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So ImageMagick has the "convert" command which I use for my (Linux) web platform to deal with image resizing and such.

Sometimes this command gets "stuck", meaning it starts eating machine resources until the entire machine is unavailable. Logging in to the machine can take minutes when this happens.

SO, I'm looking for one of two solutions:

  1. Upon using this command - is there a way to determine just how much max resources it may use?

  2. Can I run a cron script that identifies these "stuck" processes and kill them? I.e. filter on CPU time, or CPU usage and kill when over a specific threshold.

I would probably prefer solution number 2, since solution number 1 could still yield several such processes that each is limited, and stuck, and together they would still eat up my resources.

I can't identify when and why this is happening, the system is slugish and stuck until I "killall convert", then all is well. This command is run thousands of times each hour so unless I would log each and every usage in some way, I can't say which one got stuck, unfortunately.

So, basically, a shell script that identifies, kills and logs when convert gets stuck.

Any ideas?

Sandman
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  • Ah - what does ImageMagick support say to this? – TomTom Feb 16 '14 at 10:39
  • @TomTom: I haven't talked to them since it has been hard for me to find out under what circumstances this occurs. When the system is locked up, even doing a "top" or "ps" is time consuming and my first order of action is generally to "killall convert" to see if it helps, which it usually does. Not sure if I can see a log of what convert commands took time after I've killed them – Sandman Feb 16 '14 at 16:05
  • Smells like "swapping to death". – TomTom Feb 16 '14 at 16:06

2 Answers2

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Upon using this command - is there a way to determine just how much max resources it may use?

Just before invoking the convert command you can set a resource limit on the max CPU time the process can use, convert then will get killed automatically after exceeding the limit.

This will work depending upon how you invoke the command initially. The exec may be unnecessary.

#!/bin/sh
ulimit -St 60
exec /usr/bin/convert $*
## if exec not present this gets executed after.
ulimit -St unlimited
Matthew Ife
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  • Thanks - I am invoking the convert command from PHP, using the system() or shell_exec() command, would I use it like system("ulimit -St 60; convert ...; ulimit sSt unlimited") ? – Sandman Feb 16 '14 at 16:01
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I have created a script that kills some processes listed in array, if CPU usage greater than XX% for YY seconds or kill processes that running more than ZZ seconds.

You can set XX, YY, ZZ in the top of the file.

You can use a ps or top for check processes.

There's a dry run mode too, to check but not kill.

In the end, the script sends an email if some processes were killed.

Here is my repo on Github: https://github.com/padosoft/kill-process

Here're some screenshots: Sample output

Lorenzo Padovani
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