ableegoldman commented on a change in pull request #8540:
URL: https://github.com/apache/kafka/pull/8540#discussion_r414822929
##########
File path: streams/src/main/java/org/apache/kafka/streams/KafkaStreams.java
##########
@@ -701,18 +703,33 @@ private KafkaStreams(final InternalTopologyBuilder
internalTopologyBuilder,
internalTopologyBuilder,
parseHostInfo(config.getString(StreamsConfig.APPLICATION_SERVER_CONFIG)));
+ final int numStreamThreads;
+ if (internalTopologyBuilder.hasNoNonGlobalTopology()) {
+ log.warn("Overriding number of StreamThreads to zero for
global-only topology");
+ numStreamThreads = 0;
+ } else {
+ numStreamThreads =
config.getInt(StreamsConfig.NUM_STREAM_THREADS_CONFIG);
+ }
+
// create the stream thread, global update thread, and cleanup thread
- threads = new
StreamThread[config.getInt(StreamsConfig.NUM_STREAM_THREADS_CONFIG)];
+ threads = new StreamThread[numStreamThreads];
+
+ final ProcessorTopology globalTaskTopology =
internalTopologyBuilder.buildGlobalStateTopology();
+ final boolean hasGlobalTopology = globalTaskTopology != null;
+
+ if (numStreamThreads == 0 && !hasGlobalTopology) {
+ log.error("Must subscribe to at least one source topic or global
table");
+ throw new IllegalArgumentException("Topology has no stream threads
and no global threads");
Review comment:
~~Also, do we have an `InvalidTopologyException` or similar exception
already? Or were you proposing to add a new type~~
edit: Nevermind it's just `TopologyException`, found it
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