Fix nil panic from otlp exporter (open-telemetry#6633)

* fix nil panic from otlp exporter.

* fix nil panic from otlp exporter.

* fix nil panic from otlp exporter.

.chloggen/authpanic.yaml

@@ -0,0 +1,12 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: otlpexporter
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Fix nil panic from otlp exporter in case of errors during Start.
+
+# One or more tracking issues or pull requests related to the change
+issues: [6633]
+

exporter/otlpexporter/factory_test.go

@@ -206,9 +206,10 @@ func TestCreateTracesExporter(t *testing.T) {
 			err = consumer.Start(context.Background(), componenttest.NewNopHost())
 			if tt.mustFailOnStart {
 				assert.Error(t, err)
-				return
+			} else {
+				assert.NoError(t, err)
 			}
-			assert.NoError(t, err)
+			// Shutdown is called even when Start fails
 			err = consumer.Shutdown(context.Background())
 			if err != nil {
 				// Since the endpoint of OTLP exporter doesn't actually exist,

exporter/otlpexporter/otlp.go

@@ -77,7 +77,6 @@ func (e *exporter) start(ctx context.Context, host component.Host) (err error) {
 	if e.clientConn, err = e.config.GRPCClientSettings.ToClientConn(ctx, host, e.settings, grpc.WithUserAgent(e.userAgent)); err != nil {
 		return err
 	}
-
 	e.traceExporter = ptraceotlp.NewGRPCClient(e.clientConn)
 	e.metricExporter = pmetricotlp.NewGRPCClient(e.clientConn)
 	e.logExporter = plogotlp.NewGRPCClient(e.clientConn)
@@ -90,7 +89,10 @@ func (e *exporter) start(ctx context.Context, host component.Host) (err error) {
 }
 
 func (e *exporter) shutdown(context.Context) error {
-	return e.clientConn.Close()
+	if e.clientConn != nil {
+		return e.clientConn.Close()
+	}
+	return nil
 }
 
 func (e *exporter) pushTraces(ctx context.Context, td ptrace.Traces) error {