Recent Blog Posts

Properly deploying updates to or shutting down Jenkins

One of my most popular Ansible roles is the geerlingguy.jenkins role, and for good reason—Jenkins is pretty much the premiere open source CI tool, and has been used for many years by Ops and Dev teams all over the place.

As Jenkins (or other CI tools) are adopted more fully for automating all aspects of infrastructure work, you begin to realize how important the Jenkins server(s) become to your daily operations. And then you realize you need CI for your CI. And you need to have version control and deployment processes for things like Jenkins updates, job updates, etc. The geerlingguy.jenkins role helps a lot with the main component of automating Jenkins install and configuration, and then you can add on top of that a task that copies config.xml files with each job definition into your $JENKINS_HOME to ensure every job and every configuration is in code...

Getting Munin-node to monitor Nginx and Apache, the easy way

Since this is something I think I've bumped into at least eight times in the past decade, I thought I'd document, comprehensively, how I get Munin to monitor Apache and/or Nginx using the apache_* and nginx_* Munin plugins that come with Munin itself.

Besides the obvious action of symlinking the plugins into Munin's plugins folder, you should—to avoid any surprises—forcibly configure the env.url for all Apache and Nginx servers. As an example, in your munin-node configuration (on RedHat/CentOS, in /etc/munin/plugin-conf.d, add a file named something like apache or nginx):

# For Nginx:
env.url http://localhost/nginx_status

# For Apache:
env.url http://localhost/server-status?auto

Now, something that often trips me up—especially since I maintain a variety of servers and containers, with some running ancient forms of CentOS, while others are running more recent builds of Debian, Fedora, or Ubuntu—is that localhost doesn't always mean what you'd think it means.

Ansible for DevOps - 50% off on LeanPub for Black Friday 2017

Though I've had a little less time to work on the book lately, I'm still very much invested in keeping Ansible for DevOps the best and most up-to-date guide to using Ansible for infrastructure automation. It's been over two years since the first '100% complete' edition was released, and in that time I have published over 200 updates on LeanPub—and even have full test coverage for all the book's examples, which are open-sourced and available in the Ansible for DevOps GitHub repo!

Ansible for DevOps - 50% off for Black Friday 2017

For this year's Black Friday, I'm discounting the book—50% off—but only on LeanPub. I like to push readers to LeanPub, because:

Stripping the 'Vary: Host' header from an Apache response using Varnish

A colleague of mine found out that many static resource requests which should've been cached upstream by a CDN were not being cached, and the reason was an extra Vary http header being sent with the response—in this case Host.

It was hard to reproduce the issue, but in the end we found out it was related to Apache bug #58231. Basically, since we used some RewriteConds that evaluated the HTTP_HOST value before a RewriteRule, we ran into a bug where Apache would dump a Vary: Host header into the request response. When this was set, it effectively bypassed Varnish's cache, as well as our upstream CDN... and since it applied to all image, css, js, xml, etc. requests, we saw a lot of unexpected volume hitting the backend Apache servers.

To fix the issue, at least until the upstream bug is fixed in Debian, we decided to strip Host from the Vary header inside our Varnish default.vcl. Inside the vcl_backend_response, we added:

Photos of St. Michael the Archangel Catholic Parish

I was recently invited to take some pictures of the campus and interior of St. Michael the Archangel Catholic Church in Shrewsbury, MO (nestled in a neighborhood just outside of the City of St. Louis), and I just finished processing and uploading them to Flickr; see my St. Michael the Archangel photos.

St. Michael the Archangel Catholic Parish sanctuary

There are so many of these little Catholic churches in St. Louis and around the country, with so much hidden beauty. I always try to find a neat little parish near where I stay in any city I visit; usually these parishes showcase more artwork than even the diocesan cathedrals—though that's not the case in St. Louis!


Subscribe to Jeff Geerling's Blog