otlplog: document Exporter concurrency guarantees

CHANGELOG.md

@@ -20,6 +20,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Document a compatibility regression introduced in `go.opentelemetry.io/otel` v1.47.0 that breaks compilation with `go.opentelemetry.io/otel/bridge/opentracing` v1.46.0 and earlier.
   Include instructions for upgrading the bridge to v1.47.0.
   See the [bridge version compatibility documentation](bridge/opentracing/README.md#version-compatibility). (#9209)
+- Document the concurrency guarantees of the `Exporter` in `go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc`.
 
 ### Deprecated
 

exporters/otlp/otlplog/otlploggrpc/exporter.go

@@ -22,6 +22,10 @@ type logClient interface {
 // Exporter is an OpenTelemetry log exporter. It transports log data encoded as
 // OTLP protobufs using gRPC.
 // All Exporter values must be created with [New].
+//
+// Export must not be called concurrently with itself on the same Exporter.
+// Shutdown and ForceFlush are safe to call concurrently with themselves,
+// each other, and Export.
 type Exporter struct {
 	// Ensure synchronous access to the client across all functionality.
 	clientMu sync.Mutex
@@ -58,6 +62,9 @@ var transformResourceLogs = transform.ResourceLogs
 //
 // This method returns [log.ErrExporterShutdown] if called after Shutdown.
 // This method returns an error if the method is canceled by the passed context.
+//
+// Export must not be called concurrently with other Export calls.
+// It is safe to call concurrently with Shutdown and ForceFlush.
 func (e *Exporter) Export(ctx context.Context, records []log.Record) error {
 	if e.stopped.Load() {
 		return log.ErrExporterShutdown
@@ -79,6 +86,11 @@ func (e *Exporter) Export(ctx context.Context, records []log.Record) error {
 
 // Shutdown shuts down the Exporter. Calls to Export after Shutdown return
 // [log.ErrExporterShutdown]. Calls to ForceFlush perform no operation.
+//
+// Calling Shutdown more than once is safe: subsequent calls do nothing and
+// return nil.
+//
+// This method is safe to call concurrently with itself and with other methods.
 func (e *Exporter) Shutdown(ctx context.Context) error {
 	if e.stopped.Swap(true) {
 		return nil
@@ -93,6 +105,8 @@ func (e *Exporter) Shutdown(ctx context.Context) error {
 }
 
 // ForceFlush does nothing. The Exporter holds no state.
+//
+// This method is safe to call concurrently with itself and with other methods.
 func (*Exporter) ForceFlush(context.Context) error {
 	return nil
 }