gianm commented on code in PR #12848: URL: https://github.com/apache/druid/pull/12848#discussion_r936935342
########## processing/src/main/java/org/apache/druid/frame/channel/ReadableFrameChannel.java: ########## @@ -0,0 +1,75 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + */ + +package org.apache.druid.frame.channel; + +import com.google.common.util.concurrent.ListenableFuture; +import org.apache.druid.frame.Frame; + +/** + * Interface for reading a sequence of frames. Supports nonblocking reads through the {@link #canRead()} and + * {@link #readabilityFuture()} methods. + * + * May be implemented using an in-memory queue, disk file, stream, etc. + */ +public interface ReadableFrameChannel +{ + /** + * Returns whether this channel is finished. Finished channels will not generate any further frames or errors. + * + * Generally, once you discover that a channel is finished, you should call {@link #doneReading()} and then + * discard it. + * + * Note that it is possible for a channel to be unfinished and also have no available frames or errors. This happens + * when it is not in a ready-for-reading state. See {@link #readabilityFuture()} for details. + */ + boolean isFinished(); + + /** + * Returns whether this channel has a frame or error condition currently available. If this method returns true, then + * you can call {@link #read()} to retrieve the frame or error. + * + * Note that it is possible for a channel to be unfinished and also have no available frames or errors. This happens + * when it is not in a ready-for-reading state. See {@link #readabilityFuture()} for details. + */ + boolean canRead(); + + /** + * Returns the next available frame from this channel. + * + * Before calling this method, you should check {@link #canRead()} to ensure there is a frame or + * error available. + * + * @throws java.util.NoSuchElementException if there is no frame currently available + */ + Frame read(); Review Comment: Hmm. Usage in processors generally looks like this: ``` if (channel.canRead()) { // call channel.read() and handle next frame } else if (channel.isFinished()) { // handle eof } ``` It seems clear to me, so I'm inclined to leave it as-is. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
