feat(otel): support diagnostics debugging (renovatebot#41362)

Author: viceice

docs/usage/opentelemetry.md

@@ -84,6 +84,8 @@ Renovate does not currently support logging in an OTLP format.
 To help you debug, you can print the telemetry to the console.
 Use the environment variable `RENOVATE_TRACING_CONSOLE_EXPORTER`.
 
+You can also set `OTEL_LOG_LEVEL` to control the log level of OpenTelemetry's internal [diagnostics](https://opentelemetry.io/docs/languages/js/getting-started/nodejs/#troubleshooting), which can be helpful for debugging.
+
 ## Help wanted
 
 We're continually looking to improve Renovate's instrumentation, and are aware there may be gaps in instrumentation.

lib/instrumentation/index.ts

@@ -60,6 +60,16 @@ export function init(): void {
     return;
   }
 
+  // v8 ignore if -- TODO add tests
+  if (process.env.OTEL_LOG_LEVEL) {
+    api.diag.setLogger(
+      new api.DiagConsoleLogger(),
+      api.DiagLogLevel[
+        process.env.OTEL_LOG_LEVEL.toUpperCase() as keyof typeof api.DiagLogLevel
+      ],
+    );
+  }
+
   const spanProcessors: SpanProcessor[] = [];
   // add processors
   if (isTraceDebuggingEnabled()) {