serverless-s3-local writing to real S3 bucket

Question

I am using Serverless framework with the serverless-s3-local plugin to test my code during development. However, despite being in offline mode, the real S3 bucket is being written to. How can I alter my configuration to use a local fake s3 bucket when in offline mode?

Relevant serverless.yml sections:

plugins:
  - serverless-stack-output
  - serverless-plugin-include-dependencies
  - serverless-layers
  - serverless-deployment-bucket
  - serverless-s3-local
  - serverless-offline
custom:
  #...
  s3:
    bucketName: test-s3-buck
    host: localhost
  serverless-offline:
    ignoreJWTSignature: true
    httpPort: 4000
    noAuth: true
    directory: /tmp
resources:
  Resources:
    #...
    Bucket:
      Type: AWS::S3::Bucket
      Properties:
        BucketName: ${self:custom.s3.bucketName}

Endpoint Calling S3:

import boto3


def post(event, context):
    s3_path = "/test.txt"
    body = "test"
    encoded_string = body.encode("utf-8")

    s3 = boto3.resource("s3")
    bucket_name = "test-s3-buck"
    s3.Bucket(bucket_name).put_object(Key=s3_path, Body=encoded_string)

    response = {
        "statusCode": 200,
        "body": "Created."
    }
    return response

Launching Serverless Offline:

serverless offline start

Answer 1

on the readme file in serverless-s3-local we have:

  const S3 = new AWS.S3({
    s3ForcePathStyle: true,
    accessKeyId: 'S3RVER', // This specific key is required when working offline
    secretAccessKey: 'S3RVER',
    endpoint: new AWS.Endpoint('http://localhost:4569'),
  });

you can achieve the same with boto:

import boto3

client = boto3.client(
    's3',
    aws_access_key_id='S3RVER',
    aws_secret_access_key='S3RVER'
)

which means, when you run your serverless offline start you need to set the aws access key id to S3RVER and aws secret access key to S3RVER, otherwise, the real bucket will be used.

also in the readme, there's instructions to setup a s3local aws profile, https://github.com/ar90n/serverless-s3-local#triggering-aws-events-offline

another way to achieve it is to run your command with environment variables:

AWS_ACCESS_KEY_ID=S3RVER AWS_SECRET_ACCESS_KEY=S3RVER serverless offline start

in that way, the aws-sdk inside your code will read the correct values for the offline mode