gohbase: Add table and key attributes to span

Improve the observability of RPC spans by including the table and key.
The values are quoted to improve readability of table and key values
that combine printable unicode characters with non-printable raw
binary. For example, "\xc4x03Qux".

internal/observability/observability.go

@@ -27,8 +27,7 @@ func StartSpan(
 	name string,
 	opts ...trace.SpanStartOption,
 ) (context.Context, trace.Span) {
-	tracer := otel.GetTracerProvider().Tracer("gohbase")
-	return tracer.Start(ctx, name, opts...)
+	return otel.Tracer("gohbase").Start(ctx, name, opts...)
 }
 
 // ObserveWithTrace observes the value, providing the traceID as

rpc.go

@@ -19,7 +19,9 @@ import (
 	"github.com/tsuna/gohbase/internal/observability"
 	"github.com/tsuna/gohbase/region"
 	"github.com/tsuna/gohbase/zk"
+	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/codes"
+	"go.opentelemetry.io/otel/trace"
 	"google.golang.org/protobuf/proto"
 )
 
@@ -76,7 +78,11 @@ func (c *client) getRegionForRpc(ctx context.Context, rpc hrpc.Call) (hrpc.Regio
 func (c *client) SendRPC(rpc hrpc.Call) (msg proto.Message, err error) {
 	start := time.Now()
 	description := rpc.Description()
-	ctx, sp := observability.StartSpan(rpc.Context(), description)
+	ctx, sp := observability.StartSpan(rpc.Context(), description,
+		trace.WithAttributes(
+			attribute.String("table", strconv.Quote(string(rpc.Table()))),
+			attribute.String("key", strconv.Quote(string(rpc.Key()))),
+		))
 	defer func() {
 		result := "ok"
 		if err != nil {