sdk/log: Add filtering Processor example

sdk/log/example_test.go

@@ -0,0 +1,67 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package log_test
+
+import (
+	"context"
+
+	"go.opentelemetry.io/otel/log"
+	logsdk "go.opentelemetry.io/otel/sdk/log"
+)
+
+// Use a processor which sets the minimum log level for the Logs SDK.
+func ExampleProcessor_filtering() {
+	// Existing processor that emits telemetry.
+	var processor logsdk.Processor = logsdk.NewBatchProcessor(nil)
+
+	// Wrap the processor so that it respects minimum serverity level.
+	processor = NewMinSeverityProcessor(log.SeverityInfo, processor)
+
+	// The created processor can then be registered with
+	// the OpenTelemetry Logs SDK using the WithProcessor option.
+	_ = logsdk.NewLoggerProvider(
+		logsdk.WithProcessor(processor),
+	)
+}
+
+// MinSeverityProcessor is a [logsdk.Processor] that limits processing of log records
+// to only those with a [log.Severity] above a configured threshold.
+type MinSeverityProcessor struct {
+	logsdk.Processor
+	minimum log.Severity
+}
+
+// NewMinSeverityProcessor returns a [MinSeverityProcessor] that decorates the
+// processor such that only [logsdk.Record] with a [log.Severity] greater than or
+// equal to minimum is processed.
+func NewMinSeverityProcessor(minimum log.Severity, processor logsdk.Processor) *MinSeverityProcessor {
+	return &MinSeverityProcessor{
+		Processor: processor,
+		minimum:   minimum,
+	}
+}
+
+// OnEmit passes the context and record to the underlying [logsdk.Processor]
+// if the [log.Severity] of record is greater than or equal to the
+// minimum severity is configured at.
+func (s *MinSeverityProcessor) OnEmit(ctx context.Context, record logsdk.Record) error {
+	if !s.enabled(record) {
+		return nil
+	}
+	return s.Processor.OnEmit(ctx, record)
+}
+
+// Enabled returns true if the [log.Severity] of record is greater than or equal
+// to the minimum severity is configured at. It will return false if the
+// severity is less than the minimum.
+//
+// If the record severity is unset, this will return true.
+func (s *MinSeverityProcessor) Enabled(_ context.Context, record logsdk.Record) bool {
+	return s.enabled(record)
+}
+
+func (s *MinSeverityProcessor) enabled(r logsdk.Record) bool {
+	severity := r.Severity()
+	return severity == log.SeverityUndefined || s.minimum <= severity
+}