DDD Adelaide 2019 Summary

Phew! DDD Adelaide 2019 is done. Yesterday we had 150 people come along to UniSA's MOD building in the city and see 16 speakers present some awesome topics on software development.

The feedback on the day was overwhelmingly positive. I'll be catching up with co-organiser Andrew soon to debrief and also review the comments received from attendees.

Special thanks to the gold sponsors:

• Telstra Purple,
• AWS,
• Comunet,
• The University of South Australia and in particular The School of Information Technology and Mathematical Sciences, who went out of their way to provide a beautiful venue.

Here's a few of my highlights of the day:

Some kind people brought one or two donuts to share!

Lars Klint was our keynote speaker, kicking off the day.

A fantastic range of speakers, including Ming Johanson

and Liam McLennan (who incidentally was actually a speaker around 10 years ago at the last DDD Adelaide)

Really yummy catering provided by Food Lore…

… and Coffee Cart provided by B3 Coffee and sponsored by Encode Talent

It was great to see so many software developers gathered together in Adelaide.

Andrew drawing the prize winners (prizes sponsored by Octopus Deploy) and closing out the day.

Finally, special thanks to my wife and two eldest kids who also gave up their Saturday to help out as volunteers for the day. I really appreciate their support.

Trying Docker for Windows and Linux

I've been spending a bit of time trying out Docker over the past few days, with the goal of making builds more reliable and repeatable.

Docker Desktop for Windows has the ability to run in Windows mode and Linux mode. Usually that means you can only run containers of one OS at at a time.

However, if you run configure Docker to enable 'Experimental' mode, then you can actually run both platforms simultaneously.

Interestingly, when you're in this mode and you set 'Windows' as the default container platform, you don't see an extra virtual machine listed in HyperV.

Here's Docker running with Linux containers:

And here's Docker with Windows containers: Notice the VM may be there, but it is not running, even when I'm actually building a Linux container when that screenshot was taken.

So with experimental mode on, how can Docker be also running Linux containers in Windows mode?

Currently it uses something called LCOW - Linux Containers on Windows.

I know Docker also has preview support for WSL2. I think the plan is that once that ships (presumably with Windows 10 20H1) then Docker will be able to leverage that for Linux execution.

So in theory, if you need to spin up Linux and Windows containers, then this is the technology that will make that happen.

There's still a few rough edges - probably why it's all behind 'preview' or 'experimental' flags.

I hit one issue where trying to spin up a Node Linux container which has a step to run yarn resulted in some weird internal error:

Step 14/22 : RUN yarn
---> Running in eb14f055a9aa
container eb14f055a9aaa23db5f35493feec9009b775c6688e3c488b26c6880517bdd9f1 encountered an error during CreateProcess: failure in a Windows system call: Unspecified error (0x80004005)
[Event Detail: failed to run runc create/exec call for container eb14f055a9aaa23db5f35493feec9009b775c6688e3c488b26c6880517bdd9f1: exit status 1 Stack Trace:
github.com/Microsoft/opengcs/service/gcs/runtime/runc.(*container).startProcess
/go/src/github.com/Microsoft/opengcs/service/gcs/runtime/runc/runc.go:580
github.com/Microsoft/opengcs/service/gcs/runtime/runc.(*runcRuntime).runCreateCommand
/go/src/github.com/Microsoft/opengcs/service/gcs/runtime/runc/runc.go:471
github.com/Microsoft/opengcs/service/gcs/runtime/runc.(*runcRuntime).CreateContainer

No idea what's going on there other than maybe I've managed to hit some issue where some API isn't implemented?

It's strange, as a different container (based on a different Linux distribution) didn't have that problem.

So it has potential, but it's obviously a work in progress.

PowerShell ErrorAction

Many PowerShell cmdlets have a common parameter ErrorAction, that can be set to one of Continue, Ignore, Inquire, SilentlyContinue, Stop or Suspend

I've never really understood what the different between Ignore and SilentlyContinue was until today. I'd ran the following code:

Get-Service 'NonExistantService' -ErrorAction SilentlyContinue

and then happened to look in the $Error automatic variable and noticed the following:

Get-Service : Cannot find any service with service name 'NonExistantService'.
At line:1 char:1
+ Get-Service 'NonExistantService' -ErrorAction SilentlyContinue
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo          : ObjectNotFound: (NonExistantService:String) [Get-Service], ServiceCommandException
+ FullyQualifiedErrorId : NoServiceFoundForGivenName,Microsoft.PowerShell.Commands.GetServiceCommand

Whereas the following does not get added to $Error

Get-Service 'NonExistantService' -ErrorAction Ignore

That's the difference! Ignore was added in PowerShell 3.0, and quoting the documentation page "Unlike SilentlyContinue, Ignore doesn't add the error message to the $Error automatic variable."

So Ignore is probably a better option for most cases where ignoring the error is fine.