+
−/*
+
− * This Source Code Form is subject to the terms of the Mozilla Public
+
− * License, v. 2.0.  If a copy of the MPL was not distributed with this
+
− * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
− *
+
− * Copyright 1997 - July 2008 CWI, August 2008 - 2016 MonetDB B.V.
+
− */
+
−
+
−package nl.cwi.monetdb.mcl.connection;
+
−
+
−import nl.cwi.monetdb.mcl.protocol.AbstractProtocol;
+
−
+
−import java.io.IOException;
+
−import java.sql.SQLException;
+
−import java.util.concurrent.locks.Condition;
+
−import java.util.concurrent.locks.Lock;
+
−import java.util.concurrent.locks.ReentrantLock;
+
−
+
−/**
+
− * A thread to send a query to the server.  When sending large
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− * amounts of data to a server, the output buffer of the underlying
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− * communication socket may overflow.  In such case the sending
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− * process blocks.  In order to prevent deadlock, it might be
+
− * desirable that the driver as a whole does not block.  This thread
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− * facilitates the prevention of such 'full block', because this
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− * separate thread only will block.<br />
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− * This thread is designed for reuse, as thread creation costs are
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− * high.
+
− */
+
−public class SenderThread extends Thread {
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−
+
−    private enum SendThreadStatus {
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−        /** The state WAIT represents this thread to be waiting for something to do */
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−        WAIT,
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−        /** The state QUERY represents this thread to be executing a query */
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−        QUERY,
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−        /** The state SHUTDOWN is the final state that ends this thread */
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−        SHUTDOWN
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−    }
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−
+
−    private String[] templ;
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−    private String query;
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−    private AbstractProtocol protocol;
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−    private String error;
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−    private SendThreadStatus state = SendThreadStatus.WAIT;
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−    private final Lock sendLock = new ReentrantLock();
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−    private final Condition queryAvailable = sendLock.newCondition();
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−    private final Condition waiting = sendLock.newCondition();
+
−
+
−    /**
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−     * Constructor which immediately starts this thread and sets it into daemon mode.
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−     *
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−     * @param out the socket to write to
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−     */
+
−    public SenderThread(AbstractProtocol out) {
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−        super("SendThread");
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−        this.setDaemon(true);
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−        this.protocol = out;
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−        this.start();
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−    }
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−
+
−    @Override
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−    public void run() {
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−        this.sendLock.lock();
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−        try {
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−            while (true) {
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−                while (this.state == SendThreadStatus.WAIT) {
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−                    try {
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−                        this.queryAvailable.await();
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−                    } catch (InterruptedException e) {
+
−                        // woken up, eh?
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−                    }
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−                }
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−                if (this.state == SendThreadStatus.SHUTDOWN)
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−                    break;
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−
+
−                // state is QUERY here
+
−                try {
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−                    this.protocol.writeNextQuery((templ[0] == null ? "" : templ[0]), query,
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−                            (templ[1] == null ? "" : templ[1]));
+
−                } catch (IOException e) {
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−                    this.error = e.getMessage();
+
−                }
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−
+
−                // update our state, and notify, maybe someone is waiting
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−                // for us in throwErrors
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−                this.state = SendThreadStatus.WAIT;
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−                this.waiting.signal();
+
−            }
+
−        } finally {
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−            this.sendLock.unlock();
+
−        }
+
−    }
+
−
+
−    /**
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−     * Starts sending the given query over the given socket. Beware that the thread should be finished (can be assured
+
−     * by calling throwErrors()) before this method is called!
+
−     *
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−     * @param templ the query template
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−     * @param query the query itself
+
−     * @throws SQLException if this SendThread is already in use
+
−     */
+
−    public void runQuery(String[] templ, String query) throws SQLException {
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−        this.sendLock.lock();
+
−        try {
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−            if (this.state != SendThreadStatus.WAIT) {
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−                throw new SQLException("Sender Thread already in use or shutting down!", "M0M03");
+
−            }
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−            this.templ = templ;
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−            this.query = query;
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−            // let the thread know there is some work to do
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−            this.state = SendThreadStatus.QUERY;
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−            this.queryAvailable.signal();
+
−        } finally {
+
−            this.sendLock.unlock();
+
−        }
+
−    }
+
−
+
−    /**
+
−     * Returns errors encountered during the sending process.
+
−     *
+
−     * @return the errors or null if none
+
−     */
+
−    public String getErrors() {
+
−        this.sendLock.lock();
+
−        try {
+
−            // make sure the thread is in WAIT state, not QUERY
+
−            while (this.state == SendThreadStatus.QUERY) {
+
−                try {
+
−                    this.waiting.await();
+
−                } catch (InterruptedException e) {
+
−                    // just try again
+
−                }
+
−            }
+
−            if (this.state == SendThreadStatus.SHUTDOWN)
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−                this.error = "SendThread is shutting down";
+
−        } finally {
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−            this.sendLock.unlock();
+
−        }
+
−        return error;
+
−    }
+
−
+
−    /**
+
−     * Requests this SendThread to stop.
+
−     */
+
−    public void shutdown() {
+
−        sendLock.lock();
+
−        state = SendThreadStatus.SHUTDOWN;
+
−        sendLock.unlock();
+
−        this.interrupt();  // break any wait conditions
+
−    }
+
−}