in flink-connector-gcp-pubsub/src/main/java/org/apache/flink/streaming/connectors/gcp/pubsub/PubSubSource.java [171:178]
public void collect(OUT record) {
if (endOfStreamSignalled || deserializationSchema.isEndOfStream(record)) {
this.endOfStreamSignalled = true;
return;
}
ctx.collect(record);
}