Unable to connect localstack dynamodb from lambda

Question

I am getting connection refused error while connecting to dynamodb (localstack) from lambda written in Typescript

I use localstack to emulate the AWS resource and below is how I am accessing the dynamodb

import { DynamoDBClient } from "@aws-sdk/client-dynamodb";
import {
  DynamoDBDocumentClient,
  ScanCommand
} from "@aws-sdk/lib-dynamodb";

const client = new DynamoDBClient({
    region: process.env.CDK_DEFAULT_REGION,
    endpoint: 'http://localhost:4566',


});


const dynamo = DynamoDBDocumentClient.from(client);
const TABLE_NAME = process.env.TABLE_NAME || '';


export const handler = async (event: any) => {

    try {
        console.log('connecting to dyname db: ' +  TABLE_NAME)
        var body = await dynamo.send(
            new ScanCommand({ TableName: TABLE_NAME })
          );          
        const response = body?.Items;
        return { statusCode: 200, body: JSON.stringify(response) };
    } catch (dbError) {  
        console.log('Unable to get the data from dyname db: ' +  TABLE_NAME)      
        return { statusCode: 500, body: JSON.stringify(dbError) };
    }
  };

and below is the error what I am getting.

{
    "errno": -111,
    "code": "ECONNREFUSED",
    "syscall": "connect",
    "address": "127.0.0.1",
    "port": 4566,
    "$metadata": {
        "attempts": 3,
        "totalRetryDelay": 32
    }
}

where as I am able to get the details through AWS CLI command.

aws --endpoint-url=http://localhost:4566 dynamodb scan --table-name <table-name>

Answer 1

if your lambda code is running inside localstack

The LocalStack instance/resources is available at the domain localhost.localstack.cloud. All subdomains of localhost.localstack.cloud also resolve to the LocalStack instance.

I was able to connect to localstack dynamo after modifying the DynamoDBClient creation like below.

const client = new DynamoDBClient({
  region:process.env.CDK_DEFAULT_REGION,
  endpoint: 'http://localhost.localstack.cloud:4566'
});

Localstack documentation : Accessing LocalStack via the endpoint URL