[EP-tech] Eprints Server Freezes Often

Francis Jayakanth franc at ncsi.iisc.ernet.in
Sat May 19 12:22:09 BST 2012


Dear Members, Our eprints server freezes (stops responding) almost every 
week or so. The only solution to bring up the server again is to do a hard 
boot.

I have looked into the Web Server error log file and find that around the 
time the system freezes, the following error is recorded in the error log 
file:

[Thu May 18 06:10:05 2012] [error] (12)Cannot allocate memory: fork: 
Unable to fork new process

So, the obvious reason for the system freeze is, the system is running 
out of main memory. Once the server is re-booted, everything is back to 
normal, but with the passage of time, the free memory keeps gradually 
dropping.

The 'top' command issued right ofter the re-boot, gives the 
following output:

top - 12:41:49 up 2 days, 55 min,  1 user,  load average: 0.90, 0.52, 0.35
Tasks: 167 total,   1 running, 166 sleeping,   0 stopped,   0 zombie
Cpu(s):  1.1%us,  0.2%sy,  0.0%ni, 97.3%id,  1.3%wa,  0.0%hi,  0.0%si, 
0.0%st
Mem:   4051536k total,  1162736k used,  2888800k free,    23300k buffers
Swap:  8193108k total,   378836k used,  7814272k free,   438404k cached

Over the period of few hours, the the usage of the main memory gradually 
goes up.

The output of the 'top' command after 3 hours is:

top - 15:42:07 up 2 days,  4:02,  1 user,  load average: 0.23, 0.22, 0.18
Tasks: 173 total,   1 running, 172 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.0%us,  0.0%sy,  0.0%ni, 99.6%id,  0.4%wa,  0.0%hi,  0.0%si, 
0.0%st
Mem:   4051536k total,  3048740k used,  1002796k free,   129020k buffers
Swap:  8193108k total,   378828k used,  7814280k free,   796732k cached

For a time gap of 3 hours, the free memory size has come down from 
2888800k to 1002796k. The drop will continue over the period of time and 
eventually, the system freezes.

I restarted the apache server after about 3 hours and the output of the 
'top' command is:

top - 15:52:59 up 2 days,  4:07,  1 user,  load average: 0.11, 0.14, 0.16
Tasks: 168 total,   1 running, 167 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.0%us,  0.0%sy,  0.0%ni, 99.6%id,  0.4%wa,  0.0%hi,  0.0%si, 
0.0%st
Mem:   4051536k total,  1686412k used,  2365124k free,   130712k buffers
Swap:  8193108k total,   378820k used,  7814288k free,   801620k cached

More than 1.3 GB of memory has been freed after restarting the apache 
server.

How do I ensure that memory level doesn't gradually drop and eventually 
cause the server to freeze? Should something be done at the apache 
configuration level?

Any help/pointers to overcome the said problem will of great help to us.

We have recently upgraded our eprints software from eprints-3.2.8 to 
eprints-3.3.9. The above behaviour was very much there with the 3.2.8 
version as well.

Apache Server version: Apache/2.2.3 on 64-bit RHES

Many thanks in advance for your attention.


  - Francis

JRD Tata Memorial Library
IISc, Bengaluru, India

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