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::functions_v1::CloudFunctionsServiceClient(
google::cloud::functions_v1::MakeCloudFunctionsServiceConnection(
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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 page provides documentation for overriding default authentication credentials when using Google Cloud client libraries, which typically rely on Application Default Credentials.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version documented here is 2.37.0-rc, and documentation exists for versions dating back to 2.11.0, providing a historical overview of the feature's implementation.\u003c/p\u003e\n"],["\u003cp\u003eUsers can override the default authentication by using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e and providing a service account key file, with a provided example demonstrating how to load such a file.\u003c/p\u003e\n"],["\u003cp\u003eThe page highlights the \u003ccode\u003efunctions_v1::CloudFunctionsServiceClient\u003c/code\u003e and \u003ccode\u003efunctions_v2::FunctionServiceClient\u003c/code\u003e classes as examples and provides links to service account snippets for them.\u003c/p\u003e\n"],["\u003cp\u003eAdditional information and best practices for managing service account keys and authentication components are linked for further reference.\u003c/p\u003e\n"]]],[],null,[]]
