Alieh Saeedi created KAFKA-21251:
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Summary: kafka-streams-groups.sh --describe --topology: global
store sub-topology label can collide with a real subtopology id
Key: KAFKA-21251
URL: https://issues.apache.org/jira/browse/KAFKA-21251
Project: Kafka
Issue Type: Bug
Reporter: Alieh Saeedi
h2. Problem
{{TopologyDescriptionFormatter}}
(tools/src/main/java/org/apache/kafka/tools/streams/TopologyDescriptionFormatter.java)
labels global stores starting at {{{}topology.subtopologies().size(){}}}:
{{int globalStoreId = topology.subtopologies().size();for (final GlobalStore
globalStore : topology.globalStores()) { appendGlobalStore(sb, globalStore,
globalStoreId++);}}}
This assumes regular subtopologies are numbered {{{}0..N-1{}}}. In Kafka
Streams, global stores and subtopologies share one node-group id counter
({{{}InternalTopologyBuilder{}}}), so if the app defines its global store/table
first, the global store gets id {{0}} and regular subtopologies get
{{{}1..N{}}}.
h2. Example
Global store defined first, then two regular subtopologies (real ids 1, 2). CLI
output:
{{Sub-topology: 1Sub-topology: 2Sub-topology: 2 for global store (will not
generate tasks) <- collides with real sub-topology 2}}
Stock Streams {{TopologyDescription.toString()}} would label the global store
{{{}0{}}}.
h2. Impact
Cosmetic, CLI display only (KIP-1331 {{{}--describe --topology{}}}).
Stored/pushed topology data and the CRD are unaffected. Not a release blocker;
can confuse operators reading the output.
h2. Possible fixes
# Minimal: start global labels at {{max(subtopology id) + 1}} — removes the
collision, but may still differ from Streams' own id.
# Exact: carry the global store's real id in the KIP-1331 description and
print it — matches stock Streams output, but needs a protocol/API change.
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