PHP使用1个crontab管理多个crontab任务

浏览数：22 / 时间：2015年06月09日

转载来自： http://www.cnblogs.com/showker/archive/2013/09/01/3294279.html

 

http://www.binarytides.com/php-manage-multiple-cronjobs-with-a-single-crontab-entry/

 

In many php applications there are multiple tasks that need to be run via cron at different times. In a typical application you may be doing the following tasks via cronjobs : 

1. Backup database.
2. Send out email to subscribers.
3. Clear temporary files.
4. Fetch xml feeds from some source and store them in database.

So if you had separate php files doing these tasks , and had a cronjob entry for each , your cronjob could look like this :

MAILTO="[email protected]"
0 0 * * * /var/www/my_app/backup_database.php
12 2 * * * /var/www/my_app/email_to_subscribers.php
10 5 * * * /var/www/my_app/clear_temp_files.php
10 7 * * * /var/www/my_app/fetch_xml_feeds.php

The above is the simplest approach to manage multiple cronjobs for your php application. However this approach has many drawbacks :

1. Multiple entries in crontabs means more time and effort needed to edit the crontab and maintain it.

- Since this approach involves writing each task separately in the cron list , it becomes difficult to maintain.

2. The crontab command has to be used everytime a change is to be made.

- You need to either manually do a `crontab -t` in the shell prompt or make your php application do it , everytime there is a change in either the tasks or their timing.

3. If the script name changes then have to edit the crontab file again.
4. A log email would be generated for every cron run, creating multiple log emails.

- Every task that is running would generate a cronlog and email itself to the email specified

5. Inefficient when there are 10s or 100s of tasks to be run via cron.

- Do you think it is a good idea if you had many many tasks to do.

An alternative solution

How about having only 1 entry in the cronjobs, and that 1 cronjob manages the rest of the cronjobs.

1. Add only 1 task to the crontab rule say :

1 * * * * * php /path/to/cronjob.php

The cronjob.php file would run all the tasks that need to be run via cron. Its important to note that this cronjob.php will run every minute and forever. Do not be worried about it eating too much of system resources. It is a faily light thing and does not load your CPU or RAM with anything heavy.(注意这个cronjob.php会每分钟执行一次，而且一直会一直这样。不必担心这会消耗太多系统资源，这是一个非常轻量级的东西，它不会额外占用你的CPU和内存)

Now the next thing would be to make sure cronjob.php can run all the tasks at the right time.

2. Now we need to have different tasks have a different cron schedule. Lets say there are 3 different tasks to run at 3 different times :

0 5 * * * database_backup
0 5 1,15 * * monthly_sales_report
0 10 15 02 * purchase_report


 


The cronjob.php that runs every minute should have an array like this :




1 $cronjobs = array();
2  
3 $cronjobs[‘database_backup‘] = ‘0 5 * * *‘;
4 $cronjobs[‘monthly_sales_report‘] = ‘0 5 1,15 * *‘;
5 $cronjobs[‘purchase_report‘] = ‘0 10 15 02 *‘;




Now we test each job/task for the timestamp and run it like this :




1 foreach($cronjobs as $method => $cron)
2 {
3     $time = time();
4         if( is_time_cron($time , $cron) )
5     {
6         $result = $method();
7         echo $result;
8     }
9 }




is_time_cron checks if the current timestamp matches the cron schedule or not. If it matches , then the task is executed. Theis_time_cron method can be found in the previous post here.


In this approach the benefits are :


1. Only 1 crontab entry.


The crontab list is clean and your application does not overload it.


2. Easy to maintain , does not need any modification unless the script path/name changes.


The crontab once created does not need any change unless the name or path of ‘cronjob.php‘ changes. Meanwhile the jobs inside cronjob.php can change their names , schedules and anything very easily.


3. To add/edit/remove tasks or change their time schedules only the cronjob.php needs to be changed.


This means easier modification , maintenance and the application can provide simple user interface to make changes anytime without the need to use crontab commands or anything as such.


The above mentioned approach can be applied to any language , not just php.


 


 


 


附加：判断当前时间蹉是否符合某个cronjob


http://www.binarytides.com/php-check-if-a-timestamp-matches-a-given-cron-schedule/




PHP check if a timestamp matches a given cron schedule








1 desktop:~$ php -a
2 Interactive shell
3  
4 php > echo time();
5 1319362432
6 php > 




 









          

            

              
              郑重声明：本站内容如果来自互联网及其他传播媒体，其版权均属原媒体及文章作者所有。转载目的在于传递更多信息及用于网络分享，并不代表本站赞同其观点和对其真实性负责，也不构成任何其他建议。
            

          


          


          

            标签： 
            des
            
            class
            
            style
            
            com
            
            log
            
            使用
            
            src
            
            html
            
            文件
            
            des
            
            class
            
            style
            
            com
            
            log
            
            使用
            
            src
            
            html
            
            文件
            
            
            
          


          

            

              
相关文章

              
    
                
              

            

            

              
随机文章

              
            

          



          

            

              
您可能还喜欢

              
    
                
              

            


            

              
您可能还喜欢