求一个客户订阅RSS,定时更新的方法
正在制作一个网站,可以提供客户通过关键字搜索订阅本地的RSS,但是为了保护数据库的调用量,准备限制客户的调用次数。
大致思路是:用户第一次订阅是,调用数据库,生成静态XML文件。根据XML生成时间为基准,每24小时自动更新一次。
思路一:用户每次请求XML时,根据 time()-filectime 判断,如果大于 24*60*60 时,再次运行PHP文件,调用数据库,更新XML文件。问题是,既然已经生成了静态的XML文件,如何让XML通知PHP文件,告诉它:“我已经过期了,请再次更新我吧”?
思路二:把用户订阅写进SHELL里,让CRON定时后台运行。问题是:当用户订阅数成倍增长后,SHELL脚本体积不断增大,会变的繁重。另外,如果SHELL脚本在同一时间有读出和写入,SHELL脚本会不会崩溃?或者导致CRON程序被跳过?
思路三:还没想好,或许大家有更好的方法对我建议。谢谢。
BTW: 个人倾向:根据 time()-filectime 判断,这样可以排除恶意用户在第一次订阅后人间蒸发(RSS订阅被摒弃),而我的CRON程序还在为他每24小时自动的空生成一次……
------解决方案--------------------
php 可以读取xml的生成时间进行判断。不过如果有大量xml文件的时候得考虑IO瓶颈的问题。 所以如果不行的话就将生成的时间入库。用数据库来配合工作,可能会好点
xml很多吗?不多的话可以用memcache 来配合一下
------解决方案--------------------
1楼就这个意思
就是个文件缓存
abcd可以md5一下,可以防止一些特殊字符造成的麻烦,
暴力破解不是问题,因为你可以把xml放在web root外的目录, 也可以用.htaccess来控制直接访问
xml文件太多了也会有问题,根据需要到时候可以定期删除长期不更新的文件,或者分目录层次.
另: 如果是纯xml文件, file_get_contents比include快
------解决方案--------------------
xml的修改时间可以使用head方法取得last modify时间,搜索引擎蜘蛛都是这样做的。

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