AWS SAM Local + DynamoDB Local - node.js

Question

I'm currently testing out AWS SAM with DynamoDB Local using Docker.
Here is the steps that I followed (mostly found in the internet)
Create new docker network using docker network create local-dev.
Run DynamoDB Local docker run -d -v "$PWD":/dynamodb_local_db -p 8000:8000 --network local-dev --name dynamodb amazon/dynamodb-local. Until this point, I'm being able to create and list tables using AWS CLI.
Then, I proceed with running AWS SAM sam local start-api --docker-network local-dev. Everything looks okay.
Invoked lambda.js, but it looks like no result for console.log(err)or console.log(data).
I'm not sure where could it be wrong. Please help me. Thank you in advance!
lambda.js
const services = require('./services.js');
const AWS = require('aws-sdk');
let options = {
apiVersion: '2012-08-10',
region: 'ap-southeast-1',
}
if(process.env.AWS_SAM_LOCAL) {
options.endpoint = new AWS.Endpoint('http://localhost:8000')
}
const dynamoDB = new AWS.DynamoDB(options);
exports.getUser = async (event, context) => {
let params = {};
dynamoDB.listTables(params, (err, data) => {
if(err) console.log(err)
else console.log(data)
})
return true;
}
template.yaml
AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: Serverless Resources
Parameters:
FunctionsCodeBucket:
Type: String
Description: CodeBucket
FunctionsCodeKey:
Type: String
Description: CodeKey
FunctionsCodeVersion:
Type: String
Description: CodeVersion
NodeEnv:
Type: String
Description: NodeEnv
Globals:
Api:
Cors:
AllowMethods: "'OPTIONS,POST,GET,DELETE,PUT'"
AllowHeaders: "'Content-Type,X-Amz-Date,Authorization,X-Api-Key,X-Amz-Security-Token,Api-Key,api-key'"
AllowOrigin: "'*'"
Function:
Timeout: 300
Runtime: nodejs10.x
MemorySize: 128
CodeUri: ./
Resources:
DevResources:
Type: AWS::Serverless::Function
Properties:
Handler: "index.routes"
Environment:
Variables:
NODE_ENV: !Ref NodeEnv
# REGION: !Ref "AWS::Region"
Policies:
- Version: '2012-10-17'
Statement:
- Action:
- dynamodb:*
Effect: Allow
Resource: "*"
Events:
GetUser:
Type: Api
Properties:
Path: /user
Method: get

Answer 1

You lambda function does not wait for dynamoDB.listTables operation. You can fix this issue by using promisified version of dynamoDB.listTables as follows:
exports.getUser = async (event, context) => {
let params = {};
try {
const resp = await dynamoDB.listTables(params).promise();
console.log(resp);
} catch (err) {
console.log(err)
}
};
Another thing that you will likely need to do is to assign a network alias to your dynamodb container (you can do that using --network-alias=<container_name> option) for example, let's set the alias to dynamodb
docker run -d -v "$PWD":/dynamodb_local_db -p 8000:8000 --network local-dev --network-alias=dynamodb --name dynamodb amazon/dynamodb-local
After that you can use this network alias in your lambda function:
if(process.env.AWS_SAM_LOCAL) {
options.endpoint = new AWS.Endpoint('http://dynamodb:8000')
}