Aws-sam-cli: Unable to execute multiple requests in parallel through sam local start-api

[jdeon-classy]

Template:
AWSTemplateFormatVersion: '2010-09-09'
Transform: 'AWS::Serverless-2016-10-31'
Description: An AWS Serverless Specification template describing your function.
Resources:
CheckoutLambda:
Type: "AWS::Serverless::Function"
Properties:
Handler: "CheckoutLambda/index.handler"
Role: redacted
Runtime: "nodejs6.10"
Timeout: 300
Environment:
Variables:
ENV: int
Events:
CheckoutApi:
Type: Api
Properties:
Path: '/checkout/donate'
Method: post
Executing two posts in parallel:
curl -X POST http://127.0.0.1:3000/checkout/donate -H 'cache-control: no-cache' -H 'content-type: application/json' -H 'postman-token: 9f48e8af-a291-c6c6-6e9f-cc60a358a872' -d '5000' & curl -X POST http://127.0.0.1:3000/checkout/donate -H 'cache-control: no-cache' -H 'content-type: application/json' -H 'postman-token: 9f48e8af-a291-c6c6-6e9f-cc60a358a872' -d '4000'
Output from aws sam cli:
2018/02/12 14:42:53 Invoking CheckoutLambda/index.handler (nodejs6.10) 2018/02/12 14:42:53 Invoking CheckoutLambda/index.handler (nodejs6.10) START RequestId: 3c1c1ce5-fb4a-13be-4400-2fc7df6fed59 Version: $LATEST 2018-02-12T22:42:57.276Z 3c1c1ce5-fb4a-13be-4400-2fc7df6fed59 4000 START RequestId: 6d07c29d-da2e-14cc-2d1e-8996b0fccdcf Version: $LATEST 2018-02-12T22:42:57.539Z 6d07c29d-da2e-14cc-2d1e-8996b0fccdcf 5000 END RequestId: 3c1c1ce5-fb4a-13be-4400-2fc7df6fed59 REPORT RequestId: 3c1c1ce5-fb4a-13be-4400-2fc7df6fed59 Duration: 4033.19 ms Billed Duration: 4100 ms Memory Size: 0 MB Max Memory Used: 31 MB 2018/02/12 14:42:59 Function returned an invalid response (must include one of: body, headers or statusCode in the response object): unexpected end of JSON input

Another thing to note is that the function then later times out:
2018/02/12 14:26:05 Function CheckoutLambda/index.handler timed out after 300 seconds

handler(index.js)
`function sleepFor( sleepDuration ){
var now = new Date().getTime();
while(new Date().getTime() < now + sleepDuration){ /* do nothing */ }
}
function formatResponse (statusCode, body) {
return {
statusCode: statusCode,
body: JSON.stringify(body)
};
}
exports.handler = (event, context, callback) => {
console.log(event.body);
sleepFor(JSON.parse(event.body));

callback(null, formatResponse(200,'test'));
};`
This is a contrived example that I could share. But I'm running into this problem when trying to create integration tests for my lambda function. Ideally I'd like to be able to execute many tests in parallel against the locally spun-up api so that it mirrors the actual api. Thanks for anyone who looks into this! :)

PS: Sometimes it works as expected. Race condition?

[brownjava]

The code is storing per-request information in a context that spans multiple requests, so there is weird/broken behavior if you issue multiple requests at the same time. I've put together a cursory PR (sorry, haven't written much go) at https://github.com/awslabs/aws-sam-local/pull/304

[araker]

Would be really nice to have this functionality, or a queue system to handle multiple requests.

[hobotroid]

Yeah it's really difficult to develop and test an API locally when it can only handle 1 request at a time. That, coupled with the fact that each requests takes 4-8 seconds to complete (container has to spin up for every request), makes the whole process painful.

[jfuss]

Parallel Requests are now completely supported as of v.0.3.0. We even have integ tests that exercise this :)

Closing as this was addressed.

[chetan-nandrajog]

@jfuss : I am still unable to execute multiple request using sam local start-api
Using sam version SAM CLI, version 0.40.0
Whenever i try to use concurrent api call i get 503- bad gateway

[ben8p]

@chetan-nandrajog I am experimenting the same. do you use --docker-network host ?
Because that's what is causing the issue for me.
Underlying error: listen tcp :9001: bind: address already in use

[chetan-nandrajog]

@ben8p that is correct. i are using --docker-network=host . Please let me know if you find a solution for it.
Where did you see that error though?
For me the 2nd api was just stuck and i was just getting 503- bad gateway on the browser

[ben8p]

@chetan-nandrajog I will...
All Linux users must have the same issue.

Error was in the middle of Sam logs

[seawatts]

I'm also seeing this same error when running with --docker-network host

[ben8p]

Eventually I workarounded my problem by using a custom docker network instead of the host.