Override the default authentication method

This document describes how to override the default authentication used by Rust. The Rust automatically authenticate your requests to Google Cloud services, but you may occasionally need to override your default credentials.

Prerequisites

This guide uses the Cloud Natural Language API. To install this API follow the service quickstart, which shows you how to enable a service.

For complete setup instructions for the Rust libraries, see Getting started with Rust.

Dependencies

You must declare the dependencies in your Cargo.toml file:

cargo add google-cloud-language-v2 google-cloud-auth

The default credentials

The recommended way to authenticate applications in Google Cloud is to use Application Default Credentials, without any configuration the client libraries default to this credential type. See How Application Default Credentials work for information about you can configure this default without any code changes in your application.

  1. Add some use declarations to simplify the rest of the example: 

    use google_cloud_language_v2::client::LanguageService;
use google_cloud_language_v2::model::{Document, document::Type};

  2. Initialize the client using the defaults: 

    let client = LanguageService::builder().build().await?;

  3. Use this client as usual: 

    let response = client
    .analyze_sentiment()
    .set_document(
        Document::new()
            .set_content("Hello World!")
            .set_type(Type::PlainText),
    )
    .send()
    .await?;
println!("response={response:?}");

Override the default credentials: API keys

API keys are text strings that grant access to some Google Cloud services. Using API keys may simplify development as they require less configuration than other authentication methods. There are some risks associated with API keys, we recommended you read Best practices for managing API keys if you plan to use them.

  1. Write a function that receives the API key string as an input parameter: 

    pub async fn sample(key: &str) -> anyhow::Result<()> {

  2. Add some use declarations simplify the rest of the example: 

    use google_cloud_auth::credentials::api_key_credentials::Builder as ApiKeyCredentialsBuilder;
use google_cloud_language_v2::client::