Endpoint URL for DynamoDB inside localstack's Lambda function

Question

I'm using localstack for local development. I have a DynamoDB table named readings and I'd like to insert items from a lambda function.

I have deployed simple lambda function in python runtime:

import os
import boto3

def lambda_handler(events, context):
    DYNAMODB_ENDPOINT_URL = os.environ.get("DYNAMODB_ENDPOINT_URL")
    dynamodb = boto3.resource("dynamodb", endpoint_url=DYNAMODB_ENDPOINT_URL)
    readings_table = dynamodb.Table(DYNAMODB_READINGS_TABLE_NAME)

    readings_table.put_item(Item={"reading_id": "10", "other": "test"})

But I'm getting error: [ERROR] EndpointConnectionError: Could not connect to the endpoint URL: "http://localstack:4569/"

I've tried combinations of localhost and localstack along with ports: 4566 and 4569. All of them fail.

Here's my docker-compse service that I use to start localstack

    localstack:
        image: localstack/localstack:0.11.2
        ports:
            - 4566:4566
            - 8080:8080
        environment:
            SERVICES: "dynamodb,sqs,lambda,iam"
            DATA_DIR: "/tmp/localstack/data"
            PORT_WEB_UI: "8080"
            LOCALSTACK_HOSTNAME: localstack
            LAMBDA_EXECUTOR: docker
            AWS_ACCESS_KEY_ID: "test"
            AWS_SECRET_ACCESS_KEY: "test"
            AWS_DEFAULT_REGION: "us-east-1"
        volumes:
            - localstack_volume:/tmp/localstack/data
            - /var/run/docker.sock:/var/run/docker.sock
            # When a container is started for the first time, it will execute files with extensions .sh that are found in /docker-entrypoint-initaws.d. 
            # Files will be executed in alphabetical order. You can easily create aws resources on localstack using `awslocal` (or `aws`) cli tool in the initialization scripts.
            # source: https://github.com/localstack/localstack/pull/1018/files#diff-04c6e90faac2675aa89e2176d2eec7d8R185
            - ./localstack-startup-scripts/:/docker-entrypoint-initaws.d/

What would be the correct endpoint url that I have to set inside in my lambda so that I can send requests to localstack's DynamoDB?

Robert Taylor · Accepted Answer · 2020-09-21 21:10:28Z

3

According to the docs LOCALSTACK_HOSTNAME is a read-only env var:

LOCALSTACK_HOSTNAME: Name of the host where LocalStack services are available. Use this hostname as endpoint (e.g., http://${LOCALSTACK_HOSTNAME}:4566) in order to access the services from within your Lambda functions (e.g., to store an item to DynamoDB or S3 from a Lambda).

answered Sep 21, 2020 at 21:10

Robert Taylor

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r0ck · Accepted Answer · 2020-06-05 20:30:17Z

0

 try with 
 ports:      
    - "0.0.0.0:4566-4599:4566-4599"

Hope it helps

answered Jun 5, 2020 at 20:30

r0ck

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2 Comments

umat Over a year ago

Unfortunately no effect, either with endpoint url = localhost:4566 and localstack:4566 - I still get EndpointConnectionError

Mithiridi Prasanth Over a year ago

Did you find any solution for the same ?

JackOuttaBox · Accepted Answer · 2022-07-03 20:00:25Z

By following Robert Taylor's answer, I was able to get the following working in my Java Lambda (this should really be a comment in that answer, but code formatting for big snippet is not adequate in comment, so I'm sharing this as a separate answer to make people's life easier):

var url = System.getenv("LOCALSTACK_HOSTNAME");
var credentials = new BasicAWSCredentials("mock_access_key", "mock_secret_key");
var ep = new AwsClientBuilder.EndpointConfiguration(String.format("http://%s:4566",url), "us-east-1");
s3 = AmazonS3ClientBuilder.standard()
        .withEndpointConfiguration(ep)
        .withPathStyleAccessEnabled(true)
        .withCredentials(new AWSStaticCredentialsProvider(credentials))
        .build();
dynamoDBMapper = new DynamoDBMapper(
        AmazonDynamoDBClientBuilder.standard()
        .withEndpointConfiguration(ep)
        .withCredentials(new AWSStaticCredentialsProvider(credentials))
        .build()
);

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