How to invoke a lambda function in aws-sdk v3

Question

How can I invoke a lambda function using Javascript (TypeScript) aws-sdk v3?

I use the following code which does not seems to work:

// the payload (input) to the "my-lambda-func" is a JSON as follows:
const input = {
    name: 'fake-name',
    serial: 'fake-serial',
    userId: 'fake-user-id'
};

// Payload of InvokeCommandInput is of type Uint8Array
const params: InvokeCommandInput = {
    FunctionName: 'my-lambda-func-name',
    InvocationType: 'RequestResponse',
    LogType: 'Tail',
    Payload: input as unknown as Uint8Array, // <---- payload is of type Uint8Array
  };
  
  console.log('params: ', params); // <---- so far so good.
  const result = await lambda.invoke(params);
  console.log('result: ', result); // <---- it never gets to this line for some reason.

I see this error message in CloudWatch, not sure if it is relevant to my issue thought:

The first argument must be of type string or an instance of Buffer, ArrayBuffer, or Array or an Array-like Object. Received an instance of Object

Question:

Is the above code to invoke a lambda function correct? or are there any better ways?

Answer 1

As an alternative to the example above, you can avoid using an additional AWS library and use built-in Node function instead Buffer.from.

First import what you need:

import { InvokeCommand, InvokeCommandInput, InvokeCommandOutput } from '@aws-sdk/client-lambda';

Then define your function

export class LambdaService {    
    async invokeFunction(name: string): Promise<void> {
        try {
            const payload = { name: name };

            const input: InvokeCommandInput = {
                FunctionName: "my-lambda-func-name", 
                InvocationType: "Event", 
                Payload: Buffer.from(JSON.stringify(payload), "utf8"),
            };
        
            const command = new InvokeCommand(input);

            const res : InvokeCommandOutput = await lambdaClient.send(command);
        } catch (e) {
            logger.error("error triggering function", e as Error);
        }
    }
}

Then call it with:

const lambdaService = new LambdaService();
await lambdaService.invokeFunction("name");

If you miss the await, it is possible the function will start executing but never reach the last line.

Answer 2

It looks like your call to lambda.invoke() is throwing a TypeError because the payload that you are passing to it is an object when it needs to be a Uint8Array buffer.

You can modify your code as follows to pass the payload:

// import { fromUtf8 } from "@aws-sdk/util-utf8-node";

const { fromUtf8 } = require("@aws-sdk/util-utf8-node");

// the payload (input) to the "my-lambda-func" is a JSON as follows:
const input = {
  name: 'fake-name',
  serial: 'fake-serial',
  userId: 'fake-user-id'
};

// Payload of InvokeCommandInput is of type Uint8Array
const params: InvokeCommandInput = {
  FunctionName: 'my-lambda-func-name',
  InvocationType: 'RequestResponse',
  LogType: 'Tail',
  Payload: fromUtf8(JSON.stringify(input)),
};