When you run and load code using the RdKafka wrapper, you may encounter the following error:
System.TypeInitializationException: The type initializer for 'RdKafka.Internal.LibRdKafka' threw an exception. ---> System.DllNotFoundException: Unable to load DLL 'librdkafka': The specified module could not be found. (Exception from HRESULT: 0x8007007E) at RdKafka.Internal.LibRdKafka.NativeMethods.rd_kafka_version() at RdKafka.Internal.LibRdKafka..cctor() --- End of inner exception stack trace --- at RdKafka.Internal.LibRdKafka.conf_new() at RdKafka.Internal.SafeConfigHandle.Create() at Project.RdKafka.Connect.config(String brokerCsv) in C:\Project\RdKafka.fs:line 165 at Project.RdKafka.Connect.producer(String source, BrokerCsv _arg1) in C:\Project\RdKafka.fs:line 192 at Project.RdKafka.subscribeBatch[a](String brokerCsv, String group, String topic, Int32 parallelism, Int32 batchSize, Int32 batchTimeoutMs, FSharpFunc`2 batchHandle) in C:\Project\RdKafka.fs:line 537 at Project.RdKafka.subscribe(String brokerCsv, String group, String topic, Int32 parallelism, FSharpFunc`2 handle) in C:\Project\RdKafka.fs:line 638
The RdKafka C# wrapper is distributed separately from its C-native dependencies.
The two NuGet packages are:
If you’re using 0.9.1 or newer, these dependencies are already being copied to your output folder under the
x86 directories. You should see something like the following:
Mode LastWriteTime Length Name ---- ------------- ------ ---- -a---- 6/27/2016 10:19 PM 2342912 librdkafka.dll -a---- 6/27/2016 10:19 PM 77824 zlib.dll
You are missing the RdKafka.Internal.librdkafka library files. Verify that the
x86folders are included with your installer.
If you are using an older version of the C# wrapper library, the native dependencies are not copied from the nuget packages folder. In this case, you will be missing the
x86folders entirely. Simply copy these to your output folder with a pre-build event.
With the paket dependency manager, your project pre-build event would be:
xcopy /y /d /f "$(ProjectDir)..\packages\RdKafka.Internal.librdkafka\runtimes\win7-x64\native\*.*" "$(TargetDir)"
You are missing the Visual C++ Redistributable package. 64-bit RdKafka 0.9.1 requires Microsoft Visual C++ 2013 Redistributable (x64) - 12.0.30501
This is problematic because many development workstations include this dependency as part of Visual Studio. The problem only appears during deployment to production.
Docker for Windows
To resolve (3) above, you can include the C++ redistributable package within your deployment DockerFile.
# Microsoft Visual C++ 2013 Redistributable (x64) - 12.0.30501 ADD https://download.microsoft.com/download/2/E/6/2E61CFA4-993B-4DD4-91DA-3737CD5CD6E3/vcredist_x64.exe \vcredist_x64.exe RUN Start-Process -Wait -FilePath '\vcredist_x64.exe' -ArgumentList '/install /passive /norestart' RUN Remove-Item -Force /vcredist_x64.exe
Assuming, of course, that Powershell is your default shell.
# Configure Powershell as the Default Shell SHELL ["powershell", "-NoProfile", "-Command", "$ErrorActionPreference = 'Stop';"]
For more information about using RdKafka to support F# Microservices, I’ve written an extensive post here.