Voice of the DBA

Tag: Azure

Pause and Backtrack

One of the main functions for anyone that manages a database is ensuring that they can recover the system in the event of any issues. My view is that restores are the most important skill and task that need to be performed on a database. Since restores require backups, I’d then rank backups as a 1a important task. They’re a dependency and necessity to ensure that we can restore data. Having a set of the data, in a transactionally consistent state just feels critically important to me, over everything else..

I saw this new feature from Amazon Aurora for their MySQL compatible database. You can use Backtrack to rewind your database to a previous point in time. On one hand that’s an amazing feature. Make a mistake, have an error, click a few buttons and get the database restored back to the minute (or second) when you made a mistake. On the other hand, if you delete a table, do you want to roll all tables back to that point in time?

This seems like an amazing feature. Amazon takes some of the hassles of managing some backups backups. You determine how far back you want to go, in hours, up to three days. Depending on the activity in your database, they charge differently. To me, that’s interesting. It makes sense to me as a customer. I do more, they track more, I pay more. This also seems to be a way to capture more money for Amazon by cutting some of the consumer surplus that exists with flat fee pricing, which is something many of us prefer.

The way this works is also different than Azure. The Azure point in time feature allows you to go back, but you can’t restore on top of your existing database. You’d need to restore elsewhere, then play the rename game or move data between databases. While that seems inconvenient, if you’ve ever had someone restore a local SQL Server backup over a database you needed, you might appreciate the safeguards of not allowing a restore on top of an existing database. While the process might seem like a hassle, this does help prevent mistakes during a stressful situation.

Which of these do I like? I prefer the Azure one, though I’d like the restores to be more granular than a minute. The reason is that I rarely want to restore in a disaster over the existing database. In most applications I’ve managed, there are updates to multiple parts of the database. A mistake in one table doesn’t necessarily mean that data changed in other tables should be discarded. Even during deployments, when things go wrong, I’ve often just broken one set of tables and rolling back the entire database in a restore is painful. Usually I’d prefer to undo what I can and get the any missing data from a restored copy of my database.

Perhaps it’s just me, but I find the idea of allowing clients, or even many technical people, to easily roll back an entire database after a mistake to be very dangerous. By the time we recognize the mistake, verify data, notify others, we might have lots of changes in many tables. Abandoning that data for the sake of convenience is something that’s unnecessary. I also worry many people trying this feature don’t think through the implications of rolling back an entire database. If you feel differently, let me know. There are cases this is certainly helpful, but I think I’d rather have a “restore to a new db and rename both” automated task instead of AWS Backtrack.

Steve Jones

The Voice of the DBA Podcast

Listen to the MP3 Audio ( 4.3MB) podcast or subscribe to the feed at iTunes and Libsyn.

May 23, 2018
Python Jupyter Notebooks in Azure

There’s a new feature in Azure, and I stumbled on it when someone posted a link on Twitter. Apologies, I can’t remember who, but I did click on the Azure Notebooks link and was intrigued. I’ve gotten Jupyter notebooks running on my local laptop, but these are often just on one machine. Having a place to share a notebook in the cloud is cool.

Once I clicked on the link, I found these are both R and Python notebooks, as well as F#. These allow you to essentially build a page of code and share it. It’s kind of like a REPL, kind of like a story. It’s a neat way of working through a problem. I clicked the Get Started link to get going and was prompted for a User ID.

Once I had my moniker setup, the next step was to edit my profile. That’s more important than a library, right?

Of course, I needed to fill out the profile with my avatar and some information.

Next I need to create a library, which I’m guessing is a collection of notebooks. I clicked the link and had to enter a name. I decided on the classic HelloWorld name. I decided to keep this public, as I might want to share this with others.

I’ve got a library, now let’s add something. I clicked the Readme.md, but it didn’t load. There was nothing there, as this is a blank file.

I discovered I could right click the file in the list. This lets me edit it. Strange UX, but whatever. The file uses markdown as editing, which is fairly simple, but consists of a few characters to designate titles, lists, etc.

I entered some text, and then my readme appeared below my notebook list, much like it goes on Github. My screenshot got taken after I’d experimented a bit, so you see a couple python notebooks as well.

From there, I could add a notebook. I have choices. I started with Python, since that’s one of my learning goals.

I give the notebook a name and create it.

Once this is created, it appears as a Jupyter notebook. Essentially I have a repl-like command area, and once I enter code, I can click “Run” to execute it. You can see that my Hello, World program ran.

I can enter other code, and I’ve done a few things, just to practice some basics in Python. I’m working through some courses, and I’ll enter code in here to practice concepts.

Jupyter notebooks are a good way of working through a problem and showing flow. They’re especially useful for sharing information with others and letting them follow your thought process.

April 18, 2018
A New SQL Server Edition

I first heard about this edition of SQL Server over a year ago, and at the time I wasn’t sure there was much of a market for it. Microsoft disagreed, and they moved forward, putting this in preview and then finally releasing it this past week. Now you can order and set up an Azure SQL Database Managed Instance. According to Microsoft, this is an edition that is near 100% compatible with on-premises instances. The difference is this is a PaaS option that removes much of the administrative burden for patching, backup, HA, etc.

This seems like a VM that Microsoft manages and you connect to, except this isn’t really a VM. You do not have any access to the host, but you do get the option to have multiple databases and most of the features that don’t exist in Azure SQL Database are here. Keep in mind that near 100% is not 100% and there are limitations, quite a few, which may limit your ability to lift and shift your particular application.

Brent Ozar Unlimited tackled this feature first, putting together quite a few blog posts on the topic. The first one notes that a new instance might take 24 hours to deploy (in the cloud??), and theirs did. In that post, they also discuss the networking, which isn’t necessarily hard, but it’s not as simple as most DBAs and developers are used to. In fact, while reading the post, I recalled memories of my time as a network admin, learning how to migrate from IPX to IP based addressing. For those of you not used to networking terms and configuration, you might want to read about this topic from the experts.

The Azure fabric is managing all the HA behind the scenes, and I’m guessing they’ve got some advanced featuers that might end up in the box product at some point. It seems from reading Brent and Erik’s experiments that you really get a dedicated instance with some CPUs and schedulers turned off it you don’t provision the largest instance. There are new objects inside the instance, which again, might get into the box at some point.

Are Managed Instances for you? Perhaps. Removing this administrative issue might make financial sense for your organization. Not for you, but when you factor in taxes and staff to perform tedious actions, maybe this works. Certainly you should understand if you have an option here for any applications and then present this as an alternative to the business and let them decide if this makes sense. I’m not sold, but I do like the idea of this as a new cloud option. We have public, government, private, hybrid, IaaS, Paas, and SaaS options. This slips somewhere between hybrid and PaaS, giving us more choice, which I do think will work for some organizations.

I don’t know how these will perform, and really none of us do outside of Microsoft. They’ve been testing, and I hope this will work well, failover cleanly, and not be so confusing that customers find themselves misconfiguring networking. However, if you’re using parts of Azure, have AAD implemented, and want to get new instances provisioned that look mostly like what you have in your data center, take a look. Hopefully the provisioning process will smooth out and speed up, since 24 hour notice might be great for some large corporations, but it certainly doesn’t feel like the cloud to me.

Steve Jones

March 17, 2018
Use the Proper User for Azure MySQL DB

I wrote about migrating the MySQL database from a third party provide to Azure MySQL DB recently. This was due to the provider raising the price substantially for me to host the site. However, after migrating the data, I ran into an issue.

I’d read a blog on moving WordPress data and followed the instructions, but after updating my connection string, I kept getting this at tsqltuesday.com

Error Making Database Connection

It appeared big and bold in the browser, with no additional information. There was a time I dug into MySQL, but it’s been a long time. In any case, I wasn’t sure what the issue was, so I started messing around.

In MySQL Workbench, I could add a new user with their GUI and grant privileges. I did this for a user called “tsql2sday”, with a password. However, when I updated the connection string in my Azure App Service, this didn’t work.

I tried a number of items, including manually creating my own user and assigning privileges, making this a DBA (super) user, and more. Nothing seemed to work. Some of you might have even seen the error messages as I tried to get this to work.

Eventually I checked something. In the original app service connection string, my old third party database just had the user name. This was the same for my connection in MySQL workbench. However, with my new Azure MySQL database, I needed user@dbname. For me, this was tsql2sday@tsqldb in MySQL Workbench.

Once I added the @ and host to the connection string in the App Service, I could connect. Whew, as I wasn’t looking forward to another hosting bill.

I think all the data is there, but if you find issues with tsqltuesday.com, let me know.

February 20, 2018