private Set<String> globalNodeGroups() {
        final Set<String> globalGroups = new HashSet<>();
        for (final Map.Entry<Integer, Set<String>> nodeGroup : nodeGroups().entrySet()) {
            final Set<String> nodes = nodeGroup.getValue();
            for (final String node : nodes) {
                if (isGlobalSource(node)) {
                    globalGroups.addAll(nodes);
                }
            }
        }
        return globalGroups;
    }
Builds the topology for any global state stores
@return ProcessorTopology of global state
streams/src/main/java/org/apache/kafka/streams/processor/internals/InternalTopologyBuilder.java