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"]],[["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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-07-09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."],[[["The latest version available is 2.37.0-rc, with numerous other versions, starting at 2.11.0, also available for reference."],["By default, client libraries utilize Application Default Credentials for authenticating with Google Cloud Services."],["You can override the default authentication by using `UnifiedCredentialsOption`, which allows for the explicit loading of a service account key file."],["The provided code example demonstrates how to load a service account key file and create a `ReachabilityServiceClient` with the specified credentials."],["For detailed guidance on managing service account keys, refer to the \"Best practices for managing service account keys\" guide, and for more on creating credentials, check out \"Authentication Components\"."]]],[]]
