/JGRP-347)
// - Changed it back (bela Sept 4 2007): http://jira.jboss.com/jira/browse/JGRP-564
// - Moved sending up view_event out of the synchronized block (bela Nov 2011)
down_prot.down(view_event); // needed e.g. by failure detector or UDP
up_prot.up(view_event);
List<Address> tmp_mbrs = new_view.getMembers();
ack_collector.retainAll(tmp_mbrs);
merge_ack_collector.retainAll(tmp_mbrs);
if (new_view instanceof MergeView) merger.forceCancelMerge();
if (stats) {
num_views++;
prev_views.add(new Tuple<View, Long>(new_view, System.currentTimeMillis()));
}
}
@ManagedAttribute
public int getNumMembers() {
return members.size();
}
@ManagedAttribute
public String getMembers() {
return members.toString();
}
