Slow cronjobs on Cent OS 5

Your hardware seems to be good enough to process this.

1) Check if you already have hanging processes. Using the ps auxf (see tcurvelo answer), check if you have one or more processes that takes too much resources. Maybe you don't have enough resources to run your cronjob.

2) Check your network connections:If your databases and your cronjob are on a different server you should check whats the response time between these two machines. Maybe you have network issues that makes the cronjob wait for the network to send the package back.

You can use: Netcat, Iperf, mtr or ttcp

3) Server configurationIs your server is configured correctly? Your OS, MySQL are setup correctly? I would recommend to read these articles:

http://www3.wiredgorilla.com/content/view/220/53/

http://www.vr.org/knowledgebase/1002/Optimize-and-disable-default-CentOS-services.html

http://dev.mysql.com/doc/refman/5.1/en/starting-server.html

http://www.linux-mag.com/id/7473/

4) Check your database:Make sure your database has the correct indexes and make sure your queries are optimized. Read this article about the explain command

If a query with few hundreds thousands of record takes times to execute that will affect the rest of your cronjob, if you have a query inside a loop, even worse.

Read these articles:

http://dev.mysql.com/doc/refman/5.0/en/optimization.html

http://20bits.com/articles/10-tips-for-optimizing-mysql-queries-that-dont-suck/

http://blog.fedecarg.com/2008/06/12/10-great-articles-for-optimizing-mysql-queries/

5) Trace and optimized PHP code?Make sure your PHP code runs as fast as possible.

Read these articles:

http://phplens.com/lens/php-book/optimizing-debugging-php.php

http://code.google.com/speed/articles/optimizing-php.html

http://ilia.ws/archives/12-PHP-Optimization-Tricks.html

A good technique to validate your cronjob is to trace your cronjob script:Based on your cronjob process, put some debug trace including how much memory, how much time it took to execute the last process. eg:

<?phpecho "\n-------------- DEBUG --------------\n";echo "memory (start): " . memory_get_usage(TRUE) . "\n";$startTime = microtime(TRUE);// some process$end = microtime(TRUE);echo "\n-------------- DEBUG --------------\n";echo "memory after some process: " . memory_get_usage(TRUE) . "\n";echo "executed time: " . ($end-$start) . "\n";

By doing that you can easily find which process takes how much memory and how long it takes to execute it.

6) External servers/web service callsIs your cronjob calls external servers or web service? if so, make sure these are loaded as fast as possible. If you request data from a third-party server and this server takes few seconds to return an answer that will affect the speed of your cronjob specially if these calls are in loops.

Try that and let me know what you find.

The ps's output also shows when the process have started (see column STARTED).

$ ps auxfUSER    PID  %CPU %MEM     VSZ    RSS   TTY  STAT  STARTED    TIME   COMMANDroot      2   0.0  0.0       0      0   ?    S     18:55      0:00   [ktrheadd]                                                   ^^^^^^^(...)

Or you can customize the output:

$ ps axfo start,commandSTARTED   COMMAND18:55     [ktrheadd](...)

Thus, you can be sure if they are overlapping.

You should use a lockfile mechanism within your process_stats_hourly.php script. Doesn't have to be anything overly complex, you could have php write the PID which started the process to a file like /var/mydir/process_stats_hourly.txt. So if it takes longer than an hour to process the stats and cron kicks off another instance of the process_stats_hourly.php script, it can check to see if the lockfile already exists, if it does it will not run.

However you are left with the problem of how to "re-queue" the hourly script if it did find the lock file and couldn't start.