zpinto commented on code in PR #2661:
URL: https://github.com/apache/helix/pull/2661#discussion_r1367174009
##########
helix-core/src/main/java/org/apache/helix/manager/zk/ZKHelixAdmin.java:
##########
@@ -410,13 +472,260 @@ public ZNRecord update(ZNRecord currentData) {
@Override
public boolean isEvacuateFinished(String clusterName, String instanceName) {
- return !instanceHasCurrentSateOrMessage(clusterName, instanceName) &&
(getInstanceConfig(clusterName,
+ return !instanceHasCurrentStateOrMessage(clusterName, instanceName) &&
(getInstanceConfig(
+ clusterName,
instanceName).getInstanceOperation().equals(InstanceConstants.InstanceOperation.EVACUATE.name()));
}
+ /**
+ * Find the instance that this passed instance is swapping with. If the
passed instance has
+ * SWAP_OUT instanceOperation, then find the corresponding instance that has
SWAP_IN
+ * instanceOperation. If the passed instance has SWAP_IN instanceOperation,
then find the
+ * corresponding instance that has SWAP_OUT instanceOperation.
+ *
+ * @param clusterName The cluster name
+ * @param instanceConfig The instance to find the swap instance for
+ * @return The swap instance if found, null otherwise.
+ */
+ @Nullable
+ private InstanceConfig findMatchingSwapInstance(String clusterName,
+ InstanceConfig instanceConfig) {
+ String logicalIdKey =
+
ClusterTopologyConfig.createFromClusterConfig(_configAccessor.getClusterConfig(clusterName))
+ .getEndNodeType();
+
+ for (String potentialSwappingInstance : getConfigKeys(
+ new
HelixConfigScopeBuilder(HelixConfigScope.ConfigScopeProperty.PARTICIPANT,
+ clusterName).build())) {
+ InstanceConfig potentialSwappingInstanceConfig =
+ getInstanceConfig(clusterName, potentialSwappingInstance);
+
+ // Return if there is a matching Instance with the same logicalId and
opposite InstanceOperation swap operation.
+ if (potentialSwappingInstanceConfig.getLogicalId(logicalIdKey)
+ .equals(instanceConfig.getLogicalId(logicalIdKey)) && (
+ instanceConfig.getInstanceOperation()
+ .equals(InstanceConstants.InstanceOperation.SWAP_IN.name())
+ && potentialSwappingInstanceConfig.getInstanceOperation()
+ .equals(InstanceConstants.InstanceOperation.SWAP_OUT.name())) ||
(
+ instanceConfig.getInstanceOperation()
+ .equals(InstanceConstants.InstanceOperation.SWAP_OUT.name())
+ && potentialSwappingInstanceConfig.getInstanceOperation()
+ .equals(InstanceConstants.InstanceOperation.SWAP_IN.name()))) {
+ return potentialSwappingInstanceConfig;
+ }
+ }
+
+ return null;
+ }
+
+ /**
+ * Check to see if swapping between two instances is ready to be completed.
Checks: 1. Both
+ * instances must be alive. 2. Both instances must only have one session and
not be carrying over
+ * from a previous session. 3. Both instances must have no pending messages.
4. Both instances
+ * cannot have partitions in the ERROR state 4. SwapIn instance must have
correct state for all
+ * partitions that are currently assigned to the SwapOut instance.
+ * TODO: We may want to make this a public API in the future.
Review Comment:
I don't think this will work in every case because the ideal state is not
persisted in ZK without PERSIST_BEST_POSSIBLE_STATE set to true. I think that
only checking current state and no pending messages is sufficient because if
the replica from the ideal state is not already being bootstrapped on SWAP_OUT
node then it will be sent directly to SWAP_IN node right after the swap
completes.
If load balance is causing the new replica to be assigned to SWAP_OUT node
then if the ST message never gets to the SWAP_OUT node before completing the
SWAP it is okay because once we switch to the SWAP_IN node we have not dropped
the replica from its old location yet.
This means that it will still be N -> N+1 -> N for the newly assigned
replica.
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