什么是基于EventMachine的应用读取文件的最好方法？ [英] What is the best way to read files in an EventMachine-based app?

问题描述

为了不阻挡反应器，我想异步读取文件，但我发现使用EventMachine的做的没有明显的方式。我已经尝试了几种不同的方法，但他们没有感觉不错：

In order not to block the reactor I would like to read files asynchronously, but I've found no obvious way of doing it using EventMachine. I've tried a few different approaches, but none of them feels right:

• 只需读取该文件，它会阻止反应堆，但什么是地狱，它不是的是的慢（除非它是一个大的文件，然后将它肯定是）。


• 打开文件进行读取，并读取每个剔一大块（但多少看？太多了，它会阻止反应堆，太少和阅读将超过必要降低）。


• EM.popen（'猫一些/文件'，的FileReader）感觉很不可思议，但工程比上述方案更好。与 LineAndTextProtocol 读取线pretty迅速。
组合

• EM.attach ，但我还没有找到如何使用它的例子，我已经在邮件列表上找到的唯一的事情是，它是德$ p $赞成... pcated


• EM.watch ，其中我发现不知道如何使用阅读文件的示例。

• Just read the file, it'll block the reactor, but what the hell, it's not that slow (unless it's a big file, and then it definitely is).
• Open the file for reading and read a chunk on each tick (but how much to read? too much and it'll block the reactor, too little and reading will get slower than necessary).
• EM.popen('cat some/file', FileReader) feels really weird, but works better than the alternatives above. In combination with the LineAndTextProtocol it reads lines pretty swiftly.
• EM.attach, but I haven't found any examples of how to use it, and the only thing I've found on the mailing list is that it's deprecated in favour of…
• EM.watch, which I've found no examples of how to use for reading files.

你怎么一个EventMachine的反应器循环中读取文件？

How do you read files within a EventMachine reactor loop?

推荐答案

EM.attach /手表不能在文件中使用，作为一个基于磁盘的文件描述符选择/ epoll的总是会返回可读的。

EM.attach/watch cannot be used on files, as select/epoll on a disk-based file descriptor will always return readable.

归根结底，这取决于你想要做什么。如果它是一个小文件，只需File.read它。如果是较大的，可以随着时间的推移读取小块。例如，EM :: FileStreamer这样做是为了通过网络发送大文件。

Ultimately, it depends on what you're trying to do. If it's a small file, just File.read it. If it is larger, you can read small chunks over time. For example, EM::FileStreamer does this to send large file over the network.

另一种常见的用例是尾文件，并在新的阅读内容时，它改变了。这可以使用EM.watch_file实现：<一href=\"http://github.com/jordansissel/eventmachine-tail\">http://github.com/jordansissel/eventmachine-tail

Another common use-case is to tail a file and read in new contents when it changes. This can be achieved using EM.watch_file: http://github.com/jordansissel/eventmachine-tail

这篇关于什么是基于EventMachine的应用读取文件的最好方法？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！