Saturday, April 28, 2007
Thursday, April 26, 2007
Sometimes paths are hardcoded in applications -- let's say you have the path to the Apache DocumentRoot directory hardcoded inside a web application to /home/apache/www.mysite.com. You can't change the code of the web app, but you want to migrate it. You don't want to use the same path on the new server, for reasons of standardization across servers. Let's say you want to set DocumentRoot to /var/www/www.mysite.com.
But /home is NFS-mounted, so that all users can have their home directory kept in one place. One not-so-optimal solution would be to create an apache directory under /home on the NFS server. At that point, you can create a symlink to /var/www/www.mysite.com inside /home/apache. This is suboptimal because the production servers will come to depend on the NFS-mounted directory. You would like to keep things related to your web application local to each server running that application.
A better solution (suggested by my colleague Chris) is to mount a local directory, let's call it /opt/apache_home, as /home/apache. Since the servers are already using automount, this is a question of simply adding this line as the first line in /etc/auto.home:
apache -fstype=bind :/opt/apache_home
/etc/auto.home was already referenced in /etc/auto.master via this line:
Note that we're using the neat trick of mounting a local file system via the 'bind' mount type. This can be very handy in situations where symbolic links don't help, because you want to reference a real directory, not a file pointing to a directory. See also this blog post for other details and scenarios where this trick is helpful.
Now all applications that reference /home/apache will actually use /opt/apache_home.
For the specific case of the DocumentRoot scenario above, all we needed to do at this point was to create a symlink inside /opt/apache_home, pointing to the real DocumentRoot of /var/www/www.mysite.com.
One task that comes up again and again is adding, removing or updating source CIDR blocks in various security groups in an EC2 infrastructur...
I first saw nsupdate mentioned on the devops-toolchain mailing list as a tool for dynamically updating DNS zone files from the command line....
Here's a good interview question for a tester: how do you define performance/load/stress testing? Many times people use these terms inte...
Gatling is a modern load testing tool written in Scala. As part of the Jenkins setup I am in charge of , I wanted to run load tests using Ga...