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Simplify calculation in AwarenessAllocationDecider (#38091) 

Today's calculation of the maximum number of shards per attribute is rather
convoluted. This commit clarifies that it returns
ceil(shardCount/numberOfAttributes).
This commit is contained in:
David Turner 2019-02-20 08:55:04 +00:00
parent 00a26b9dd2
commit efffb3d5b7
1 changed files with 7 additions and 19 deletions
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26
server/src/main/java/org/elasticsearch/cluster/routing/allocation/decider/AwarenessAllocationDecider.java
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@ -136,7 +136,7 @@ public class AwarenessAllocationDecider extends AllocationDecider {
int shardCount = indexMetaData.getNumberOfReplicas() + 1; // 1 for primary
for (String awarenessAttribute : awarenessAttributes) {
// the node the shard exists on must be associated with an awareness attribute
if (!node.node().getAttributes().containsKey(awarenessAttribute)) {
if (node.node().getAttributes().containsKey(awarenessAttribute) == false) {
return allocation.decision(Decision.NO, NAME,
"node does not contain the awareness attribute [%s]; required attributes cluster setting [%s=%s]",
awarenessAttribute, CLUSTER_ROUTING_ALLOCATION_AWARENESS_ATTRIBUTE_SETTING.getKey(),
@ -160,7 +160,7 @@ public class AwarenessAllocationDecider extends AllocationDecider {
if (moveToNode) {
if (shardRouting.assignedToNode()) {
String nodeId = shardRouting.relocating() ? shardRouting.relocatingNodeId() : shardRouting.currentNodeId();
if (!node.nodeId().equals(nodeId)) {
if (node.nodeId().equals(nodeId) == false) {
// we work on different nodes, move counts around
shardPerAttribute.putOrAdd(allocation.routingNodes().node(nodeId).node().getAttributes().get(awarenessAttribute),
0, -1);
@ -175,28 +175,16 @@ public class AwarenessAllocationDecider extends AllocationDecider {
List<String> fullValues = forcedAwarenessAttributes.get(awarenessAttribute);
if (fullValues != null) {
for (String fullValue : fullValues) {
if (!shardPerAttribute.containsKey(fullValue)) {
if (shardPerAttribute.containsKey(fullValue) == false) {
numberOfAttributes++;
}
}
}
// TODO should we remove ones that are not part of full list?
int averagePerAttribute = shardCount / numberOfAttributes;
int totalLeftover = shardCount % numberOfAttributes;
int requiredCountPerAttribute;
if (averagePerAttribute == 0) {
// if we have more attributes values than shard count, no leftover
totalLeftover = 0;
requiredCountPerAttribute = 1;
} else {
requiredCountPerAttribute = averagePerAttribute;
}
int leftoverPerAttribute = totalLeftover == 0 ? 0 : 1;
int currentNodeCount = shardPerAttribute.get(node.node().getAttributes().get(awarenessAttribute));
// if we are above with leftover, then we know we are not good, even with mod
if (currentNodeCount > (requiredCountPerAttribute + leftoverPerAttribute)) {
final int currentNodeCount = shardPerAttribute.get(node.node().getAttributes().get(awarenessAttribute));
final int maximumNodeCount = (shardCount + numberOfAttributes - 1) / numberOfAttributes; // ceil(shardCount/numberOfAttributes)
if (currentNodeCount > maximumNodeCount) {
return allocation.decision(Decision.NO, NAME,
"there are too many copies of the shard allocated to nodes with attribute [%s], there are [%d] total configured " +
"shard copies for this shard id and [%d] total attribute values, expected the allocated shard count per " +
@ -205,7 +193,7 @@ public class AwarenessAllocationDecider extends AllocationDecider {
shardCount,
numberOfAttributes,
currentNodeCount,
requiredCountPerAttribute + leftoverPerAttribute);
maximumNodeCount);
}
}