Voice of the DBA

Author: way0utwest

  • Always Canary

    Deploying software is hard. Despite decades of experience working to update software smoothly, it seems that many of us tasked with that responsibility find ourselves nervous about making changes. This is especially true for database changes, where we must not only update the schema and code, but we must preserve the data as well. If only we could drop and recreate the database during every deployment.

    One of the ways in which you can make changes in a live environment is to have a second system already in place and running. With a second system available, you can stop the secondary system from handling user requests, make changes, test them, and if things are working well, you can have users connect to the updated system while you take the one one offline and perform your updates there.

    This is the same process that many people use to patch clustered database servers, though the “rolling upgrades” are usually done for patches from Microsoft. It would be great if we could easily apply this same system for our schema upgrades. Deploy our changes to the passive node, have the application able to connect to this node through some switch, test the changes, and if things are working, switch users over. The problem is that our databases on the passive node aren’t live.

    Really the ability to deploy database changes to a live system and perform checks requires a strong architecture in both the database and application to support this. Your code must be able to handle additions to the database objects without breaking. The use of feature flags, turning functionality on and off with switches, allows certain users to test new features without most clients being aware of the changes.

    It’s a pattern that more and more software companies are using when they want to deploy changes rapidly to systems for limited numbers of users. However it’s not a design pattern that is widely used. I hope we get more sample applications and reference architectures in the future that will help developers and DBAs code more robust and resilient applications, allowing changes to be deployed live without affecting every user.

    Steve Jones

    The Voice of the DBA Podcast

    Listen to the MP3 Audio ( 2.5MB) podcast or subscribe to the feed at iTunes and LibSyn. feed

  • The Value of Code

    It seems that many businesses can operate with a large margin for error. Managers can make some poor decisions, processes can be a bit inefficient, and employees can be disengaged, yet companies can still turn a profit. Non-profits, and certainly government organizations, can run without optimizing their work, much to the chagrin of many. However I continue to find companies that look for ways to not only become more efficient, but also to fundamentally alter their business models by better understanding their particular market. They can turn profits (or operate efficiently) far in excess of the averages for their industry with one tool: software.

    There’s a belief in many of these highly optimized companies that data contains lots of value, but in order to understand and harness the information contained within data, an enterprise must be willing to invest in better software. That requires better software developers. In a forward looking enterprise, that means lots of opportunity for those of us that work with data and build software.

    Those of us that create technical solutions need to learn to better interpret data and find ways to help our clients find and understand the patterns revealed by our software. Those of us that primarily manage data, need to better understand how software renders and showcases information compiled in our databases. We truly have the ability to reshape the way organizations run with our technological skills.

    Computing power continues to grow, accessibility to information improves, and our enterprises become more dependent on our systems. Now is the beginning of an era where we will have tremendous influence in helping change the way business works. I’d urge all of you to continue to look for new ways to manipulate data and find ways that showcase the value that software can bring to your organization. Even if your current company doesn’t value your skills, I bet another one will sometime in the future.

    Steve Jones

    The Voice of the DBA Podcast

    Listen to the MP3 Audio ( 2.3MB) podcast or subscribe to the feed at iTunes and LibSyn.

  • Creating Placeholder Files

    I recently wrote about placeholders for disk space. While you can use any file, like large images, video, etc., I’ve found a really simple, easy way to build these files on Windows.

    Contig.exe

    There’s a sysinternals utility called Contig. You can download it from Microsoft and then unzip it on your system. It’s a command line utility, so you can use the /? to get the parameters from it, but here’s what you need to do: use the -n parameter, with a filename and a size.

    That simple. Here’s a sample call:

    placeholders1

    And in text:

    contig -n Hold1.place 1073741824

    That creates a 1GB file (roughly) on my system. I can then copy this file as many times as I want to save space.

    I use folder in the root called placeholder. I put one file in there and then copy it a few times to reserve space.

    Why that size? 1024 * 1024 * 1024.

  • Your Best Work

    Interviewing is hard. We also know that most of us don’t do it well, as evidenced by the choices we make when hiring. How many people have performed at the level you expected when you hired them? There are people that outperform your evaluation, but many more underperform your expectations. I think this is partially that it’s hard to evaluate someone’s skills in a short period of time, but also that the performance someone gives is impacted by the environment they work in. That’s hard to simulate in an interview.

    However, if we ignore that and look to find some method to at least evaluate a technologist’s skills, what do we do? We test, we quiz, we try strange questions. I read an account from a programmer looking to hire other programmers, titled How I ended up conducting the most successful technical interviews with a single question. It’s a good story, and it drew me in as the author followed the same path I’ve followed before.

    Then he exposed his question: tell me about the best project you’ve ever created. It’s simple, and I think it probably works well. Programming is a creative endeavor and those that love doing it, keep doing it. They will have projects they are proud of, if they continue to work to improve their craft. They’ll also be passionate about what they do. I don’t know if this would work in other areas, like system administration, but I’d like to think that most people have done something they’re proud of.

    However I don’t think this guarantees great workers. I guess you can evaluate the way someone approached their project, and how they dealt with issues, but passion does not always equate to great work. I’m an amateur woodworker, and I’m quite proud of my flagpole, but I’m not sure many of you would want to pay me to build one for you. My skill have a long way to go before I could make a living at that craft.

    Steve Jones