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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Properties fd Numeric file descriptor associated with the buffer event. Remember how much we wrote, and if we wwith have more data to write, wait for the ljbevent to become writable again. Simpler approaches are good enough sometimes, though. Libevent is rock solid — it handles the event loop for memcache, among other things. It isn’t snake oil – it works and works well in the right situations. Numeric file descriptor associated with the buffer event.
Fast portable non-blocking network programming with Libevent | Hacker News
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 An event occured during a read operation on the bufferevent. Also, some observations on server design from Jeff Darcy http: But it’s a fxst That no common means have been invented for that is what I’m sad about.
I submitted the link. Multiple requests can be running in parallel without fully blocking each other. Where I work, there’s one single library for concurrency, and every program or toolkit uses it. RoboTeddy on Jan 11, Libevent is rock solid — it handles the event loop for memcache, among other portale. A “buffer event” consists of an underlying transport like a socketa read buffer, and a write buffer.
Fast portable non-blocking network programming with Libevent wangafu. When this flag is set, the bufferevent defers all of its callbacks. If I had to speculate: On the other nno, say you run a thread per socket – that’s not effective as the memory usage for reserving thread progrqmming space will limit your pprogramming connection count. It’s too bad that no standard method for a asynchronous events has been developed for Unix in general.
Decide that we want to write some data to a connection; put that data in a buffer. That means you’ll often be stuck with limited capabilties, unless you write your own libraries or hack up existing ones. Underlying input buffer object EventBuffer. Thanks to you and ajross, this really helps. Sure, but libraries underneath you have to cooperate for you to use it to the fullest potential.
Usually an application wants to perform some amount of data buffering in addition to just responding to events. It’s frombut is a good overview of well-understood techniques. What exactly is it that made this thing the snake oil of the week? There’s a Python project called gevent http: Lots of huge sites rely on memcache, for example, which would suck if it didn’t use event-based IO. When we want to write data, for example, the usual pattern looks like:.
We do a lot of network programming, so it would be unthinkable for any performance intensive application to do blocking calls exclusively.
If you run a single thread without the event based approacheach request must wait for preceding requests to finish entirely before running. But it’s difficult and error-prone. It was used heavily in the 90’s when threaded multiplexing was still new and threads were expensiveand it works well enough. It feels sort of like writing in continuation-passing-style.
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. The short answer may very well be no, since it somewhat depends on the programming language one chooses to use.
Event programming is useful in that it effectively performs cooperative multitasking without the overhead of thread stack space. EOF Got an end-of-file indication on the buffer event. Netwrk 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. Within a single thread they do serialize, but only by the length of your callbacks.
RoboTeddy on Jan 11, If I had to speculate: It splits sequential algorithms up into multiple callbacks with manually managed shared state.
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.
The EventBufferEvent class
I have used it to much success — some people don’t like the minimalist style. An event occured during a write operation on the bufferevent. Instead of regular events, which give callbacks when the underlying transport is ready to be read or written, a buffer event invokes its user-supplied callbacks when it has read or written enough data.
And the truth isn’t like that at all, and in fact these are truths that we’ve all known for years now But most apps don’t fall into those categories, and I’m not getting any of that vibe from this. 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. When the buffer event is freed, close the underlying transport. Edit Report a Bug. It’s not a standard part of Unix, of course, but it seems reasonably portable.
I know what you mean about an event loop complicating error handling from callbacks, though.