[instrumentation/google.golang.org/grpc/otelgrpc] Do not assume Handl…

…eRPC receives a gRPCContext (#4825)

* [instrumentation/google.golang.org/grpc/otelgrpc] Add safeguard to HandleRPC

To help prevent crashes such as open-telemetry/opentelemetry-collector/issues/9296, check if the context is nil before proceeding.

This is inspired by: https://github.com/grpc/grpc-go/blob/ddd377f19841eae70862559c854d957d61b3b692/stats/opencensus/opencensus.go#L204-L207

* Add changelog entry

* Create and handle error

* Make check a bit more clear

* Update instrumentation/google.golang.org/grpc/otelgrpc/stats_handler.go

Co-authored-by: Anthony Mirabella <a9@aneurysm9.com>

* Remove unused code

* additional check for gctx

---------

Co-authored-by: Anthony Mirabella <a9@aneurysm9.com>

CHANGELOG.md

@@ -36,6 +36,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 ### Fixed
 
 - Fix `NewServerHandler` in `go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc` to correctly set the span status depending on the gRPC status. (#4587)
+- The `stats.Handler` from `go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc` now does not crash when receiving an unexpected context. (#4825)
 - Update `go.opentelemetry.io/contrib/detectors/aws/ecs` to fix the task ARN when it is not valid. (#3583)
 - Do not panic in `go.opentelemetry.io/contrib/detectors/aws/ecs` when the container ARN is not valid. (#3583)
 

instrumentation/google.golang.org/grpc/otelgrpc/stats_handler.go

@@ -135,10 +135,14 @@ func (h *clientHandler) HandleConn(context.Context, stats.ConnStats) {
 
 func (c *config) handleRPC(ctx context.Context, rs stats.RPCStats, isServer bool) { // nolint: revive  // isServer is not a control flag.
 	span := trace.SpanFromContext(ctx)
-	gctx, _ := ctx.Value(gRPCContextKey{}).(*gRPCContext)
+	var metricAttrs []attribute.KeyValue
 	var messageId int64
-	metricAttrs := make([]attribute.KeyValue, 0, len(gctx.metricAttrs)+1)
-	metricAttrs = append(metricAttrs, gctx.metricAttrs...)
+
+	gctx, _ := ctx.Value(gRPCContextKey{}).(*gRPCContext)
+	if gctx != nil {
+		metricAttrs = make([]attribute.KeyValue, 0, len(gctx.metricAttrs)+1)
+		metricAttrs = append(metricAttrs, gctx.metricAttrs...)
+	}
 
 	switch rs := rs.(type) {
 	case *stats.Begin:
@@ -199,8 +203,10 @@ func (c *config) handleRPC(ctx context.Context, rs stats.RPCStats, isServer bool
 		elapsedTime := float64(rs.EndTime.Sub(rs.BeginTime)) / float64(time.Millisecond)
 
 		c.rpcDuration.Record(ctx, elapsedTime, metric.WithAttributes(metricAttrs...))
-		c.rpcRequestsPerRPC.Record(ctx, atomic.LoadInt64(&gctx.messagesReceived), metric.WithAttributes(metricAttrs...))
-		c.rpcResponsesPerRPC.Record(ctx, atomic.LoadInt64(&gctx.messagesSent), metric.WithAttributes(metricAttrs...))
+		if gctx != nil {
+			c.rpcRequestsPerRPC.Record(ctx, atomic.LoadInt64(&gctx.messagesReceived), metric.WithAttributes(metricAttrs...))
+			c.rpcResponsesPerRPC.Record(ctx, atomic.LoadInt64(&gctx.messagesSent), metric.WithAttributes(metricAttrs...))
+		}
 	default:
 		return
 	}