Function wait

src/Storages/System/StorageSystemStackTrace.cpp:187–230

Wait for data in pipe and read it.

/// Wait for data in pipe and read it.
bool wait(int timeout_ms)
{
    while (true)
    {
        int fd = notification_pipe.fds_rw[0];
        pollfd poll_fd{fd, POLLIN, 0};

        int poll_res = poll(&poll_fd, 1, timeout_ms);
        if (poll_res < 0)
        {
            if (errno == EINTR)
            {
                --timeout_ms;   /// Quite a hacky way to update timeout. Just to make sure we avoid infinite waiting.
                if (timeout_ms == 0)
                    return false;
                continue;
            }

            throw ErrnoException(ErrorCodes::CANNOT_READ_FROM_FILE_DESCRIPTOR, "Cannot poll pipe");
        }
        if (poll_res == 0)
            return false;

        int notification_num = 0;
        ssize_t read_res = ::read(fd, &notification_num, sizeof(notification_num));

        if (read_res < 0)
        {
            if (errno == EINTR)
                continue;

            throw ErrnoException(ErrorCodes::CANNOT_READ_FROM_FILE_DESCRIPTOR, "Cannot read from pipe");
        }

        if (read_res == sizeof(notification_num))
        {
            if (notification_num == sequence_num.load(std::memory_order_relaxed))
                return true;
            continue; /// Drain delayed notifications.
        }

        throw Exception(ErrorCodes::LOGICAL_ERROR, "Read wrong number of bytes from pipe");
    }
}

using ThreadIdToName = std::unordered_map<UInt64, String, DefaultHash<UInt64>>;