in flink-connector/flink-connector-gcp-pubsub/src/main/java/com/google/pubsub/flink/internal/source/reader/PubSubSplitReader.java [101:108]
public synchronized void handleSplitsChanges(SplitsChange<SubscriptionSplit> splitsChange) {
if (!(splitsChange instanceof SplitsAddition)) {
throw new IllegalArgumentException("Unexpected split event " + splitsChange);
}
for (SubscriptionSplit newSplit : splitsChange.splits()) {
subscribers.computeIfAbsent(newSplit.splitId(), (splitId) -> factory.get());
}
}