Unless otherwise configured, the client libraries use Application Default Credentials to authenticate with Google Cloud Services. While this works for most applications, in some cases you may need to override this default. You can do so by providing the UnifiedCredentialsOption The following example shows how to explicitly load a service account key file:
[](std::string const& keyfile) {
auto is = std::ifstream(keyfile);
is.exceptions(std::ios::badbit); // Minimal error handling in examples
auto contents = std::string(std::istreambuf_iterator<char>(is.rdbuf()), {});
auto options =
google::cloud::Options{}.set<google::cloud::UnifiedCredentialsOption>(
google::cloud::MakeServiceAccountCredentials(contents));
return google::cloud::servicecontrol_v1::QuotaControllerClient(
google::cloud::servicecontrol_v1::MakeQuotaControllerConnection(
options));
}
Follow these links to find examples for other *Client classes:
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14 UTC."],[[["\u003cp\u003eThis document provides a reference for various versions of service control, ranging from version 2.11.0 up to the latest release candidate, 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eThe default authentication with Google Cloud Services utilizes Application Default Credentials, but they can be overridden as needed.\u003c/p\u003e\n"],["\u003cp\u003eOverriding default authentication can be accomplished by using the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, such as loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eExamples for different client classes, including \u003ccode\u003eQuotaControllerClient\u003c/code\u003e and \u003ccode\u003eServiceControllerClient\u003c/code\u003e for both \u003ccode\u003eservicecontrol_v1\u003c/code\u003e and \u003ccode\u003eservicecontrol_v2\u003c/code\u003e, are available for reference.\u003c/p\u003e\n"],["\u003cp\u003eFor detailed guidance on service account key management, the document suggests referring to the "Best practices for managing service account keys" guide.\u003c/p\u003e\n"]]],[],null,[]]
