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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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, specifically within the logging context.\u003c/p\u003e\n"],["\u003cp\u003eThe default authentication method uses Application Default Credentials, but users can override this by using the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e with a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe document includes code examples demonstrating how to explicitly load a service account key file and apply it using the \u003ccode\u003egoogle::cloud::UnifiedCredentialsOption\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eLinks to examples for various client classes, including \u003ccode\u003eConfigServiceV2Client\u003c/code\u003e, \u003ccode\u003eLoggingServiceV2Client\u003c/code\u003e, and \u003ccode\u003eMetricsServiceV2Client\u003c/code\u003e, are provided for implementing service account authentication.\u003c/p\u003e\n"],["\u003cp\u003eThe content also directs users to the "Best practices for managing service account keys" guide and the "Authentication Components" documentation for more in-depth information.\u003c/p\u003e\n"]]],[],null,[]]
