feat: add a config option for custom GCS endpoints (#16419)

(cherry picked from commit f1ebd97)

docs/sources/shared/configuration.md

@@ -2319,6 +2319,10 @@ The `gcs_storage_config` block configures the connection to Google Cloud Storage
 # CLI flag: -<prefix>.gcs.bucketname
 [bucket_name: <string> | default = ""]
 
+# Custom GCS endpoint URL.
+# CLI flag: -<prefix>.gcs.endpoint
+[endpoint: <string> | default = ""]
+
 # Service account key content in JSON format, refer to
 # https://cloud.google.com/iam/docs/creating-managing-service-account-keys for
 # creation.

pkg/storage/chunk/client/gcp/gcs_object_client.go

@@ -37,6 +37,7 @@ type GCSObjectClient struct {
 // GCSConfig is config for the GCS Chunk Client.
 type GCSConfig struct {
 	BucketName       string         `yaml:"bucket_name"`
+	Endpoint         string         `yaml:"endpoint"`
 	ServiceAccount   flagext.Secret `yaml:"service_account"`
 	ChunkBufferSize  int            `yaml:"chunk_buffer_size"`
 	RequestTimeout   time.Duration  `yaml:"request_timeout"`
@@ -57,6 +58,7 @@ func (cfg *GCSConfig) RegisterFlags(f *flag.FlagSet) {
 // RegisterFlagsWithPrefix registers flags with prefix.
 func (cfg *GCSConfig) RegisterFlagsWithPrefix(prefix string, f *flag.FlagSet) {
 	f.StringVar(&cfg.BucketName, prefix+"gcs.bucketname", "", "Name of GCS bucket. Please refer to https://cloud.google.com/docs/authentication/production for more information about how to configure authentication.")
+	f.StringVar(&cfg.Endpoint, prefix+"gcs.endpoint", "", "Custom GCS endpoint URL.")
 	f.Var(&cfg.ServiceAccount, prefix+"gcs.service-account", "Service account key content in JSON format, refer to https://cloud.google.com/iam/docs/creating-managing-service-account-keys for creation.")
 	f.IntVar(&cfg.ChunkBufferSize, prefix+"gcs.chunk-buffer-size", 0, "The size of the buffer that GCS client for each PUT request. 0 to disable buffering.")
 	f.DurationVar(&cfg.RequestTimeout, prefix+"gcs.request-timeout", 0, "The duration after which the requests to GCS should be timed out.")
@@ -109,6 +111,10 @@ func newBucketHandle(ctx context.Context, cfg GCSConfig, hedgingCfg hedging.Conf
 		opts = append(opts, option.WithTelemetryDisabled())
 	}
 
+	if cfg.Endpoint != "" {
+		opts = append(opts, option.WithEndpoint(cfg.Endpoint))
+	}
+
 	client, err := clientFactory(ctx, opts...)
 	if err != nil {
 		return nil, err