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::logging_v2::ConfigServiceV2Client(
google::cloud::logging_v2::MakeConfigServiceV2Connection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 in Google Cloud C++ client libraries, starting with version 2.17.0 and listing versions up to 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eClient libraries typically use Application Default Credentials, but you can override this by employing the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e with service account key files or other authentication methods.\u003c/p\u003e\n"],["\u003cp\u003eThe example provided demonstrates how to load a service account key file to explicitly set authentication credentials using \u003ccode\u003egoogle::cloud::MakeServiceAccountCredentials\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eSpecific examples are available for \u003ccode\u003elogging_v2::ConfigServiceV2Client\u003c/code\u003e, \u003ccode\u003elogging_v2::LoggingServiceV2Client\u003c/code\u003e, and \u003ccode\u003elogging_v2::MetricsServiceV2Client\u003c/code\u003e demonstrating how to handle service accounts.\u003c/p\u003e\n"],["\u003cp\u003eFor further information on managing service account keys and creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects, consult the best practices guide and the authentication components section, respectively.\u003c/p\u003e\n"]]],[],null,[]]
