JavaScriptEngineSwitcher crashes in a dockerized .NET Core application

[omg-a-bear]

I'm pre-rendering some javascript server side in a current project, using ReactJS.NET which in turn relies heavily on JavaScriptEngineSwitcher.

Running the project from a host OS, I have no problems what so ever. I'm using ChakraCore as the engine to pre-render my React components, and I have NuGet references for the following dependencies:

- JavaScriptEngineSwitcher.ChakraCore
- JavaScriptEngineSwitcher.ChakraCore.Native.debian-x64
- JavaScriptEngineSwitcher.ChakraCore.Native.osx-x64
- JavaScriptEngineSwitcher.ChakraCore.Native.win-x64

Running the project with dotnet run succeeds in Windows, Mac OS X and Ubuntu/Debian. Publishing the application and running it from the publish directory succeeds in all operating systems as well (using dotnet publish -c Release -o <MYPATH> && cd <MYPATH> && dotnet <DLLFILE>).

However, when creating a Docker container from my published files and running the application from a container (using base image microsoft/aspnetcore:1.1.1) I get the following exception (runtime, on first page load):

React.TinyIoC.TinyIoCResolutionException: Unable to resolve type: React.ReactEnvironment ---> React.TinyIoC.TinyIoCResolutionException: Unable to resolve type: React.JavaScriptEngineFactory ---> React.Exceptions.VroomJsInitialisationException: Failed to initialise VroomJs. This is most likely caused by the native library (libVroomJsNative.so) being out of date or your system lacking a compatible version of V8.

It seems like ChakraCore isn't registered as my default engine, or .NET Core can't find the library file? I register ChakraCore as my default javascript engine using;

services.AddJsEngineSwitcher(options =>
    options.DefaultEngineName = ChakraCoreJsEngine.EngineName
).AddChakraCore();

I've even tried using a ChakraCore binary (libChakraCore.so) compiled in my Docker image, but without success. Is there anything I'm missing, or is it something I'm missing in my setup?

I realize the problem might lie in ReactJS.NET as well - but since the main problem seems to be that the default engine isn't initialized I'm guessing it has something to do with JavaScriptEngineSwitcher.

[Taritsyn]

Hello, Björn!

options.DefaultEngineName = ChakraCoreJsEngine.EngineName

As far as I know, that this option is not used in ReactJS.NET version 3.X. The same error (Failed to initialise VroomJs.) is already registered in issue tracker of React.NET - “Cannot force to use Chakra engine instead of VroomJs”.

[omg-a-bear]

Hello Taritsyn, and thank you for the quick response!

I saw that thread when googling for a solution, but I'm not sure that it applies to my situation? The thing I think is weird, is that I can run the application without any problems on a fresh installation of Ubuntu - without Chrome or V8 installed on the system. Nodejs is however installed on that Ubuntu machine, so maybe libVroomJs is available through nodejs in that case?

[Taritsyn]

In your case, need to build the native assemblies of VroomJs - https://github.com/pauldotknopf/vroomjs-core#maclinux. But as far as I am aware, that this build script is not working.

I recommend you to read the “VroomJsInitialisationException: Failed to initialise VroomJs” discussion.

[Daniel15]

ReactJS.NET iterates through all the engine factories and uses the first working one (see https://github.com/reactjs/React.NET/blob/master/src/React.Core/JavaScriptEngineFactory.cs#L254), so you just need to register your preferred engine first. It could be modified to use DefaultEngineName and fall back to checking the other engines - Feel free to send a pull request for that 😃

Note that ReactJS.NET has a default engine configuration (see https://github.com/reactjs/React.NET/blob/master/src/React.Core/JavaScriptEngineFactory.cs#L358-L384) that's used if you don't configure JavaScriptEngineSwitcher yourself. If you do configure JavaScriptEngineSwitcher, your config will override ReactJS.NET's one. So just call EngineFactories.AddChakraCore() and you should be fine.