From b651199e3a27de260a0d6c3447f35a2f5895860a Mon Sep 17 00:00:00 2001
From: Gabriel Harnagea <gabriel.harnagea06@gmail.com>
Date: Tue, 18 Aug 2026 12:07:44 +0200
Subject: [PATCH] gcs: support custom GCS API endpoint via endpoint config
 option

Adds an Endpoint field to gcs.Config, wired via option.WithEndpoint()
for both the HTTP and gRPC client paths. Enables use of GCP regional
endpoints (https://cloud.google.com/storage/docs/regional-endpoints).
Left empty by default so behavior is unchanged.

For thanos-io/thanos#7862.

Signed-off-by: Gabriel Harnagea <gabriel.harnagea06@gmail.com>
---
 CHANGELOG.md              | 1 +
 README.md                 | 3 +++
 providers/gcs/gcs.go      | 9 ++++++++-
 providers/gcs/gcs_test.go | 7 +++++++
 4 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5c59f03443..5c863eb163 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ NOTE: As semantic versioning states all 0.y.z releases can contain breaking chan
 We use *breaking :warning:* to mark changes that are not backward compatible (relates only to v0.y.z releases.)
 
 ## Unreleased
+- GCS: Add support for setting custom GCS endpoint via `endpoint` config option, for regional GCS endpoints.
 - [#165](https://github.com/thanos-io/objstore/pull/165) GCS: Upgrade cloud.google.com/go/storage version to `v1.50.0`.
 - [#38](https://github.com/thanos-io/objstore/pull/38) GCS: Upgrade cloud.google.com/go/storage version to `v1.43.0`.
 - [#145](https://github.com/thanos-io/objstore/pull/145) Include content length in the response of Get and GetRange.
diff --git a/README.md b/README.md
index 1e310d5912..9fc8a67a43 100644
--- a/README.md
+++ b/README.md
@@ -389,6 +389,7 @@ type: GCS
 config:
   bucket: ""
   service_account: ""
+  endpoint: ""
   use_grpc: false
   grpc_conn_pool_size: 0
   http_config:
@@ -413,6 +414,8 @@ config:
 prefix: ""
 ```
 
+The `endpoint` option overrides the default GCS API endpoint. Leave it empty to use the client library's default, or configure a [GCP regional endpoint](https://cloud.google.com/storage/docs/regional-endpoints).
+
 ###### Using GOOGLE_APPLICATION_CREDENTIALS
 
 Application credentials are configured via JSON file and only the bucket needs to be specified, the client looks for:
diff --git a/providers/gcs/gcs.go b/providers/gcs/gcs.go
index 5a79062efe..2f16d51ce3 100644
--- a/providers/gcs/gcs.go
+++ b/providers/gcs/gcs.go
@@ -43,7 +43,11 @@ var DefaultConfig = Config{
 type Config struct {
 	Bucket         string `yaml:"bucket"`
 	ServiceAccount string `yaml:"service_account"`
-	UseGRPC        bool   `yaml:"use_grpc"`
+	// Endpoint overrides the default GCS API endpoint. It is useful for GCP regional endpoints.
+	// See https://cloud.google.com/storage/docs/regional-endpoints.
+	// If empty, the client library's default endpoint is used.
+	Endpoint string `yaml:"endpoint"`
+	UseGRPC  bool   `yaml:"use_grpc"`
 	// GRPCConnPoolSize controls the size of the gRPC connection pool and should only be used
 	// when direct path is not enabled.
 	// See https://pkg.go.dev/cloud.google.com/go/storage#hdr-Experimental_gRPC_API for more details
@@ -116,6 +120,9 @@ func NewBucketWithConfig(ctx context.Context, logger log.Logger, gc Config, comp
 	opts = append(opts,
 		option.WithUserAgent(fmt.Sprintf("thanos-%s/%s (%s)", component, version.Version, runtime.Version())),
 	)
+	if gc.Endpoint != "" {
+		opts = append(opts, option.WithEndpoint(gc.Endpoint))
+	}
 
 	if !gc.UseGRPC {
 		var err error
diff --git a/providers/gcs/gcs_test.go b/providers/gcs/gcs_test.go
index 5393408db8..b040ed41cb 100644
--- a/providers/gcs/gcs_test.go
+++ b/providers/gcs/gcs_test.go
@@ -104,6 +104,13 @@ chunk_size_bytes: 1024`,
 	}
 }
 
+func TestParseConfig_Endpoint(t *testing.T) {
+	cfg, err := parseConfig([]byte(`bucket: abcd
+endpoint: https://storage.example.com`))
+	testutil.Ok(t, err)
+	testutil.Equals(t, "https://storage.example.com", cfg.Endpoint)
+}
+
 func TestParseConfig_HTTPConfig(t *testing.T) {
 	for _, tc := range []struct {
 		name       string