Add spanner emulator env var detection

go.mod

@@ -55,6 +55,7 @@ require (
 	github.com/shopspring/decimal v1.3.1
 	github.com/spf13/cobra v1.4.0
 	github.com/spf13/pflag v1.0.5
+	github.com/spf13/viper v1.11.0
 	github.com/stretchr/testify v1.7.1
 	go.buf.build/protocolbuffers/go/prometheus/prometheus v1.2.2
 	go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.31.0
@@ -139,7 +140,6 @@ require (
 	github.com/spf13/afero v1.8.2 // indirect
 	github.com/spf13/cast v1.4.1 // indirect
 	github.com/spf13/jwalterweatherman v1.1.0 // indirect
-	github.com/spf13/viper v1.11.0 // indirect
 	github.com/stretchr/objx v0.3.0 // indirect
 	github.com/subosito/gotenv v1.2.0 // indirect
 	github.com/xeipuuv/gojsonpointer v0.0.0-20190905194746-02993c407bfb // indirect

internal/datastore/spanner/migrations/driver.go

@@ -7,6 +7,7 @@ import (
 	"cloud.google.com/go/spanner"
 	admin "cloud.google.com/go/spanner/admin/database/apiv1"
 	"github.com/rs/zerolog/log"
+	"github.com/spf13/viper"
 	"google.golang.org/api/option"
 	"google.golang.org/grpc/codes"
 
@@ -16,6 +17,7 @@ import (
 const (
 	tableSchemaVersion = "schema_version"
 	colVersionNum      = "version_num"
+	emulatorSettingKey = "SPANNER_EMULATOR_HOST"
 )
 
 // SpannerMigrationDriver can migrate a Cloud Spanner instance
@@ -28,8 +30,11 @@ type SpannerMigrationDriver struct {
 // NewSpannerDriver returns a migration driver for the given Cloud Spanner instance
 func NewSpannerDriver(database, credentialsFilePath string) (SpannerMigrationDriver, error) {
 	ctx := context.Background()
-
-	log.Info().Str("spanner-emulator-host", os.Getenv("SPANNER_EMULATOR_HOST")).Msg("spanner emulator")
+	setting, found := detectEmulatorSetting()
+	if found {
+		os.Setenv(emulatorSettingKey, setting)
+	}
+	log.Info().Str("spanner-emulator-host", os.Getenv(emulatorSettingKey)).Msg("spanner emulator")
 	log.Info().Str("credentials", credentialsFilePath).Str("db", database).Msg("connecting")
 	client, err := spanner.NewClient(ctx, database, option.WithCredentialsFile(credentialsFilePath))
 	if err != nil {
@@ -84,3 +89,12 @@ func (smd SpannerMigrationDriver) Close() error {
 }
 
 var _ migrate.Driver = SpannerMigrationDriver{}
+
+func detectEmulatorSetting() (string, bool) {
+	viper.BindEnv(emulatorSettingKey)
+	val := viper.GetString(emulatorSettingKey)
+	if len(val) > 0 {
+		return val, true
+	}
+	return "", false
+}

internal/datastore/spanner/spanner.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"os"
+	"strings"
 	"time"
 
 	"cloud.google.com/go/spanner"
@@ -58,6 +59,11 @@ func NewSpannerDatastore(database string, opts ...Option) (datastore.Datastore,
 		return nil, fmt.Errorf(errUnableToInstantiate, err)
 	}
 
+	setting, found := detectEmulatorSetting()
+	if found {
+		os.Setenv("SPANNER_EMULATOR_HOST", setting)
+	}
+
 	config.gcInterval = common.WithJitter(0.2, config.gcInterval)
 	log.Info().Float64("factor", 0.2).Msg("gc configured with jitter")
 	log.Info().Str("spanner-emulator-host", os.Getenv("SPANNER_EMULATOR_HOST")).Msg("spanner emulator")
@@ -136,3 +142,15 @@ func statementFromSQL(sql string, args []interface{}) spanner.Statement {
 		Params: params,
 	}
 }
+
+func detectEmulatorSetting() (string, bool) {
+	for _, env := range os.Environ() {
+		varPair := strings.SplitN(env, "=", 2)
+		key := varPair[0]
+		value := varPair[1]
+		if strings.Contains(key, "SPANNER_EMULATOR_HOST") && len(value) > 0 {
+			return value, true
+		}
+	}
+	return "", false
+}