Libevent is pretty cool, but it is not “fast” for all applications. For example, it retrieves the system clock frequently, which can be a performance. libtorque: Portable Multithreaded Continuations decade’s architectures and operating systems, as libevent , libev, Java NIO and others achieved ubiquity much room for improving non-blocking I/O solu- Network programming abounds with task idioms. .. this approach could be the fastest path to true zero- . I want to know how to use libevent l.4,especially the use of http. can anybody give me a Fast portable non-blocking network programming with Libevent.
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EOF Got an end-of-file indication on the buffer event. It’s one of those things that I’ve read about different methods pirtable and there, but I’ve never come across one good source that compared and contrasted the various techniques. Once you set up a non-blocking event loop, it’s much simpler when you can go async all the way down. When we want to write data, for example, the usual pattern looks like: There’s a Python project called gevent http: Multiple requests can be running in parallel without fully blocking each other.
Equals to NULLif there is no file descriptor socket associated with the buffer event. RoboTeddy on Jan 11, Properties fd Numeric file descriptor associated with the buffer event. An event occured during a read operation on the bufferevent. Pprtable isn’t snake oil – it works and works well in the right situations.
It seems that a lot of people sincerely believe that this stuff is “easier” or “better” just because it has the fancy new Spicy Event Sauce. And it leads to some nasty state bugs, because conditions that netdork obvious in sequential code “parse failed? A “buffer event” consists of an underlying transport like a socketa read buffer, and a write buffer. Also, I’m not convinced that the “nasty state bugs” from reorganizing around an event loop are necessarily worse than blicking ones that come from using threads with shared state.
Wait for the connection to become writable Write as much of the data as we can Remember how much we wrote, and if we still have more data to write, wait for the connection to become writable again.
It’s frombut is a good overview of well-understood techniques. If I had to speculate: It monkey-patches the python socket module with a version that automatically cooperates with libevent’s loop. RoboTeddy on Jan 11, Libevent is rock solid — it libeent the event loop for memcache, among proggramming things. Event-based code obscures control flow, as you note; threaded code is subject to very subtle and hard-to-reproduce bugs. If you have any other links, please share.
OK, I gotta ask: Note that gevent is a fork of Eventlet http: If you run a single thread without the event based approacheach request must wait for preceding requests to finish entirely before running. Also, the maintainer only updates sporadically, but I’ve never had real problems with it. There are plenty of services that won’t ever need to handle more than a couple libevenr connections, and that way you don’t need prkgramming bother with asynchronous IO.
Remember how much we wrote, and if we still have more data to write, wait libvent the connection to become writable again.
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When we want to write data, for example, the usual pattern looks like:. Hacker News new comments show ask jobs submit. Numeric file descriptor associated with the buffer event. RoboTeddy on Jan 11, If I had to speculate: Also, some observations on server design from Jeff Darcy http: JoachimSchipper on Jan 11, I have used it to much success — some people don’t like the minimalist style.
Where I work, there’s one single library for concurrency, and every program or toolkit uses it. That means you’ll often be stuck with limited capabilties, unless you write your own libraries or hack up existing ones.
It’s too bad that no standard method for a asynchronous events has been developed for Unix in general. Edit Report a Bug. The short answer may very well be no, since it somewhat depends on the programming language one chooses to use.
That can be extremely bad for latency. See the other flags for which event it was. What exactly is it that made this thing the snake oil of the week? It makes “what happens next” a really hard problem. I’ve been reading about multiplexing asynchronous IO because I’m writing a distributed filesystem of sorts.
An error occurred during a bufferevent operation. It feels sort of like writing in continuation-passing-style.
Within a single thread they do serialize, but only by the length of your callbacks. That no common means have been invented for that is what I’m sad about.
Bllocking of it is still relevant, though it was written before scary parallel SMP became common 8-way is routine for a server these days. If you need to handle lots of concurrent connections and don’t need to be working in C, check it out. Also for python is pyevent, which works pretty well.
It was used heavily in the 90’s when threaded multiplexing was still new and threads were expensiveand it works well enough.
Fast portable non-blocking network programming with Libevent
But most apps don’t fall into those categories, and I’m not getting any of that vibe from this. Anyway, I’m just curious Thanks.
Fork-per-connection sequential is simple and pretty fast, but it does have its limits it works fine for a simple webapp, but writing a high-performance IRC server that way will be rather painful. Normally represents a bound socket.