LocalCloud Cloud Functions (2nd Gen) Local Emulator
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Cloud Functions (2nd Gen)

Cloud Functions runs functions in response to HTTP requests or events. LocalCloud stores function metadata and routes supported invocations to a handler you run locally.

When to use Cloud Functions (2nd Gen)

Typical uses

Use when a small handler processes an HTTP request or event and can run as an independently invoked function. Locally, test routing to your own running handler.

Examples

  • HTTP function handlers
  • Pub/Sub-triggered application logic

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Example usage

Service ID: cloudfunctions. Starts by default. Use an already running LocalCloud runtime for the examples below.

Export the local project and mapped endpoints in your client process, then use the client settings below. First-time setup 

# Export GOOGLE_CLOUD_PROJECT and CLOUD_FUNCTIONS_EMULATOR_HOST
eval "$(localcloud env)"

REST gateway examples use the generated HTTP address in SERVICE_USAGE_EMULATOR_HOST; native SDKs can use a different protocol.

Java · REST

List registered functions

List registered handlers; Cloud Functions connects small functions to HTTP requests and events.

Call the Google Cloud REST API with the JDK HTTP client. Requires JDK 17+. Results reflect resources already created in your local project.

Discovery check · reads existing local state.

Save as Hello.java

import java.net.URI;
import java.net.http.*;
import java.time.Duration;
import java.util.Objects;

public class Hello {
  public static void main(String[] args) throws Exception {
    var project = Objects.requireNonNull(System.getenv("GOOGLE_CLOUD_PROJECT"));
    var endpoint = Objects.requireNonNull(System.getenv("SERVICE_USAGE_EMULATOR_HOST"));
    var url = URI.create(endpoint.replaceAll("/+$", "") + "/v1/projects/" + project + "/locations/us-central1/functions");
    var request = HttpRequest.newBuilder(url).timeout(Duration.ofSeconds(30)).GET().build();
    var client = HttpClient.newBuilder().connectTimeout(Duration.ofSeconds(10)).build();
    var response = client.send(request, HttpResponse.BodyHandlers.ofString());
    if (response.statusCode() >= 400) {
      throw new IllegalStateException(response.statusCode() + ": " + response.body());
    }
    System.out.println(response.body());
  }
}

Run the example

java Hello.java

Verify the result

The request succeeds. An empty list or no printed rows is valid before matching resources exist. Continue with the documented workflows for a resource test.

Verify a resource workflow by creating isolated state, performing the operation, and reading the result back. Run cleanup even after a failure; delete only test-owned resources.

Connection failed? Check localcloud status --verbose, enabled services, and client exports. Stop accidental Google Cloud calls; correct local routing before retrying.

Documented workflows

  • Second-generation function metadata CRUD

    Create and update a second-generation function resource, then read back its configuration. Use this path to test deployment metadata independently of function execution.

  • HTTP forwarding and Pub/Sub trigger routing

    Run your own HTTP execution target, register its forwarding configuration, and invoke the function route. For a Pub/Sub trigger, publish a local event and assert what reaches that target.

Service boundaries

  • Requires your own execution target
  • No source builds or managed function containers
  • No Firestore/Storage/Audit Log Eventarc triggers or Google identity tokens

Code examples and integrations

Integration

Build an integration test loop

Start the runtime, verify readiness, exercise your SDK, and clean up test state.

Open guide
Agent testing

Use Cloud Functions (2nd Gen) with an AI agent

Before the agent changes application logic, have it create local Cloud Functions (2nd Gen) state, read it back with the project SDK, and note which feature the check covered. That first local call catches accidental production routing and needs no GCP account, service-account key, or billing project.

Configure this repo

Set up this repository to use LocalCloud for local GCP development. First read https://local.cloud/ai/agents.md, then inspect this repo, identify the GCP services and SDK language, configure emulator environment variables, and run the narrowest integration test against localhost. Do not use real GCP credentials or production endpoints.

Production endpoints, auth, IAM, quotas, regional behavior, and final release validation still need the target Google Cloud project.

Agent resources has more prompts and the AGENTS.md template.

Related guides

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