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::managedidentities_v1::ManagedIdentitiesServiceClient(
google::cloud::managedidentities_v1::
MakeManagedIdentitiesServiceConnection(options));
}
[[["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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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\u003eThe latest version available is 2.37.0-rc, with a history of versions available, including 2.36.0, 2.35.0, and down to 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eClient libraries default to using Application Default Credentials for Google Cloud Service authentication, which may need to be overridden in certain cases.\u003c/p\u003e\n"],["\u003cp\u003eAuthentication can be overridden by providing the UnifiedCredentialsOption, exemplified by loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eFor creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects, users can refer to the Authentication Components documentation.\u003c/p\u003e\n"],["\u003cp\u003eConsult the \u003ca href=\"https://cloud.google.com/iam/docs/best-practices-for-managing-service-account-keys\"\u003eBest practices for managing service account keys\u003c/a\u003e guide for more details on the management of service account keys.\u003c/p\u003e\n"]]],[],null,[]]
