Write HTTP functions

In Cloud Run functions, you use HTTP functions when you want to invoke a function via an HTTP(S) request. To allow for HTTP semantics, HTTP function signatures accept HTTP-specific arguments.

Implementation

The following example shows a basic HTTP function source file for each runtime. See Source directory structure for information about where to locate your source code.

Node.js 

const functions = require('@google-cloud/functions-framework');

// Register an HTTP function with the Functions Framework
functions.http('myHttpFunction', (req, res) => {
  // Your code here

  // Send an HTTP response
  res.send('OK');
});

In Node.js, you register an HTTP handler function with the Functions Framework for Node.js. Your HTTP handler function must be an Express middleware function that accepts the request and response arguments and sends an HTTP response.

Cloud Run functions automatically parses the request body for you based on the request's Content-Type header using body-parser, so you can access the req.body and req.rawBody objects in your HTTP handler.

The function entry point is the name with which the handler is registered with the Functions Framework. In this example, the entry point is myHttpFunction.

Python 

import functions_framework

# Register an HTTP function with the Functions Framework
@functions_framework.http
def my_http_function(request):
  # Your code here

  # Return an HTTP response
  return 'OK'

In Python, you register an HTTP handler function with the Functions Framework for Python. Your HTTP handler function must accept a Flask request object as an argument and return a value that Flask can convert into an HTTP response object.

The function entry point is the name of the handler function registered with the Functions Framework. In this example, the entry point is my_http_function.

Go 

package myhttpfunction

import (
    "fmt"
    "net/http"

    "github.com/GoogleCloudPlatform/functions-framework-go/functions"
)

func init() {
    // Register an HTTP function with the Functions Framework
    functions.HTTP("MyHTTPFunction", myHTTPFunction)
}

// Function myHTTPFunction is an HTTP handler
func myHTTPFunction(w http.ResponseWriter, r *http.Request) {
    // Your code here

    // Send an HTTP response
    fmt.Fprintln(w, "OK")
}

In Go, you register an HTTP handler function with the Functions Framework for Go in your init() function. Your HTTP handler function must use the standard http.HandlerFunc interface to send an HTTP response.

The function entry point is the name with which the handler is registered with the Functions Framework. In this example, the entry point is MyHTTPFunction.

Your HTTP handler function must implement the standard http.HandlerFunc interface. It accepts an http.ResponseWriter interface that your function uses to create a reply to the request, and a pointer to an http.Request struct containing the details of the inbound HTTP request.

Java 

package myhttpfunction;

import com.google.cloud.functions.HttpFunction;
import com.google.cloud.functions.HttpRequest;
import com.google.cloud.functions.HttpResponse;

// Define a class that implements the HttpFunction interface
public class MyHttpFunction implements HttpFunction {
  // Implement the service() method to handle HTTP requests
  @Override
  public void service(HttpRequest request, HttpResponse response) throws Exception {
    // Your code here

    // Send an HTTP response
    response.getWriter().write("OK");
  }
}

In Java, you use the Functions Framework Java API to implement an HTTP handler class with the HttpFunction interface. The service() method must send an HTTP response.

The function entry point is the fully-qualified name of the HTTP handler class, including the package name. In this example, the entry point is myhttpfunction.MyHttpFunction.

Your service method receives an HttpRequest object describing the inbound HTTP request, and an HttpResponse object that your function populates with a response message.

C# 

using Google.Cloud.Functions.Framework;
using Microsoft.AspNetCore.Http;
using System.Threading.Tasks;

namespace MyProject
{
    // Define a class that implements the IHttpFunction interface
    public class MyHttpFunction : IHttpFunction
    {
        // Implement the HandleAsync() method to handle HTTP requests
        public async Task HandleAsync(HttpContext context)
        {
            // Your code here

            // Send an HTTP response
            await context.Response.WriteAsync("OK");
        }
    }
}

In .NET runtimes, you use the Functions Framework for .NET to implement an HTTP handler class with the IHttpFunction interface. The HandleAsync() method accepts a standard ASP.NET HttpContext object as an argument and must send an HTTP response.

The function entry point is the fully-qualified name of the HTTP handler class, including the namespace. In this example, the entry point is MyProject.MyHttpFunction.

Ruby 

require "functions_framework"

# Register an HTTP function with the Functions Framework
FunctionsFramework.http "my_http_function" do |request|
  # Your code here

  # Return an HTTP response
  "OK"
end

In Ruby, you register an HTTP handler function with the Functions Framework for Ruby. Your HTTP handler function must accept a Rack request object as an argument and return a value that can be used as an HTTP response.

The function entry point is the name with which the handler is registered with the Functions Framework. In this example, the entry point is my_http_function.

PHP 

<?php

use Google\CloudFunctions\FunctionsFramework;
use Psr\Http\Message\ServerRequestInterface;

// Register an HTTP function with the Functions Framework
FunctionsFramework::http('myHttpFunction', 'myHttpHandler');

// Define your HTTP handler
function myHttpHandler(ServerRequestInterface $request): string
{
    // Your code here

    // Return an HTTP response
    return 'OK';
}

In PHP, you register an HTTP handler function with the Functions Framework for PHP. Your HTTP handler function must accept an argument that implements the PSR-7 ServerRequestInterface interface, and must return an HTTP response as either a string or an object that implements the PSR-7 ResponseInterface interface.

The function entry point is the name with which the handler is registered with the Functions Framework. In this example, the entry point is myHttpFunction.

HTTP requests and responses

HTTP functions accept the HTTP request methods listed on the page HTTP triggers. Your HTTP handler can inspect the request method and perform different actions based on the method.

Your function must send an HTTP response. If the function creates background tasks (such as with threads, futures, JavaScript Promise objects, callbacks, or system processes), you must terminate or otherwise resolve these tasks before sending an HTTP response. Any tasks not terminated before the HTTP response is sent might not be completed, and might cause undefined behavior.

See HTTP triggers for more information about HTTP functions and associated options.

Handling CORS

Cross-Origin Resource Sharing (CORS) is a way to let applications running on one domain access resources from another domain. For example, you might need to let your domain make requests to the Cloud Run functions domain to access your function.

If CORS is not set up properly, you might see errors like the following:

XMLHttpRequest cannot load https://YOUR_FUNCTION_URL.
No 'Access-Control-Allow-Origin' header is present on the requested resource.
Origin 'https://YOUR_DOMAIN' is therefore not allowed access.

To allow cross-origin requests to your function, set the Access-Control-Allow-Origin header as appropriate on your HTTP response. For preflighted cross-origin requests, you must respond to the preflight OPTIONS request with a 204 response code and additional headers.

Node.js 

const functions = require('@google-cloud/functions-framework');

/**
 * HTTP function that supports CORS requests.
 *
 * @param {Object} req Cloud Function request context.
 * @param {Object} res Cloud Function response context.
 */
functions.http('corsEnabledFunction', (req, res) => {
  // Set CORS headers for preflight requests
  // Allows GETs from any origin with the Content-Type header
  // and caches preflight response for 3600s

  res.set('Access-Control-Allow-Origin', '*');

  if (req.method === 'OPTIONS') {
    // Send response to OPTIONS requests
    res.set('Access-Control-Allow-Methods', 'GET');
    res.set('Access-Control-Allow-Headers', 'Content-Type');
    res.set('Access-Control-Max-Age', '3600');
    res.status(204).send('');
  } else {
    res.send('Hello World!');
  }
});

Python 

import functions_framework

@functions_framework.http
def cors_enabled_function(request):
    # For more information about CORS and CORS preflight requests, see:
    # https://developer.mozilla.org/en-US/docs/Glossary/Preflight_request

    # Set CORS headers for the preflight request
    if request.method == "OPTIONS":
        # Allows GET requests from any origin with the Content-Type
        # header and caches preflight response for an 3600s
        headers = {
            "Access-Control-Allow-Origin": "*",
            "Access-Control-Allow-Methods": "GET",
            "Access-Control-Allow-Headers": "Content-Type",
            "Access-Control-Max-Age": "3600",
        }

        return ("", 204, headers)

    # Set CORS headers for the main request
    headers = {"Access-Control-Allow-Origin": "*"}

    return ("Hello World!", 200, headers)

Go 


// Package http provides a set of HTTP Cloud Functions samples.
package http

import (
	"fmt"
	"net/http"

	"github.com/GoogleCloudPlatform/functions-framework-go/functions"
)

// CORSEnabledFunction is an example of setting CORS headers.
// For more information about CORS and CORS preflight requests, see
// https://developer.mozilla.org/en-US/docs/Glossary/Preflight_request.
func CORSEnabledFunction(w http.ResponseWriter, r *http.Request) {
	// Set CORS headers for the preflight request
	if r.Method == http.MethodOptions {
		w.Header().Set("Access-Control-Allow-Origin", "*")
		w.Header().Set("Access-Control-Allow-Methods", "POST")
		w.Header().Set("Access-Control-Allow-Headers", "Content-Type")
		w.Header().Set("Access-Control-Max-Age", "3600")
		w.WriteHeader(http.StatusNoContent)
		return
	}
	// Set CORS headers for the main request.
	w.Header().Set("Access-Control-Allow-Origin", "*")
	fmt.Fprint(w, "Hello, World!")
}

func init() {
	functions.HTTP("CORSEnabledFunction", CORSEnabledFunction)
}

Java 


import com.google.cloud.functions.HttpFunction;
import com.google.cloud.functions.HttpRequest;
import com.google.cloud.functions.HttpResponse;
import java.io.BufferedWriter;
import java.io.IOException;
import java.net.HttpURLConnection;

public class CorsEnabled implements HttpFunction {
  // corsEnabled is an example of setting CORS headers.
  // For more information about CORS and CORS preflight requests, see
  // https://developer.mozilla.org/en-US/docs/Glossary/Preflight_request.
  @Override
  public void service(HttpRequest request, HttpResponse response)
      throws IOException {
    // Set CORS headers
    //   Allows GETs from any origin with the Content-Type
    //   header and caches preflight response for 3600s
    response.appendHeader("Access-Control-Allow-Origin", "*");

    if ("OPTIONS".equals(request.getMethod())) {
      response.appendHeader("Access-Control-Allow-Methods", "GET");
      response.appendHeader("Access-Control-Allow-Headers", "Content-Type");
      response.appendHeader("Access-Control-Max-Age", "3600");
      response.setStatusCode(HttpURLConnection.HTTP_NO_CONTENT);
      return;
    }

    // Handle the main request.
    BufferedWriter writer = response.getWriter();
    writer.write("CORS headers set successfully!");
  }
}

C# 

using Google.Cloud.Functions.Framework;
using Microsoft.AspNetCore.Http;
using System.Net;
using System.Threading.Tasks;

namespace Cors;

// For more information about CORS and CORS preflight requests, see
// https://developer.mozilla.org/en-US/docs/Glossary/Preflight_request.
public class Function : IHttpFunction
{
    public async Task HandleAsync(HttpContext context)
    {
        HttpRequest request = context.Request;
        HttpResponse response = context.Response;

        // Set CORS headers
        //   Allows GETs from any origin with the Content-Type
        //   header and caches preflight response for 3600s

        response.Headers.Append("Access-Control-Allow-Origin", "*");
        if (HttpMethods.IsOptions(request.Method))
        {
            response.Headers.Append("Access-Control-Allow-Methods", "GET");
            response.Headers.Append("Access-Control-Allow-Headers", "Content-Type");
            response.Headers.Append("Access-Control-Max-Age", "3600");
            response.StatusCode = (int) HttpStatusCode.NoContent;
            return;
        }

        await response.WriteAsync("CORS headers set successfully!", context.RequestAborted);
    }
}

Ruby 

FunctionsFramework.http "cors_enabled_function" do |request|
  # For more information about CORS and CORS preflight requests, see
  # https://developer.mozilla.org/en-US/docs/Glossary/Preflight_request
  # for more information.

  # Set CORS headers for the preflight request
  if request.options?
    # Allows GET requests from any origin with the Content-Type
    # header and caches preflight response for an 3600s
    headers = {
      "Access-Control-Allow-Origin"  => "*",
      "Access-Control-Allow-Methods" => "GET",
      "Access-Control-Allow-Headers" => "Content-Type",
      "Access-Control-Max-Age"       => "3600"
    }
    [204, headers, []]
  else
    # Set CORS headers for the main request
    headers = {
      "Access-Control-Allow-Origin" => "*"
    }

    [200, headers, ["Hello World!"]]
  end
end

PHP 


use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;
use GuzzleHttp\Psr7\Response;

function corsEnabledFunction(ServerRequestInterface $request): ResponseInterface
{
    // Set CORS headers for preflight requests
    // Allows GETs from any origin with the Content-Type header
    // and caches preflight response for 3600s
    $headers = ['Access-Control-Allow-Origin' => '*'];

    if ($request->getMethod() === 'OPTIONS') {
        // Send response to OPTIONS requests
        $headers = array_merge($headers, [
            'Access-Control-Allow-Methods' => 'GET',
            'Access-Control-Allow-Headers' => 'Content-Type',
            'Access-Control-Max-Age' => '3600'
        ]);
        return new Response(204, $headers, '');
    } else {
        return new Response(200, $headers, 'Hello World!');
    }
}

CORS limitations

For preflighted cross-origin requests, preflight OPTIONS requests are sent without an Authorization header, so they will be rejected on all HTTP functions that require authentication. Because the preflight requests fail, the main requests will also fail. To work around this limitation, use one of the following options:

Next steps