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::datastream_v1::DatastreamClient(
google::cloud::datastream_v1::MakeDatastreamConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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\u003eThis page provides documentation for overriding default authentication credentials when using Google Cloud client libraries, with version-specific information ranging from 2.11.0 to 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eThe default authentication method utilizes Application Default Credentials, but custom authentication can be implemented when needed.\u003c/p\u003e\n"],["\u003cp\u003eOverriding authentication is achieved by setting the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e and the page demonstrates doing so through loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eUsers should consult the best practices guide for managing service account keys for more details on key management.\u003c/p\u003e\n"],["\u003cp\u003eAdditional details on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects can be found in the Authentication Components documentation.\u003c/p\u003e\n"]]],[],null,[]]
