Hidden gems from Build 2015

With the long list of announcements at Build, it’s hard to separate the good from the great stuff.

2 things on my radar that can make or break the success of Windows 10:

Universal Windows Platform Bridge for Classic Windows Applications
Windows has a huge portfolio of existing Win32, WPF and .NET apps. Unfortunately until now, they were not available through the Windows Store. This made the Windows Store the loser in the big number game about “which store has the most apps?”. With the announcement at Build, this will change: Microsoft announced Project Centennial, a bridge which will allow an existing Classic Windows application to be converted to a Universal Windows app and made available in the Windows Store. These apps will not only have the same install and update user experience that the Store provides today, they will also be able to call the Universal Windows Platform APIs and use new platform capabilities like Action Center, Actionable Notifications, and enhanced Live Tiles.

To make it even better, Microsoft brought the same security features of WinRT apps to the .NET and Win32 world.Registry and app data access are isolated for the app. So when your app thinks it is writing to the registry, it’s actually being stored in a per app hive, which can be easily removed. This is all done without having to make major changes to your code.

Universal Windows Platform Bridge for Web Apps
Microsoft also provides a similar story for hosted web apps, where existing web apps can be published to the Windows Store. Developers may start with a preexisting web site URL, place it in a manifest and create an app targeting the Universal Windows Platform.

Full access to the platform is possible including calling APIs directly from scripts hosted on a server, leveraging Cortana integration and authentication. Web developers are able to directly call platform APIs through JavaScript hosted on their server when their hosted content is running as an application on Windows.

Podman– Command execution failed with exit code 125

After updating WSL on one of the developer machines, Podman failed to work. When we took a look through Podman Desktop, we noticed that Podman had stopped running and returned the following error message: Error: Command execution failed with exit code 125 Here are the steps we tried to fix the issue: We started by running podman info to get some extra details on what could be wrong: >podman info OS: windows/amd64 provider: wsl version: 5.3.1 Cannot connect to Podman. Please verify your connection to the Linux system using `podman system connection list`, or try `podman machine init` and `podman machine start` to manage a new Linux VM Error: unable to connect to Podman socket: failed to connect: dial tcp 127.0.0.1:2655: connectex: No connection could be made because the target machine actively refused it. That makes sense as the podman VM was not running. Let’s check the VM: >podman machine list NAME ...

Cache stampede: when our cache turned against us

While investigating some performance issues, we ran into an ASP.NET Core API that cached a fairly expensive aggregation query for 60 seconds. Under normal load, that was fine: one request rebuilds the cache, everyone else reads from it. Under peak load, dozens of requests would arrive in that same expiry window, all see a cache miss, and all fire the same expensive query in parallel. The database didn't like that. That was the moment when our caching layer stopped helping and started hurting. A burst of requests comes in at the same time, all miss the cache, and all go hammer the database or the downstream API at once. That's a cache stampede . The cache was supposed to protect our backend, and for a few hundred milliseconds it did the opposite. Why this happens IMemoryCache.GetOrCreate (and its async sibling) looks like it protects you, but it doesn't add any locking on its own. Look at the naive version: public async Task<Report> GetReportAsync(string key) ...

A complex system designed from scratch never works

A few years ago, I worked as an architect on a big mainframe rewrite. I still count it as one of my failures. Not because the technology was wrong, but because I couldn't convince the management team to simplify the approach. Years later, the organization is still struggling to get the new system up and running. I left the project at the time, because I couldn't put my name behind an approach that would take very long and cost a lot of money without a working system to show for it along the way. Gall’s Law That memory keeps coming back to me, because it's a textbook case of Gall's Law playing out in real life. Gall's Law , from John Gall's Systemantics , states it plainly: A complex system that works is invariably found to have evolved from a simple system that worked. A complex system designed from scratch never works, and it cannot be patched to make it work. You have to start over with a simple system that works. What does that mean in practice,...

The art of simplicity

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