[Page Feedback]: Please add Go examples of how to create LoggerProvider for doing recording and asserting in unit tests

[jcranfordbeyondtrust]

URL

https://opentelemetry.io/docs/specs/otel/logs/sdk_exporters/

Description

Need example of how to create an in-memory log.NewLoggerProvider, for use in unit tests.

Only a stdout exporter is present in the docs.

[jcranfordbeyondtrust]

I am trying to create otel providers for unit testing, to record in-memory metrics, spans, and logs for doing assertions.

In my example below, I am trying to create them to use in gofiber unit test, but the same use case for recording all 3 probably applies to other libs that support otel instrumentation too.

I found working code for creating TextMapPropagator, MeterProvider, and TracerProvider suitable for unit testing here:

• https://github.com/gofiber/contrib/blob/main/opafiber/fiber_test.go

However, there are no examples for recording logs and asserting.

I did a lot of googling, looking through otel docs and code, but I can't find any working code examples for how to create LoggerProvider for capturing logs, and using it for assertions in unit testing.

package main

import (
	"github.com/gofiber/contrib/otelfiber/v2"
	"github.com/gofiber/fiber/v2"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/log/logtest"
	"go.opentelemetry.io/otel/propagation"
	"go.opentelemetry.io/otel/sdk/log"
	"go.opentelemetry.io/otel/sdk/metric"
	"go.opentelemetry.io/otel/sdk/trace"
	"go.opentelemetry.io/otel/sdk/trace/tracetest"
	"testing"
)

func TestOtelMetersTracersLoggers(t *testing.T) {
	metricReader := metric.NewManualReader()
	spanRecorder := tracetest.NewSpanRecorder()
	logRecorder := logtest.NewRecorder()

	// Create otel providers suitable for unit testing
	TextMapPropagator := propagation.TraceContext{}
	MeterProvider := metric.NewMeterProvider(metric.WithReader(metricReader))
	TracerProvider := trace.NewTracerProvider(trace.WithSpanProcessor(spanRecorder))
	LoggerProvider := log.NewLoggerProvider(log.WithProcessor(logRecorder)) // COMPILE ERROR: Cannot use logRecorder (type *Recorder) as the type Processor Type does not implement Processor as some methods are missing
	otel.SetTextMapPropagator(TextMapPropagator)
	otel.SetMeterProvider(MeterProvider)
	otel.SetTracerProvider(TracerProvider)
	otel.SetLogger(LoggerProvider) // COMPILE ERROR: Cannot use 'LoggerProvider' (type *LoggerProvider) as the type logr. Logger

	// Try using the above Otel providers in a library
	app := fiber.New()
	app.Use(
		otelfiber.Middleware(
			otelfiber.WithServerName("localhost"),
			otelfiber.WithPort(8080),
			otelfiber.WithCollectClientIP(true),
			otelfiber.WithPropagators(TextMapPropagator),
			otelfiber.WithTracerProvider(TracerProvider),
			otelfiber.WithMeterProvider(MeterProvider),
			otelfiber.WithLoggerProvider(LoggerProvider), // COMPILE ERROR: Unresolved reference 'WithLoggerProvider'
		),
	)
}

It would be great if otel Go docs (and source) could include examples for how to create each of the providers suitable for unit testing. Thank you.

[jcranfordbeyondtrust]

Note, https://opentelemetry.io/docs/specs/otel/logs/sdk_exporters/ only lists a Standard output exporter for logger. Unfortunately that isn't what I need.

---

For tracing, there is a tracetest.NewSpanRecorder. It is suitable for passing into trace.WithSpanProcessor.

TracerProvider := trace.NewTracerProvider(trace.WithSpanProcessor(spanRecorder)) // Compiles OK

---

For logger, there is a logtest.NewRecorder. That name is similar to tracetest.NewSpanRecorder.

I had hoped logtest.NewRecorder might be usable as log.Processor, but no luck. Unfortunately, I can't seem to use logtest.NewRecorder as a log.Processor or log.Exporter because:

• logtest.NewRecorder doesn't implement log.Processor methods, so I can't pass it into log.WithProcessor

LoggerProvider := log.NewLoggerProvider(log.WithProcessor(logRecorder)) // Compile fails

• logtest.NewRecorder doesn't implement log.Exporter methods, so I can't pass it into log.NewSimpleProcessor or log.NewBatchProcessor

LoggerProvider := log.NewLoggerProvider(log.WithProcessor(log.NewSimpleProcessor(logRecorder))) // Compile fails

LoggerProvider := log.NewLoggerProvider(log.WithProcessor(log.NewBatchProcessor(logRecorder))) // Compile fails

[svrnm]

@open-telemetry/go-approvers PTAL

[pellared]

@jcranfordbeyondtrust
In otel.io you should check: https://opentelemetry.io/docs/languages/go/instrumentation/#logs-sdk
Then when reading the packages documentation would find two packages that facilitate unit testing:

• https://pkg.go.dev/go.opentelemetry.io/otel/log/logtest
• https://pkg.go.dev/go.opentelemetry.io/otel/sdk/log/logtest

Probably you want https://pkg.go.dev/go.opentelemetry.io/otel/log/logtest#Recorder for testing instrumentation.