/** Compute balance plan */
public BalancePlan(Balancer balancer, List<DatanodeInfo> datanodes) {
if (datanodes == null || datanodes.isEmpty()) {
throw new IllegalArgumentException("cannot prepare plan for empty cluster");
}
avgRemaining = computeAvgRemaining(datanodes);
lowerRemainingThreshold = Math.max(avgRemaining / 2, avgRemaining - balancer.threshold);
upperRemainingThreshold = Math.min(PERCENTAGE_BASE, avgRemaining + balancer.threshold);
if (lowerRemainingThreshold > upperRemainingThreshold) {
throw new IllegalStateException("lowerThresh > upperThresh");
}
LOG.info(
"balanced range: [ "
+ lowerRemainingThreshold
+ ", "
+ upperRemainingThreshold
+ " ], average remaining: "
+ avgRemaining);
long overLoadedBytes = 0L, underLoadedBytes = 0L;
Bucket clusterBucket = new Bucket();
Map<Node, Bucket> rackBuckets = new HashMap<Node, Bucket>();
for (DatanodeInfo datanode : datanodes) {
// Update network topology
cluster.add(datanode);
// Create bucket if none
assert datanode.getParent() != null : "node outside of any rack";
Bucket bucket = rackBuckets.get(datanode.getParent());
if (bucket == null) {
bucket = new Bucket();
rackBuckets.put(datanode.getParent(), bucket);
}
// Put DataNode into chosen bucket
BalancerDatanode datanodeS;
if (getRemaining(datanode) < avgRemaining) {
// Above average utilized
datanodeS = balancer.getSource(datanode, avgRemaining);
bucket.addSource((Source) datanodeS);
clusterBucket.addSource((Source) datanodeS);
if (isOverUtilized(datanodeS)) {
overLoadedBytes +=
(long)
((lowerRemainingThreshold - datanodeS.getCurrentRemaining())
* datanodeS.getDatanode().getCapacity()
/ PERCENTAGE_BASE);
}
} else {
// Below average utilized
datanodeS = new Target(datanode, avgRemaining);
bucket.addTarget((Target) datanodeS);
clusterBucket.addTarget((Target) datanodeS);
if (isUnderUtilized(datanodeS)) {
underLoadedBytes +=
(long)
((datanodeS.getCurrentRemaining() - upperRemainingThreshold)
* datanodeS.getDatanode().getCapacity()
/ PERCENTAGE_BASE);
}
}
// Update all DataNodes list
this.datanodes.put(datanode.getStorageID(), datanodeS);
}
bytesLeftToMove = Math.max(overLoadedBytes, underLoadedBytes);
logImbalancedNodes();
// Balance each rack bucket separately
for (Bucket bucket : rackBuckets.values()) {
double rackAverage = bucket.computeAvgRemaining();
if (lowerRemainingThreshold <= rackAverage && rackAverage <= upperRemainingThreshold) {
bucket.updatePlan();
}
// If perfectly balanced rack renders only over or underutilized DataNodes
// we do not bother balancing it
}
// Balance cluster-wide afterwards
clusterBucket.externalUpdate();
clusterBucket.updatePlan();
bytesToMove = 0L;
for (Source src : sources) {
bytesToMove += src.scheduledSize;
}
logPlanOutcome();
}
