.net output in Docker logs

Question

I''m trying to get log output (Console.WriteLine(..)) in my Docker logs, but I'm getting zero avail.

I've tried:

Console.WriteLine(..)

Trace.WriteLine(..)

Flushing the console, flushing the trace.

I can see these outputs in a VS output window when I'm debugging, so they go somoewhere.

I'm on windows Container, using microsoft/aspnet:4.7.1-windowsservercore-1709 and net4.7

These are the logs I get on container start

 docker logs -f exportapi
ERROR ( message:Cannot find requested collection element. )
Applied configuration changes to section "system.applicationHost/applicationPools" for "MACHINE/WEBROOT/APPHOST" at configuration commit path "MACHINE/WEBROOT/APPHOST"

Answer 1

You have many good lateral options, like self-contained/server-contained executables (eg. Dotnet Core using microsoft/dotnet:runtime would proxy Console.WriteLine by default off the dotnet new web scaffold). Zero-configuration STDOUT logging has never been a common approach on IIS, but these modern options adopt it as best practice (logging should be a transparent backing service).

If you want or need a chain of three programs/assemblies to get your web service up (ServiceMonitor, W3SVC, and finally your assembly), then you need something like this: https://blog.sixeyed.com/relay-iis-log-entries-to-read-them-in-docker/

Overriding the entrypoint to tail more logs than the image does by default is unfortunately a common hack (not just in Microsoft land). So, in your case, I believe you need at least a trace listener config to emit Trace.WriteLine, and then the above approach to emit it: https://docs.microsoft.com/en-us/dotnet/framework/debug-trace-profile/how-to-create-and-initialize-trace-listeners