private ByteBuffer merge(
ContextState mergedState, ContextState leftState, ContextState rightState) {
while (leftState.hasRemaining() && rightState.hasRemaining()) {
int cmp = leftState.compareIdTo(rightState);
if (cmp == 0) {
Relationship rel = compare(leftState, rightState);
if (rel == Relationship.DISJOINT) // two local shards
mergedState.writeLocal(
leftState.getCounterId(),
leftState.getClock() + rightState.getClock(),
leftState.getCount() + rightState.getCount());
else if (rel == Relationship.GREATER_THAN) leftState.copyTo(mergedState);
else // EQUAL or LESS_THAN
rightState.copyTo(mergedState);
rightState.moveToNext();
leftState.moveToNext();
} else if (cmp > 0) {
rightState.copyTo(mergedState);
rightState.moveToNext();
} else // cmp < 0
{
leftState.copyTo(mergedState);
leftState.moveToNext();
}
}
while (leftState.hasRemaining()) {
leftState.copyTo(mergedState);
leftState.moveToNext();
}
while (rightState.hasRemaining()) {
rightState.copyTo(mergedState);
rightState.moveToNext();
}
return mergedState.context;
}
/**
* Return a context w/ an aggregated count for each counter id.
*
* @param left counter context.
* @param right counter context.
*/
public ByteBuffer merge(ByteBuffer left, ByteBuffer right) {
boolean leftIsSuperSet = true;
boolean rightIsSuperSet = true;
int globalCount = 0;
int localCount = 0;
int remoteCount = 0;
ContextState leftState = ContextState.wrap(left);
ContextState rightState = ContextState.wrap(right);
while (leftState.hasRemaining() && rightState.hasRemaining()) {
int cmp = leftState.compareIdTo(rightState);
if (cmp == 0) {
Relationship rel = compare(leftState, rightState);
if (rel == Relationship.GREATER_THAN) rightIsSuperSet = false;
else if (rel == Relationship.LESS_THAN) leftIsSuperSet = false;
else if (rel == Relationship.DISJOINT) leftIsSuperSet = rightIsSuperSet = false;
if (leftState.isGlobal() || rightState.isGlobal()) globalCount += 1;
else if (leftState.isLocal() || rightState.isLocal()) localCount += 1;
else remoteCount += 1;
leftState.moveToNext();
rightState.moveToNext();
} else if (cmp > 0) {
leftIsSuperSet = false;
if (rightState.isGlobal()) globalCount += 1;
else if (rightState.isLocal()) localCount += 1;
else remoteCount += 1;
rightState.moveToNext();
} else // cmp < 0
{
rightIsSuperSet = false;
if (leftState.isGlobal()) globalCount += 1;
else if (leftState.isLocal()) localCount += 1;
else remoteCount += 1;
leftState.moveToNext();
}
}
if (leftState.hasRemaining()) rightIsSuperSet = false;
else if (rightState.hasRemaining()) leftIsSuperSet = false;
// if one of the contexts is a superset, return it early.
if (leftIsSuperSet) return left;
else if (rightIsSuperSet) return right;
while (leftState.hasRemaining()) {
if (leftState.isGlobal()) globalCount += 1;
else if (leftState.isLocal()) localCount += 1;
else remoteCount += 1;
leftState.moveToNext();
}
while (rightState.hasRemaining()) {
if (rightState.isGlobal()) globalCount += 1;
else if (rightState.isLocal()) localCount += 1;
else remoteCount += 1;
rightState.moveToNext();
}
leftState.reset();
rightState.reset();
return merge(
ContextState.allocate(globalCount, localCount, remoteCount), leftState, rightState);
}
/**
* Determine the count relationship between two contexts.
*
* <p>EQUAL: Equal set of nodes and every count is equal. GREATER_THAN: Superset of nodes and
* every count is equal or greater than its corollary. LESS_THAN: Subset of nodes and every count
* is equal or less than its corollary. DISJOINT: Node sets are not equal and/or counts are not
* all greater or less than.
*
* <p>Strategy: compare node logical clocks (like a version vector).
*
* @param left counter context.
* @param right counter context.
* @return the Relationship between the contexts.
*/
public Relationship diff(ByteBuffer left, ByteBuffer right) {
Relationship relationship = Relationship.EQUAL;
ContextState leftState = ContextState.wrap(left);
ContextState rightState = ContextState.wrap(right);
while (leftState.hasRemaining() && rightState.hasRemaining()) {
// compare id bytes
int compareId = leftState.compareIdTo(rightState);
if (compareId == 0) {
long leftClock = leftState.getClock();
long rightClock = rightState.getClock();
long leftCount = leftState.getCount();
long rightCount = rightState.getCount();
// advance
leftState.moveToNext();
rightState.moveToNext();
// process clock comparisons
if (leftClock == rightClock) {
if (leftCount != rightCount) {
// Inconsistent shard (see the corresponding code in merge()). We return DISJOINT in
// this
// case so that it will be treated as a difference, allowing read-repair to work.
return Relationship.DISJOINT;
}
} else if ((leftClock >= 0 && rightClock > 0 && leftClock > rightClock)
|| (leftClock < 0 && (rightClock > 0 || leftClock < rightClock))) {
if (relationship == Relationship.EQUAL) relationship = Relationship.GREATER_THAN;
else if (relationship == Relationship.LESS_THAN) return Relationship.DISJOINT;
// relationship == Relationship.GREATER_THAN
} else {
if (relationship == Relationship.EQUAL) relationship = Relationship.LESS_THAN;
else if (relationship == Relationship.GREATER_THAN) return Relationship.DISJOINT;
// relationship == Relationship.LESS_THAN
}
} else if (compareId > 0) {
// only advance the right context
rightState.moveToNext();
if (relationship == Relationship.EQUAL) relationship = Relationship.LESS_THAN;
else if (relationship == Relationship.GREATER_THAN) return Relationship.DISJOINT;
// relationship == Relationship.LESS_THAN
} else // compareId < 0
{
// only advance the left context
leftState.moveToNext();
if (relationship == Relationship.EQUAL) relationship = Relationship.GREATER_THAN;
else if (relationship == Relationship.LESS_THAN) return Relationship.DISJOINT;
// relationship == Relationship.GREATER_THAN
}
}
// check final lengths
if (leftState.hasRemaining()) {
if (relationship == Relationship.EQUAL) return Relationship.GREATER_THAN;
else if (relationship == Relationship.LESS_THAN) return Relationship.DISJOINT;
}
if (rightState.hasRemaining()) {
if (relationship == Relationship.EQUAL) return Relationship.LESS_THAN;
else if (relationship == Relationship.GREATER_THAN) return Relationship.DISJOINT;
}
return relationship;
}
