OneSizeFitsQuorum commented on code in PR #16604:
URL: https://github.com/apache/iotdb/pull/16604#discussion_r2438055725
##########
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/planner/plan/AbstractFragmentParallelPlanner.java:
##########
@@ -133,13 +132,29 @@ protected TDataNodeLocation
selectTargetDataNode(TRegionReplicaSet regionReplica
if (regionReplicaSet.getDataNodeLocationsSize() !=
availableDataNodes.size()) {
LOGGER.info("available replicas: {}", availableDataNodes);
}
+ int targetIndex = getTargetIndex(availableDataNodes);
+ return availableDataNodes.get(targetIndex);
+ }
+
+ private int getTargetIndex(List<TDataNodeLocation> availableDataNodes) {
int targetIndex;
- if (!selectRandomDataNode || queryContext.getSession() == null) {
+ if (ReadConsistencyLevel.STRONG == this.readConsistencyLevel
+ || queryContext.getSession() == null) {
targetIndex = 0;
- } else {
+ } else if (ReadConsistencyLevel.WEAK == this.readConsistencyLevel) {
targetIndex = (int) (queryContext.getSession().getSessionId() %
availableDataNodes.size());
+ } else if (ReadConsistencyLevel.FOLLOWER_READ ==
this.readConsistencyLevel) {
+ // The first available data node is always leader which is guaranteed by
ConfigNode and
+ // PartitionFetcher in DataNode
+ // We only need to randomly choose any one from [1,
availableDataNodes.size()).
+ // SessionId is a unchanged long value for each connection, so we can
use that as random seed
+ targetIndex =
Review Comment:
When we only have one replica, maybe we should return 0 even user set
consistency_level to follower_read?, return a number >= 1 will cause an error?
##########
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/planner/plan/AbstractFragmentParallelPlanner.java:
##########
@@ -133,13 +132,29 @@ protected TDataNodeLocation
selectTargetDataNode(TRegionReplicaSet regionReplica
if (regionReplicaSet.getDataNodeLocationsSize() !=
availableDataNodes.size()) {
LOGGER.info("available replicas: {}", availableDataNodes);
}
+ int targetIndex = getTargetIndex(availableDataNodes);
+ return availableDataNodes.get(targetIndex);
+ }
+
+ private int getTargetIndex(List<TDataNodeLocation> availableDataNodes) {
int targetIndex;
- if (!selectRandomDataNode || queryContext.getSession() == null) {
+ if (ReadConsistencyLevel.STRONG == this.readConsistencyLevel
+ || queryContext.getSession() == null) {
targetIndex = 0;
- } else {
+ } else if (ReadConsistencyLevel.WEAK == this.readConsistencyLevel) {
targetIndex = (int) (queryContext.getSession().getSessionId() %
availableDataNodes.size());
+ } else if (ReadConsistencyLevel.FOLLOWER_READ ==
this.readConsistencyLevel) {
+ // The first available data node is always leader which is guaranteed by
ConfigNode and
+ // PartitionFetcher in DataNode
+ // We only need to randomly choose any one from [1,
availableDataNodes.size()).
+ // SessionId is a unchanged long value for each connection, so we can
use that as random seed
+ targetIndex =
Review Comment:
When we only have one replica, maybe we should return 0 even user set
consistency_level to follower_read, return a number >= 1 will cause an error?
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