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Allow one search shard to fall back to undesired allocation #113847

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merged 2 commits into from
Oct 1, 2024
Merged

Allow one search shard to fall back to undesired allocation #113847

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ce4db3c
Allow one search shard to fall back to undesired allocation
pxsalehi Oct 1, 2024
a76f6ee
First check throttled
pxsalehi Oct 1, 2024
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25 changes: 21 additions & 4 deletions ...java/org/elasticsearch/cluster/routing/allocation/allocator/DesiredBalanceReconciler.java
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Original file line number Diff line number Diff line change
Expand Up @@ -305,7 +305,7 @@ private void allocateUnassigned() {
unallocatedStatus = AllocationStatus.NO_ATTEMPT;
} else {
unallocatedStatus = AllocationStatus.DECIDERS_NO;
final var nodeIdsIterator = new NodeIdsIterator(shard, assignment);
final var nodeIdsIterator = new NodeIdsIterator(shard, assignment, routingNodes);
while (nodeIdsIterator.hasNext()) {
final var nodeId = nodeIdsIterator.next();
final var routingNode = routingNodes.node(nodeId);
Expand Down Expand Up @@ -367,7 +367,7 @@ private void allocateUnassigned() {
private final class NodeIdsIterator implements Iterator<String> {

private final ShardRouting shard;

private final RoutingNodes routingNodes;
/**
* Contains the source of the nodeIds used for shard assignment. It could be:
* * desired - when using desired nodes
Expand All @@ -380,8 +380,9 @@ private final class NodeIdsIterator implements Iterator<String> {

private boolean wasThrottled = false;

NodeIdsIterator(ShardRouting shard, ShardAssignment assignment) {
NodeIdsIterator(ShardRouting shard, ShardAssignment assignment, RoutingNodes routingNodes) {
this.shard = shard;
this.routingNodes = routingNodes;

var forcedInitialAllocation = allocation.deciders().getForcedInitialShardAllocationToNodes(shard, allocation);
if (forcedInitialAllocation.isPresent()) {
Expand All @@ -396,7 +397,10 @@ private final class NodeIdsIterator implements Iterator<String> {

@Override
public boolean hasNext() {
if (nodeIds.hasNext() == false && source == NodeIdSource.DESIRED && shard.primary() && wasThrottled == false) {
if (nodeIds.hasNext() == false
&& source == NodeIdSource.DESIRED
&& wasThrottled == false
&& useFallback(shard, routingNodes)) {
var fallbackNodeIds = allocation.routingNodes().getAllNodeIds();
logger.debug("Shard [{}] assignment is temporarily not possible. Falling back to {}", shard.shardId(), fallbackNodeIds);
nodeIds = allocationOrdering.sort(fallbackNodeIds).iterator();
Expand All @@ -405,6 +409,19 @@ public boolean hasNext() {
return nodeIds.hasNext();
}

private boolean useFallback(ShardRouting shard, RoutingNodes routingNodes) {
if (shard.primary()) {
return true;
}
if (shard.role().equals(ShardRouting.Role.SEARCH_ONLY)) {
// Allow only one search shard to fall back to allocation to an undesired node
return routingNodes.assignedShards(shard.shardId())
.stream()
.noneMatch(s -> s.role().equals(ShardRouting.Role.SEARCH_ONLY));
}
return false;
}

@Override
public String next() {
return nodeIds.next();
Expand Down