大文件下载中的SocketTimeoutException问题定位

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
/**
     * Performs a blocking write using the byte buffer for data to be written
     * If the <code>selector</code> parameter is null, then it will perform a busy write that could
     * take up a lot of CPU cycles.
     *
     * @param buf ByteBuffer - the buffer containing the data, we will write as long as <code>(buf.hasRemaining()==true)</code>
     * @param socket SocketChannel - the socket to write data to
     * @param writeTimeout long - the timeout for this write operation in milliseconds, -1 means no timeout
     * @return the number of bytes written
     * @throws EOFException if write returns -1
     * @throws SocketTimeoutException if the write times out
     * @throws IOException if an IO Exception occurs in the underlying socket logic
     */
    public int write(ByteBuffer buf, NioChannel socket, long writeTimeout)
            throws IOException {
        SelectionKey key = socket.getIOChannel().keyFor(socket.getSocketWrapper().getPoller().getSelector());
        if (key == null) {
            throw new IOException(sm.getString("nioBlockingSelector.keyNotRegistered"));
        }
        KeyReference reference = keyReferenceStack.pop();
        if (reference == null) {
            reference = new KeyReference();
        }
        NioSocketWrapper att = (NioSocketWrapper) key.attachment();
        int written = 0;
        boolean timedout = false;
        int keycount = 1; //assume we can write
        long time = System.currentTimeMillis(); //start the timeout timer
        try {
            while (!timedout && buf.hasRemaining()) {
                if (keycount > 0) { //only write if we were registered for a write
                    int cnt = socket.write(buf); //write the data
                    if (cnt == -1) {
                        throw new EOFException();
                    }
                    written += cnt;
                    if (cnt > 0) {
                        time = System.currentTimeMillis(); //reset our timeout timer
                        continue; //we successfully wrote, try again without a selector
                    }
                }
                try {
                    if (att.getWriteLatch() == null || att.getWriteLatch().getCount() == 0) {
                        att.startWriteLatch(1);
                    }
                    poller.add(att, SelectionKey.OP_WRITE, reference);
                    att.awaitWriteLatch(AbstractEndpoint.toTimeout(writeTimeout), TimeUnit.MILLISECONDS);
                } catch (InterruptedException ignore) {
                    // Ignore
                }
                if (att.getWriteLatch() != null && att.getWriteLatch().getCount() > 0) {
                    //we got interrupted, but we haven't received notification from the poller.
                    keycount = 0;
                } else {
                    //latch countdown has happened
                    keycount = 1;
                    att.resetWriteLatch();
                }

                if (writeTimeout > 0 && (keycount == 0)) {
                    timedout = (System.currentTimeMillis() - time) >= writeTimeout;
                }
            }
            if (timedout) {
                throw new SocketTimeoutException();
            }
        } finally {
            poller.remove(att, SelectionKey.OP_WRITE);
            if (timedout && reference.key != null) {
                poller.cancelKey(reference.key);
            }
            reference.key = null;
            keyReferenceStack.push(reference);
        }
        return written;
    }