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June 19, 2009

Reducing I/O Priority on RedHat Enterprise Linux V4.0

Filed under: Operating Systems — Tags: , , — Greg Larkin @ 2:45 pm

Hi everyone,

I have some servers with RHEL4 installed on them, and I’ve noticed a problem every time I start processes that saturate the I/O channels, such as VMware’s vmware-vdiskmanager. This tool performs various operations on VMware virtual disk files, and when creating a new one, the load average on the server tends to spike into the double digits. As you can imagine, this negatively affects virtual machines running at the same time!

After some searching, I found the ionice tool that looked like a perfect solution to the problem. Unfortunately, it doesn’t run on the 2.6.9 vintage kernel supplied with RHEL4. Back to the drawing board!

After more searching, I came across a forum thread and a link to an ionice replacement for RHEL4, written in Perl. I downloaded it and tried it out, and it appears to work as advertised. My heavy I/O operations take longer now (fine), and the load average stays within acceptable limits (great!).

The script has some hard-coded values, and it can be easily tweaked as needed. Thanks to Greg Bell at ServEdge for writing it!


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April 15, 2008

Keeping VMware Management Log Files Under Control – Take 2

Filed under: Operating Systems — Tags: , , — Greg Larkin @ 7:12 am

Hi everyone,

In a previous post, I postulated a solution for rotating the Apache log files produced by the VMware MUI application. Unfortunately, the MUI version of Apache doesn’t work well with logrotate, as I discovered over the weekend.

After receiving an alert on the cell phone in the middle of the night that the MUI was down, I discovered this in the /var/log/vmware-mui/error_log file:

[Sun Apr 13 04:02:03 2008] [error] Could not destroy the stale named pipe directory: /var/run/vmware//httpd/21157\n
[Sun Apr 13 04:02:03 2008] [error] VMWARE PANIC: \nNOT_IMPLEMENTED F(4023):707\n
[Sun Apr 13 04:02:03 2008] [error] Panic: Could not allocate temporary context.\n

Ok, perhaps there’s a better solution than logrotate and one that I’m already using with Apache in all of the SourceHosting.net virtual machines. A while back, I discovered the httplog tool, which builds on the premise of the standard rotatelogs tool that’s part of the Apache distribution. Since it doesn’t restart Apache when it rotates its log files, I suspected it might work well with the MUI.

Since the MUI is running on a RHEL4 system, I created an RPM of httplog instead of installing directly from the source distro. After many years working with Linux and FreeBSD, I much prefer everything to be installed from an RPM or a port, just for sanity’s sake and managing future upgrades.

The next step is to integrate the httplog command into the MUI’s httpd.conf file, found in /usr/lib/vmware-mui/apache/conf. If you’d like to update your file, download this patch file, and run the following commands (after installing httplog):

rm -f /etc/logrotate.d/httpd.vmware
/etc/rc.d/init.d/httpd.vmware stop
patch -b --verbose  /usr/lib/vmware-mui/apache/conf/httpd.conf < httpd.conf.httplog-patch
/etc/rc.d/init.d/httpd.vmware start

After starting up httpd.vmware, your /var/log/vmware-mui directory should look something like this:
total 16
lrwxrwxrwx  1 root root   36 Apr 14 17:12 error_log -> /var/log/vmware-mui/200815-error_log
-rw-r--r--  1 root root  186 Apr 14 17:12 200815-error_log
lrwxrwxrwx  1 root root   41 Apr 14 17:12 ssl_engine_log -> /var/log/vmware-mui/200815-ssl_engine_log
lrwxrwxrwx  1 root root   42 Apr 14 17:16 ssl_request_log -> /var/log/vmware-mui/200815-ssl_request_log
lrwxrwxrwx  1 root root   37 Apr 14 17:16 access_log -> /var/log/vmware-mui/200815-access_log
-rw-r--r--  1 root root  396 Apr 14 17:31 200815-ssl_request_log
-rw-r--r--  1 root root 3820 Apr 14 17:31 200815-ssl_engine_log
-rw-r--r--  1 root root  328 Apr 14 17:31 200815-access_log

I’ve got my httplog process configured to encode the week number into the Apache log filenames, rotate them each week and compress the rotated logs. If you want to automatically remove compressed logs after a certain number of weeks, a simple cron job accomplishes that.

httplog accepts many different filename configurations, so man httplog for more information or post questions here.


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April 14, 2008

Small Tweak To Get Httplog To Build On RHEL4

Filed under: Operating Systems — Tags: , — Greg Larkin @ 5:32 pm

Hi everyone,

In a future post to follow very shortly, I’ll discuss a change to the VMware MUI application that relies on the httplog tool to perform Apache log rotation.

The first thing I had to do was get httplog installed on the RHEL4 system here. I quickly discovered that the source distribution wasn’t too good at detecting the proper version of zlib and configuring the Makefile accordingly. If you don’t have exactly zlib v1.1.3, the configure script assumes that you don’t have it at all. If you have a later version of zlib (like RHEL4 does), you have to do some hand-editing of the source code to build the tool.

I found an httplog SRPM online, but the .spec file wasn’t quite up to snuff. I added some dependencies and tweaked the configure script a bit. If you just want to install the tool, download the httplog RPM, or you can make additional tweaks with the httplog SRPM.


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