Can't run AWS SAM CLI under Docker

Question

I'm trying to create a Docker image for AWS SAM CLI, but invoking any function gives an error: "Unable to import module 'index'". I can run the same test case outside of Docker sucessfully. You can clone the test case here or see the files below.

I already tried the following:

Setting permissions of files and parent folder to 777 (or 755).
Disabling SELinux in the Docker daemon (or enabling it).
Running Docker under privileged mode (or not).
I get the same error using an old (SAM 0.22) Docker image.
Running the same function locally as described below (works).
Zipping the folder and running on AWS (works).

These solutions probably don't apply:

The format of the zip file incorrectly including the parent folder (no zip file is used).
Issues related to NPM dependencies or node_modules (index.js has no dependencies).
Compilation errors in index.js (syntax is correct, works outside of Docker and on AWS).
The volume is being mounted on the host as described here.

Dockerfile

FROM alpine:3.6
WORKDIR /usr/src/app
RUN apk add --no-cache py-pip
RUN pip install --no-cache-dir aws-sam-cli

event.json

{}

index.js

exports.handler = function(event, context, callback) {
    return callback(null, {
        'body': 'Hello, World!'
    });
};

template.yml

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Resources:
  HelloWorld:
    Type: AWS::Serverless::Function
    Properties:
      FunctionName: HelloWorld
      CodeUri: .
      Handler: index.handler
      Runtime: nodejs6.10
      Timeout: 300

To run SAM locally:

sam local invoke -t template.yml -e event.json HelloWorld

Running SAM locally succeeds:

{"body":"Hello, World!"}

To run SAM under Docker:

docker build -t hello .
docker run \
    -v $(pwd):/usr/src/app \
    -v /var/run/docker.sock:/var/run/docker.sock \
    hello sam local invoke -t template.yml -e event.json HelloWorld

Running SAM under Docker fails:

Unable to import module 'index': Error
    at Function.Module._resolveFilename (module.js:469:15)
    at Function.Module._load (module.js:417:25)
    at Module.require (module.js:497:17)
    at require (internal/module.js:20:19)

OS: Ubuntu 16.04.1 x86_64

Docker version: 18.03.1-ce

SAM CLI version: 0.3.0

Any updates on this issue? – Jannik Weichert Aug 23 '18 at 12:11 — Jannik Weichert, Aug 23 '18 at 12:11

score 2 · Answer 1 · answered Aug 23 '18 at 13:42

You have to reference the directory relative to your host hard drive, not the first docker container drive tree.

To do so with SAM cli, use option --docker-volume-basedir "$PWD" (or -v "$PWD") on sam local invoke.

From: sam local invoke --help

--docker-volume-basedir value, -v value Optional. Specifies the location basedir where the SAM file exists. If the Docker is running on a remote machine, you must mount the path where the SAM file exists on the docker machine and modify this value to match the remote machine. [$SAM_DOCKER_VOLUME_BASEDIR]

So with your above setup, to run SAM under docker:

docker build -t hello .
docker run \
    -v /var/run/docker.sock:/var/run/docker.sock \
    hello sam local invoke -t template.yml -e event.json HelloWorld -v $(pwd)

Can't run AWS SAM CLI under Docker

1 Answers1