fix(spanner): pass userAgent to cloud spanner requests (#6598)

* fix(spanner): pass userAgent to cloud spanner requests

* incorporating requested changes

spanner/client.go

@@ -134,6 +134,15 @@ type ClientConfig struct {
 	// override the default values.
 	CallOptions *vkit.CallOptions
 
+	// UserAgent is the prefix to the user agent header. This is used to supply information
+	// such as application name or partner tool.
+	//
+	// Internal Use Only: This field is for internal tracking purpose only,
+	// setting the value for this config is not required.
+	//
+	// Recommended format: ``application-or-tool-ID/major.minor.version``.
+	UserAgent string
+
 	// logger is the logger to use for this client. If it is nil, all logging
 	// will be directed to the standard logger.
 	logger *log.Logger
@@ -211,7 +220,7 @@ func NewClientWithConfig(ctx context.Context, database string, config ClientConf
 		config.incStep = DefaultSessionPoolConfig.incStep
 	}
 	// Create a session client.
-	sc := newSessionClient(pool, database, sessionLabels, metadata.Pairs(resourcePrefixHeader, database), config.logger, config.CallOptions)
+	sc := newSessionClient(pool, database, config.UserAgent, sessionLabels, metadata.Pairs(resourcePrefixHeader, database), config.logger, config.CallOptions)
 	// Create a session pool.
 	config.SessionPoolConfig.sessionLabels = sessionLabels
 	sp, err := newSessionPool(sc, config.SessionPoolConfig)

spanner/sessionclient.go

@@ -21,6 +21,7 @@ import (
 	"fmt"
 	"log"
 	"reflect"
+	"strings"
 	"sync"
 	"time"
 
@@ -90,6 +91,7 @@ type sessionClient struct {
 	connPool      gtransport.ConnPool
 	database      string
 	id            string
+	userAgent     string
 	sessionLabels map[string]string
 	md            metadata.MD
 	batchTimeout  time.Duration
@@ -98,10 +100,11 @@ type sessionClient struct {
 }
 
 // newSessionClient creates a session client to use for a database.
-func newSessionClient(connPool gtransport.ConnPool, database string, sessionLabels map[string]string, md metadata.MD, logger *log.Logger, callOptions *vkit.CallOptions) *sessionClient {
+func newSessionClient(connPool gtransport.ConnPool, database, userAgent string, sessionLabels map[string]string, md metadata.MD, logger *log.Logger, callOptions *vkit.CallOptions) *sessionClient {
 	return &sessionClient{
 		connPool:      connPool,
 		database:      database,
+		userAgent:     userAgent,
 		id:            cidGen.nextID(database),
 		sessionLabels: sessionLabels,
 		md:            md,
@@ -322,7 +325,14 @@ func (sc *sessionClient) nextClient() (*vkit.Client, error) {
 	if err != nil {
 		return nil, err
 	}
-	client.SetGoogleClientInfo("gccl", internal.Version)
+	clientInfo := []string{"gccl", internal.Version}
+	if sc.userAgent != "" {
+		agentWithVersion := strings.SplitN(sc.userAgent, "/", 2)
+		if len(agentWithVersion) == 2 {
+			clientInfo = append(clientInfo, agentWithVersion[0], agentWithVersion[1])
+		}
+	}
+	client.SetGoogleClientInfo(clientInfo...)
 	if sc.callOptions != nil {
 		client.CallOptions = mergeCallOptions(client.CallOptions, sc.callOptions)
 	}