Adds support to Firestore backends for custom databases (#47540)

Firestore has supported multiple databases in a project for a while
(see https://cloud.google.com/blog/products/databases/manage-multiple-firestore-databases-in-a-project),
however, Teleport only allowed using the default database in the project.
The DatabaseID is now exposed in the file config, and if provided
both the state and events backends will use the appropriate database.

Closes #37227.

docs/pages/reference/backends.mdx

@@ -1270,6 +1270,10 @@ teleport:
     # Name of the Firestore table.
     collection_name: Example_TELEPORT_FIRESTORE_TABLE_NAME
 
+    # An optional database id to use. If not provided the default
+    # database for the project is used.
+    database_id: Example_TELEPORT_FIRESTORE_DATABASE_ID
+
     credentials_path: /var/lib/teleport/gcs_creds
 
     # This setting configures Teleport to send the audit events to three places:
@@ -1278,7 +1282,7 @@ teleport:
     # database table, so attempting to use the same table for both will result in errors.
     # When using highly available storage like Firestore, you should make sure that the list always specifies
     # the High Availability storage method first, as this is what the Teleport web UI uses as its source of events to display.
-    audit_events_uri:  ['firestore://Example_TELEPORT_FIRESTORE_EVENTS_TABLE_NAME', 'file:///var/lib/teleport/audit/events', 'stdout://']
+    audit_events_uri:  ['firestore://Example_TELEPORT_FIRESTORE_EVENTS_TABLE_NAME?projectID=$PROJECT_ID&credentialsPath=$CREDENTIALS_PATH&databaseID=$DATABASE_ID', 'file:///var/lib/teleport/audit/events', 'stdout://']
 
     # This setting configures Teleport to save the recorded sessions in GCP storage:
     audit_sessions_uri: gs://Example_TELEPORT_GCS_BUCKET/records

lib/backend/firestore/firestorebk.go

@@ -16,6 +16,7 @@ package firestore
 
 import (
 	"bytes"
+	"cmp"
 	"context"
 	"encoding/base64"
 	"errors"
@@ -57,6 +58,9 @@ type Config struct {
 	DisableExpiredDocumentPurge bool `json:"disable_expired_document_purge,omitempty"`
 	// EndPoint is used to point the Firestore clients at emulated Firestore storage.
 	EndPoint string `json:"endpoint,omitempty"`
+	// DatabaseID is the identifier of a specific Firestore database to use. If not specified, the
+	// default database for the ProjectID is used.
+	DatabaseID string `json:"database_id,omitempty"`
 }
 
 type backendConfig struct {
@@ -265,26 +269,36 @@ func (t ownerCredentials) GetRequestMetadata(context.Context, ...string) (map[st
 func (t ownerCredentials) RequireTransportSecurity() bool { return false }
 
 // CreateFirestoreClients creates a firestore admin and normal client given the supplied parameters
-func CreateFirestoreClients(ctx context.Context, projectID string, endPoint string, credentialsFile string) (*apiv1.FirestoreAdminClient, *firestore.Client, error) {
+func CreateFirestoreClients(ctx context.Context, projectID, database string, endpoint string, credentialsFile string) (*apiv1.FirestoreAdminClient, *firestore.Client, error) {
 	var args []option.ClientOption
 
-	if endPoint != "" {
+	if endpoint != "" {
 		args = append(args,
 			option.WithTelemetryDisabled(),
 			option.WithoutAuthentication(),
-			option.WithEndpoint(endPoint),
+			option.WithEndpoint(endpoint),
 			option.WithGRPCDialOption(grpc.WithTransportCredentials(insecure.NewCredentials())),
 			option.WithGRPCDialOption(grpc.WithPerRPCCredentials(ownerCredentials{})),
 		)
 	} else if credentialsFile != "" {
 		args = append(args, option.WithCredentialsFile(credentialsFile))
 	}
 
-	firestoreClient, err := firestore.NewClient(ctx, projectID, args...)
+	firestoreAdminClient, err := apiv1.NewFirestoreAdminClient(ctx, args...)
 	if err != nil {
 		return nil, nil, ConvertGRPCError(err)
 	}
-	firestoreAdminClient, err := apiv1.NewFirestoreAdminClient(ctx, args...)
+
+	if database == "" {
+		firestoreClient, err := firestore.NewClient(ctx, projectID, args...)
+		if err != nil {
+			return nil, nil, ConvertGRPCError(err)
+		}
+
+		return firestoreAdminClient, firestoreClient, nil
+	}
+
+	firestoreClient, err := firestore.NewClientWithDatabase(ctx, projectID, database, args...)
 	if err != nil {
 		return nil, nil, ConvertGRPCError(err)
 	}
@@ -328,7 +342,7 @@ func New(ctx context.Context, params backend.Params, options Options) (*Backend,
 	}
 
 	closeCtx, cancel := context.WithCancel(ctx)
-	firestoreAdminClient, firestoreClient, err := CreateFirestoreClients(closeCtx, cfg.ProjectID, cfg.EndPoint, cfg.CredentialsPath)
+	firestoreAdminClient, firestoreClient, err := CreateFirestoreClients(closeCtx, cfg.ProjectID, cfg.DatabaseID, cfg.EndPoint, cfg.CredentialsPath)
 	if err != nil {
 		cancel()
 		return nil, trace.Wrap(err)
@@ -886,7 +900,8 @@ func ConvertGRPCError(err error, args ...interface{}) error {
 }
 
 func (b *Backend) getIndexParent() string {
-	return "projects/" + b.ProjectID + "/databases/(default)/collectionGroups/" + b.CollectionName
+	database := cmp.Or(b.backendConfig.Config.DatabaseID, "(default)")
+	return "projects/" + b.ProjectID + "/databases/" + database + "/collectionGroups/" + b.CollectionName
 }
 
 func (b *Backend) ensureIndexes(adminSvc *apiv1.FirestoreAdminClient) error {

lib/events/firestoreevents/firestoreevents.go

@@ -15,6 +15,7 @@
 package firestoreevents
 
 import (
+	"cmp"
 	"context"
 	"encoding/json"
 	"errors"
@@ -198,6 +199,8 @@ func (cfg *EventsConfig) SetFromURL(url *url.URL) error {
 	}
 	cfg.ProjectID = projectIDParamString
 
+	cfg.DatabaseID = url.Query().Get("databaseID")
+
 	eventRetentionPeriodParamString := url.Query().Get(eventRetentionPeriodPropertyKey)
 	if eventRetentionPeriodParamString == "" {
 		cfg.RetentionPeriod = defaultEventRetentionPeriod
@@ -572,7 +575,8 @@ type searchEventsFilter struct {
 }
 
 func (l *Log) getIndexParent() string {
-	return "projects/" + l.ProjectID + "/databases/(default)/collectionGroups/" + l.CollectionName
+	database := cmp.Or(l.Config.DatabaseID, "(default)")
+	return "projects/" + l.ProjectID + "/databases/" + database + "/collectionGroups/" + l.CollectionName
 }
 
 func (l *Log) ensureIndexes(adminSvc *apiv1.FirestoreAdminClient) error {