"argument list too long" when passing a large custom event

[shinichy]

I debugged aws/aws-sam-cli#188 and found that a large binary data is passed as a body like below and it causes argument list too long error.

{"httpMethod":"POST","body":"<large data>","resource":"/","requestContext":{"resourcePath":"/","httpMethod":"POST","stage":"prod","identity":{"sourceIp":"127.0.0.1:49921"}},"queryStringParameters":{},"headers":{"Accept":"*/*","Content-Length":"128680","Content-Type":"application/x-www-form-urlencoded","Expect":"100-continue","User-Agent":"curl/7.54.0"},"pathParameters":null,"stageVariables":null,"path":"/"}

Is there a way to pass a large custom event?

[mhart]

Yes, you can use the AWS_LAMBDA_EVENT_BODY env variable instead of passing over the command line

[mhart]

See https://github.com/lambci/docker-lambda/blob/master/nodejs6.10/run/awslambda-mock.js#L4 for details

[shinichy]

I tried AWS_LAMBDA_EVENT_BODY but still I get the same error.
Looks like both command line argument and env variable have the same limitation.
https://stackoverflow.com/questions/28865473/setting-environment-variable-to-a-large-value-argument-list-too-long

I think docker-lambda needs an option to read from stdin or a file for a large json.

index.js

exports.handler = function(event, context, cb) {
  console.log(event)
  cb()
}

Generate a large json and run with it

LARGE_DATA=`printf 'a%.0s' {1..500000}`; LARGE_JSON="{\"body\": \"$LARGE_DATA\"}"; docker run -v "$PWD":/var/task -e AWS_LAMBDA_EVENT_BODY=$LARGE_JSON lambci/lambda index.handler

[franciscohanna92]

@mhart How I pass data using that env variable? I'm facing this same issue running my lambda function + API locally. It works when deployed though.

[mhart]

Added support for events via stdin using an DOCKER_LAMBDA_USE_STDIN env variable. So:

echo '{"some": "event"}' | docker run --rm -v "$PWD":/var/task -i -e DOCKER_LAMBDA_USE_STDIN=1 lambci/lambda

Should work on all runtimes

[shinichy]

@mhart Great! Thank you!!