java 可伸縮阻塞隊列實現

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最近一年多寫的最虐心的代碼。必須好好複習java並發了。搞了一晚上終於測試都跑通過了，特此紀念，以資鼓勵!

 

import java.util.ArrayList;import java.util.List;import java.util.concurrent.ArrayBlockingQueue;import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;/** * 實現可調整大小的阻塞隊列，支援資料移轉平衡reader,writer讀取吸入速度，達到最大吞吐 * @author hanjie * */public class RecordBuffer {    public static final Record CLOSE_RECORD = new Record() {        @Override        public Object getColumnValue(String columnName) {            // TODO Auto-generated method stub            return null;        }    };        public static final Record SWITCH_QUEUE_RECORD = new Record() {        @Override        public Object getColumnValue(String columnName) {            // TODO Auto-generated method stub            return null;        }    };        public Lock switchingQueueLock = new ReentrantLock();    public Condition readerSwitched = switchingQueueLock.newCondition();    public Condition writerSwitched = switchingQueueLock.newCondition();    public Condition switchFinished = switchingQueueLock.newCondition();        public volatile boolean readerSwitchSuccess = true;    public volatile boolean writerSwitchSuccess = true;    public volatile boolean switchingQueue = false;    public volatile boolean closed = false;    private volatile ArrayBlockingQueue<Record> queue;    private TaskCounter taskCounter;        public RecordBuffer(TaskCounter taskCounter, int size) {        this.queue = new ArrayBlockingQueue<Record>(size);        this.taskCounter = taskCounter;    }    public void resize(int newSize) {        try {                        if(closed){                return;            }                switchingQueueLock.lock();            try {                //double check下，要不可能writer收到CLOSED_record已經 退出了。writerSwitched.await() 會hang住                if(closed){                    return;                }                this.switchingQueue = true;                        ArrayBlockingQueue<Record> oldQueue = queue;                queue = new ArrayBlockingQueue<Record>(newSize);                this.readerSwitchSuccess = false;                this.writerSwitchSuccess = false;                                //先拯救下writer，可能writer剛好阻塞到take上,失敗也沒關係，說明老隊列不空，writer不會阻塞到take                oldQueue.offer(SWITCH_QUEUE_RECORD);                while (!writerSwitchSuccess) {                    writerSwitched.await();                }                //writer先切換隊列，然後reader可能阻塞在最後一個put上,清空下老隊列拯救reader，讓它順利醒來                transferOldQueueRecordsToNewQueue(oldQueue);                                                while (!readerSwitchSuccess) {                    readerSwitched.await();                }                //前面的清空，剛好碰到reader要put最後一個，非阻塞式清空動作就有殘留最後一個put                transferOldQueueRecordsToNewQueue(oldQueue);                                this.switchingQueue = false;                this.switchFinished.signalAll();            } finally {                switchingQueueLock.unlock();            }        } catch (InterruptedException e) {            Thread.currentThread().interrupt();            throw new RuntimeException(e);        }    }    private void transferOldQueueRecordsToNewQueue(ArrayBlockingQueue<Record> oldQueue)            throws InterruptedException {        List<Record> oldRecords = new ArrayList<Record>(oldQueue.size());        Record record = null;        while ((record = oldQueue.poll()) != null) {            oldRecords.add(record);        }        // 轉移老隊列剩下的記錄到新隊列        for (int i = 0; i < oldRecords.size(); i++) {            queue.put(oldRecords.get(i));        }    }    public void close() {        this.closed = true;        switchingQueueLock.lock();        try {            //如果正在切換隊列， 等切換做完才能，發送最後一個CLOSE            while (switchingQueue) {                switchFinished.await();            }                        this.queue.put(CLOSE_RECORD);        } catch (InterruptedException e) {            Thread.currentThread().interrupt();            throw new RuntimeException(e);        }        finally{            switchingQueueLock.unlock();        }    }    public void put(Record record) {        try {                        if (!queue.offer(record)) {                taskCounter.incrBufferFullCount();                if (!readerSwitchSuccess) {                    notifyReaderSwitchSuccess();                }                queue.put(record);            }            taskCounter.incrReadCount();        } catch (InterruptedException e) {            Thread.currentThread().interrupt();            throw new RuntimeException(e);        }    }    private void notifyReaderSwitchSuccess() {        System.out.println("reader switch");        switchingQueueLock.lock();        try {            readerSwitchSuccess = true;            readerSwitched.signalAll();        } finally {            switchingQueueLock.unlock();        }    }    public Record take() {        try {                        Record record = queue.poll();            //如果拿到了切換記錄，則切換隊列重試            if(record == SWITCH_QUEUE_RECORD){                if (!writerSwitchSuccess) {                    notifyWriterSwitchSuccess();                }                record = queue.poll();            }                        if (record == null) {                taskCounter.incrBufferEmptyCount();                                //調用take先檢查是否正在切換,保證拿到新的隊列                if (!writerSwitchSuccess) {                    notifyWriterSwitchSuccess();                }                record = queue.take();                //如果很不幸剛好在take阻塞時候，切換，只能發送一個切換記錄將其喚醒                if(record == SWITCH_QUEUE_RECORD){                    if (!writerSwitchSuccess) {                        notifyWriterSwitchSuccess();                    }                    record = queue.take();                }            }            if (record == CLOSE_RECORD) {                if (!writerSwitchSuccess) {                    notifyWriterSwitchSuccess();                }                return null;            }            taskCounter.incrWriteCount();            return record;        } catch (InterruptedException e) {            Thread.currentThread().interrupt();            throw new RuntimeException(e);        }    }    private void notifyWriterSwitchSuccess() {        System.out.println("writer switch");        switchingQueueLock.lock();        try {            writerSwitchSuccess = true;            writerSwitched.signalAll();        } finally {            switchingQueueLock.unlock();        }    }}

 

java 可伸縮阻塞隊列實現