Step Functions AWS SAM CLI Local Connection Refused Error - amazon-web-services

Question

Following the steps in the AWS documentation
https://docs.aws.amazon.com/step-functions/latest/dg/sfn-local-lambda.html
using aws-stepfuncitons-local docker container
I'm getting a connection refused error at the last step
2019-05-28 12:37:05.004: arn:aws:states:us-east-1:123456789012:execution:HelloWorld:test :
{
"Type":"ExecutionFailed",
"PreviousEventId":5,
"ExecutionFailedEventDetails":
{
"Error":"Lambda.SdkClientException",
"Cause":"Unable to execute HTTP request: Connect to 127.0.0.1:3001 [/127.0.0.1] failed: Connection refused (Connection refused)"
}
}
Any help on how to resolve it would be greatly appreciated.

Answer 1

The docker container can't talk to services on the host network. To get it to work you need to add '--network host'.
Example:
docker run -p 8083:8083 --network host --env-file aws-stepfunctions-local-credentials.txt amazon/aws-stepfunctions-local
More details here and here

Answer 2

Just update LAMBDA_ENDPOINT to http://host.docker.internal:3001

Answer 3

It took me a few days, so that's what works for me:
on my Mac: LAMBDA_ENDPOINT=http://host.docker.internal:5000/ (5000 for moto_server, use 3001 otherwise) works.
And use docker run -p 8083:8083 --env-file aws-stepfunctions-local-credentials.txt amazon/aws-stepfunctions-local
on ubuntu-latest (github action), however, this combination works:
LAMBDA_ENDPOINT=http://127.0.0.1:5000/
docker run -p 8083:8083 --env-file aws-stepfunctions-local-credentials.txt amazon/aws-stepfunctions-local --network host
=> note the additional --network host
To handle both cases inside the same codebase (in python):
_, output = subprocess.getstatusoutput('uname -s')
if output == 'Darwin': # on a Mac
sam_step_function_local_cmd = subprocess.Popen(
[
'docker', 'run',
'-p=8083:8083',
'--env-file=aws-stepfunctions-local-credentials-mac.txt',
'amazon/aws-stepfunctions-local:1.7.3'
],
stdout=subprocess.PIPE,
stderr=subprocess.STDOUT
)
else: # on linux
sam_step_function_local_cmd = subprocess.Popen(
[
'docker', 'run',
'-p=8083:8083',
'--env-file=aws-stepfunctions-local-credentials-linux.txt',
'--network=host',
'amazon/aws-stepfunctions-local:1.7.3'
],
stdout=subprocess.PIPE,
stderr=subprocess.STDOUT
)
try:
mock_ssm(
func
)(*args, **kwargs)
finally:
sam_step_function_local_cmd.terminate()
aws-stepfunctions-local-credentials-linux.txt:
AWS_DEFAULT_REGION=eu-west-1
LAMBDA_ENDPOINT=http://127.0.0.1:5000/
aws-stepfunctions-local-credentials-mac.txt:
AWS_DEFAULT_REGION=eu-west-1
LAMBDA_ENDPOINT=http://host.docker.internal:5000/