/// <summary> 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.
/// </summary>
/// <param name="v">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.
/// </param>
internal virtual MergeData consolidateMergeData(System.Collections.ArrayList v)
{
MergeData ret = null;
MergeData tmp_data;
long logical_time = 0; // for new_vid
ViewId new_vid, tmp_vid;
MergeView new_view;
View tmp_view;
Membership new_mbrs = new Membership();
int num_mbrs = 0;
Digest new_digest = null;
Address new_coord;
System.Collections.ArrayList subgroups = System.Collections.ArrayList.Synchronized(new System.Collections.ArrayList(11));
// contains a list of Views, each View is a subgroup
for (int i = 0; i < v.Count; i++)
{
tmp_data = (MergeData)v[i];
gms.Stack.NCacheLog.Debug("merge data is " + tmp_data);
tmp_view = tmp_data.View;
if (tmp_view != null)
{
tmp_vid = tmp_view.Vid;
if (tmp_vid != null)
{
// compute the new view id (max of all vids +1)
logical_time = System.Math.Max(logical_time, tmp_vid.Id);
}
}
// merge all membership lists into one (prevent duplicates)
new_mbrs.add(tmp_view.Members);
subgroups.Add(tmp_view.Clone());
}
// the new coordinator is the first member of the consolidated & sorted membership list
new_mbrs.sort();
num_mbrs = new_mbrs.size();
new_coord = num_mbrs > 0 ? (Address)new_mbrs.elementAt(0) : null;
if (new_coord == null)
{
gms.Stack.NCacheLog.Error("CoordGmsImpl.consolodateMergeData", "new_coord is null.");
return null;
}
// should be the highest view ID seen up to now plus 1
new_vid = new ViewId(new_coord, logical_time + 1);
// determine the new view
new_view = new MergeView(new_vid, new_mbrs.Members, subgroups);
gms.Stack.NCacheLog.Debug("new merged view will be " + new_view);
// determine the new digest
new_digest = consolidateDigests(v, num_mbrs);
if (new_digest == null)
{
gms.Stack.NCacheLog.Error("CoordGmsImpl.consolidateMergeData", "digest could not be consolidated.");
return null;
}
gms.Stack.NCacheLog.Debug("consolidated digest=" + new_digest);
ret = new MergeData(gms.local_addr, new_view, new_digest);
return ret;
}
/// <summary> Invoked upon receiving a MERGE event from the MERGE layer. Starts the merge protocol.
/// See description of protocol in DESIGN.
/// </summary>
/// <param name="other_coords">A list of coordinators (including myself) found by MERGE protocol
/// </param>
public override void merge(System.Collections.ArrayList other_coords)
{
Membership tmp;
Address leader = null;
if (merging)
{
gms.Stack.NCacheLog.Warn("CoordGmsImpl.merge", "merge already in progress, discarded MERGE event");
return;
}
if (other_coords == null)
{
gms.Stack.NCacheLog.Warn("CoordGmsImpl.merge", "list of other coordinators is null. Will not start merge.");
return;
}
if (other_coords.Count <= 1)
{
gms.Stack.NCacheLog.Error("CoordGmsImpl.merge", "number of coordinators found is " + other_coords.Count + "; will not perform merge");
return;
}
/* Establish deterministic order, so that coords can elect leader */
tmp = new Membership(other_coords);
tmp.sort();
leader = (Address)tmp.elementAt(0);
gms.Stack.NCacheLog.Debug("coordinators in merge protocol are: " + tmp);
if (leader.Equals(gms.local_addr))
{
gms.Stack.NCacheLog.Debug("I (" + leader + ") will be the leader. Starting the merge task");
startMergeTask(other_coords);
}
}
