wg-serverless/proposals/function-signatures-examples.md

Function signatures work stream

There are multiple providers that have different ways to handle functions. Using multiple providers, switching providers and developing functions would be significantly better experiences if there was a common structure for function signatures.

Examples

Javascript/ NodeJS examples

• AWS Lambda

exports.myHandler = function(event, context) {
   ...
}

• Azure Functions

// You must include a context, but other arguments are optional
module.exports = function(context) {
    // Additional inputs can be accessed by the arguments property
    if(arguments.length === 4) {
        context.log('This function has 4 inputs');
    }
};

// or you can include additional inputs in your arguments
module.exports = function(context, myTrigger, myInput, myOtherInput) {
    // function logic goes here :)
};

• Google Cloud Functions

/**
 * HTTP Cloud Function.
 *
 * @param {Object} req Cloud Function request context.
 * @param {Object} res Cloud Function response context.
 */
exports.helloGET = (req, res) => {
  res.send('Hello World!');
};

• OpenFaaS

module.exports = (callback, context) => {
    callback(null, {"message": "You said: " + context})
}

• OpenWhisk

function main(args) {
    return {payload: 'Hello world'};
}

Go examples

• AWS Lambda

package main

import (
        "fmt"
        "context"
        "github.com/aws/aws-lambda-go/lambda"
)

type MyEvent struct {
        Name string `json:"name"`
}

func HandleRequest(ctx context.Context, name MyEvent) (string, error) {
        return fmt.Sprintf("Hello %s!", name.Name ), nil
}

func main() {
        lambda.Start(HandleRequest)
}

• Google Cloud Functions

package main

import (
        "fmt"
        "log"

        // Imports the Google Cloud Storage client package.
        "cloud.google.com/go/storage"
        "golang.org/x/net/context"
)

func main() {
        ctx := context.Background()
        ...
}

• Nuclio

package handler

import (
    "github.com/nuclio/nuclio-sdk-go"
)

func Handler(context *nuclio.Context, event nuclio.Event) (interface{}, error) {
    context.Logger.Info("Request received: %s", event.GetPath())

    return nuclio.Response{
        StatusCode:  200,
        ContentType: "application/text",
        Body: []byte("Response from handler"),
    }, nil
}

• OpenFaaS

package main

import (
    "fmt"
    "io/ioutil"
    "log"
    "os"
)

func main() {
    input, err := ioutil.ReadAll(os.Stdin)
    if err != nil {
        log.Fatalf("Unable to read standard input: %s", err.Error())
    }
    fmt.Println(string(input))
}

• OpenWhisk

package main

import "encoding/json"
import "fmt"
import "os"

func main() {
    //program receives one argument: the JSON object as a string
    arg := os.Args[1]

    // unmarshal the string to a JSON object
    var obj map[string]interface{}
    json.Unmarshal([]byte(arg), &obj)

    // can optionally log to stdout (or stderr)
    fmt.Println("hello Go action")

    name, ok := obj["name"].(string)
    if !ok { name = "Stranger" }

    // last line of stdout is the result JSON object as a string
    msg := map[string]string{"msg": ("Hello, " + name + "!")}
    res, _ := json.Marshal(msg)
    fmt.Println(string(res))
}