105 lines
5.2 KiB
Java
105 lines
5.2 KiB
Java
/*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/*
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* Copyright 2015 ScyllaDB
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*
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* Modified by ScyllaDB
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*/
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package org.apache.cassandra.streaming;
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/**
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* Handles the streaming a one or more section of one of more sstables to and
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* from a specific remote node.
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*
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* Both this node and the remote one will create a similar symmetrical
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* StreamSession. A streaming session has the following life-cycle:
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*
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* 1. Connections Initialization
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*
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* (a) A node (the initiator in the following) create a new StreamSession,
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* initialize it (init()) and then start it (start()). Start will create a
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* {@link ConnectionHandler} that will create two connections to the remote node
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* (the follower in the following) with whom to stream and send a StreamInit
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* message. The first connection will be the incoming connection for the
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* initiator, and the second connection will be the outgoing. (b) Upon reception
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* of that StreamInit message, the follower creates its own StreamSession,
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* initialize it if it still does not exist, and attach connecting socket to its
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* ConnectionHandler according to StreamInit message's isForOutgoing flag. (d)
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* When the both incoming and outgoing connections are established,
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* StreamSession calls StreamSession#onInitializationComplete method to start
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* the streaming prepare phase (StreamResultFuture.startStreaming()).
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*
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* 2. Streaming preparation phase
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*
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* (a) This phase is started when the initiator onInitializationComplete()
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* method is called. This method sends a PrepareMessage that includes what
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* files/sections this node will stream to the follower (stored in a
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* StreamTransferTask, each column family has it's own transfer task) and what
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* the follower needs to stream back (StreamReceiveTask, same as above). If the
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* initiator has nothing to receive from the follower, it goes directly to its
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* Streaming phase. Otherwise, it waits for the follower PrepareMessage. (b)
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* Upon reception of the PrepareMessage, the follower records which
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* files/sections it will receive and send back its own PrepareMessage with a
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* summary of the files/sections that will be sent to the initiator (prepare()).
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* After having sent that message, the follower goes to its Streamning phase.
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* (c) When the initiator receives the follower PrepareMessage, it records which
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* files/sections it will receive and then goes to his own Streaming phase.
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*
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* 3. Streaming phase
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*
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* (a) The streaming phase is started by each node (the sender in the follower,
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* but note that each side of the StreamSession may be sender for some of the
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* files) involved by calling startStreamingFiles(). This will sequentially send
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* a FileMessage for each file of each SteamTransferTask. Each FileMessage
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* consists of a FileMessageHeader that indicates which file is coming and then
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* start streaming the content for that file (StreamWriter in
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* FileMessage.serialize()). When a file is fully sent, the fileSent() method is
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* called for that file. If all the files for a StreamTransferTask are sent
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* (StreamTransferTask.complete()), the task is marked complete
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* (taskCompleted()). (b) On the receiving side, a SSTable will be written for
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* the incoming file (StreamReader in FileMessage.deserialize()) and once the
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* FileMessage is fully received, the file will be marked as complete
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* (received()). When all files for the StreamReceiveTask have been received,
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* the sstables are added to the CFS (and 2ndary index are built,
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* StreamReceiveTask.complete()) and the task is marked complete
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* (taskCompleted()) (b) If during the streaming of a particular file an I/O
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* error occurs on the receiving end of a stream (FileMessage.deserialize), the
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* node will retry the file (up to DatabaseDescriptor.getMaxStreamingRetries())
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* by sending a RetryMessage to the sender. On receiving a RetryMessage, the
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* sender simply issue a new FileMessage for that file. (c) When all transfer
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* and receive tasks for a session are complete, the move to the Completion
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* phase (maybeCompleted()).
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*
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* 4. Completion phase
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*
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* (a) When a node has finished all transfer and receive task, it enter the
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* completion phase (maybeCompleted()). If it had already received a
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* CompleteMessage from the other side (it is in the WAIT_COMPLETE state), that
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* session is done is is closed (closeSession()). Otherwise, the node switch to
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* the WAIT_COMPLETE state and send a CompleteMessage to the other side.
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*/
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public class StreamSession {
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public static enum State {
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INITIALIZED, PREPARING, STREAMING, WAIT_COMPLETE, COMPLETE, FAILED,
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}
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}
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