Can an AWS Lambda function call another

Question

I have 2 Lambda functions - one that produces a quote and one that turns a quote into an order. I'd like the Order lambda function to call the Quote function to regenerate the quote, rather than just receive it from an untrusted client.

I've looked everywhere I can think of - but can't see how I'd go about chaining or calling the functions...surely this exists!

Solution 1

I found a way using the aws-sdk.

var aws = require('aws-sdk');
var lambda = new aws.Lambda({
  region: 'us-west-2' //change to your region
});

lambda.invoke({
  FunctionName: 'name_of_your_lambda_function',
  Payload: JSON.stringify(event, null, 2) // pass params
}, function(error, data) {
  if (error) {
    context.done('error', error);
  }
  if(data.Payload){
   context.succeed(data.Payload)
  }
});

You can find the doc here: http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/Lambda.html

Solution 2

You should chain your Lambda functions via SNS. This approach provides good performance, latency and scalability for minimal effort.

Your first Lambda publishes messages to your SNS Topic and the second Lambda is subscribed to this topic. As soon as messages arrive in the topic, second Lambda gets executed with the message as it's input parameter.

See Invoking Lambda functions using Amazon SNS notifications.

You can also use this approach to Invoke cross-account Lambda functions via SNS.

Solution 3

here's a sample code for python,

from boto3 import client as boto3_client
from datetime import datetime
import json

lambda_client = boto3_client('lambda')

def lambda_handler(event, context):
    msg = {"key":"new_invocation", "at": datetime.now()}
    invoke_response = lambda_client.invoke(FunctionName="another_lambda_",
                                           InvocationType='Event',
                                           Payload=json.dumps(msg))
    print(invoke_response)

Btw, you would need to add a policy like this to your lambda role as well

   {
        "Sid": "Stmt1234567890",
        "Effect": "Allow",
        "Action": [
            "lambda:InvokeFunction"
        ],
        "Resource": "*"
    }

Solution 4

Since this question was asked, Amazon has released Step Functions (https://aws.amazon.com/step-functions/).

One of the core principles behind AWS Lambda is that you can focus more on business logic and less on the application logic that ties it all together. Step functions allows you to orchestrate complex interactions between functions without having to write the code to do it.

Solution 5

This solution is done using boto3 and Python:

import boto3
import json

lambda_client = boto3.client('lambda', region_name='eu-west-1')

def lambda_handler(event, context):
    lambda_client.invoke(FunctionName = 'function_name', InvocationType = 'RequestResponse', Payload = json.dumps(event))
    
    return True

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