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::trace_v1::TraceServiceClient(
google::cloud::trace_v1::MakeTraceServiceConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 lists various versions of the \u003ccode\u003etrace-override-authentication\u003c/code\u003e documentation, ranging from version 2.11.0 up to the latest release candidate 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eThe documentation explains how to override the default Application Default Credentials (ADC) used by client libraries for Google Cloud Service authentication, which is necessary in specific scenarios.\u003c/p\u003e\n"],["\u003cp\u003eOverriding default credentials can be achieved by providing the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, with an example provided demonstrating how to load a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eExamples are provided for both \u003ccode\u003etrace_v1::TraceServiceClient\u003c/code\u003e and \u003ccode\u003etrace_v2::TraceServiceClient\u003c/code\u003e classes, showcasing how to handle service accounts.\u003c/p\u003e\n"],["\u003cp\u003eIt's essential to review the "Best practices for managing service account keys" guide and the "Authentication Components" for more in-depth information on service account key management and creating credentials objects.\u003c/p\u003e\n"]]],[],null,[]]
