boolean isEndOfStream(SystemStream systemStream) {
    return eosStates.entrySet().stream()
        .filter(entry -> entry.getKey().getSystemStream().equals(systemStream))
        .allMatch(entry -> entry.getValue().isEndOfStream());
  }
Update the state upon receiving an end-of-stream message.
@param eos message of {@link EndOfStreamMessage}
@param ssp system stream partition
samza-core/src/main/java/org/apache/samza/operators/impl/EndOfStreamStates.java