in pulsar-client-reactive-api/src/main/java/org/apache/pulsar/reactive/client/internal/api/InflightLimiter.java [321:325]
void maybeAddToPending() {
if (this.requestedDemand.get() > 0 && !isDisposed() && this.inflightForSubscription.get() == 0) {
InflightLimiter.this.pendingSubscriptions.add(this);
}
}