threadedfilewriter.cpp

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// C++ headers
#include <cerrno>
#include <csignal>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
 
// Qt headers
#include <QString>
 
// MythTV headers
#include "threadedfilewriter.h"
#include "mythlogging.h"
#include "mythcorecontext.h"
 
#include "mythtimer.h"
#include "compat.h"
#include "mythdate.h"
 
#define LOC QString("TFW(%1:%2): ").arg(m_filename).arg(m_fd)
 
void TFWWriteThread::run(void)
{
    RunProlog();
    m_parent->DiskLoop();
    RunEpilog();
}
 
void TFWSyncThread::run(void)
{
    RunProlog();
    m_parent->SyncLoop();
    RunEpilog();
}
 
const uint ThreadedFileWriter::kMaxBufferSize   = 8 * 1024 * 1024;
const uint ThreadedFileWriter::kMinWriteSize    = 64 * 1024;
const uint ThreadedFileWriter::kMaxBlockSize    = 1 * 1024 * 1024;
 
bool ThreadedFileWriter::ReOpen(const QString& newFilename)
{
    Flush();
 
    m_bufLock.lock();
 
    if (m_fd >= 0)
    {
        close(m_fd);
        m_fd = -1;
    }
 
    if (m_registered)
    {
        gCoreContext->UnregisterFileForWrite(m_filename);
    }
 
    if (!newFilename.isEmpty())
        m_filename = newFilename;
 
    m_bufLock.unlock();
 
    return Open();
}
 
bool ThreadedFileWriter::Open(void)
{
    m_ignoreWrites = false;
 
    if (m_filename == "-")
        m_fd = fileno(stdout);
    else
    {
        QByteArray fname = m_filename.toLocal8Bit();
        m_fd = open(fname.constData(), m_flags, m_mode);
    }
 
    if (m_fd < 0)
    {
        LOG(VB_GENERAL, LOG_ERR, LOC +
            QString("Opening file '%1'.").arg(m_filename) + ENO);
        return false;
    }
 
    gCoreContext->RegisterFileForWrite(m_filename);
    m_registered = true;
 
    LOG(VB_FILE, LOG_INFO, LOC + "Open() successful");
 
#ifdef _WIN32
    _setmode(m_fd, _O_BINARY);
#endif
    if (!m_writeThread)
    {
        m_writeThread = new TFWWriteThread(this);
        m_writeThread->start();
    }
 
    if (!m_syncThread)
    {
        m_syncThread = new TFWSyncThread(this);
        m_syncThread->start();
    }
 
    return true;
}
 
ThreadedFileWriter::~ThreadedFileWriter()
{
    Flush();
 
    {  /* tell child threads to exit */
        QMutexLocker locker(&m_bufLock);
        m_inDtor = true;
        m_bufferSyncWait.wakeAll();
        m_bufferHasData.wakeAll();
    }
 
    if (m_writeThread)
    {
        m_writeThread->wait();
        delete m_writeThread;
        m_writeThread = nullptr;
    }
 
    while (!m_writeBuffers.empty())
    {
        delete m_writeBuffers.front();
        m_writeBuffers.pop_front();
    }
 
    while (!m_emptyBuffers.empty())
    {
        delete m_emptyBuffers.front();
        m_emptyBuffers.pop_front();
    }
 
    if (m_syncThread)
    {
        m_syncThread->wait();
        delete m_syncThread;
        m_syncThread = nullptr;
    }
 
    if (m_fd >= 0)
    {
        close(m_fd);
        m_fd = -1;
    }
 
    gCoreContext->UnregisterFileForWrite(m_filename);
    m_registered = false;
}
 
int ThreadedFileWriter::Write(const void *data, uint count)
{
    if (count == 0)
        return 0;
 
    QMutexLocker locker(&m_bufLock);
 
    if (m_ignoreWrites)
        return -1;
 
    uint written    = 0;
    uint left       = count;
 
    while (written < count)
    {
        uint towrite = (left > kMaxBlockSize) ? kMaxBlockSize : left;
 
        if ((m_totalBufferUse + towrite) > (kMaxBufferSize * (m_blocking ? 1 : 8)))
        {
            if (!m_blocking)
            {
                LOG(VB_GENERAL, LOG_ERR, LOC +
                    "Maximum buffer size exceeded."
                    "\n\t\t\tfile will be truncated, no further writing "
                    "will be done."
                    "\n\t\t\tThis generally indicates your disk performance "
                    "\n\t\t\tis insufficient to deal with the number of on-going "
                    "\n\t\t\trecordings, or you have a disk failure.");
                m_ignoreWrites = true;
                return -1;
            }
            if (!m_warned)
            {
                LOG(VB_GENERAL, LOG_WARNING, LOC +
                    "Maximum buffer size exceeded."
                    "\n\t\t\tThis generally indicates your disk performance "
                    "\n\t\t\tis insufficient or you have a disk failure.");
                m_warned = true;
            }
            // wait until some was written to disk, and try again
            if (!m_bufferWasFreed.wait(locker.mutex(), 1000))
            {
                LOG(VB_GENERAL, LOG_DEBUG, LOC +
                    QString("Taking a long time waiting to write.. "
                            "buffer size %1 (needing %2, %3 to go)")
                    .arg(m_totalBufferUse).arg(towrite)
                    .arg(towrite-(kMaxBufferSize-m_totalBufferUse)));
            }
            continue;
        }
 
        TFWBuffer *buf = nullptr;
 
        if (!m_writeBuffers.empty() &&
            (m_writeBuffers.back()->data.size() + towrite) < kMinWriteSize)
        {
            buf = m_writeBuffers.back();
            m_writeBuffers.pop_back();
        }
        else
        {
            if (!m_emptyBuffers.empty())
            {
                buf = m_emptyBuffers.front();
                m_emptyBuffers.pop_front();
                buf->data.clear();
            }
            else
            {
                buf = new TFWBuffer();
            }
        }
 
        m_totalBufferUse += towrite;
 
        const char *cdata = (const char*) data + written;
        buf->data.insert(buf->data.end(), cdata, cdata+towrite);
        buf->lastUsed = MythDate::current();
 
        m_writeBuffers.push_back(buf);
 
        if ((m_writeBuffers.size() > 1) || (buf->data.size() >= kMinWriteSize))
        {
            m_bufferHasData.wakeAll();
        }
 
        written += towrite;
        left    -= towrite;
    }
 
    LOG(VB_FILE, LOG_DEBUG, LOC + QString("Write(*, %1) total %2 cnt %3")
            .arg(count,4).arg(m_totalBufferUse).arg(m_writeBuffers.size()));
 
    return count;
}
 
long long ThreadedFileWriter::Seek(long long pos, int whence)
{
    QMutexLocker locker(&m_bufLock);
    m_flush = true;
    while (!m_writeBuffers.empty())
    {
        m_bufferHasData.wakeAll();
        if (!m_bufferEmpty.wait(locker.mutex(), 2000))
        {
            LOG(VB_GENERAL, LOG_WARNING, LOC +
                QString("Taking a long time to flush.. buffer size %1")
                    .arg(m_totalBufferUse));
        }
    }
    m_flush = false;
    return lseek(m_fd, pos, whence);
}
 
void ThreadedFileWriter::Flush(void)
{
    QMutexLocker locker(&m_bufLock);
    m_flush = true;
    while (!m_writeBuffers.empty())
    {
        m_bufferHasData.wakeAll();
        if (!m_bufferEmpty.wait(locker.mutex(), 2000))
        {
            LOG(VB_GENERAL, LOG_WARNING, LOC +
                QString("Taking a long time to flush.. buffer size %1")
                    .arg(m_totalBufferUse));
        }
    }
    m_flush = false;
}
 
void ThreadedFileWriter::Sync(void) const
{
    if (m_fd >= 0)
    {
#if defined(_POSIX_SYNCHRONIZED_IO) && _POSIX_SYNCHRONIZED_IO > 0
        // fdatasync tries to avoid updating metadata, but will in
        // practice always update metadata if any data is written
        // as the file will usually have grown.
        fdatasync(m_fd);
#else
        fsync(m_fd);
#endif
    }
}
 
void ThreadedFileWriter::SetWriteBufferMinWriteSize(uint newMinSize)
{
    QMutexLocker locker(&m_bufLock);
    if (newMinSize > 0)
        m_tfwMinWriteSize = newMinSize;
    m_bufferHasData.wakeAll();
}
 
void ThreadedFileWriter::SyncLoop(void)
{
    QMutexLocker locker(&m_bufLock);
    while (!m_inDtor)
    {
        locker.unlock();
 
        Sync();
 
        locker.relock();
 
        if (m_ignoreWrites && m_registered)
        {
            // we aren't going to write to the disk anymore, so can de-register
            gCoreContext->UnregisterFileForWrite(m_filename);
            m_registered = false;
        }
        m_bufferSyncWait.wait(&m_bufLock, 1000);
    }
}
 
void ThreadedFileWriter::DiskLoop(void)
{
#ifndef _WIN32
    // don't exit program if file gets larger than quota limit..
    signal(SIGXFSZ, SIG_IGN);
#endif
 
    QMutexLocker locker(&m_bufLock);
 
    // Even if the bytes buffered is less than the minimum write
    // size we do want to write to the OS buffers periodically.
    // This timer makes sure we do.
    MythTimer minWriteTimer;
    MythTimer lastRegisterTimer;
    minWriteTimer.start();
    lastRegisterTimer.start();
 
    uint64_t total_written = 0LL;
 
    while (!m_inDtor)
    {
        if (m_ignoreWrites)
        {
            while (!m_writeBuffers.empty())
            {
                delete m_writeBuffers.front();
                m_writeBuffers.pop_front();
            }
            while (!m_emptyBuffers.empty())
            {
                delete m_emptyBuffers.front();
                m_emptyBuffers.pop_front();
            }
            m_bufferEmpty.wakeAll();
            m_bufferHasData.wait(locker.mutex());
            continue;
        }
 
        if (m_writeBuffers.empty())
        {
            m_bufferEmpty.wakeAll();
            m_bufferHasData.wait(locker.mutex(), 1000);
            TrimEmptyBuffers();
            continue;
        }
 
        auto mwte = minWriteTimer.elapsed();
        if (!m_flush && (mwte < 250ms) && (m_totalBufferUse < kMinWriteSize))
        {
            m_bufferHasData.wait(locker.mutex(), (250ms - mwte).count());
            TrimEmptyBuffers();
            continue;
        }
 
        if (m_fd == -1)
        {
            m_bufferHasData.wait(locker.mutex(), 200);
            TrimEmptyBuffers();
            continue;
        }
 
        TFWBuffer *buf = m_writeBuffers.front();
        m_writeBuffers.pop_front();
        m_totalBufferUse -= buf->data.size();
        m_bufferWasFreed.wakeAll();
        minWriteTimer.start();
 
 
        const void *data = (buf->data).data();
        uint sz = buf->data.size();
 
        bool write_ok = true;
        uint tot = 0;
        uint errcnt = 0;
 
        LOG(VB_FILE, LOG_DEBUG, LOC + QString("write(%1) cnt %2 total %3")
                .arg(sz).arg(m_writeBuffers.size())
                .arg(m_totalBufferUse));
 
        MythTimer writeTimer;
        writeTimer.start();
 
        while ((tot < sz) && !m_inDtor)
        {
            locker.unlock();
 
            int ret = write(m_fd, (char *)data + tot, sz - tot);
 
            if (ret < 0)
            {
                if (errno == EAGAIN)
                {
                    LOG(VB_GENERAL, LOG_WARNING, LOC + "Got EAGAIN.");
                }
                else
                {
                    errcnt++;
                    LOG(VB_GENERAL, LOG_ERR, LOC + "File I/O " +
                        QString(" errcnt: %1").arg(errcnt) + ENO);
                }
 
                if ((errcnt >= 3) || (ENOSPC == errno) || (EFBIG == errno))
                {
                    locker.relock();
                    write_ok = false;
                    break;
                }
            }
            else
            {
                tot += ret;
                total_written += ret;
                LOG(VB_FILE, LOG_DEBUG, LOC +
                    QString("total written so far: %1 bytes")
                    .arg(total_written));
            }
 
            locker.relock();
 
            if ((tot < sz) && !m_inDtor)
                m_bufferHasData.wait(locker.mutex(), 50);
        }
 
 
        if (lastRegisterTimer.elapsed() >= 10s)
        {
            gCoreContext->RegisterFileForWrite(m_filename, total_written);
            m_registered = true;
            lastRegisterTimer.restart();
        }
 
        buf->lastUsed = MythDate::current();
        m_emptyBuffers.push_back(buf);
 
        if (writeTimer.elapsed() > 1s)
        {
            LOG(VB_GENERAL, LOG_WARNING, LOC +
                QString("write(%1) cnt %2 total %3 -- took a long time, %4 ms")
                    .arg(sz).arg(m_writeBuffers.size())
                    .arg(m_totalBufferUse).arg(writeTimer.elapsed().count()));
        }
 
        if (!write_ok && ((EFBIG == errno) || (ENOSPC == errno)))
        {
            QString msg;
            switch (errno)
            {
                case EFBIG:
                    msg =
                        "Maximum file size exceeded by '%1'"
                        "\n\t\t\t"
                        "You must either change the process ulimits, configure"
                        "\n\t\t\t"
                        "your operating system with \"Large File\" support, "
                        "or use"
                        "\n\t\t\t"
                        "a filesystem which supports 64-bit or 128-bit files."
                        "\n\t\t\t"
                        "HINT: FAT32 is a 32-bit filesystem.";
                    break;
                case ENOSPC:
                    msg =
                        "No space left on the device for file '%1'"
                        "\n\t\t\t"
                        "file will be truncated, no further writing "
                        "will be done.";
                    break;
            }
 
            LOG(VB_GENERAL, LOG_ERR, LOC + msg.arg(m_filename));
            m_ignoreWrites = true;
        }
    }
}
 
void ThreadedFileWriter::TrimEmptyBuffers(void)
{
    QDateTime cur = MythDate::current();
    QDateTime cur_m_60 = cur.addSecs(-60);
 
    QList<TFWBuffer*>::iterator it = m_emptyBuffers.begin();
    while (it != m_emptyBuffers.end())
    {
        if (((*it)->lastUsed < cur_m_60) ||
            ((*it)->data.capacity() > 3 * (*it)->data.size() &&
             (*it)->data.capacity() > 64 * 1024LL))
        {
            delete *it;
            it = m_emptyBuffers.erase(it);
            continue;
        }
        ++it;
    }
}
 
bool ThreadedFileWriter::SetBlocking(bool block)
{
    bool old = m_blocking;
    m_blocking = block;
    return old;
}