<?php

echo "\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";

通过这样做，您可以轻松地找到哪个进程占用了多少内存以及执行它需要多长时间。

6) 外部服务器/Web 服务调用
您的 cronjob 是调用外部服务器还是 Web 服务？如果是这样，请确保尽快加载它们。如果您从第三方服务器请求数据，并且该服务器需要几秒钟的时间才能返回答案，这将影响您的 cronjob 的速度，特别是如果这些调用处于循环中。

尝试一下，然后让我知道你发现了什么。

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 configuration
Is 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:

<?php

echo "\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 calls
Is 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.

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旧伤还要旧人安 2024-12-19 06:56:39

ps 的输出还显示进程何时启动（请参阅STARTED 列）。

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

或者您可以自定义输出：

$ ps axfo start,command
STARTED   COMMAND
18:55     [ktrheadd]
(...)

因此，您可以确定它们是否重叠。

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

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

Or you can customize the output:

$ ps axfo start,command
STARTED   COMMAND
18:55     [ktrheadd]
(...)

Thus, you can be sure if they are overlapping.

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牵强ㄟ 2024-12-19 06:56:39

您应该在 process_stats_hourly.php 脚本中使用锁定文件机制。不必过于复杂，您可以让 php 将启动进程的 PID 写入 /var/mydir/process_stats_hourly.txt 等文件。因此，如果处理统计数据的时间超过一个小时，并且 cron 启动 process_stats_hourly.php 脚本的另一个实例，它可以检查锁定文件是否已存在，如果存在，则不会运行。

然而，如果每小时脚本确实找到了锁定文件并且无法启动，那么您将面临如何“重新排队”的问题。

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浪菊怪哟 2024-12-19 06:56:39

您可以在运行时间过长的进程之一上使用 strace -p 1234，其中 1234 是相关进程 ID。也许你会明白为什么它这么慢，甚至被阻塞。

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听你说爱我 2024-12-19 06:56:39

Cent OS 中是否有任何工具或我可以做的事情来确保我的 cronjob 每小时运行一次并且不会与下一个任务重叠？

是的。 CentOS 的标准 util-linux 软件包为文件系统锁定提供了便利的命令行。正如 Digital Precision 建议的，锁定文件是一种简单的方法同步进程。

尝试按如下方式调用您的 cronjob：

flock -n /var/tmp/stats.lock process_stats_hourly.php || logger -p cron.err 'Unable to lock stats.lock'

您需要编辑路径并根据需要调整 $PATH。该调用将尝试锁定 stats.lock，如果成功则生成统计脚本，否则放弃并记录失败。

或者，您的脚本可以调用 PHP 的 flock() 本身来达到相同的效果，但是 flock(1) 实用程序已经为您准备好了。

Is there any tool in Cent OS or something I can do to make sure my cronjob will run every hour and not overlapping the next one?

Yes. CentOS' standard util-linux package provides a command-line convenience for filesystem locking. As Digital Precision suggested, a lockfile is an easy way to synchronize processes.

Try invoking your cronjob as follows:

flock -n /var/tmp/stats.lock process_stats_hourly.php || logger -p cron.err 'Unable to lock stats.lock'

You'll need to edit paths and adjust for $PATH as appropriate. That invocation will attempt to lock stats.lock, spawning your stats script if successful, otherwise giving up and logging the failure.

Alternatively your script could call PHP's flock() itself to achieve the same effect, but the flock(1) utility is already there for you.