实现一个简单的服务端推送方案-实例篇Polling(服务端阻塞读,SLEE_MySQL
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前面讲过一篇《实现一个简单的服务端推送方案-实例篇Polling(服务端阻塞读)》，那篇文章服务端利用Gearman队列来实现阻塞读，这篇服务器端用原生MySQL的Sleep函数来实现阻塞读，这篇文章也是另一篇文章《使用MySQL构建一个队列表》的实例实现。
客户端代码，JS库为prototype.js：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=gb2312" /><title>无标题文档</title><script language="JavaScript" type="text/javascript" src="./prototype.js"></script></head><body><script language="JavaScript"> var Class = { create: function() { return function() { this.initialize.apply(this, arguments); } } } var Comet = Class.create(); Comet.prototype = { maxvid: 0, url: './backend.php', noerror: true, initialize: function(){ }, connect: function(){ this.ajax = new Ajax.Request(this.url, { method: 'get', parameters: { 'maxvid': this.maxvid }, onSuccess: function(transport){ var response = transport.responseText.evalJSON(); this.comet.maxvid = response['vid']; this.comet.handleResponse(response); this.comet.noerror = true; }, onComplete: function(transport){ if (!this.comet.noerror) setTimeout(function(){ comet.connect() }, 5000); else this.comet.connect(); this.comet.noerror = false; } }); this.ajax.comet = this; }, handleResponse: function(response){ $('content').innerHTML += '<p>' + response['msg'] + '</p>'; } } var comet = new Comet(); comet.connect();</script><p id="content"></p></body></html>服务器端代码，backend.php，在这里当读不到新数据时，就调用"带注释的Sleep函数"来阻塞，阻塞直到超时或线程被KILL
<?phpheader("Cache-Control: no-cache, must-revalidate");header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");flush();//控制浏览器前端不要缓存结果，每次都要重新查询$maxvid = $_GET["maxvid"];//$maxvid = -1;error_log(date("[Y-m-d H:i:s]")." > "."maxvid: ".$maxvid."/n", 3 , "/usr/local/apache2219/logs/php_log");$dblnk = mysql_connect('localhost:3306', 'root', 'cpyf');mysql_select_db('test', $dblnk);if ( $maxvid <= 0 ) { $result = mysql_query("select max(vid) from vdooropen"); $result = mysql_fetch_row($result); $maxvid = $result[0]; error_log(date("[Y-m-d H:i:s]")." > "."maxvid: ".$maxvid."/n", 3 , "/usr/local/apache2219/logs/php_log");}while (1){ $result = mysql_query("select * from vdooropen where vid > $maxvid order by vid limit 1"); $num = mysql_num_rows($result); if ( $num > 0 ) break; mysql_query("/*!999999 wait queue msg */ SELECT SLEEP(300)"); if ( mysql_errno() != 0 ) { mysql_close($dblnk); //必须先关闭 $dblnk = mysql_connect('localhost:3306', 'root', 'cpyf'); mysql_select_db('test', $dblnk); }}$result = mysql_fetch_row($result);// 返回 JSON 数组$response = array();$response['vid'] = $result[0];$response['msg'] = $result[0].",".$result[1].",".$result[2].",".$result[3].",".$result[4];$responseText = json_encode($response);error_log(date("[Y-m-d H:i:s]")." < ".$responseText."/n", 3 , "/usr/local/apache2219/logs/php_log");echo $responseText;flush();?>当新增加数据后，通过show processlist找到带注释的Sleep线程，并KILL掉，阻塞就会退出。增加数据代码如下：
<?php$dblnk = mysql_connect('localhost:3306', 'root', 'cpyf');mysql_select_db('test', $dblnk);mysql_query('insert into vdooropen values(0, 2001, "0863030900020185","20130510-115152","D")');mysql_query('insert into vdooropen values(0, 2001, "0863030900020185","20130510-115152","D")');mysql_query('insert into vdooropen values(0, 2001, "0863030900020185","20130510-115152","D")');mysql_query('insert into vdooropen values(0, 2001, "0863030900020185","20130510-115152","D")');mysql_query('insert into vdooropen values(0, 2001, "0863030900020185","20130510-115152","D")');$result = mysql_query("SHOW PROCESSLIST");$num = mysql_num_rows($result);for ($i = 0; $i < $num; $i++) { $row = mysql_fetch_row($result); if ( strstr($row[7], "wait queue msg") != NULL ) { echo "KILL ".$row[0] . "/n"; mysql_query("KILL ".$row[0]); }}?>
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