Windows event log

[MisterDA]

This PR integrates the scheduler and workers services with the Windows Event Log by using the win-eventlog package. We still log on Prometheus, the two reporters are combined.

Windows services cannot log onto standard output/error, so when used as services, the workers and the scheduler use a file formatter for Prometheus logging.

The worker doesn't expose Prometheus cmdliner options, so does it make sense to even use Prometheus for logging?

Debug events are too verbose and are not reported into the Windows event log.

[MisterDA]

I think I forgot this, I'll do a fixup of the last commit.

diff --git a/bin/worker.ml b/bin/worker.ml
index 0102a85..ebf4bf1 100644
--- a/bin/worker.ml
+++ b/bin/worker.ml
@@ -43,7 +43,7 @@ let update_normal () =
   Lwt.return (fun () -> Lwt.return ())

 let main default_level ?formatter registration_path capacity name allow_push prune_threshold state_dir obuilder =
-  setup_log ?formatter default_level "ocluster-worker";
+  setup_log ?formatter default_level name;
   let update =
     if Sys.file_exists "/.dockerenv" then update_docker
     else update_normal

[MisterDA]

Ok, I've now added the DLL that Windows Event viewer needs to print the logged messages nicely. It needs to be registered with Windows:

set REG_DLL_PATH=%PREFIX%\lib\ocluster\dllprovider.dll
set REG_PATH=HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\EventLog\Application
set REG_WORKER_PATH=%REG_PATH%\%WORKER_NAME%
set REG_SCHEDULER_PATH=%REG_PATH%\ocluster-scheduler

reg ADD "%REG_WORKER_PATH%" /v CategoryCount        /t REG_DWORD /d 0x00000001
reg ADD "%REG_WORKER_PATH%" /v CategoryMessageFile  /t REG_SZ    /d "%REG_DLL_PATH%"
reg ADD "%REG_WORKER_PATH%" /v EventMessageFile     /t REG_SZ    /d "%REG_DLL_PATH%"
reg ADD "%REG_WORKER_PATH%" /v ParameterMessageFile /t REG_SZ    /d "%REG_DLL_PATH%"
reg ADD "%REG_WORKER_PATH%" /v TypesSupported       /t REG_DWORD /d 0x00000007

reg ADD "%REG_SCHEDULER_PATH%" /v CategoryCount        /t REG_DWORD /d 0x00000001
reg ADD "%REG_SCHEDULER_PATH%" /v CategoryMessageFile  /t REG_SZ    /d "%REG_DLL_PATH%"
reg ADD "%REG_SCHEDULER_PATH%" /v EventMessageFile     /t REG_SZ    /d "%REG_DLL_PATH%"
reg ADD "%REG_SCHEDULER_PATH%" /v ParameterMessageFile /t REG_SZ    /d "%REG_DLL_PATH%"
reg ADD "%REG_SCHEDULER_PATH%" /v TypesSupported       /t REG_DWORD /d 0x00000007

There's just one type of message, the simplicity is intentional.

[MisterDA]

I now think that logging should use TraceLogging on Windows. There are examples of a TraceLogging easy-to-use wrapper with a dynamic implementation that doesn't require to register all logging messages. There are also examples of backend for TraceLogging using LTTng, a library available on Linux, that can help if someone tries to build an OCaml wrapper for TraceLogging.