Not a bad way to spend a friday afternoon..Here are my raw notes. I make up these tech notes for myself and this is not a bad addition:
Fri Mar 31 14:56:32 EDT 2017 LESSON: SIMPLE ACTIVE-ACTIVE HTTPD CLUSTER
This is based on the RedHat manual "Linux 7 High Availability Add On
Administration" except that this follows an active-active setup and assumes
there is a cluster filesystem available.
PACKAGES NEEDED:
wget - needed by pacemaker (for status checks; supposedly "curl" is also
supported and must be specified by the ocf client= option)
lynx - OPTIONAL; to test status yourself.
ASSUMED CONDITIONS:
- httpd is already installed; furthermore it is enabled and running as stock
via systemd
- there is a clustered gfs filesystem on /volumes/data1 (for common
html content)
PART 1: HTTPD
Set up the document root as desired. In this example, the html documents
are rooted at /volumes/data1/www and is common to all nodes. In the config
file /etc/httpd/conf/httpd.conf:
DocumentRoot "/volumes/data1/www"
<Directory "/volumes/data1/www">
AllowOverride None
Require all granted
</Directory>
Put some data on the directory; in this simple example there would be a file
named /volumes/data1/www/index.html
<html>
<body>
<h1>hello</h1>
This is a test website from JondZ
</body>
</html>
At the end of the config, put the following; this is used by pacmaker to check
status.
<Location /server-status>
SetHandler server-status
Order deny,allow
Deny from all
Allow from 127.0.0.1
</Location>
Use lynx to check that it works:
lynx http://127.0.0.1/server-status
When satisfied that things are working, disable httpd activation by systemd;
the service will be managed by pacemaker instead.
systemctl disable httpd
systemctl stop httpd
PART 2: LOGROTATE
Edit the file /etc/logrotate.d/httpd and modify the "postrotate" section:
# This is the old stuff. Comment this out.
# Since httpd is going to be managed
# by pacemaker, not by systemd, this is no longer valid:
#
# /bin/systemctl reload httpd.service > /dev/null 2>/dev/null || true
#
# This is the correct line that RedHat recommends. Note that
# the PID file is produced by pacemaker (or httpd itself?) and is
# probably true only as long as httpd is not managed by systemd.
#
/usr/sbin/httpd -f /etc/httpd/conf/httpd.conf -c \
"PidFile /var/run/httpd.pid" -k graceful > /dev/null 2>/dev/null \
|| true
#
# This is how I personally respawn apache on old production systems
# but this NO LONGER RELIABLY WORKS (need testing).
#
# /sbin/apachectl graceful > /dev/null 2>/dev/null && true
Test logrotate. First of all make sure that /var/run/httpd.pid is current.
Then force rotations by "logrotate -f /etc/logrotate.conf". Also watch the
pid changes on the httpd processes (on a separate terminal you could say
watch -n1 "ps -efww | grep httpd" and watch the pid's being replaced.
PART 3: PCS RESOURCE ENTRY
I added the pcs resource as follows:
pcs resource create batwww apache
configfile="/etc/httpd/conf/httpd.conf"
statusurl="http://127.0.0.1/server-status" clone
The option "clone" makes the httpd run an all nodes (instead of just one
instance).
JondZ 201703
No comments:
Post a Comment