Apache's httpd is a good web server. OpenBSD is a good operating system. How can we make the combination work even better?
We can add compression of the HTTP data transfer if the client's browser supports it (and unless they are using something truly ancient or bizarre, it should).
This should improve page load time and it may significantly reduce bandwidth utilization at both the server and client ends. How much of an improvement? Since images are already compressed, the improvement you get will depend on how much of a typical page is HTML (the content and the markup, including style details) as opposed to image comment.
But won't this increase the server CPU load? Surprisingly, not nearly as much as you would expect! That is, unless you are dynamically generating your pages, and maybe not even then. Linux Journal had an article about this.
load averages: 0.14, 0.17, 0.16 07:45:33
29 processes: 28 idle, 1 on processor
CPU states: 0.1% user, 0.0% nice, 1.7% system, 0.6% interrupt, 97.6% idle
Memory: Real: 21M/180M act/tot Free: 820M Swap: 0K/262M used/tot
PID USERNAME PRI NICE SIZE RES STATE WAIT TIME CPU COMMAND
27771 67 2 0 3048K 5148K sleep netcon 38:21 0.10% httpd
16649 0 2 0 1168K 1752K sleep select 261:34 0.00% sendmail
26110 67 2 0 3048K 5148K sleep netcon 41:38 0.00% httpd
17808 67 2 0 2756K 6356K sleep select 138:35 0.00% httpd
14891 67 2 0 3068K 5192K sleep netcon 40:40 0.00% httpd
20093 67 2 0 3052K 5168K sleep netcon 40:09 0.00% httpd
9049 67 2 0 3000K 5096K sleep netcon 39:44 0.00% httpd
20840 67 2 0 3112K 5188K sleep netcon 39:04 0.00% httpd
25575 67 2 0 3048K 5144K sleep netcon 38:53 0.00% httpd
13770 67 -6 0 3136K 5196K sleep piperd 38:05 0.00% httpd
12574 67 2 0 3028K 5120K sleep netcon 37:42 0.00% httpd
7279 67 2 0 3128K 5228K sleep netcon 37:36 0.00% httpd
7736 73 2 0 572K 708K sleep poll 38:02 0.00% syslogd
17351 0 2 0 668K 856K idle select 22:35 0.00% cron
10037 0 2 0 552K 1204K idle select 7:44 0.00% sshd
23887 83 2 0 380K 780K idle poll 12:38 0.00% ntpd
1 0 10 0 380K 292K idle wait 0:26 0.00% init
25931 0 2 0 384K 720K idle poll 0:18 0.00% ntpd
If you are concerned, at right is the result of using PHP to run the command:
top -d 1
on this server as it was generating this page. Really. You can click the Reload button and you will see that things change slightly. The time (end of first line) is UTC. I would expect the CPU to be almost 100% idle, unless you happen to have loaded this page while the server is busy running a scheduled job or some other infrequent task.
OpenBSD comes with something that isn't exactly Apache's httpd. The web server is the result of an OpenBSD code audit, bug patching, and hardening of something out of the Apache 1.3 web server product line. As the OpenBSD documentation says, "The OpenBSD team has added default chrooting, privilege revocation, and other security-related improvements."
The mod_gzip Apache module is not included in the stock OpenBSD distribution. It is part of the packages and ports system. If you have downloaded the full set of packages, you have the file you need. If not, it can be as simple as this if you use csh/tcsh:
# setenv PKG_PATH ftp://ftp.openbsd.org/pub/OpenBSD/`uname -r`/packages/`uname -m` # pkg_add mod_gzip
Or, for bash/ksh:
# PKG_PATH=ftp://ftp.openbsd.org/pub/OpenBSD/`uname -r`/packages/`uname -m` # pkg_add mod_gzip
Notice that those are backquotes for command substitution! The two uname commands run first, producing output similar to 4.7 and i386. Those results are then placed into the assignment of the shell variable.
Michael Schröpl has a nice description of how to get mod_gzip to work in many situations, click here to see that. I have based what I did on his work, with some additions required for OpenBSD or any other similarly configured chroot environment.
Become root, start editing /var/www/conf/httpd.conf, and search for the string mod_gzip. When you installed that package, a post-install script within the package should have added a line loading that module. If it did not, find the area of the file where modules are loaded and add a similar line (and, to help yourself in the future, a comment!) like the following:
# Add compression LoadModule gzip_module /usr/lib/apache/modules/mod_gzip.so
Now add a stanza directly below that. It should be similar to the following, but you may want to adjust the minimum and maximum file sizes:
<IfModule mod_gzip.c> # Turn it on: mod_gzip_on Yes # Enable "partial content negotiation" and the serving # of compressed versions if those files are available, # along with the updating of the compressed versions # when the originals are updated: mod_gzip_can_negotiate Yes mod_gzip_static_suffix .gz AddEncoding gzip .gz mod_gzip_update_static No # Allow the chunks to be joined into one compresable packet # with a HTTP head deleted: mod_gzip_dechunk Yes # Specify a range of file sizes in bytes for compression. # There's no point in compressing tiny files, and compression # of enormous files will delay the start of transmission. mod_gzip_minimum_file_size 500 mod_gzip_maximum_file_size 6000000 # Allow any client speaking HTTP/1.0 and later and behaving # in a reasonable fashion: mod_gzip_min_http 1000 mod_gzip_handle_methods GET POST # Compress anything named *.html and of MIME type text/*: mod_gzip_item_include file \.html$ mod_gzip_item_include mime ^text/.* # Do NOT compress images (no point!) and CSS style data # (that would confuse really old Netscape): mod_gzip_item_exclude file \.css$ mod_gzip_item_exclude mime ^image/.$ # Where is the working area for temporary files and the # compression cache? mod_gzip_temp_dir /tmp # See Michael Schröpl's page for optional logging in case # you need to do some debugging. </IfModule>
Here is the trick required to get this to work on OpenBSD or any other chroot environment, something that isn't frequently mentioned in the documentation.
Remember that you told your compression module to use /tmp as a working area. However, the OpenBSD web server process is using chroot to run in an unusual environment (unless you have changed /etc/rc.conf to make it behave otherwise).
The httpd process is running in a "sandbox" of sorts. Its notion of the root of the file system isn't the real root. This means that there is no ".." directory, no way to go up one level and get out of the chroot jail (or gaol as it's spelled in Britain).
What the httpd process thinks is / is really the /var/www directory. So, we have to create something that will appear to be a proper /tmp for that process. Do this:
# cd /var/www # mkdir tmp # chmod 1777 tmp
Stop the running web server process:
# pkill httpd
Make sure that really worked:
# ps axuww | egrep 'PID|httpd' # lsof -i tcp:80
You may need to give an active request a moment or two to complete. And lsof is in /usr/local/sbin if root doesn't have that in the path.
Once the coast is clear, start a fresh web server process:
# /usr/sbin/httpd
Yes, I probably could have done this with a HUP signal, but killing it off and starting a new one makes it a little easier to avoid sysadmin confusion. If you are concerned about not refusing a single request, look into doing it this way:
# pkill -HUP httpd
This page exists as an HTML file on the server containing a block like the below. The web server process executes the PHP code on the server and inserts the output in the page.
<pre style="background: #000000; color: #00ff00;
font-size: 9pt;
padding-left: 3px; padding-right: 3px;
padding-top: 5px; padding-bottom: 5px;
border-style: solid;
border-width: medium;
border-color: orange;">
<?php @ passthru ('top -d 1 | grep -v "^$"'); ?>
</pre>
</div>
And, because of the chroot issue discussed above I had to do the following on the server to get those two commands to work:
# cd /var/www # mkdir usr usr/bin # cp /bin/sh bin # cp /usr/bin/grep /usr/bin/top usr/bin # ldd bin/sh usr/bin/* [ ... hmm, need to include some shared libraries ... ] # mkdir usr/lib usr/libexec # cp /usr/lib/libc.so.* /usr/lib/libcurses.so.* /usr/lib/libz.so.* /usr/lib # cp /usr/libexec/ld.so usr/libexec
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| © Bob Cromwell Feb 2012. Created with /bin/vi and ImageMagick, hosted on OpenBSD with Apache. Root password available here, privacy policy here. |
