异步读取 inotify 描述符失败
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【中文标题】异步读取 inotify 描述符失败【英文标题】:Asynchronous reading on the inotify descriptor failed 【发布时间】:2013-05-06 10:06:46 【问题描述】:我正在写一个基于源码的监控文件程序:https://github.com/kvikas/file-monitor-service/blob/master/
我的程序使用 boost::asio::stream_descriptor::async_read_some() 异步读取 inotify 描述符 http://linux.die.net/man/7/inotify
我的代码如下:
构造函数:
void init()
int fd = inotify_init1(IN_NONBLOCK);
int wd = inotify_add_watch(fd_, "./test.txt", IN_ALL_EVENTS);
stream_.reset(new boost::asio::posix::stream_descriptor(io_service_, fd_)));
异步读取:
template<typename Monitor_Handler>
void async_monitor(Monitor_Handler handler)
stream_->async_read_some(boost::asio::buffer(buffer_),
boost::bind(&monitor::handle_monitor<Monitor_Handler>,
shared_from_this(), boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred, handler));
处理程序:
template<typename Monitor_Handler>
void handle_monitor(const boost::system::error_code &ec,
std::size_t bytes_transferred, Monitor_Handler handler)
//process buffer
async_monitor(handler);
错误在于,首先调用了几次handle_monitor(多个事件,例如MODIFY,ACCESS,OPEN ...),以进行受监视文件的第一次更改。之后再次调用 async_read_some 方法,但我不再收到信号(不再调用 handle_monitor)
但是,当我尝试重置 inotify 描述并再次读取受监控的文件时 ==> 它起作用了,handle_monitor 被调用以在此类受监控的文件中进行新的更改。
修改代码:
template<typename Monitor_Handler>
void handle_monitor(const boost::system::error_code &ec,
std::size_t bytes_transferred, Monitor_Handler handler)
//process buffer
async_monitor(handler);
init();//for resetting the inotify desciptor
你们能帮我解释一下吗????我很想得到你的答案.....
【问题讨论】:
你能把boost::asio
和inotify
结合起来吗?
【参考方案1】:
我觉得这很可疑
void init()
int fd = inotify_init1(IN_NONBLOCK);
int wd = inotify_add_watch(fd_, "./test.txt", IN_ALL_EVENTS);
stream_.reset(new boost::asio::posix::stream_descriptor(io_service_, fd_)));
您应该使用从notify_init1()
返回的值创建stream_descriptor
,这将是fd
而不是fd_
。我假设fd_
是一个类成员,并且可能未初始化或初始化为0
。
【讨论】:
感谢您的回答,我重写了 fd 变量。但这不是问题。我缩小了这个问题的问题范围。 ***.com/questions/16397293/…你能帮我解释一下吗。希望看到你的回答【参考方案2】:我会说,而不是使用
int length = ::read(inotifyFd, buf, sizeof(buf));
inFd->async_read_some(boost::asio::null_buffers(),
boost::bind(&observeFilesystem,
boost::asio::placeholders::error))
最好如下完全利用aync_read_some
inFd->async_read_some(
boost::asio::buffer(buf, EVENT_BUF_LEN),
boost::bind(&observeFilesystem,
boost::asio::placeholders::error));
【讨论】:
【参考方案3】:#include <string>
#include <algorithm>
#include <cstring>
#include <assert.h>
#include <sys/signalfd.h>
#include <sys/inotify.h>
#include <boost/asio.hpp>
#include <boost/array.hpp>
#include <boost/bind.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/enable_shared_from_this.hpp>
#include <iostream>
//compile with
//-------------
//g++ -std=c++0x -g -I/usr/local/include -I/home/rk/Downloads/websocketpp/src asio.cc -L/home/rk/Downloads/websocketpp -L/usr/local/lib/ -lwebsocketpp -lboost_thread -lboost_exception -lboost_date_time -lboost_regex -lboost_system -o asio
static int inotifyFd = -1;
static int signalFd = -1;
static boost::asio::io_service gIoSvc;
//A simple test program to test whether signalfd works with boost::asio or not.
static boost::asio::posix::stream_descriptor *gwMqFd = nullptr; //message queue on which the gateway listens for control requests.
static boost::asio::posix::stream_descriptor *inFd = nullptr; //message queue on which the gateway listens for control requests.
static void
handleMqRead(boost::system::error_code ec)
std::cerr<<"\nRecvd signal";
struct signalfd_siginfo fdsi;
memset(&fdsi, 0, sizeof(fdsi));
ssize_t s = ::read(signalFd, &fdsi, sizeof(struct signalfd_siginfo));
if (s != sizeof(struct signalfd_siginfo))
std::cerr<<"read() on signalfd returns inconsistent size.";
return;
gwMqFd->async_read_some(boost::asio::null_buffers(),
boost::bind(&handleMqRead,
boost::asio::placeholders::error));
return;
#define EVENT_SIZE (sizeof (struct inotify_event))
#define EVENT_BUF_LEN (1024*(EVENT_SIZE + 16))
static void
observeFilesystem(boost::system::error_code ec)
std::cerr<<"\nDirectory modified ...";
char buf[EVENT_BUF_LEN];
int length = ::read(inotifyFd, buf, sizeof(buf));
inFd->async_read_some(boost::asio::null_buffers(),
boost::bind(&observeFilesystem,
boost::asio::placeholders::error));
return;
int
main(int argc, char* argv[])
try
inFd = new boost::asio::posix::stream_descriptor(gIoSvc);
gwMqFd = new boost::asio::posix::stream_descriptor(gIoSvc);
sigset_t signalMask;
sigemptyset(&signalMask);
sigaddset(&signalMask, SIGCHLD);
sigaddset(&signalMask, SIGTERM);
sigprocmask(SIG_BLOCK, &signalMask, nullptr);
signalFd = signalfd(-1, &signalMask, SFD_NONBLOCK | SFD_CLOEXEC);
assert(signalFd > 0);
gwMqFd->assign(signalFd);
gwMqFd->async_read_some(boost::asio::null_buffers(),
boost::bind(&handleMqRead,
boost::asio::placeholders::error));
inotifyFd = inotify_init();
assert(inotifyFd > 0);
inFd->assign(inotifyFd);
std::string fqpn = ".";
inotify_add_watch(inotifyFd, fqpn.c_str(), IN_CREATE | IN_DELETE | IN_DELETE_SELF | IN_MOVE_SELF | IN_MODIFY);
inFd->async_read_some(boost::asio::null_buffers(),
boost::bind(&observeFilesystem,
boost::asio::placeholders::error));
gIoSvc.run();
catch (std::exception& e)
std::cerr << "Exception: " << e.what() << std::endl;
return 0;
【讨论】:
-1。没有给出解释。它依赖于github.com/zaphoyd/websocketpp .. 一个替代但更高级别的库。为 +1 添加一些解释 :)以上是关于异步读取 inotify 描述符失败的主要内容,如果未能解决你的问题,请参考以下文章
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