mirror of
http://github.com/valkey-io/valkey
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45 lines
2.7 KiB
HTML
45 lines
2.7 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
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<html>
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<head>
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<link type="text/css" rel="stylesheet" href="style.css" />
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</head>
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<body>
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<div id="page">
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<div id='header'>
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<a href="index.html">
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<img style="border:none" alt="Redis Documentation" src="redis.png">
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<div id="pagecontent">
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<div class="index">
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<!-- This is a (PRE) block. Make sure it's left aligned or your toc title will be off. -->
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<b>EventLibray: Contents</b><br> <a href="#Event Library">Event Library</a><br> <a href="#Why is an Event Library needed at all?">Why is an Event Library needed at all?</a>
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<h1 class="wikiname">EventLibray</h1>
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<div class="summary">
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<h1><a name="Event Library">Event Library</a></h1><h2><a name="Why is an Event Library needed at all?">Why is an Event Library needed at all?</a></h2>Let us figure it out through a series of Q&As.<br/><br/>Q: What do you expect a network server to be doing all the time? <br/>
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A: Watch for inbound connections on the port its listening and accept them.<br/><br/>Q: Calling <a href="http://man.cx/accept%282%29" target="_blank">accept</a> yields a descriptor. What do I do with it?<br/>
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A: Save the descriptor and do a non-blocking read/write operation on it.<br/><br/>Q: Why does the read/write have to be non-blocking?<br/>
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A: If the file operation ( even a socket in Unix is a file ) is blocking how could the server for example accept other connection requests when its blocked in a file I/O operation.<br/><br/>Q: I guess I have to do many such non-blocking operations on the socket to see when it's ready. Am I right?<br/>
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A: Yes. That is what an event library does for you. Now you get it.<br/><br/>Q: How do Event Libraries do what they do?<br/>
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A: They use the operating system's <a href="http://www.devshed.com/c/a/BrainDump/Linux-Files-and-the-Event-Poll-Interface/" target="_blank">polling</a> facility along with timers.<br/><br/>Q: So are there any open source event libraries that do what you just described? <br/>
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A: Yes. Libevent and Libev are two such event libraries that I can recall off the top of my head.<br/><br/>Q: Does Redis use such open source event libraries for handling socket I/O?<br/>
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A: No. For various <a href="http://groups.google.com/group/redis-db/browse_thread/thread/b52814e9ef15b8d0/" target="_blank">reasons</a> Redis uses its own event library.
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</div>
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</body>
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</html>
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