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::managedkafka_v1::ManagedKafkaClient(
google::cloud::managedkafka_v1::MakeManagedKafkaConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 release candidate version is 2.37.0-rc, and there are documented versions available from 2.26.0 up to 2.36.0.\u003c/p\u003e\n"],["\u003cp\u003eBy default, client libraries authenticate using Application Default Credentials, but you can override this using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eOverriding the default authentication can be done by loading a service account key file, as demonstrated in the provided code example.\u003c/p\u003e\n"],["\u003cp\u003eFor detailed information on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects, refer to the Authentication Components documentation.\u003c/p\u003e\n"],["\u003cp\u003eThe example of overriding the default credentials in the content uses a relatively easy to understand method, but the user is referred to a guide on best practices.\u003c/p\u003e\n"]]],[],null,[]]
