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 [19], 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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It splits sequential algorithms up into multiple callbacks with manually managed shared state. Portbale, but libraries underneath you have to cooperate for you to use it to the fullest potential. The short answer may very well be no, since it somewhat depends on the programming language one chooses to use.

Thanks to you and ajross, this really helps.

Fast portable non-blocking network programming with Libevent | Hacker News

An event occured during a write operation on the bufferevent. But it’s difficult and error-prone.

JoachimSchipper on Jan 11, One problem with using an event dispatcher like libevent is that libraries that make their own blocking calls won’t cooperate. Numeric file descriptor associated with the buffer event. It’s frombut is a good overview of well-understood techniques. I submitted the link.

When we want to write data, for example, the usual pattern looks like: Decide that we want to write some data to a connection; put that data in a buffer. And the truth isn’t like that at all, and in jon these are truths that we’ve all known for years now RoboTeddy on Jan 11, Libevent is rock solid — it handles the event loop for memcache, among other things.



Also, some observations on server design from Jeff Darcy http: OK, I gotta ask: When the buffer event is freed, close the underlying transport. RoboTeddy on Jan 11, If I had to speculate: It monkey-patches the python socket module with a version that automatically libeveng with tast loop.

If you have any other links, please share. Event programming is useful in that it effectively performs cooperative multitasking without the overhead of thread stack space. Fast portable non-blocking network programming with Libevent wangafu.

Fast portable non-blocking network programming with Libevent

Edit Report a Bug. Lots of huge sites rely on memcache, for example, which would suck if it didn’t use event-based IO. RoboTeddy on Jan 11, Again, event stuff has been here forever, and clearly is appropriate for some tasks.

If you run a single thread without the event based approacheach request must wait for preceding requests to finish entirely before running. It’s one of those things that I’ve read about different methods here and there, but I’ve never come across one good source that compared and contrasted the various techniques. It feels sort of like writing in continuation-passing-style.

Once you set up a non-blocking event loop, it’s much simpler when you can go async all the way down.

It’s too bad that no standard method for a blocknig events has been developed for Unix in general. JoachimSchipper on Jan 11, 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. Most of it is still ndtwork, though it was written before scary parallel SMP became common 8-way is routine for a server these days.

Sequential code is very readable, but not efficient at scale. Anyway, I’m just curious Thanks.

Fast portable non-blocking network programming with Libevent

Usually an application wants to perform some amount bon data buffering in addition to just responding to events. Also for python is pyevent, which works pretty well.


Remember how much we wrote, and if we still have more data to write, wait for the connection to become writable again. Multiple requests can be running in parallel without fully blocking each other. If you need to handle lots of concurrent connections and don’t need to be working in C, check it out. So if you’re writing the client handler for a database, or something like memcached, you need this technique whether you need an abstraction library is another argument This will close an underlying socket, free an underlying netwoek event, etc.

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Event-based code obscures control flow, as you note; threaded code is subject to very subtle and hard-to-reproduce bugs. Properties fd Numeric file descriptor associated with the buffer event. When we want to write data, for example, the usual pattern looks like:. When this flag is set, the bufferevent defers all of its callbacks.

Within a single thread they do serialize, but only by the length of your callbacks. If I had to speculate: It wasn’t too long ago when people were excited about fork-for-each-connection servers, though at least half of it was “OMG Unix system calls from Ruby” from people who probably don’t know C. It was used heavily in the 90’s when threaded multiplexing was still new and threads were expensiveand it works well enough.

That means you’ll often be stuck with limited capabilties, unless you write your own libraries or hack up existing ones. This is hardly a new idea, in fact it’s very well-traveled ground.