I have a small .net application that I wanted to run on Linux since it is a deamon/service sort of app. Basically is an app that peridically retrieves data from a REST service and stores it to a PostgreSQL database using LLBLGenPro 5.0 CTP2. So I created a .net 4.6.1 console application that uses HttpClient/ModernHttpClient package, NLog package for logging and System.Collections.Immutable package for immutable collecitons obviously. That was on Windows using Visual Studio 2015. After I added all the necessary code it run perfectly well on Windows.
Then I tried to open the same solution on Linux. I cloned the repository and opened it in MonoDevelop 5.10/Mono 4.2.1 (both latest). And it didn’t work out of the box. I stumbled over several issues I will describe here.
MonoDevelop doesn’t work with anything over .net 4.5 for the time being due to the MSBuild thing – at least that was the complaint.
Hence I downgraded my project to .net 4.5. No problems since I didn’t use anything .net 4.6ish.
It won’t install System.Collection.Immutable package because System.Linq package (which System.Collection.Immutable depends on for some reason) won’t install unless NuGet Package Manager is 3.0 or newer. MonoDevelop uses NuGet Package Manager 2.8.7. While this is only a NuGet Package installation issue, it is annoying. First, because System.Collection.Immutable doesn’t really require System.Linq package on Mono/.net 4.5 and next becuse it isn’t smooth as it should be. Funny thing is that at NuGet web page it says that System.Collection.Immutable requires NuGet 2.8.6 or higher. I guess it should be 3.0 or higher since a package that it depends on requires it.
Hence I dropped System.Collection.Immutable package which wasn’t difficult because I wasn’t using it extensively. Hopefully MonoDevelop catches up with NuGet and that is fixed.
ModernHttpClient speeds up communication since it uses native networking libraries. However it won’t work on Linux.
Dropped it since it doesn’t affect the functionallity at all.
I had configure NLog though nlog.config file. And it works on Windows perfectly. Hower when run on Linux I didn’t get any output whatsoever. Just like there was no configuration file. As a Windows guy I was a bit puzzled why. Since NLog is open source, I downloaded the code and tried debugging. Sadly MonoDevelop didn’t allow me to step into NLog code for some reason but luckily old school “Console.WriteLine” approach worked as usual. After some strategically placed Console.WriteLine calls within NLog library I found the reason, which might be apparent to a Linux guy. Bloody file name casing. I was using nlog.config and Windows doesn’t care about file name casing.
On Linux file name casing does and thus changing the name to NLog.config did the trick.
Linux specific addition
If app wants to gracefully handle SIGTERM signal (like when somebody/something tries to kill it) it might use UnixSignalWaiter NuGet package. While only at version 0.0.1 it seems to work just fine. It is also safe to use it on non-Linux systems where it does nothing (one might also check whether the feature is supported).
If .NET Core has proper database support (PostgreSQL in my case, but more more importantly LLBLGenPro doesn’t work due to lack of ado.net support – I don’t know about you but for me the proper ado.net stack on server is one of the most important aspects) I’d try to use it as well. But since it doesn’t, well, someday in the future I guess.
Anyway, after learning all the problems and the workarounds above I feel more confident in my Mono/Linux skills and the application compiles fine and works as expected. I also think that Xamarin/mono guys are doing really great job. Kudos.
Did I mention that I’m using Docker to run the application? I guess that’s a topic for a future post.