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Category: Containers

Image Caching with Docker

Published 2020-04-03 by Kevin Feasel

etash2901 at the Knoldus blog walks us through the way Docker caches images:

If the objects on the file system that Docker is about to produce have not changed between builds, reusing a cache of a previous build on the host is a great time-saver. It makes building a new container really, really fast. None of those file structures have to be created and written to disk this time — the reference to them is sufficient to locate and reuse the previously built structures.

This is an order of magnitude faster than a a fresh build. If you’re building many containers, this reduced build-time means getting that container into production costs less, as measured by compute time.

Click through for some advice on how to minimize the amount of time you spend waiting for image layers to download or process.

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Using Ephemeral Containers for Debugging Kubernetes-Based Applications

Published 2020-04-01 by Kevin Feasel

Praveen Sripati walks us through the notion of Ephemeral Containers:

It’s always CRITICAL to pack a Container image with the minimal binaries required as this makes the surface area of attack minimal, upgrading the image and testing also becomes easier as there are less variables to be addressed. Distroless Docker images can be used for the same. In the above diagram Container (A) has only the application and the dependent binaries and nothing more. So, if there are no debugging tools in the Container (A) nor any way to check the status of the process then how do we debug any problem in the application? Once a pod is created, it’s even not possible to add Containers to it for additional debugging tools.
That’s where the Ephemeral Containers come into picture as in the Container (B) in the above picture. These Containers are temporary that can be included in the Pod dynamically with additional debugging tools. Once a Ephemeral Container has been created, we can connect to it as usual using the kubectl attach, kubectl exec and kubectl logs commands.

It’s an interesting approach to the problem.

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Diving into Kubernetes: a Workshop

Published 2020-04-01 by Kevin Feasel

Chris Adkin has been busy:

I have not blogged for a while, it was my hope to produce part 5 in the series of creating a Kubernetes cluster for production grade Big Data Clusters. However, there is a very good reason for this, and that is because I have been working on a one day workshop to be delivered at SQL Bits in September, the material can be found here, enjoy !

I’ve only looked at the module listings, but Chris does a great job putting long-form articles together, so I’ve already added it to my todos.

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Running SQL Server on a Windows Container

Published 2020-03-18 by Kevin Feasel

Jamie Wick takes us through the less-trodden path:

SQL Server containers are gaining popularity as a way of enhancing and standardizing development environments for Windows & Linux based SQL databases. SQL containers allow developers to have their ‘own’ dedicated copy of a database, usually without the need for extensive server infrastructures. Additionally, a single computer can host multiple containers, each with a different edition/version of SQL Server. This allows the user to quickly switch between environments, without the need to reinstall. Currently, a popular option for implementing containers on Windows-based computers uses Docker.

For those not familiar with containerization, here is a Microsoft article on Windows containers.

I’d definitely prefer to use Linux containers, even on Windows machines. But if Windows-based containers is your thing (or you need to use them for some reason), Jamie’s got you covered.

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Restoring Databases Inside a Container

Published 2020-03-16 by Kevin Feasel

Aaron Bertrand has a quick-and-easy method of restoring databases in a Docker container:

I have been using Docker containers for local development and testing for some time now; I first blogged about my steps into this brave new world back in late 2016. Most of the time, I just need to create some throwaway database, with a throwaway table, to prove a point or to validate an answer I’ve supplied.

Sometimes, though, I need to work with a real database. It’s a little trickier to do this in a container, because it’s isolated — I can’t just attach or restore from my Downloads folder. I could fire up a VM and attach there, but I actually don’t even use Parallels on my work laptop, and I find that using VMs leads to response times that are a lot more sluggish across the board.

It’s not too difficult to get files into your containers, provided your instance will have a total size less than the size of the container, and this quick tutorial proved to be very helpful.

Read on for the walkthrough. Aaron notes that this is a Mac-specific walkthrough, though the Windows and Linux versions are pretty similar as well, as we still create persistent volumes.

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MR3: Hive on Kubernetes

Published 2020-02-21 by Kevin Feasel

Alex Woodie reports on a DataMonad production:

MR3 is a software product developed by a team led by Sungwoo Park. The software, which is not open source, is sold by a Delaware-based software company called DataMonad. After prototyping a Java-based execution engine called MR2 in the 2013 timeframe, development of Scala-based MR3 began in 2015. The first release of MR3 was delivered in early 2018, and version 1.0 was released yesterday.

According to DataMonad, MR3 is an execution engine for big data processing, and Hive is the first and main application that’s been configured to run on it (Tez is also supported). The company says MR3 offers comparable performance to the latest release of Hive, dubbed LLAP, but without the technical complexity.

The closed-sourcedness is a bit of a downer, but I like having more competition in the space.

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Should DBAs Learn Kubernetes?

Published 2020-02-06 by Kevin Feasel

Randolph West makes me violate Betteridge’s Law of Headlines:

So this question, whether a SQL Server DBA really needs to know about Kubernetes, is really a question about whether DBAs need to know about the plumbing that runs the infrastructure upon which our databases reside.

In October 2018 I asked, “What is a DBA anyway?” It was a week after another post where I declared the DBA role “history.” My answer is:

Yes! You need to know Kubernetes if you’re a SQL Server DBA.

I agree with Randolph that it’s useful for a DBA to have at least some working understanding of Kubernetes, especially around being able to troubleshoot database issues on the platform. Read on for Randolph’s take on the matter.

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Using Windows Subsystem for Linux 2 in Windows 10

Published 2020-02-05 by Kevin Feasel

Max Trinidad is excited about Windows Subsystem for Linux 2:

First, I love WSL (Windows Subsystem for Linux)! It’s a great addition to Windows 10, and everyone should learn how to use it.

To get started, follow the instructions on how to get your WSL 1 Linux Distro installed. And, begin with installing Ubuntu 18.04.

Now, get Docker Desktop (), which can be installed in Windows 10 RTM Build 18363 with WSL 1.

One of the key benefits around WSL 2 is that your Docker containers will run natively rather than through a VM. That’s a pretty big deal in terms of performance and production-readiness. That Docker capability is currently in preview, but I’d expect it to make its way to production sooner than later.

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