[Google Cloud Storage] Add support for alternative_host for system te…

…sts (#34413)

* [Google Cloud Storage] Add support for alternative_host to override HTTP client for system tests

* update changelog

CHANGELOG.next.asciidoc

@@ -183,6 +183,7 @@ https://github.com/elastic/beats/compare/v8.2.0\...main[Check the HEAD diff]
 - Add beta `take over` mode for `filestream` for simple migration from `log` inputs {pull}34292[34292]
 - Add pagination support for Salesforce module. {issue}34057[34057] {pull}34065[34065]
 - Allow users to redact sensitive data from CEL input debug logs. {pull}34302[34302]
+- Added support for HTTP destination override to Google Cloud Storage input. {pull}34413[34413]
 
 *Auditbeat*
 

x-pack/filebeat/input/gcs/client.go

@@ -7,6 +7,7 @@ package gcs
 import (
 	"context"
 	"errors"
+	"net/url"
 
 	"cloud.google.com/go/storage"
 	"google.golang.org/api/option"
@@ -15,6 +16,15 @@ import (
 )
 
 func fetchStorageClient(ctx context.Context, cfg config, log *logp.Logger) (*storage.Client, error) {
+	if cfg.AlternativeHost != "" {
+		var h *url.URL
+		h, err := url.Parse(cfg.AlternativeHost)
+		if err != nil {
+			return nil, err
+		}
+		h.Path = "storage/v1/"
+		return storage.NewClient(ctx, option.WithEndpoint(h.String()), option.WithoutAuthentication())
+	}
 	if cfg.Auth.CredentialsJSON != nil {
 		return storage.NewClient(ctx, option.WithCredentialsJSON([]byte(cfg.Auth.CredentialsJSON.AccountKey)))
 	} else if cfg.Auth.CredentialsFile != nil {

x-pack/filebeat/input/gcs/config.go

@@ -27,6 +27,8 @@ type config struct {
 	ParseJSON     *bool          `config:"parse_json,omitempty"`
 	BucketTimeOut *time.Duration `config:"bucket_timeout,omitempty"`
 	Buckets       []bucket       `config:"buckets" validate:"required"`
+	// This field is only used for system test purposes, to override the HTTP endpoint.
+	AlternativeHost string `config:"alternative_host,omitempty"`
 }
 
 // bucket contains the config for each specific object storage bucket in the root account