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::networkmanagement_v1::ReachabilityServiceClient(
google::cloud::networkmanagement_v1::MakeReachabilityServiceConnection(
options));
}
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-03-14 UTC."],[[["The latest release candidate version is 2.37.0-rc, and the content provides access to documentation for a range of versions from 2.11.0 up to the latest release candidate."],["The default authentication method for client libraries is Application Default Credentials, but these can be overridden when needed."],["You can override the default authentication by utilizing the UnifiedCredentialsOption and providing credentials, such as loading a service account key file."],["The provided example demonstrates overriding authentication by explicitly loading a service account key file using `UnifiedCredentialsOption` and `MakeServiceAccountCredentials`."],["It is recommended that you review the \"Best practices for managing service account keys\" guide and the Authentication Components page to get more details and learn about other `Credentials` object factory functions."]]],[]]