drcrallen commented on a change in pull request #6629: Add support parallel
combine in brokers
URL: https://github.com/apache/incubator-druid/pull/6629#discussion_r240755841
##########
File path:
server/src/main/java/org/apache/druid/client/CachingClusteredClient.java
##########
@@ -285,12 +301,72 @@ public CachingClusteredClient(
List<Sequence<T>> sequencesByInterval = new
ArrayList<>(alreadyCachedResults.size() + segmentsByServer.size());
addSequencesFromCache(sequencesByInterval, alreadyCachedResults);
addSequencesFromServer(sequencesByInterval, segmentsByServer);
- return Sequences
- .simple(sequencesByInterval)
- .flatMerge(seq -> seq, query.getResultOrdering());
+ return merge(sequencesByInterval);
});
}
+ private Sequence<T> merge(List<Sequence<T>> sequencesByInterval)
+ {
+ final int numParallelCombineThreads =
QueryContexts.getNumBrokerParallelCombineThreads(query);
+
+ if (numParallelCombineThreads > 0) {
+ final ReserveResult reserveResult =
processingThreadResourcePool.reserve(query, numParallelCombineThreads);
+ if (!reserveResult.isOk()) {
+ throw new ISE(
+ "Not enough processing threads. The query needs [%d] threads,
but only [%d] were available",
+ numParallelCombineThreads,
+ reserveResult.getNumAvailableResources()
+ );
+ }
+ return parallelMerge(sequencesByInterval,
reserveResult.getResources());
+ } else if (numParallelCombineThreads ==
QueryContexts.NUM_CURRENT_AVAILABLE_THREADS) {
+ final ReserveResult reserveResult =
processingThreadResourcePool.reserve(query, numParallelCombineThreads);
+ if (reserveResult.isOk()) {
+ return parallelMerge(sequencesByInterval,
reserveResult.getResources());
+ } else {
+ return sequentialMerge(sequencesByInterval);
+ }
+ } else if (numParallelCombineThreads ==
QueryContexts.NO_PARALLEL_COMBINE_THREADS) {
+ return sequentialMerge(sequencesByInterval);
+ } else {
+ throw new ISE(
Review comment:
Suggest making the check simply
```java
if (numParallelCombineThreads == QueryContexts.NO_PARALLEL_COMBINE_THREADS) {
return sequentialMerge(sequencesByInterval);
}
final ReserveResult reserveResult =
processingThreadResourcePool.reserve(query, numParallelCombineThreads);
if (reserveResult.isOk()) {
return parallelMerge(sequencesByInterval,
reserveResult.getResources());
} else {
return sequentialMerge(sequencesByInterval);
}
```
and have `processingThreadResourcePool.reserve` handle the positive or
negative cases (negative meaning all available, positive meaning no more than
that number)
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