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::dataproc_v1::AutoscalingPolicyServiceClient(
google::cloud::dataproc_v1::MakeAutoscalingPolicyServiceConnection(
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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-07-09 UTC."],[[["This page provides documentation for overriding default authentication credentials when using Google Cloud client libraries, specifically focusing on the `UnifiedCredentialsOption`."],["The latest release is version 2.37.0-rc, with multiple other versions available ranging down to 2.11.0, each with documentation pertaining to dataproc override authentication."],["The default authentication method uses Application Default Credentials, but developers can override this by loading a service account key file using the provided code example."],["There are specific examples available for various `*Client` classes such as `AutoscalingPolicyServiceClient`, `BatchControllerClient`, `ClusterControllerClient`, and others, all pertaining to service account snippets."],["Referencing the 'Authentication Components' section provides further information on the factory functions for creating `google::cloud::Credentials` objects, and the 'Best Practices for managing service account keys' guide is recommended for service key management."]]],[]]