feat(spanner): add support of using multiplexed session with ReadOnly…

…Transactions (#10269)

* feat(spanner): add support of using multiplexed session with ReadOnlyTransactions

* fallback to regular sessions if backend returns Unimplemented error

* add metic label for is_multiplexed filter

* fix integration tests

* refresh multiplex session asynchronously

* fix  env

* fix permission issue

* fix presubmit file

* fixed tests

* incorporate changes

* fix tests

* incorporate changes

* fix vet

* fix vet

* fix tests

* remove idempotent assignment

* incorporate changes

* fix integration test for TestIntegration_DbRemovalRecovery

* add TODO comment for TestIntegration_DbRemovalRecovery integration tests

spanner/client.go

@@ -334,18 +334,20 @@ type ClientConfig struct {
 }
 
 type openTelemetryConfig struct {
-	meterProvider           metric.MeterProvider
-	attributeMap            []attribute.KeyValue
-	otMetricRegistration    metric.Registration
-	openSessionCount        metric.Int64ObservableGauge
-	maxAllowedSessionsCount metric.Int64ObservableGauge
-	sessionsCount           metric.Int64ObservableGauge
-	maxInUseSessionsCount   metric.Int64ObservableGauge
-	getSessionTimeoutsCount metric.Int64Counter
-	acquiredSessionsCount   metric.Int64Counter
-	releasedSessionsCount   metric.Int64Counter
-	gfeLatency              metric.Int64Histogram
-	gfeHeaderMissingCount   metric.Int64Counter
+	meterProvider                  metric.MeterProvider
+	attributeMap                   []attribute.KeyValue
+	attributeMapWithMultiplexed    []attribute.KeyValue
+	attributeMapWithoutMultiplexed []attribute.KeyValue
+	otMetricRegistration           metric.Registration
+	openSessionCount               metric.Int64ObservableGauge
+	maxAllowedSessionsCount        metric.Int64ObservableGauge
+	sessionsCount                  metric.Int64ObservableGauge
+	maxInUseSessionsCount          metric.Int64ObservableGauge
+	getSessionTimeoutsCount        metric.Int64Counter
+	acquiredSessionsCount          metric.Int64Counter
+	releasedSessionsCount          metric.Int64Counter
+	gfeLatency                     metric.Int64Histogram
+	gfeHeaderMissingCount          metric.Int64Counter
 }
 
 func contextWithOutgoingMetadata(ctx context.Context, md metadata.MD, disableRouteToLeader bool) context.Context {